[Elecraft] K2: Attempting K2 SSB modulation and ALC mods, but board too old?

[Andreas Hofmann]

Thanks for the prompt reply.

I have made both the mods you mentioned below (filer bandwidth and A2B).  In CW the K2 functions flawlessly, I get out more than 100W out on most bands.

I am using the MH2 or Heil Pro set and just get horrible audio reports and the ALC does not play well.  On 40, the ALC comes on with 4 LEDs, but without reaching 100W; on other bands ALC never lights any LEDs.  It may be possibly that the SSB board is just misaligned.  It was my understanding that the filters for SSB are only used in receive, but in transmit the same filter as in CW is used, so alignment may not be the problem.

Should I start with redoing all alignment steps for the SSB board?

Thanks
Andy, KU7T

From: Johnny Siu [mailto:vr2xmc at yahoo.com.hk]
Sent: Friday, September 28, 2012 10:56 PM
To: Andreas Hofmann; Elecraft at mailman.qth.net
Subject: K2: Attempting K2 SSB modulation and ALC mods, but board too old?

Hello Andy,

Although I built a number of K2 in the past with much higher serial numbers, I have recently been doing the upgrade of a K2 in the region of #18xx.  I am in the same boat as yours.

The KSB2 with mine is also Rev.D like yours. Perhaps, I would like to share with you the following:

1. I got good power output and audio in SSB even when I am using an Adzen dynamic microphone worthing US$20.  This microphone is not so sensitive and I have to set SSBA3 and SSBC3.  If I use an Elecraft MH2, I need to reduce the setting to SSBA2 and SSBC2.

2. I have no problem to get 10w or slightly over in SSB measured by my LP100A.

3. There is not much difference between Rev D and Rev G other than Elecraft can no longer get the 8 pin SSM2165 for U3, so the design have to be changed to the SSM2166 14 pin device.  Therefore, I did not ask for a change of a new PCB.  I don't think you need that either.

Therefore, before doing any modification, I would suggest the following:

a. make sure the basic K2 (without KSB2)TX power and RX performance are according to the specifications;
b. upon installation of KSB2, check the power output by key down or pressing TUNE, see whether you are able to get the same power output as the basic K2

The REV D KSB2 gives an IF bandwidth of 2.1Khz.  Elecraft eventually did some changes in component values and gives you the choice between 2.4 / 2.6Khz.  The details are given here:

http://www.elecraft.com/manual/SSBCAPKT.pdf

In fact, there are a number of hardware changes since #2555, I would suggest you read the following;

http://www.elecraft.com/manual/k2a2binstr.pdf

All the hardware modifications are not difficult to be handled.  Even I am not a radio man by professional, I still manage to do that.

Finally, if you have problems, please feel free to email support at elecraft.com<mailto:support at elecraft.com> Elecraft staff are always there to give you guidance.

TNX & 73,
Johnny VR2XMC
寄件人︰ Andreas Hofmann <Andreas.Hofmann at microsoft.com<mailto:Andreas.Hofmann at microsoft.com>>
收件人︰ "Elecraft at mailman.qth.net<mailto:Elecraft at mailman.qth.net>" <Elecraft at mailman.qth.net<mailto:Elecraft at mailman.qth.net>>
傳送日期︰ 2012年09月29日 (週六) 12:42 PM
主題︰ [Elecraft] K2: Attempting K2 SSB modulation and ALC mods, but board too old?

Hi,

I never used my K2 for SSB, but now I would like too. My 9 year old daughter wants to get on it and I am getting my first yagi, so I do not need to use CW all the time :).

My K2 is S/N 2555. I have very inadequate power out and compression really distorts my audio (60 W on 40 with SSBA3, 5 W with SSBA 1).  From reading and some suggestions I found out, I probably should do these mods: http://www.qrpproject.de/Media/pdf/SSBModsUK.pdf. This should fix weak and raspy modulation.  Eventually, I really would like to have adequate SSB output/modulation and also add the DSP board.

Now, the issue is my SSB board is revision D, and the mods document describes I should have Rev E.  I seem to have 2 options:

1.      Figure out the difference between Rev D and Rev E (or Rev G as it is current) and fix my board up, or

2.      Get a new SSB board for $120 and do the mods on that one.


For 1) I am not sure if this is easily done. Where can I find out what the differences are between these boards.I know I have the filters matched between the RF and SSB boards, so this could create problems when getting a new board as in option 2), unless I reuse the old filters. Would it be possible to get the new board, use the old filters and plug it in in my rather old RF board?

I am not sure what I should do.  Any recommendations are appreciated.

Thanks
Andy,
KU7T, K2 #2555