Re: 2 meter amp for K3 or KX3

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Re: 2 meter amp for K3 or KX3

Joel R. Hallas
The problem with most 2 meter "brick" type amplifiers, is that while they
may have an "SSB" switch position, it generally only changes the TR
switching method, and doesn't make them linear. The only medium-power 2 M
amp I found that was linear, while we were testing them for QST was the
Tokyo Hy-Power 300 W amp, that was in a whole different price category from
the bricks, until they discontinued it.

While transmit linearity may not be a big deal for casual operation, the
consequences of transmit IMD for other folks in busy areas during a VHF
contest (about the only time people around here are on 2 M SSB) can be as
severe as on the HF bands. Since I couldn't seem to generate any interest
from Eric and Wayne in offering a suitable amplifier, I commissioned Jim
Klitzing, W6PQL to come up with a lower power version of his excellent 2
meter kilowatt that he published in QST. He did, and you can read about it
in:

May 2013 - QST (Pg. 30)
Build a Linear 2 Meter 80 W All Mode Amplifier

It can put out 100 W on CW, 80 W on SSB, with HF like IMD. It is fairly
simple because it is based on a single amplifier module, and costs less to
build than a brick. For this application, you can eliminate the automatic
switching circuitry, although it doesn't take much, and then can be used
with your FM handheld. It doesn't include a preamp because the K3 has a
better NF than most preamps.

It can operate at almost any input level (including that of the KX3 2 meter
mod, I believe) by setting the input attenuator. Because its current drain
is less than the K3 during 100 W transmit, it can be run from the same power
supply, since the K3 HF PA is off when on 2 meters. I have one and have been
very happy with it. I believe Jim offers various parts kits on his website.

You do have to remember to switch it off when you go to 6 meters, since the
amp quiescent current is high enough when the PTT switches to pop the PS
breaker with 100 W on 6. You learn quickly.  
 

Regards, Joel Hallas, W1ZR
Westport, CT


Subject: [Elecraft] Suggestions for a 2 meter amp?
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I installed the internal 2 meter module in my K3 so now I'm in the
market for a good Amplifier to bring it up to at least 100 watts.

The K3 puts out 10 watts so the amp needs to be 10 Watts input

Any Suggestions?



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Re: 2 meter amp for K3 or KX3

Jim Bennett
I second Joel's comments - it is a fun amp to build and operate. I put mine together last year and it has been a nice addition to my station. I drive it with my K3.

Jim / W6JHB


On   Wednesday, Apr 16, 2014, at  Wednesday, 11:28 AM, Joel Hallas wrote:

> The problem with most 2 meter "brick" type amplifiers, is that while they
> may have an "SSB" switch position, it generally only changes the TR
> switching method, and doesn't make them linear. The only medium-power 2 M
> amp I found that was linear, while we were testing them for QST was the
> Tokyo Hy-Power 300 W amp, that was in a whole different price category from
> the bricks, until they discontinued it.
>
> While transmit linearity may not be a big deal for casual operation, the
> consequences of transmit IMD for other folks in busy areas during a VHF
> contest (about the only time people around here are on 2 M SSB) can be as
> severe as on the HF bands. Since I couldn't seem to generate any interest
> from Eric and Wayne in offering a suitable amplifier, I commissioned Jim
> Klitzing, W6PQL to come up with a lower power version of his excellent 2
> meter kilowatt that he published in QST. He did, and you can read about it
> in:
>
> May 2013 - QST (Pg. 30)
> Build a Linear 2 Meter 80 W All Mode Amplifier
>
> It can put out 100 W on CW, 80 W on SSB, with HF like IMD. It is fairly
> simple because it is based on a single amplifier module, and costs less to
> build than a brick. For this application, you can eliminate the automatic
> switching circuitry, although it doesn't take much, and then can be used
> with your FM handheld. It doesn't include a preamp because the K3 has a
> better NF than most preamps.
>
> It can operate at almost any input level (including that of the KX3 2 meter
> mod, I believe) by setting the input attenuator. Because its current drain
> is less than the K3 during 100 W transmit, it can be run from the same power
> supply, since the K3 HF PA is off when on 2 meters. I have one and have been
> very happy with it. I believe Jim offers various parts kits on his website.
>
> You do have to remember to switch it off when you go to 6 meters, since the
> amp quiescent current is high enough when the PTT switches to pop the PS
> breaker with 100 W on 6. You learn quickly.  
>
>
> Regards, Joel Hallas, W1ZR
> Westport, CT
>
>
> Subject: [Elecraft] Suggestions for a 2 meter amp?
> Message-ID: <[hidden email]>
> Content-Type: text/plain; charset=us-ascii
>
> I installed the internal 2 meter module in my K3 so now I'm in the
> market for a good Amplifier to bring it up to at least 100 watts.
>
> The K3 puts out 10 watts so the amp needs to be 10 Watts input
>
> Any Suggestions?
>
>
>
> ______________________________________________________________
> 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: 2 meter amp for K3 or KX3

Edward R Cole
In reply to this post by Joel R. Hallas
Just a comment that I have built W6PQL amps (300w 1296 amp) (better
quality than the commercial amps like Mirage).

I had forgotten that Jim (Klitzing) had the 80w 2m linear article in
QST (here is link to his
webpage):.http://www.w6pql.com/2_meter_80w_all_mode_amplifier.htm

Note: he offers the pcb with some components pre-installed but it
should still be considered a kit (type you solder things together),
so is not a ready to use unit.  BTW the amplifier module drives with
50mw so even the KX3-2m is able to drive one.  Running 1w drive
requires a 13-dB input attenuator which can be built-in with the amp.

I built some kits for others and with the interest shown here for a
2m amp, would an assembled 2m amp be of interest?
I can research the costs to build one these if there is.  I can guess
the cost will be near the same for a 100w Mirage.

73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
     [hidden email]

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