Larry Schimelpfenig k7sv at comcast.net
Sat Apr 11 11:04:06 PDT 2009

What I'm about to relate here may very well be posted at other spots on the 
Inet, but I haven't had much luck in finding it, so this will hopefully be 
helpful to contesters using the Elecraft K3 on phone.

I address two points. First is setting the crystal filter center frequency 
offset which greatly affects transmit audio quality. Second is use of the 
rear panel mike and audio in jacks in conjunction with sound card voice 

We don't operate a lot of ssb from NR4M, but it's on the rise (don't blame 
Steve - a gun was held to his head). Somehow or other we decided to make an 
M/M effort in the ARRL SSB DX test. We spent hours trying to get good audio 
out of the K3. We were using a Heil headset with the HC-4 element.

To make a long story short, while going through the menus I found  FLx FRQ 
in the configuration menu. After reading about this menu item I played with 
it a little to see if it made a difference. Did it ever!

The 5 pole crystal filters have a label on them specifying what the offset 
should be. Most are labled "-0.91".  At some point we had done a master 
reset of the radio which set the offset at "0.0".  When we set the offset 
to -0.89 as the filter in one of the K3s was labled, we received great audio 

One of the contesting stations in MD was having transmit audio problems with 
the K3s there and they weren't sure that the 20M stack was working correctly 
as well. This morning four or five stations including the one with audio 
problems did some horse racing and got comparative audio reports from 
European stations.

I told the station with problems about the filter offset. Interestingly 
enough they were using the eight pole ssb filters that should not have 
required offset according to the manual. On a whim, they tried the offset 
adjustment and found that made a difference. When we were done both of their 
K3s went from sounding terrible to being quite acceptable.

Has anyone else using the eight pole ssb filter had to adjust the offset to 
get it to sound decent on transmit?

In addition to a couple pair of Heil headsets with HC-4 elements, we have a 
couple of very comfortable headsets with hi fidelity mikes. We found that by 
adjusting the transmit audio equalizer, we could get pretty decent sounding 
audio from the hifi mike.

The problem was that when we recorded the voice keyer messages on the 
computer and played them back through the radio there was one problem when 
using mike input and another when using line input. It appears that there is 
no transformer isolation on the mike input which resulted in hum and other 
extraneous noises. When running the audio into line in, it doesn't get 
pushed through the transmit audio equalizer. Ken K4ZW said he ended up using 
an extrernal isolation transformer and ran the sound card input into the 
rear mike jack.

It would be nice if Elecraft could run the line in through the transmit 
audio equalizer when in the ssb mode!

If there is detailed information regarding either of these subjects on the 
web, I'd appreciate knowing where! Otherwise, I hope it might be useful.

73 de Lar K7SV

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