[DSP-10] CW transmit has a raspy sound

[Mike Niswonger]

    Computer UPS' are notorious for radiated magnetic fields, 
particularly of they have a plastic case - but even steel cased ones can 
cause problems...

       Mike Niswonger, W4CMN

Bob Larkin wrote:
> Hi Lee -
>
> I'll send this to the group, as there may be others that are 
> interested, or that might have suggestions.
>
> At this point, I just ran your WAV files through Spectran and looked 
> at the spectrum. You might try this to see as we will all see the same 
> thing, and it also plays the sound to let you correlate the observations.
>
> When I look at the SSB spectrums, I see a triple spectrum, the voice, 
> and a replica 120 Hz above and below.  Also, the 19680 signal has the 
> same side bands.
>
> This is probably not from the power supply, as there doesn't seem to 
> be any AC from the mike preamp (at 120 Hz), but rather as modulation 
> side bands only.  My guess is that the 19.68 osc is getting modulated 
> by a local magnetic field from a power supply. Try moving the box and 
> see what happens. The 19.68 core does not have a magnetic cover and I 
> have seen this effect before.  Everyone should be careful about 
> sitting the DSP-10 on top of a power supply, or other magnetic radiators.
>
> The second observation, is that  the CW signal might have above 
> average phase noise. Try tuning the 126 Mhz VCO slightly lower in 
> frequency and see what happens. If the VCO control voltage is too low, 
> it gets low loop gain and poor control from the PLL.
>
> Let us know!
>
> 73,
> Bob  W7PUA
>
>
> At 08:10 AM 12/18/2005, you wrote:
>> Hi bob,
>>
>> I've uploaded some wav files to my server.  The URL is
>> http://www.aa1yn.com/dsp-10/wav/
>>
>> Let me know if you need/want any more.  The file names should be self 
>> explanatory but I can clarify any.
>>
>> You can contact me directly via email - aa1yn at aa1yn dot com
>>
>> Lee - AA1YN
>> At 03:04 PM 12/13/2005 -0800, you wrote:
>>> Hi Lee -
>>>
>>> None of the local folks have this. Ron has this problem. Could 
>>> either of you provide a WAV file of this over the air??  Or scope 
>>> pictures of the drive to the transmit mixer?  I really am puzzled.
>>>
>>> Thanks,
>>> Bob W7PUA
>>>
>>> At 02:16 PM 12/13/2005, you wrote:
>>>> One problem I have always had with my DSP-10 is a very raspy 
>>>> sounding CW or Sideband signal on the air.  Anyone else have this 
>>>> and has anyone else solved this?
>>>>
>>>>
>>>> Lee Scott - AA1YN http://www.aa1yn.com
>>>> Home of the VHF & Up Register http://www.aa1yn.com/vhf
>>>> Home of the VHF Talk chatroom http://vhftalk.aa1yn.com
>>>> Hooksett, NH
>>>> FN43gc52
>>>>
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>
>
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