[Elecraft] K2/100 & AGC pumping - more

Mon Jan 27 10:57:08 2003

By AGC pumping I mean the background noise fluctuates up and down at about a
1 second period. The left two S meter segments turn on and off with the
change in noise level.

I found a couple more clues:
1- The noise stops when I turn off the I/O port at the K2. It also stops if
I disconnect the I/O cable or halt the computer. Now don't jump to the
conclusion this is computer noise... it isn't. (read my prior post)

2- I have the amp mounted to the top of the K2. I removed the two rear and
side screws and loosened the two near the front panel. While experiencing
the problem I carefully raised the rear of the amp to increase the
separation between the I/O circuitry on the amplifier and the K2 receiver.
The noise dropped to zero as I raised the amp by about 1/2 inch.

next step... I will add some copper foil shielding and see if that cures it.

Has anyone else experienced this?
Tnx
Larry, WW2J (K2/100 #2897)
----- Original Message -----
From: "Larry Lavery" <[email protected]>
To: <[email protected]>
Sent: Saturday, January 25, 2003 3:53 PM
Subject: [Elecraft] K2/100 & AGC pumping

My K2/100 (#2897) works fine except for minor AGC pumping on CW and SSB. The
AGC pumping can be stopped when:
1- the AGC is turned off
2- The amplifier is physically removed from the K2 but electrically
connected.
3- The amplifier is mounted to the K2 but electrically disconnected.

My theory is that the amplifier's MCU is generating noise that is getting
into the receiver. Has anyone experienced this or know of a fix?

background...
The K2/100 includes the KAF2, KSB2 and KNB2 options. It also has the 2nd
XFIL mod.

The K2/100 was built with the KAF2 and KSB2 options and no AGC pumping was
evident. The problem started after the KNB2 and 2nd XFIL mod were installed.
Also, the sidetone was moved to 650Hz and the CW filters were re-centered
around 650 Hz using Spectrogram.

tnx..
Larry, WW2J

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