[Elecraft] [K2] Transmit Audio Problems

[Don Wilhelm]

Mike,

I can't say for certain, but yes, your carrier balance may not be 
optimized *and* your SSB OP1 filter settings may not be correct. Either 
or both could cause the condition you state.

Carrier Balance - you do not have to connect a mic when doing that - the 
mic may pick up ambient noise which will mask the balance point.
All you need to do is close the PTT line, so plug a key (or paddles) 
into the key jack and close the DOT paddle while in SSB mode (which will 
assert PTT without any audio).  Monitor the RF output from the K2 with a 
monitor receiver or on a 'scope set for a very sensitive vertical gain 
and adjust the pot for minimum RF output.  You may have to compromise 
between LSB and USB - start with LSB first and then check USB.

Once you have accomplished the carrier suppression, then you should turn 
your attention to the passband positioning of the K2's OP1 filter in the 
LSB and USB FL1 positions - those are what is used for transmit.

The KSB2 manual gives you some 'bogey values' for the BFO settings based 
on your KSB2 crystal set.
You can do better if you refine those settings by using a wideband noise 
generator and an audio spectrum analyzer like Spectrogram to view the 
position of the passband.
See my webpage (www.w3fpr.com) article on K2 Dial Calibration for 
further information and the Tom Hammond N0SS (SK) website at 
http://www.mmccs.com/mmarc/n0ss/ for information about using Spectrogram 
to align the K2 filters. Note that this is a static website - none of 
the kits mentioned are available since Tom's passing, but the 
information is valuable.  For basics, the low frequency corner of the 
SSB passband should be positioned close to 300 Hz.

If you do not have a wideband Noise Generator such as the Elecraft 
N-Gen, you can use antenna noise on a dead band when aligning the 
filters - be certain that there are no signals within the passband.
If you want to construct an easy wideband noise generator, take a look 
at the information at http://www.mmccs.com/mmarc/n0ss/index_ele_kits.html
Note that kits are not available since Tom is SK, but the circuit is 
easy to construct with 'flying leads', perfboard, and several other methods.

73,
Don W3FPR
On 6/3/2014 7:54 PM, Michael Eberle wrote:
> I recently started trying to use my K2 for digital modes and noticed 
> my transmit audio seems to have some buzz or him in it.  I never 
> really noticed it before on SSB, but if I listen carefully it sounds 
> robotic, like talking in front of a fan.  When monitoring the SSB 
> signal on my K3/P3, I noticed that the carrier is not fully 
> suppressed.  It is adjusted as low as it will go with the carrier 
> balance pot on the SSB board.
>
> Do I have my filters set incorrectly or should I be checking for 
> assembly errors such as toroids wound wrong, wrong component values, 
> or bad solder joints?
>
> Thanks,
> Mike
> KI0HA