kx3 receiver versus K3s receiver

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kx3 receiver versus K3s receiver

K7TV
Both the kx3 and the K3 are excellent. The KX3 may sound slightly more
natural, but overall I prefer the K3 because of better ergonomics and some
aspects of performance. Recently I got interested in SO2R and added a
KXPA100 to my KX3 for use as the second radio. In side by side comparison it
became clear that the KX3 is much more vulnerable to interference than is
the K3. With my antennas close together, the KX3 was marginally useable
receiving on 40 while the K3 transmitted on higher bands, but totally
unuseable with the K3 on 40 and the KX3 on a higher band. There are a lot of
variables involved, but I got the same result with a portable setup at a
different location. Most people will never run two rigs set up close
together with antennas close together, but I plan to buy another K3 and sell
the KXPA100. The KX3 is still wonderful for light weight portable operation.

 

73,

Erik K7TV

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Re: kx3 receiver versus K3s receiver

Ignacy
Perhaps as it should be. A bigger and more expensive radio is a better radio but one cannot take the bigger radio everywhere. I assume you had roofing filters in KX3.

I used KX3 directly driving Expert 1.3k for at Easter Island during CQ WW SSB and a few days later in CW. KX3 was reliable and worked pretty well. But I had a feeling that discerning call signs in pileups was a bit worse in KX3. Also, a better speech processor makes K3 about 1-2 S stronger than KX3 at same peak power so no one can win a SSB contest with KX3. But KX3 is about 20% weight and 10% of volume.  

Ignacy, NO9E
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Re: kx3 receiver versus K3s receiver

K9MA
The KX3 "roofing filters" are audio filters.  (I wouldn't even call them
"roofing" filters.)  They are analog filters, which can improve
rejection of adjacent signals which might overload the ADC.  They will
not, however, reject the "audio image", on the other side of zero beat.  
I'd expect, especially during contests, the the effect would show up
once in a while, probably making a weak signal totally unintelligible.  
Has anyone noticed this effect?  Especially on CW, it would be fairly
unlikely, as the interfering signal would have to fall within the narrow
passband on the other side of zero beat.

73,

Scott  K9MA


On 1/9/2017 11:54, Ignacy wrote:

> Perhaps as it should be. A bigger and more expensive radio is a better radio
> but one cannot take the bigger radio everywhere. I assume you had roofing
> filters in KX3.
>
> I used KX3 directly driving Expert 1.3k for at Easter Island during CQ WW
> SSB and a few days later in CW. KX3 was reliable and worked pretty well. But
> I had a feeling that discerning call signs in pileups was a bit worse in
> KX3. Also, a better speech processor makes K3 about 1-2 S stronger than KX3
> at same peak power so no one can win a SSB contest with KX3. But KX3 is
> about 20% weight and 10% of volume.
>
> Ignacy, NO9E
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/kx3-receiver-versus-K3s-receiver-tp7625537p7625595.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
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--
Scott  K9MA

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Re: kx3 receiver versus K3s receiver

Brendon Whateley
I'm not sure why you would think this is a problem, the "other side" signal
is removed by the I/Q decoding technique, not by filtering. The filters do
the job of roofing filters, reducing and removing near in strong signals --
from the IF signal that just happens now to be at baseband frequencies.

If I'm missing something, please educate me on what I'm missing?

- Brendon
KK6AYI

On Mon, Jan 9, 2017 at 10:24 AM, K9MA <[hidden email]> wrote:

> The KX3 "roofing filters" are audio filters.  (I wouldn't even call them
> "roofing" filters.)  They are analog filters, which can improve rejection
> of adjacent signals which might overload the ADC.  They will not, however,
> reject the "audio image", on the other side of zero beat.  I'd expect,
> especially during contests, the the effect would show up once in a while,
> probably making a weak signal totally unintelligible.  Has anyone noticed
> this effect?  Especially on CW, it would be fairly unlikely, as the
> interfering signal would have to fall within the narrow passband on the
> other side of zero beat.
>
> 73,
>
> Scott  K9MA
>
>
> On 1/9/2017 11:54, Ignacy wrote:
>
>> Perhaps as it should be. A bigger and more expensive radio is a better
>> radio
>> but one cannot take the bigger radio everywhere. I assume you had roofing
>> filters in KX3.
>>
>> I used KX3 directly driving Expert 1.3k for at Easter Island during CQ WW
>> SSB and a few days later in CW. KX3 was reliable and worked pretty well.
>> But
>> I had a feeling that discerning call signs in pileups was a bit worse in
>> KX3. Also, a better speech processor makes K3 about 1-2 S stronger than
>> KX3
>> at same peak power so no one can win a SSB contest with KX3. But KX3 is
>> about 20% weight and 10% of volume.
>>
>> Ignacy, NO9E
>>
>>
>>
>> --
>> View this message in context: http://elecraft.365791.n2.nabb
>> le.com/kx3-receiver-versus-K3s-receiver-tp7625537p7625595.html
>> Sent from the Elecraft mailing list archive at Nabble.com.
>> ______________________________________________________________
>> 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]
>>
>
>
> --
> Scott  K9MA
>
> [hidden email]
>
>
> ______________________________________________________________
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Re: kx3 receiver versus K3s receiver

K9MA
The I/Q decoding happens after digitization. If a strong signal
overloads the ADC, all bets are off.  Without the audio filters, that
strong signal could be quite far away.  (The other low pass filters seem
to cut off around 14 kHz.)  In any case, it could be well outside your
DSP passband. The optional audio filters are two pole active low pass
filters, with bandwidths of something like 700 Hz and 1.6 kHz.  There
are two:  I and Q.  But, because the IF is baseband, where both sides of
zero beat are present, these filters can reject signals on the "wrong"
side.  Indeed, they couldn't, or the I/Q decoding couldn't remove one of
them.


73,

Scott  K9MA

On 1/9/2017 17:23, Brendon Whateley wrote:

> I'm not sure why you would think this is a problem, the "other side"
> signal is removed by the I/Q decoding technique, not by filtering. The
> filters do the job of roofing filters, reducing and removing near in
> strong signals -- from the IF signal that just happens now to be at
> baseband frequencies.
>
> If I'm missing something, please educate me on what I'm missing?
>
> - Brendon
> KK6AYI
>
> On Mon, Jan 9, 2017 at 10:24 AM, K9MA <[hidden email]
> <mailto:[hidden email]>> wrote:
>
>     The KX3 "roofing filters" are audio filters.  (I wouldn't even
>     call them "roofing" filters.)  They are analog filters, which can
>     improve rejection of adjacent signals which might overload the
>     ADC.  They will not, however, reject the "audio image", on the
>     other side of zero beat.  I'd expect, especially during contests,
>     the the effect would show up once in a while, probably making a
>     weak signal totally unintelligible.  Has anyone noticed this
>     effect? Especially on CW, it would be fairly unlikely, as the
>     interfering signal would have to fall within the narrow passband
>     on the other side of zero beat.
>
>     73,
>
>     Scott  K9MA
>
>
>     On 1/9/2017 11:54, Ignacy wrote:
>
>         Perhaps as it should be. A bigger and more expensive radio is
>         a better radio
>         but one cannot take the bigger radio everywhere. I assume you
>         had roofing
>         filters in KX3.
>
>         I used KX3 directly driving Expert 1.3k for at Easter Island
>         during CQ WW
>         SSB and a few days later in CW. KX3 was reliable and worked
>         pretty well. But
>         I had a feeling that discerning call signs in pileups was a
>         bit worse in
>         KX3. Also, a better speech processor makes K3 about 1-2 S
>         stronger than KX3
>         at same peak power so no one can win a SSB contest with KX3.
>         But KX3 is
>         about 20% weight and 10% of volume.
>
>         Ignacy, NO9E
>
>
>


--
Scott  K9MA

[hidden email]

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Re: kx3 receiver versus K3s receiver

Ignacy
To eliminate problems caused by the I/Q decoding and reduce costs, KX3S will include direct sampling.
Please post April 1st.
Ignacy, NO9E