Auto-spot, tuning aids, and the arcane history of CW pitch-matching

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Auto-spot, tuning aids, and the arcane history of CW pitch-matching

wayne burdick
Administrator
Elecraft's auto-spot and CWT features -- available on the K3/K3S/KX2/KX3 -- are very useful tools for CW operators, especially those not experienced in pitch-matching. Here's a bit of history on where these features came from and how they work.


CW Spotting History

When a station finishes a CQ in CW mode, the operator faces the challenge of copying someone who's calling back. Callers may be weak or obscured by QRM; the op can usually deal with both problems by narrowing the filter passband. However, callers may also be off frequency. A calling station may be using a wide filter passband themselves, not attempting to carefully match their VFO frequency to that of the CQing station. The result may be no QSO, even when propagation is excellent.

In the Days of Yore, a frequency offset between stations didn't always matter. Sometimes both stations used crystal-controlled transmitters, so operators had to patient tune around after calling CQ.

As a 14-year-old novice I embraced this operating style for a year or so, armed with a dozen or so crusty FT-243 crystals for my Heath HW-16. I nearly wore out the socket swapping them in and out. After calling CQ, it was not unusual to find a caller 30 or more kHz away! (Away from "where" was a poorly answered question, as my Hallicrafters receiver dial wasn't exactly digital.)

Fortunately I soon acquired an outboard VFO, a life-changing addition to my station. Jealous friends doubled up on their paper routes to pay for their own. Girls suddenly paid more attention to me.

These days virtually everyone has a VFO, along with the expectation that they won't have to tune theirs very far, if at all, to tune you in. Not only that, they're stable and well calibrated, not like the beasts we had to skillfully tame. Progress!


Manual Spotting (SPOT switch)

Once I had a VFO I quickly learned to do *manual* pitch matching. Older rigs did't provide a way to do that explicitly, so you'd improvise. Basically, you had to coerce a very weak signal out of your own transmitter, say by turning on only the driver, then tune the transmit VFO until you could hear your signal on your own receiver -- superimposed on the calling station, at the same pitch. This is what we call spotting.

Of course spotting is a lot more convenient these days, as many rigs include a SPOT switch. This function is easy for a modern transceiver designer to add, because the radio's firmware is quite capable of turning on only the CW sidetone without transmitting.

That is the purpose of the SPOT switch on all Elecraft transceivers. Tap SPOT, and you'll hear your sidetone pitch. Most people can do a good job of adjusting the VFO such that the CQing station's pitch matches that of the SPOT tone. This ensures that when you call them, you'll be close to their own frequency.


Tuning Aids: Filtering (APF), PLL (NE567), and Spectral (CWT)

Since not everyone has an inherent musical ear, various hardware-enhanced means of tuning in CW signals have been developed.

The simplest method is to just narrow your receiver passband so much that, if you can hear a station calling CQ at all, you're guaranteed to be "right on top of him." This assumes that your transceiver enforces alignment between its transmit and receive pitch...true of all Elecraft gear.

Narrow filtering has gone through decades of evolution. Some filters were based on op-amps (active filters), while others were based on LC filtering, conscripting humongous toroidal cores scavenged from telco equipment. I acquired my stash of these from a haphazard mound of old switching racks, decaying in an abandoned aircraft hanger on the Bermuda U.S. Navy base. (That irresistible junk pile was also a mother load of TO5 transistors, multi-pound electrolytic capacitors, and tetanus, but that's another story.) Typically the toroids were 88 millihenries -- a huge value for a high-Q inductor, permitting resonance in the low audio range.

Later, such filters migrated to digital signal processing, in the form of switched-capacitor ICs or DSPs. You can still buy these switched-capacitor chips, like the MF10, from various sources. It's instructive to roll your own tunable filter, just for fun.

Whether passive or active, the goal of filtering is typically to achieve a narrow passband, say 250 Hz or less. With DSP, nearly perfect filters with "brick wall" passbands can be created. But these have the disadvantage of ringing like a bell when pinged by a CW signal or noise, making copy difficult.

One solution incorporated into the K-line and KX-line is the Audio Peaking Filter (APF), which provides a 30-Hz bandwidth at -3 dB, but broad skirts, preventing ringing from occurring. As our customers will attest, APF works like magic on weak signals obscured by noise.

Another forerunner to DSP techniques was the audio phase-locked-loop, using inexpensive ICs like the legendary LM567. When locked on a signal that matched its center frequency, the circuit would turn on an LED, alerting the operator that the VFO was now properly tuned.

With the DSPs in our K-line and KX-line radios, we can provide a much more powerful tool: CWT, or "CW Tuning Aid." When enabled, CWT turns the upper portion of the rig's S-meter into something of a mini spectrum analyzer. The pitch of the strongest signal in the passband is analyzed by the DSP, then represented as a single segment of the bar graph. For CWT-enhanced manual spotting, the operator simply tunes the VFO slowly until the center CWT segment is flashing along with the keyed signal.

Manual tuning with CWT can also be used in FSK-D and PSK-D modes as described in the owner's manual.


Closing the Loop:  Auto-Spotting (SPOT + CWT)

The Elecraft K3/K3S/KX2/KX3 take CW tuning another step forward by providing a way to *automatically* retune the VFO frequency to match that of a received signal. How does this work?

When CWT is turned on, firmware treats the SPOT switch as AUTO-SPOT. The DSP analyzes the incoming signal, and with a bit of processing, determines its exact audio pitch. From there all that's needed is a bit of math to offset the VFO to match this pitch to the CW sidetone.

There's another subtlety, though. Since a CW signal is generally being keyed on and off, the CWT algorithm has to ensure that it doesn't "take off," chasing a signal that's not there. To avoid this, we keep track of the energy in the passband, and slew the VFO incrementally over an average of about 0.5 second, moving only when the target signal is present.


How to Use Auto-Spot

I encourage you to give the auto-spot feature a try. It's best to start with a fairly narrow passband, say 400-600 Hz; narrower if there's a lot of QRM. Find a signal, turn on CWT, then tap SPOT to tune it in. A second tap of SPOT may get even closer, especially if there's a lot of band noise.

Auto-spot can also be used in Elecraft's PSK-D mode, i.e. for PSK31/PSK63. As with CW mode, just turn on CWT, tune in a prospective signal, and tap SPOT. Since PSK auto-decoding requires very accurate tuning, it's best to set the filter bandwidth to 50 Hz, then let auto-spot dial things in down to the last 2 or 3 Hz. If you have text decode turned on, you should start seeing text characters scroll by after auto-tuning has completed. Tapping a second time or fine-tuning the VFO a bit in 1 Hz steps may improve copy.

73,
Wayne
N6KR




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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Nr4c
Wayne,  thanks for this historical description.  I have used these tools myself a lot over the years. They are one reason I have purchased my K3, K3S and KX3(however sold to purchase K3S).

Now, one thing you missed...  when you’re working a big pileup and you feel you just can’t get through, it may be that all your “buddies” are doing the same thing, using Auto-Spot!

Now turn on XIT and set it to 12-20 Hz either way. Now your signal will be just a little different from all the others and you have a better chance of being heard.  

Sent from my iPhone
...nr4c. bill


> On Jan 22, 2019, at 12:09 AM, Wayne Burdick <[hidden email]> wrote:
>
> Elecraft's auto-spot and CWT features -- available on the K3/K3S/KX2/KX3 -- are very useful tools for CW operators, especially those not experienced in pitch-matching. Here's a bit of history on where these features came from and how they work.
>
>
> CW Spotting History
>
> When a station finishes a CQ in CW mode, the operator faces the challenge of copying someone who's calling back. Callers may be weak or obscured by QRM; the op can usually deal with both problems by narrowing the filter passband. However, callers may also be off frequency. A calling station may be using a wide filter passband themselves, not attempting to carefully match their VFO frequency to that of the CQing station. The result may be no QSO, even when propagation is excellent.
>
> In the Days of Yore, a frequency offset between stations didn't always matter. Sometimes both stations used crystal-controlled transmitters, so operators had to patient tune around after calling CQ.
>
> As a 14-year-old novice I embraced this operating style for a year or so, armed with a dozen or so crusty FT-243 crystals for my Heath HW-16. I nearly wore out the socket swapping them in and out. After calling CQ, it was not unusual to find a caller 30 or more kHz away! (Away from "where" was a poorly answered question, as my Hallicrafters receiver dial wasn't exactly digital.)
>
> Fortunately I soon acquired an outboard VFO, a life-changing addition to my station. Jealous friends doubled up on their paper routes to pay for their own. Girls suddenly paid more attention to me.
>
> These days virtually everyone has a VFO, along with the expectation that they won't have to tune theirs very far, if at all, to tune you in. Not only that, they're stable and well calibrated, not like the beasts we had to skillfully tame. Progress!
>
>
> Manual Spotting (SPOT switch)
>
> Once I had a VFO I quickly learned to do *manual* pitch matching. Older rigs did't provide a way to do that explicitly, so you'd improvise. Basically, you had to coerce a very weak signal out of your own transmitter, say by turning on only the driver, then tune the transmit VFO until you could hear your signal on your own receiver -- superimposed on the calling station, at the same pitch. This is what we call spotting.
>
> Of course spotting is a lot more convenient these days, as many rigs include a SPOT switch. This function is easy for a modern transceiver designer to add, because the radio's firmware is quite capable of turning on only the CW sidetone without transmitting.
>
> That is the purpose of the SPOT switch on all Elecraft transceivers. Tap SPOT, and you'll hear your sidetone pitch. Most people can do a good job of adjusting the VFO such that the CQing station's pitch matches that of the SPOT tone. This ensures that when you call them, you'll be close to their own frequency.
>
>
> Tuning Aids: Filtering (APF), PLL (NE567), and Spectral (CWT)
>
> Since not everyone has an inherent musical ear, various hardware-enhanced means of tuning in CW signals have been developed.
>
> The simplest method is to just narrow your receiver passband so much that, if you can hear a station calling CQ at all, you're guaranteed to be "right on top of him." This assumes that your transceiver enforces alignment between its transmit and receive pitch...true of all Elecraft gear.
>
> Narrow filtering has gone through decades of evolution. Some filters were based on op-amps (active filters), while others were based on LC filtering, conscripting humongous toroidal cores scavenged from telco equipment. I acquired my stash of these from a haphazard mound of old switching racks, decaying in an abandoned aircraft hanger on the Bermuda U.S. Navy base. (That irresistible junk pile was also a mother load of TO5 transistors, multi-pound electrolytic capacitors, and tetanus, but that's another story.) Typically the toroids were 88 millihenries -- a huge value for a high-Q inductor, permitting resonance in the low audio range.
>
> Later, such filters migrated to digital signal processing, in the form of switched-capacitor ICs or DSPs. You can still buy these switched-capacitor chips, like the MF10, from various sources. It's instructive to roll your own tunable filter, just for fun.
>
> Whether passive or active, the goal of filtering is typically to achieve a narrow passband, say 250 Hz or less. With DSP, nearly perfect filters with "brick wall" passbands can be created. But these have the disadvantage of ringing like a bell when pinged by a CW signal or noise, making copy difficult.
>
> One solution incorporated into the K-line and KX-line is the Audio Peaking Filter (APF), which provides a 30-Hz bandwidth at -3 dB, but broad skirts, preventing ringing from occurring. As our customers will attest, APF works like magic on weak signals obscured by noise.
>
> Another forerunner to DSP techniques was the audio phase-locked-loop, using inexpensive ICs like the legendary LM567. When locked on a signal that matched its center frequency, the circuit would turn on an LED, alerting the operator that the VFO was now properly tuned.
>
> With the DSPs in our K-line and KX-line radios, we can provide a much more powerful tool: CWT, or "CW Tuning Aid." When enabled, CWT turns the upper portion of the rig's S-meter into something of a mini spectrum analyzer. The pitch of the strongest signal in the passband is analyzed by the DSP, then represented as a single segment of the bar graph. For CWT-enhanced manual spotting, the operator simply tunes the VFO slowly until the center CWT segment is flashing along with the keyed signal.
>
> Manual tuning with CWT can also be used in FSK-D and PSK-D modes as described in the owner's manual.
>
>
> Closing the Loop:  Auto-Spotting (SPOT + CWT)
>
> The Elecraft K3/K3S/KX2/KX3 take CW tuning another step forward by providing a way to *automatically* retune the VFO frequency to match that of a received signal. How does this work?
>
> When CWT is turned on, firmware treats the SPOT switch as AUTO-SPOT. The DSP analyzes the incoming signal, and with a bit of processing, determines its exact audio pitch. From there all that's needed is a bit of math to offset the VFO to match this pitch to the CW sidetone.
>
> There's another subtlety, though. Since a CW signal is generally being keyed on and off, the CWT algorithm has to ensure that it doesn't "take off," chasing a signal that's not there. To avoid this, we keep track of the energy in the passband, and slew the VFO incrementally over an average of about 0.5 second, moving only when the target signal is present.
>
>
> How to Use Auto-Spot
>
> I encourage you to give the auto-spot feature a try. It's best to start with a fairly narrow passband, say 400-600 Hz; narrower if there's a lot of QRM. Find a signal, turn on CWT, then tap SPOT to tune it in. A second tap of SPOT may get even closer, especially if there's a lot of band noise.
>
> Auto-spot can also be used in Elecraft's PSK-D mode, i.e. for PSK31/PSK63. As with CW mode, just turn on CWT, tune in a prospective signal, and tap SPOT. Since PSK auto-decoding requires very accurate tuning, it's best to set the filter bandwidth to 50 Hz, then let auto-spot dial things in down to the last 2 or 3 Hz. If you have text decode turned on, you should start seeing text characters scroll by after auto-tuning has completed. Tapping a second time or fine-tuning the VFO a bit in 1 Hz steps may improve copy.
>
> 73,
> Wayne
> N6KR
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Elecraft mailing list
Yet another trick learnt by hard experience given away for free :-(

Regards,

Mike VP8NO

On 22/01/2019 11:14, Nr4c wrote:
> Now, one thing you missed...  when you’re working a big pileup and you feel you just can’t get through, it may be that all your “buddies” are doing the same thing, using Auto-Spot!
>
> Now turn on XIT and set it to 12-20 Hz either way. Now your signal will be just a little different from all the others and you have a better chance of being heard.
>
> Sent from my iPhone
> ...nr4c. bill
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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

David Gilbert
In reply to this post by wayne burdick

Wayne, you forgot clicking on the DX Cluster spot.  ;)

I'm being facetious, of course, but the practice of simply clicking on a
cluster spot does point out a problem with zero beating by any means ...
if every calling station is zero beat the station calling CQ isn't going
to copy anyone.

Zero beat isn't always a good thing.

73,
Dave  AB7E


On 1/21/2019 10:09 PM, Wayne Burdick wrote:

> Elecraft's auto-spot and CWT features -- available on the K3/K3S/KX2/KX3 -- are very useful tools for CW operators, especially those not experienced in pitch-matching. Here's a bit of history on where these features came from and how they work.
>
>
> CW Spotting History
>
> When a station finishes a CQ in CW mode, the operator faces the challenge of copying someone who's calling back. Callers may be weak or obscured by QRM; the op can usually deal with both problems by narrowing the filter passband. However, callers may also be off frequency. A calling station may be using a wide filter passband themselves, not attempting to carefully match their VFO frequency to that of the CQing station. The result may be no QSO, even when propagation is excellent.
>
> In the Days of Yore, a frequency offset between stations didn't always matter. Sometimes both stations used crystal-controlled transmitters, so operators had to patient tune around after calling CQ.
>
> As a 14-year-old novice I embraced this operating style for a year or so, armed with a dozen or so crusty FT-243 crystals for my Heath HW-16. I nearly wore out the socket swapping them in and out. After calling CQ, it was not unusual to find a caller 30 or more kHz away! (Away from "where" was a poorly answered question, as my Hallicrafters receiver dial wasn't exactly digital.)
>
> Fortunately I soon acquired an outboard VFO, a life-changing addition to my station. Jealous friends doubled up on their paper routes to pay for their own. Girls suddenly paid more attention to me.
>
> These days virtually everyone has a VFO, along with the expectation that they won't have to tune theirs very far, if at all, to tune you in. Not only that, they're stable and well calibrated, not like the beasts we had to skillfully tame. Progress!
>
>
> Manual Spotting (SPOT switch)
>
> Once I had a VFO I quickly learned to do *manual* pitch matching. Older rigs did't provide a way to do that explicitly, so you'd improvise. Basically, you had to coerce a very weak signal out of your own transmitter, say by turning on only the driver, then tune the transmit VFO until you could hear your signal on your own receiver -- superimposed on the calling station, at the same pitch. This is what we call spotting.
>
> Of course spotting is a lot more convenient these days, as many rigs include a SPOT switch. This function is easy for a modern transceiver designer to add, because the radio's firmware is quite capable of turning on only the CW sidetone without transmitting.
>
> That is the purpose of the SPOT switch on all Elecraft transceivers. Tap SPOT, and you'll hear your sidetone pitch. Most people can do a good job of adjusting the VFO such that the CQing station's pitch matches that of the SPOT tone. This ensures that when you call them, you'll be close to their own frequency.
>
>
> Tuning Aids: Filtering (APF), PLL (NE567), and Spectral (CWT)
>
> Since not everyone has an inherent musical ear, various hardware-enhanced means of tuning in CW signals have been developed.
>
> The simplest method is to just narrow your receiver passband so much that, if you can hear a station calling CQ at all, you're guaranteed to be "right on top of him." This assumes that your transceiver enforces alignment between its transmit and receive pitch...true of all Elecraft gear.
>
> Narrow filtering has gone through decades of evolution. Some filters were based on op-amps (active filters), while others were based on LC filtering, conscripting humongous toroidal cores scavenged from telco equipment. I acquired my stash of these from a haphazard mound of old switching racks, decaying in an abandoned aircraft hanger on the Bermuda U.S. Navy base. (That irresistible junk pile was also a mother load of TO5 transistors, multi-pound electrolytic capacitors, and tetanus, but that's another story.) Typically the toroids were 88 millihenries -- a huge value for a high-Q inductor, permitting resonance in the low audio range.
>
> Later, such filters migrated to digital signal processing, in the form of switched-capacitor ICs or DSPs. You can still buy these switched-capacitor chips, like the MF10, from various sources. It's instructive to roll your own tunable filter, just for fun.
>
> Whether passive or active, the goal of filtering is typically to achieve a narrow passband, say 250 Hz or less. With DSP, nearly perfect filters with "brick wall" passbands can be created. But these have the disadvantage of ringing like a bell when pinged by a CW signal or noise, making copy difficult.
>
> One solution incorporated into the K-line and KX-line is the Audio Peaking Filter (APF), which provides a 30-Hz bandwidth at -3 dB, but broad skirts, preventing ringing from occurring. As our customers will attest, APF works like magic on weak signals obscured by noise.
>
> Another forerunner to DSP techniques was the audio phase-locked-loop, using inexpensive ICs like the legendary LM567. When locked on a signal that matched its center frequency, the circuit would turn on an LED, alerting the operator that the VFO was now properly tuned.
>
> With the DSPs in our K-line and KX-line radios, we can provide a much more powerful tool: CWT, or "CW Tuning Aid." When enabled, CWT turns the upper portion of the rig's S-meter into something of a mini spectrum analyzer. The pitch of the strongest signal in the passband is analyzed by the DSP, then represented as a single segment of the bar graph. For CWT-enhanced manual spotting, the operator simply tunes the VFO slowly until the center CWT segment is flashing along with the keyed signal.
>
> Manual tuning with CWT can also be used in FSK-D and PSK-D modes as described in the owner's manual.
>
>
> Closing the Loop:  Auto-Spotting (SPOT + CWT)
>
> The Elecraft K3/K3S/KX2/KX3 take CW tuning another step forward by providing a way to *automatically* retune the VFO frequency to match that of a received signal. How does this work?
>
> When CWT is turned on, firmware treats the SPOT switch as AUTO-SPOT. The DSP analyzes the incoming signal, and with a bit of processing, determines its exact audio pitch. From there all that's needed is a bit of math to offset the VFO to match this pitch to the CW sidetone.
>
> There's another subtlety, though. Since a CW signal is generally being keyed on and off, the CWT algorithm has to ensure that it doesn't "take off," chasing a signal that's not there. To avoid this, we keep track of the energy in the passband, and slew the VFO incrementally over an average of about 0.5 second, moving only when the target signal is present.
>
>
> How to Use Auto-Spot
>
> I encourage you to give the auto-spot feature a try. It's best to start with a fairly narrow passband, say 400-600 Hz; narrower if there's a lot of QRM. Find a signal, turn on CWT, then tap SPOT to tune it in. A second tap of SPOT may get even closer, especially if there's a lot of band noise.
>
> Auto-spot can also be used in Elecraft's PSK-D mode, i.e. for PSK31/PSK63. As with CW mode, just turn on CWT, tune in a prospective signal, and tap SPOT. Since PSK auto-decoding requires very accurate tuning, it's best to set the filter bandwidth to 50 Hz, then let auto-spot dial things in down to the last 2 or 3 Hz. If you have text decode turned on, you should start seeing text characters scroll by after auto-tuning has completed. Tapping a second time or fine-tuning the VFO a bit in 1 Hz steps may improve copy.
>
> 73,
> Wayne
> N6KR
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

K9MA
In reply to this post by wayne burdick
Back in my college days at W9YT, we had a Drake line, separate
transmitter and receivers. When searching and pouncing in a contest, you
had to spot the transmitter before every contact. Spotting required
turning one of the rotary switches on the transmitter, a cumbersome
process. Imagine doing that a couple thousand times in a weekend. At
some point, we came up with the idea to hook a foot switch up to do the
spotting, which made it much easier, and save a lot of wear and tear on
the rotary switch, not to mention the operator's wrist.

In those days, 40-50 years ago, transceivers just didn't work well on
CW, so almost all CW operators used separate transmitters and receivers.
Some, like the Drake line, could transceive, but had the same problem on
CW. Transceivers didn't account for the BFO offset, and there was no RIT
or XIT. If you called another station in transceive mode, you would be
700 Hz or so off frequency. Two transceivers pretty much couldn't work
each other at all. Sometime while I was inactive in the late 70's and
80's, that problem was solved, and we no longer had to spot before every
contact. I think that solution had to wait for frequency synthesis, as
it otherwise would have required additional (expensive) crystals. Does
anyone know of a non-synthesized transceiver that didn't have the CW
offset problem?

73,
Scott K9MA


On 1/21/2019 23:09, Wayne Burdick wrote:
> Elecraft's auto-spot and CWT features -- available on the K3/K3S/KX2/KX3 -- are very useful tools for CW operators, especially those not experienced in pitch-matching. Here's a bit of history on where these features came from and how they work.


--
Scott  K9MA

[hidden email]

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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

K9MA
In reply to this post by David Gilbert
On 1/22/2019 10:59, David Gilbert wrote:
>
> Wayne, you forgot clicking on the DX Cluster spot. ;)

Everyone zero beat was, I think, a bigger problem before skimmers.
Skimmer spots often seem to be quite a ways off frequency, probably
because their SDR receivers aren't all that stable. Some may be in
unheated buildings, too.

73,

Scott K9MA

--
Scott  K9MA

[hidden email]

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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

n0uk
In reply to this post by K9MA


--
73 Chris Cox, N0UK, G4JEC
[hidden email]

On Tue, 22 Jan 2019, K9MA wrote:

> transmitter before every contact. Spotting required turning one of the rotary
> switches on the transmitter, a cumbersome process. Imagine doing that a couple
> thousand times in a weekend. At some point, we came up with the idea to hook a
> foot switch up to do the spotting, which made it much easier, and save a lot
> of wear and tear on the rotary switch, not to mention the operator's wrist.
>
> In those days, 40-50 years ago, transceivers just didn't work well on CW, so
> almost all CW operators used separate transmitters and receivers. Some, like
> the Drake line, could transceive, but had the same problem on CW. Transceivers
> didn't account for the BFO offset, and there was no RIT or XIT. If you called
> another station in transceive mode, you would be 700 Hz or so off frequency.
> Two transceivers pretty much couldn't work each other at all. Sometime while I
> was inactive in the late 70's and 80's, that problem was solved, and we no
> longer had to spot before every contact. I think that solution had to wait for
> frequency synthesis, as it otherwise would have required additional
> (expensive) crystals. Does anyone know of a non-synthesized transceiver that
> didn't have the CW offset problem?
>
> 73,
> Scott K9MA
>
>
> On 1/21/2019 23:09, Wayne Burdick wrote:
> > Elecraft's auto-spot and CWT features -- available on the K3/K3S/KX2/KX3 --
> > are very useful tools for CW operators, especially those not experienced in
> > pitch-matching. Here's a bit of history on where these features came from
> > and how they work.
>
>
> --
> Scott  K9MA
>
> [hidden email]
>
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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

n0uk
In reply to this post by K9MA
The transceive problem didn't seem to exist on any older non-synthesized
transceiver that I have used, including FT-101 series, TS-520/820 and
later, KW Electronics KW-2000E.  these were all '70s era transceivers.

--
73 Chris Cox, N0UK, G4JEC
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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Bob McGraw - K4TAX
In reply to this post by Elecraft mailing list
Another trick which works well.   Tune to a WWV frequency in CW mode. 
Press SPOT and the radio will jump on the exact carrier frequency.   The
SPOT function can pull on to the WWV frequency as far away as about 100
Hz.  Once the radio has  resolved SPOT, the readout / display is the
frequency of WWV +/- the error in Hz. Thus the readout of 9.999.992 is
indicating being 8 Hz low.

 From a cold start, FP being 19°C, I find  -8 Hz error on 10 MHz WWV. 
After about 15 minutes the FP is 25°C and the error is -1 Hz.  I've
tweaked the REF CAL such that after 1/2 hr. in receive tuning to WWV
from both higher and lower will produce a reading of 10.000.000.   Will
all stations pse QNZ  QNN.

73

Bob, K4TAX


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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Don Wilhelm
In reply to this post by n0uk
In that era, SSB capable transceivers often offset the BFO by using a
different BFO crystal for CW transmit or CW receive - but that technique
slaved you to one sideband and one CW pitch.
There were other ways of doing the offset as well, but it was usually
done by shifting the BFO frequency.

73,
Don W3FPR

On 1/22/2019 1:54 PM, Chris Cox, N0UK wrote:

> The transceive problem didn't seem to exist on any older non-synthesized
> transceiver that I have used, including FT-101 series, TS-520/820 and
> later, KW Electronics KW-2000E.  these were all '70s era transceivers.
>
> --
> 73 Chris Cox, N0UK, G4JEC
> [hidden email]
>
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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Elecraft mailing list
In reply to this post by K9MA
Re:  "Does anyone know of a non-synthesized transceiver that didn't have the CW offset problem?"

My TenTec 540 doesn't have that problem, but my much older TenTec PM-3A does.  If my memory is correct, the Heathkit HW8 has the problem, but they fixed it in the HW9 with a small capacitor that switches in and out for RX/TX to shift the VFO.

There are others.

Mark
KE6BB



Sent via the Samsung Galaxy Tab E, an AT&T 4G LTE tablet
-------- Original message --------From: K9MA <[hidden email]> Date: 1/22/19  9:11 AM  (GMT-08:00) To: [hidden email] Subject: Re: [Elecraft] Auto-spot, tuning aids,
  and the arcane history of CW pitch-matching
Back in my college days at W9YT, we had a Drake line, separate
transmitter and receivers. When searching and pouncing in a contest, you
had to spot the transmitter before every contact. Spotting required
turning one of the rotary switches on the transmitter, a cumbersome
process. Imagine doing that a couple thousand times in a weekend. At
some point, we came up with the idea to hook a foot switch up to do the
spotting, which made it much easier, and save a lot of wear and tear on
the rotary switch, not to mention the operator's wrist.

In those days, 40-50 years ago, transceivers just didn't work well on
CW, so almost all CW operators used separate transmitters and receivers.
Some, like the Drake line, could transceive, but had the same problem on
CW. Transceivers didn't account for the BFO offset, and there was no RIT
or XIT. If you called another station in transceive mode, you would be
700 Hz or so off frequency. Two transceivers pretty much couldn't work
each other at all. Sometime while I was inactive in the late 70's and
80's, that problem was solved, and we no longer had to spot before every
contact. I think that solution had to wait for frequency synthesis, as
it otherwise would have required additional (expensive) crystals. Does
anyone know of a non-synthesized transceiver that didn't have the CW
offset problem?

73,
Scott K9MA


On 1/21/2019 23:09, Wayne Burdick wrote:
> Elecraft's auto-spot and CWT features -- available on the K3/K3S/KX2/KX3 -- are very useful tools for CW operators, especially those not experienced in pitch-matching. Here's a bit of history on where these features came from and how they work.


--
Scott  K9MA

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Re: [KX3] Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Howard Hoyt
In reply to this post by wayne burdick
Hi Mel,

I experienced the same reading Wayne's highly informative post!!

I started off in 1970 with a homebrew 6L6/807 xtal xmtr with maybe 12
xtals and a Hallicrafters S-38 which gave me hundreds of mesmerizing
hours in my parents basement.  That rig gave me my first huge shock as
well, so it is indeed memorable.  What idiot thought it was a good idea
to put the 500 V B+ connection on an unguarded terminal strip on the
back panel?  Wait, that was me...

Still, I thought I was in heaven until my high school club bought a
Drake R-4B/T-4XB which blew me away and I ended up owning a pair in the
early 1980s and still love the Drake twins to this day. However they
have been gathering dust since I got my K3, which is the best rig
overall I have used to date, and love my KX3 in the car and on travel.

Although it works well, I don't use Auto Spot is because it scrambles my
feeble brain as to where I am tuned; I am just not used to a rig
changing frequency without me intentionally doing it.  Perhaps this is a
mental artifact of heavy contesting, where I am loathe to leave a good
RUN frequency, indeed I often lock VFO A so I don't accidentally bump
the VFO A knob.

Cheers & 73,
Howie / WA4PSC


On 1/22/2019 1:51 PM, Mel Snyder [hidden email] [KX3] wrote:

>
> Wow, this is *great,* Wayne! Thanks. I am away from home, but will be
> interested to test the auto-spot when I get home.
>
>
> A wonderful trip down memory lane. While you were swapping crystals
> with your HW-16, I was a few years ahead of you as KN3AFW, swapping
> them first into my home-brew 6AG7-6L6 rig, and then, a borrowed Eico 720.
>
> I still own a lovely Johnson Ranger II, and an SB-301 Heathkit
> receiver with the original 500Hz filter, the combination of which
> require your explained tuning the VFO to the note of the received
> signal. But both are on my list to sell, along with my HW-9 and
> FT-707, inasmuch with my KX3 for good band conditions and my
> inherited/restored TS-940S when they’re poor, they are all surplus
> space-consumers.
>
> Every time I turn on my KX3, I am in awe of how far ham radio has
> progressed in the past 61 years since I was licensed. Like taking a
> cell call on my Apple Watch, it’s beyond anything I dreamed of as a
> kid back then. So glad I stopped by the Elecraft exhibit at the 2014
> Hartford ARRL convention, and was taken by the enthusiasm of KX3 users
> that gathered there - and decided to join the cult.
>
> Mel, W3PYF
>
>
>
>> On Jan 22, 2019, at 12:09 AM, Wayne Burdick [hidden email]
>> <mailto:[hidden email]> [KX3] <[hidden email]
>> <mailto:[hidden email]>> wrote:
>>
>> Elecraft's auto-spot and CWT features -- available on the
>> K3/K3S/KX2/KX3 -- are very useful tools for CW operators, especially
>> those not experienced in pitch-matching. Here's a bit of history on
>> where these features came from and how they work.
>>
>> CW Spotting History
>>
>> When a station finishes a CQ in CW mode, the operator faces the
>> challenge of copying someone who's calling back. Callers may be weak
>> or obscured by QRM; the op can usually deal with both problems by
>> narrowing the filter passband. However, callers may also be off
>> frequency. A calling station may be using a wide filter passband
>> themselves, not attempting to carefully match their VFO frequency to
>> that of the CQing station. The result may be no QSO, even when
>> propagation is excellent.
>>
>> In the Days of Yore, a frequency offset between stations didn't
>> always matter. Sometimes both stations used crystal-controlled
>> transmitters, so operators had to patient tune around after calling CQ.
>>
>> As a 14-year-old novice I embraced this operating style for a year or
>> so, armed with a dozen or so crusty FT-243 crystals for my Heath
>> HW-16. I nearly wore out the socket swapping them in and out. After
>> calling CQ, it was not unusual to find a caller 30 or more kHz away!
>> (Away from "where" was a poorly answered question, as my
>> Hallicrafters receiver dial wasn't exactly digital.)
>>
>> Fortunately I soon acquired an outboard VFO, a life-changing addition
>> to my station. Jealous friends doubled up on their paper routes to
>> pay for their own. Girls suddenly paid more attention to me.
>>
>> These days virtually everyone has a VFO, along with the expectation
>> that they won't have to tune theirs very far, if at all, to tune you
>> in. Not only that, they're stable and well calibrated, not like the
>> beasts we had to skillfully tame. Progress!
>>
>> Manual Spotting (SPOT switch)
>>
>> Once I had a VFO I quickly learned to do *manual* pitch matching.
>> Older rigs did't provide a way to do that explicitly, so you'd
>> improvise. Basically, you had to coerce a very weak signal out of
>> your own transmitter, say by turning on only the driver, then tune
>> the transmit VFO until you could hear your signal on your own
>> receiver -- superimposed on the calling station, at the same pitch.
>> This is what we call spotting.
>>
>> Of course spotting is a lot more convenient these days, as many rigs
>> include a SPOT switch. This function is easy for a modern transceiver
>> designer to add, because the radio's firmware is quite capable of
>> turning on only the CW sidetone without transmitting.
>>
>> That is the purpose of the SPOT switch on all Elecraft transceivers.
>> Tap SPOT, and you'll hear your sidetone pitch. Most people can do a
>> good job of adjusting the VFO such that the CQing station's pitch
>> matches that of the SPOT tone. This ensures that when you call them,
>> you'll be close to their own frequency.
>>
>> Tuning Aids: Filtering (APF), PLL (NE567), and Spectral (CWT)
>>
>> Since not everyone has an inherent musical ear, various
>> hardware-enhanced means of tuning in CW signals have been developed.
>>
>> The simplest method is to just narrow your receiver passband so much
>> that, if you can hear a station calling CQ at all, you're guaranteed
>> to be "right on top of him." This assumes that your transceiver
>> enforces alignment between its transmit and receive pitch...true of
>> all Elecraft gear.
>>
>> Narrow filtering has gone through decades of evolution. Some filters
>> were based on op-amps (active filters), while others were based on LC
>> filtering, conscripting humongous toroidal cores scavenged from telco
>> equipment. I acquired my stash of these from a haphazard mound of old
>> switching racks, decaying in an abandoned aircraft hanger on the
>> Bermuda U.S. Navy base. (That irresistible junk pile was also a
>> mother load of TO5 transistors, multi-pound electrolytic capacitors,
>> and tetanus, but that's another story.) Typically the toroids were 88
>> millihenries -- a huge value for a high-Q inductor, permitting
>> resonance in the low audio range.
>>
>> Later, such filters migrated to digital signal processing, in the
>> form of switched-capacitor ICs or DSPs. You can still buy these
>> switched-capacitor chips, like the MF10, from various sources. It's
>> instructive to roll your own tunable filter, just for fun.
>>
>> Whether passive or active, the goal of filtering is typically to
>> achieve a narrow passband, say 250 Hz or less. With DSP, nearly
>> perfect filters with "brick wall" passbands can be created. But these
>> have the disadvantage of ringing like a bell when pinged by a CW
>> signal or noise, making copy difficult.
>>
>> One solution incorporated into the K-line and KX-line is the Audio
>> Peaking Filter (APF), which provides a 30-Hz bandwidth at -3 dB, but
>> broad skirts, preventing ringing from occurring. As our customers
>> will attest, APF works like magic on weak signals obscured by noise.
>>
>> Another forerunner to DSP techniques was the audio phase-locked-loop,
>> using inexpensive ICs like the legendary LM567. When locked on a
>> signal that matched its center frequency, the circuit would turn on
>> an LED, alerting the operator that the VFO was now properly tuned.
>>
>> With the DSPs in our K-line and KX-line radios, we can provide a much
>> more powerful tool: CWT, or "CW Tuning Aid." When enabled, CWT turns
>> the upper portion of the rig's S-meter into something of a mini
>> spectrum analyzer. The pitch of the strongest signal in the passband
>> is analyzed by the DSP, then represented as a single segment of the
>> bar graph. For CWT-enhanced manual spotting, the operator simply
>> tunes the VFO slowly until the center CWT segment is flashing along
>> with the keyed signal.
>>
>> Manual tuning with CWT can also be used in FSK-D and PSK-D modes as
>> described in the owner's manual..
>>
>> Closing the Loop: Auto-Spotting (SPOT + CWT)
>>
>> The Elecraft K3/K3S/KX2/KX3 take CW tuning another step forward by
>> providing a way to *automatically* retune the VFO frequency to match
>> that of a received signal. How does this work?
>>
>> When CWT is turned on, firmware treats the SPOT switch as AUTO-SPOT.
>> The DSP analyzes the incoming signal, and with a bit of processing,
>> determines its exact audio pitch. From there all that's needed is a
>> bit of math to offset the VFO to match this pitch to the CW sidetone.
>>
>> There's another subtlety, though. Since a CW signal is generally
>> being keyed on and off, the CWT algorithm has to ensure that it
>> doesn't "take off," chasing a signal that's not there. To avoid this,
>> we keep track of the energy in the passband, and slew the VFO
>> incrementally over an average of about 0.5 second, moving only when
>> the target signal is present.
>>
>> How to Use Auto-Spot
>>
>> I encourage you to give the auto-spot feature a try. It's best to
>> start with a fairly narrow passband, say 400-600 Hz; narrower if
>> there's a lot of QRM. Find a signal, turn on CWT, then tap SPOT to
>> tune it in. A second tap of SPOT may get even closer, especially if
>> there's a lot of band noise.
>>
>> Auto-spot can also be used in Elecraft's PSK-D mode, i.e. for
>> PSK31/PSK63. As with CW mode, just turn on CWT, tune in a prospective
>> signal, and tap SPOT. Since PSK auto-decoding requires very accurate
>> tuning, it's best to set the filter bandwidth to 50 Hz, then let
>> auto-spot dial things in down to the last 2 or 3 Hz. If you have text
>> decode turned on, you should start seeing text characters scroll by
>> after auto-tuning has completed. Tapping a second time or fine-tuning
>> the VFO a bit in 1 Hz steps may improve copy.
>>
>> 73,
>> Wayne
>> N6KR
>>
>
> __._,_.___
> ------------------------------------------------------------------------
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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Dave New, N8SBE
In reply to this post by wayne burdick
When I upgraded from my K3 to a K3s, I took the opportunity to order a
10 MHz Ref In option.

I finally got around to hooking it up to a Leo Bodnar GPS receiver I
picked up at Dayton a year ago, and now the K3s is rock solid spot on
frequency.

Don't know how i did without it all these years...

73,

-- Dave, N8SBE

-------- Original Message --------
Subject: Re: [Elecraft] Auto-spot, tuning aids, and the arcane history
of CW pitch-matching
From: Bob McGraw K4TAX <[hidden email]>
Date: Tue, January 22, 2019 3:14 pm
To: [hidden email]

Another trick which works well.   Tune to a WWV frequency in CW mode.
Press SPOT and the radio will jump on the exact carrier frequency.   The
SPOT function can pull on to the WWV frequency as far away as about 100
Hz.  Once the radio has  resolved SPOT, the readout / display is the
frequency of WWV +/- the error in Hz. Thus the readout of 9.999.992 is
indicating being 8 Hz low.

 From a cold start, FP being 19°C, I find  -8 Hz error on 10 MHz WWV.
After about 15 minutes the FP is 25°C and the error is -1 Hz.  I've
tweaked the REF CAL such that after 1/2 hr. in receive tuning to WWV
from both higher and lower will produce a reading of 10.000.000.   Will
all stations pse QNZ  QNN.

73

Bob, K4TAX



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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Dave New, N8SBE
In reply to this post by wayne burdick
I'm a great fan of using the auto-spot feature, and love to show it off
to all shack visitors, as an example of yet another reason they need to
upgrade to Elecraft, from whatever boat anchor they are still using...

73,

-- Dave, N8SBE
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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Wes Stewart-2
In reply to this post by Dave New, N8SBE
Are you serious?

Wes  N7WS

On 1/22/2019 1:45 PM, Dave New, N8SBE wrote:
> Don't know how i did without it all these years...
>
> 73,
>
> -- Dave, N8SBE
>

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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

ab2tc
In reply to this post by n0uk
Hi all,

Agreed; the problem can easily be solved in analog radios without frequency
synthesis by offsetting the BFO frequency by those 700Hz or so in transmit.
In down conversion machines with a single IF in the 8-9MHz range that could
easily be done by pulling the BFO crystal. The Drake TR4 undoubtedly worked
this way. I bought my first transceiver in 1969 (I think), a Yaesu FT-200, I
think it was called in the US. In Europe it was sold as Sommerkamp FT-250.
As the Drake TR4 it was down conversion with a single 9MHz IF and worked CW
by pulling the BFO crystal into the passband of the 9MHz crystal filter on
transmit.

Another technical solution, which was used in the Collins KWM2 (and probably
KWM1) was to keep the balanced (de)modulator balanced and inject an audio
tone into it on transmit. Clearly the spectral purity of the CW signal would
be less than ideal in this case, but I am not sure if FCC type approval was
needed in those days. Nor am I sure what the the FCC spec for "inband" (read
close in) spurs would be.

AB2TC - Knut


n0uk wrote
> The transceive problem didn't seem to exist on any older non-synthesized
> transceiver that I have used, including FT-101 series, TS-520/820 and
> later, KW Electronics KW-2000E.  these were all '70s era transceivers.
>
>
>
> --
> 73 Chris Cox, N0UK, G4JEC

> chrisc@

>
> _
> <snip>





--
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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

K9MA
In reply to this post by Bob McGraw - K4TAX
On 1/22/2019 14:14, Bob McGraw K4TAX wrote:
> Another trick which works well.   Tune to a WWV frequency in CW mode.
> Press SPOT and the radio will jump on the exact carrier frequency.

You can do the same thing, of course, by listening to the beat between
the sidetone and the carrier. I was able to get 3 Hz closer that way,
within the 1 Hz tuning resolution. 3 Hz is close enough, though.

When listening for the beats, you have to match the volume of the
sidetone and carrier, or you won't hear them. You don't need a musical
ear, just a functioning one.

73,

Scott K9MA

--
Scott  K9MA

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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Elecraft mailing list
In reply to this post by wayne burdick
Thanks, Wayne!  This is one of the best entries into these threads I’ve ever read.  And, yes, I've experimented with Auto Spot in CWT mode.

And: > “the Audio Peaking Filter (APF), …provides a 30-Hz bandwidth at -3 dB, but broad skirts, preventing ringing from occurring. As our customers will attest, APF works like magic on weak signals obscured by noise…”  To which I also attest! ^_^

And, the VFO and IF passband tracking exactly on the user setable CW sidetone (A 440, in my case) is one of the main things which made me fall in love with Elecraft.

72 de KX2CW  ..
~Joan

Darmok and Jalad at Tanagra, said Piglet.
Shaka, when the walls fell, said Pooh.

> On Jan 21, 2019, at 21:09, Wayne Burdick <[hidden email]> wrote:
>
> Elecraft's auto-spot and CWT features -- available on the K3/K3S/KX2/KX3 -- are very useful tools for CW operators, especially those not experienced in pitch-matching. Here's a bit of history on where these features came from and how they work.
>
>
> CW Spotting History
>
> When a station finishes a CQ in CW mode, the operator faces the challenge of copying someone who's calling back. Callers may be weak or obscured by QRM; the op can usually deal with both problems by narrowing the filter passband. However, callers may also be off frequency. A calling station may be using a wide filter passband themselves, not attempting to carefully match their VFO frequency to that of the CQing station. The result may be no QSO, even when propagation is excellent.
>
> In the Days of Yore, a frequency offset between stations didn't always matter. Sometimes both stations used crystal-controlled transmitters, so operators had to patient tune around after calling CQ.
>
> As a 14-year-old novice I embraced this operating style for a year or so, armed with a dozen or so crusty FT-243 crystals for my Heath HW-16. I nearly wore out the socket swapping them in and out. After calling CQ, it was not unusual to find a caller 30 or more kHz away! (Away from "where" was a poorly answered question, as my Hallicrafters receiver dial wasn't exactly digital.)
>
> Fortunately I soon acquired an outboard VFO, a life-changing addition to my station. Jealous friends doubled up on their paper routes to pay for their own. Girls suddenly paid more attention to me.
>
> These days virtually everyone has a VFO, along with the expectation that they won't have to tune theirs very far, if at all, to tune you in. Not only that, they're stable and well calibrated, not like the beasts we had to skillfully tame. Progress!
>
>
> Manual Spotting (SPOT switch)
>
> Once I had a VFO I quickly learned to do *manual* pitch matching. Older rigs did't provide a way to do that explicitly, so you'd improvise. Basically, you had to coerce a very weak signal out of your own transmitter, say by turning on only the driver, then tune the transmit VFO until you could hear your signal on your own receiver -- superimposed on the calling station, at the same pitch. This is what we call spotting.
>
> Of course spotting is a lot more convenient these days, as many rigs include a SPOT switch. This function is easy for a modern transceiver designer to add, because the radio's firmware is quite capable of turning on only the CW sidetone without transmitting.
>
> That is the purpose of the SPOT switch on all Elecraft transceivers. Tap SPOT, and you'll hear your sidetone pitch. Most people can do a good job of adjusting the VFO such that the CQing station's pitch matches that of the SPOT tone. This ensures that when you call them, you'll be close to their own frequency.
>
>
> Tuning Aids: Filtering (APF), PLL (NE567), and Spectral (CWT)
>
> Since not everyone has an inherent musical ear, various hardware-enhanced means of tuning in CW signals have been developed.
>
> The simplest method is to just narrow your receiver passband so much that, if you can hear a station calling CQ at all, you're guaranteed to be "right on top of him." This assumes that your transceiver enforces alignment between its transmit and receive pitch...true of all Elecraft gear.
>
> Narrow filtering has gone through decades of evolution. Some filters were based on op-amps (active filters), while others were based on LC filtering, conscripting humongous toroidal cores scavenged from telco equipment. I acquired my stash of these from a haphazard mound of old switching racks, decaying in an abandoned aircraft hanger on the Bermuda U.S. Navy base. (That irresistible junk pile was also a mother load of TO5 transistors, multi-pound electrolytic capacitors, and tetanus, but that's another story.) Typically the toroids were 88 millihenries -- a huge value for a high-Q inductor, permitting resonance in the low audio range.
>
> Later, such filters migrated to digital signal processing, in the form of switched-capacitor ICs or DSPs. You can still buy these switched-capacitor chips, like the MF10, from various sources. It's instructive to roll your own tunable filter, just for fun.
>
> Whether passive or active, the goal of filtering is typically to achieve a narrow passband, say 250 Hz or less. With DSP, nearly perfect filters with "brick wall" passbands can be created. But these have the disadvantage of ringing like a bell when pinged by a CW signal or noise, making copy difficult.
>
> One solution incorporated into the K-line and KX-line is the Audio Peaking Filter (APF), which provides a 30-Hz bandwidth at -3 dB, but broad skirts, preventing ringing from occurring. As our customers will attest, APF works like magic on weak signals obscured by noise.
>
> Another forerunner to DSP techniques was the audio phase-locked-loop, using inexpensive ICs like the legendary LM567. When locked on a signal that matched its center frequency, the circuit would turn on an LED, alerting the operator that the VFO was now properly tuned.
>
> With the DSPs in our K-line and KX-line radios, we can provide a much more powerful tool: CWT, or "CW Tuning Aid." When enabled, CWT turns the upper portion of the rig's S-meter into something of a mini spectrum analyzer. The pitch of the strongest signal in the passband is analyzed by the DSP, then represented as a single segment of the bar graph. For CWT-enhanced manual spotting, the operator simply tunes the VFO slowly until the center CWT segment is flashing along with the keyed signal.
>
> Manual tuning with CWT can also be used in FSK-D and PSK-D modes as described in the owner's manual.
>
>
> Closing the Loop:  Auto-Spotting (SPOT + CWT)
>
> The Elecraft K3/K3S/KX2/KX3 take CW tuning another step forward by providing a way to *automatically* retune the VFO frequency to match that of a received signal. How does this work?
>
> When CWT is turned on, firmware treats the SPOT switch as AUTO-SPOT. The DSP analyzes the incoming signal, and with a bit of processing, determines its exact audio pitch. From there all that's needed is a bit of math to offset the VFO to match this pitch to the CW sidetone.
>
> There's another subtlety, though. Since a CW signal is generally being keyed on and off, the CWT algorithm has to ensure that it doesn't "take off," chasing a signal that's not there. To avoid this, we keep track of the energy in the passband, and slew the VFO incrementally over an average of about 0.5 second, moving only when the target signal is present.
>
>
> How to Use Auto-Spot
>
> I encourage you to give the auto-spot feature a try. It's best to start with a fairly narrow passband, say 400-600 Hz; narrower if there's a lot of QRM. Find a signal, turn on CWT, then tap SPOT to tune it in. A second tap of SPOT may get even closer, especially if there's a lot of band noise.
>
> Auto-spot can also be used in Elecraft's PSK-D mode, i.e. for PSK31/PSK63. As with CW mode, just turn on CWT, tune in a prospective signal, and tap SPOT. Since PSK auto-decoding requires very accurate tuning, it's best to set the filter bandwidth to 50 Hz, then let auto-spot dial things in down to the last 2 or 3 Hz. If you have text decode turned on, you should start seeing text characters scroll by after auto-tuning has completed. Tapping a second time or fine-tuning the VFO a bit in 1 Hz steps may improve copy.
>
> 73,
> Wayne
> N6KR
>
>
>
>
>
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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Dave New, N8SBE
In reply to this post by wayne burdick


> Are you serious?

> Wes  N7WS

Wes,

Yes.  I'm a stickler for accuracy.  It always bothered me that the
so-called 'temperature compensated' LO in the K3 was not actively being
steered by temperature compensation (i.e. I could only put static
temperature offsets into the rig memory from the data sheet that came
with the oscillator). That was a 'feature' that was never released. At
HF frequencies, it was only an annoyance, but using UHF transverters,
the error compounds (I'm using a crystal oven in my UHF transverter, but
the lack of one in the K3 caused drifting).

I use a Citizen watch with WWVB reception, so the time on my wrist is
never more than 50 ms off.

Anally yours,

-- Dave, N8SBE

On 1/22/2019 1:45 PM, Dave New, N8SBE wrote:
> Don't know how i did without it all these years...
>
> 73,
>
> -- Dave, N8SBE
>

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Re: Auto-spot, tuning aids, and the arcane history of CW pitch-matching

Wes Stewart-2
You should be subscribed to Timenuts.

But clearly one of us is confused. If you're using an OCXO in your transverter
and up converting the K3, how does K3 drift/inaccuracy "compound" at UHF?

Can you read that watch to 50 ms?  What are you going to do when WWVB goes QRT?

Wes  N7WS

On 1/23/2019 12:26 PM, Dave New, N8SBE wrote:

>
> Wes,
>
> Yes.  I'm a stickler for accuracy.  It always bothered me that the
> so-called 'temperature compensated' LO in the K3 was not actively being
> steered by temperature compensation (i.e. I could only put static
> temperature offsets into the rig memory from the data sheet that came
> with the oscillator). That was a 'feature' that was never released. At
> HF frequencies, it was only an annoyance, but using UHF transverters,
> the error compounds (I'm using a crystal oven in my UHF transverter, but
> the lack of one in the K3 caused drifting).
>
> I use a Citizen watch with WWVB reception, so the time on my wrist is
> never more than 50 ms off.
>
> Anally yours,
>
> -- Dave, N8SBE
>

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