[Elecraft] K2 KSB2 low output

Don Wilhelm donwilh at embarqmail.com
Tue Sep 12 00:04:20 EDT 2017


Gernot,

To check for filter attenuation, I suggest you do so in receive using an 
audio spectrum analyzer running on your computer to view the filter 
amplitude.  Feed the K2 with a broadband signal generator although noise 
on a portion of a band with no signals will also work.

Compare the amplitude of the noise signal using the CW filter (width 
about 700 Hz is ideal) with the amplitude from the OP1 SSB filter.
The amplitude should be about the same.  If they are about the same, the 
filter is OK.

Check the position of the filter passband (again with the noise source 
and the audio spectrum analyzer) - the filter should extend from about 
300 Hz to 2300Hz if you have the older 2.1kHz width filter.  If the 
newer 2.4kHz width, it should extend from about 300Hz to 2600Hz.
Adjust the BFO to align the filter passband properly.

For audio spectrum analyzers, you can use SpectrumLab or download 
Spectrogram from my website www.w3fpr.com.

If the filter on receive shows near the same amplitude as the CW filter, 
then the filter itself is OK.  Look for the problem at D14, R10, or R11 
- check soldering.  You should also check to be certain that the TXS 
signal from U1 pin 15 is at least 5 volts during SSB transmit.  If not, 
replace U1.

Try setting the SSBC parameter to 3-1 and see if the response improves.

73,
Don W3FPR

On 9/11/2017 7:53 PM, gt-i at gmx.net wrote:
> Hello list,
> I recently tried to use my K2 on SSB. To my suprise, there was very 
> little output. Even with full power it only showed the first bar. I did 
> some SSB QSOs during the first years...
> Digging deeper, I found the DSB signal showed a Vpp of ~1V, but after 
> the filter the SSB signal was only 20mV or so. Is this kind of loss 
> normal for a 7-pole filter? If not, any hints how to repair the filter?
> tnx es 73
> Gernot DF5RF
> 
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