[DSP-10] CW transmit has a raspy sound

[Roger Hayward]

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
>>>
>>>_______________________________________________
>>>DSP-10 mailing list
>>>DSP-10 at mailman.qth.net
>>>http://mailman.qth.net/mailman/listinfo/dsp-10


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