[Elecraft] NG0R - KSB2 low audio level

[John Hoaglun]

Hi Don,

That info was in the email chain until your response trimmed down the message.  :-)

I am using an (older) Icom HM-36 mic (and have tested with two Heil
headsets with similar results).  The menu is set to:  SSBA=3 and
SSBC=4-1  I also indicated that I had tested (during my original
testing) with a modulated CW signal from the computer as well with
similar results... the SSB audio is very low.  

You had asked two other questions in the original email chain:  The K2
S/N is 6119 and the SSB board was bought and assembled a couple of
years ago. 

Looking at the schematic I am not seeing much in the way of adjustments
on the SSB circuit beyond the the compression at the SSM2165 which
controlled by the MCU.

A pre-amp is a kludgy solution IMO. (It might be ok to use it for a quick test
to see if that is the problem.)

Thoughts?  Guidance from anyone else with a K2+HM-36 ?


Thanks, JH

-- 
John Hoaglun
NG0R - EN25
http://www.hoaglun.com



On Sat, 2011-01-22 at 23:03 -0500, Don Wilhelm wrote:

> John,
> 
> Welcome back.
> 
> What microphone are you using?  And what is the compression set at?
> 
> In my experience, the K2 SSBC parameter should be set at 2:1 or higher 
> (I actually prefer 3:1) no matter what the microphone.  The SSBA menu 
> parameter will (of course) depend on the microphone being used - SSBA = 
> 1 for high output microphones and either SSBA = 2 or 3 for low output 
> microphones).
> 
> Bottom line - I would look at the mic levels first.  If the compression 
> level does not even things out, then perhaps a microphone preamplifier 
> may be in order.  If the mic is one using the Heil HC4 or HC5 element, 
> those are low output microphones and may need a pre-amp.  Those 
> microphones with an electret element have high level output (like the 
> Elecraft MH2, MD2 or ProSet-K2) and do not need increased mic gain.
> 
> 73,
> Don W3FPR
> 
> On 1/22/2011 10:29 PM, John Hoaglun wrote:
> > Hi Don&  list
> >
> > Now that I am back from my business trip I am able to get back to the
> > work bench.
> >
> > I put the K2 on the work bench tonight to run the test:
> > K2+20dB directional coupler+20dB pad :  running @ 7.04mhz at 2w
> >
> > CW vs SSB is about a 3dB difference on my Booton microwatt meter.
> >
> > My oscope was showing a similar result.
> >
> > The SSB levels appear to be down which is consistent with what I saw
> > last weekend when I was looking at this. It does not appear to have
> > anything to do with the transverters.
> >
> > Any suggestions on where to look in the SSB or ALC circuits or someplace
> > else?
> >
> > Thanks, JH
> >