K3 SSB transmit IMD

[Dave Hachadorian]

I'm a little unsure about what the ARRL is saying in their
evaluation of the K3's transmit IMD. Here's what I THINK
they are saying:

ARRL's K3/10 measured -23dB worst case. They contacted
Elecraft about this low reading, and Elecraft told them it
should be "significantly better" than that, and Elecraft is
working with ARRL to see why their K3/10 had such a low
reading.

Elecraft also seems to have made a general recommendation
for ALL K3's that until the IMD problem is resolved, the low
power amp should be run at no more than 8 watts on 17 meters
and higher. ARRL then got ahold of a K3/100 and measured IMD
at the output of the low power amp, with that amp running 8
watts, and measured IMD at -27dB.

Am I reading that correctly? So for best IMD, until the
issue is resolved, the K3 needs to be throttled back on 17
meters and above? Is that like 80 watts or so on a K3/100?

Thanks.

Dave Hachadorian, K6LL
Yuma, AZ


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[Darwin, Keith]

I got a different read.

- ARRL measured -23 dB on the QRP rig.

- ARRL checked the K3/100 (which they have) at the QRP level and got -27
dB.

- ARRL called Elecraft.  They talked.

- ARRL published the value from the K3/100 number.

- ARRL reported that Elecraft suggested those worried about the IMD
performance on 17m could QRP to 8 watts.

I didn't see anything in there where either the ARRL or Elecraft
admitted that there is any problem; only some confusion and disparity on
the measurements.

- Keith N1AS -
- K2 5411.ssb.100 -
- K3 Wave 3 -

-----Original Message-----
I'm a little unsure about what the ARRL is saying in their evaluation of
the K3's transmit IMD. Here's what I THINK they are saying:

*snip*
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[Buck - k4ia]

If I set my CMP to 0, it sounds like it is  turned all the way up.  If I set
the CMP to 1, it calms down and works as I  would expect.  In other words, I
don't see a way to turn the CMP  off.

Am I missing  something?

k4ia
Buck
#101



In a message dated  2/29/2008 2:33:21 P.M. Eastern Standard Time,
[hidden email] writes:
>  There was a suggestion the internal two tone test oscillator gives
>  better results by some 3dB than can be obtained by feeding an external
>  two tone into the K3... That would put the above figures at about the
>  same as the ARRL measurements.

If you have CMP set to 0, set the external  2-tone oscillator (Elecraft
2T, of course) to a reasonable output level, and  adjust MIC GAIN so you
get full power but little or no ALC action, the IMD  is the same as with
the internal two tone test oscillator.

Or at  least it is so reported today at one of the Elecraft  labs!

73,

Lyle  KK7P

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[Dave Hachadorian]

----- Original Message -----
From: "Darwin, Keith" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Friday, February 29, 2008 6:41 PM
Subject: RE: [Elecraft] K3 SSB transmit IMD


I got a different read.

- ARRL measured -23 dB on the QRP rig.

- ARRL checked the K3/100 (which they have) at the QRP level
and got -27
dB.

- ARRL called Elecraft.  They talked.

- ARRL published the value from the K3/100 number.

- ARRL reported that Elecraft suggested those worried about
the IMD
performance on 17m could QRP to 8 watts.

I didn't see anything in there where either the ARRL or
Elecraft
admitted that there is any problem; only some confusion and
disparity on
the measurements.

- Keith N1AS -
- K2 5411.ssb.100 -
- K3 Wave 3 -
--------------------------------

The key statement is that ARRL tested the second radio "in
accordance with (Elecraft's) new guideline..."

To me, that means they had to throttle the 10 watt PA back
to 8 watts (Elecraft's new guideline) to get the -27 dB
reading. If you run the 10W PA at full power on 17 meters
and above, IMD will be worse than -27dB.

N6KR's message earlier this morning indicates that Elecraft
is working to improve the SSB setup procedure or SSB
algorithm to improve the real-world (tones externally
applied) IMD. I think I've got it straight.

Dave Hachadorian, K6LL
Yuma, AZ

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