[DSP-10] CW transmit has a raspy sound

[Lee Scott - AA1YN]

Here is what I have found so far,

The sidebands are not there on either 10MHz nor on 124MHz but are there on 
the 19.68Mhz osc.  The closest power supply is about 5 feet away as is a 
CRT monitor.  The closest UPS is 15 feet away.  Tomorrow I will try a 
different PS and turn off the CRT.  I use an old laptop for the PC on the 
DSP-10 so no high current display. I am seeing the sidebands using both the 
internal 10MHz osc and my GPS osc.  I have a few other things to try. I 
also want to take a closer look at the DC filtering on the board around the 
19.68 osc and I'm going to try a different location to see if there is any 
effect.

Lee - AA1YN
At 07:51 PM 12/19/2005 -0800, you wrote:
>Team:
>
>I witnessed similar problems (in receive), after hooking up an external 10
>MHz OCXO.  The OCXO was plenty stable, but the power supply I built to drive
>it did not have sufficient filtering on it.  Indeed, 60Hz sidebands were
>prevelant on the 10 MHz OCXO, which crept in to the receive chain....
>
>Happy holidays to the group.
>
>Roger Hayward
>ARS KA7EXM
>
>
>-----Original Message-----
>From: dsp-10-bounces at mailman.qth.net [mailto:dsp-10-bounces at mailman.qth.net]
>On Behalf Of Bob Larkin
>Sent: Monday, December 19, 2005 2:00 PM
>To: Discussion of DSP-10 2-meter transceiver
>Subject: Re: [DSP-10] CW transmit has a raspy sound
>
>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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