[Premium-Rx] Old DSP Lab boards

Mon Feb 14 14:12:32 EST 2005

These are probably too old to do any good, but I kept a couple of ADSP-21020 lab board from the early 1990s if anyone can use them.  This was a 32 bit floating point DSP processor that ran at 25 mHz (I think).  These board were complete with memory, A/D and D/A converters (16 bit 48 kHz 2 channel), audio amplifiers, and a "supervisor" processor with serial port (2106 I think).  One was used for testing a couple of algorithms and the other was never used.  There is a GNU C compiler and documentation for the compiler, lab, and processors.  I had forgotten about having them until you mentioned the demo board for the AD9956.  I think the compiler is on 3 ½" floppies.  There is probably 20 pounds of stuff including some of the lab demo programs.  As I remember the boards need +/- 15 and +5 volts, maybe -5.  We were using them for a project to analyze sounds from underground storage tanks.  

Barry

________________________________

From: premium-rx-bounces at ml.skirrow.org [mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of Brian D. Comer
Sent: Monday, February 14, 2005 11:45 AM
To: premium-rx at ml.skirrow.org
Subject: RE: [Premium-Rx] Clean LOs

Francis

I think that the best synthesizers today use both DDS and PLL. I am currently working on a synthesizer for 2.4 GHz for military use using the AD9956. This could turn out to be a very good device. This device has all the circuitry required for a clean synthesizer, with the exception of the VCO. In the project that I am doing with AD9956 I have yet to get the device programmed completely so have not done any tests on spectral purity. The device is probably too small for most amateur work and I cannot assemble it or remove it from a board even though I have a fairly good set up and can handle 0402 parts with little difficulty. Analog devices have a demo board for this part that could be very interesting but I do not have one.

 I believe that the main problem with the RA6830 synthesizer is that it does not use enough bits for the D to A in the fractional N loop coupled with very poor ground loops in the 60 Hz supply. 

 73 Brian

KF6C

-----Original Message-----
From: premium-rx-bounces at ml.skirrow.org [mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of Carcia, Francis A HS
Sent: Monday, February 14, 2005 5:26 AM
To: premium-rx at ml.skirrow.org
Subject: RE: [Premium-Rx] Clean LOs

    Brian,

What would you consider a good synthesizer? I agree the layout of the 6830 synthesizer needs some help. I have not found the correct setting of the analog compensation. Also The phase noise gets worse when the AUX output is connected. I suspect the grounding of the VCO connectors and

cables need termination to the case. I plan to build my own VCO. I have a mini circuits VCO running

4X that I might try. I would use local voltage regulation. I have checked a number of receivers and yet to find one better. The closest was the old WJ 8718.   fc 

	-----Original Message-----
	From: Brian D. Comer [mailto:bcomer at cox.net]
	Sent: Friday, February 11, 2005 10:26 PM
	To: premium-rx at ml.skirrow.org
	Subject: FW: [Premium-Rx] Clean LOs

	-----Original Message-----
	From: Brian D. Comer [mailto:bcomer at cox.net] 
	Sent: Friday, February 11, 2005 4:00 PM
	To: 'Michael O'Beirne'
	Subject: RE: [Premium-Rx] Clean LOs

	I do not support the idea that frequency synthesizers are necessarily a problem and would not consider the using of anything else for a high performance receiver today. That is not to say that they are necessarily good and I find the ones in the RA 6830 an example of a bad design or at least bad implementation. There are of course may other very poor synthesizers out there.

	On the great HP 8640, many years ago I had access to one when it had only just been released to the market. I took it home and used it as an LO for a home brew 2 meter transceiver. The reports that I received were that I had very bad FM on the my signal. The HP 8640 uses a frequency locked loop which can very easily be frequency modulated by strong signals, so take care when use it as an LO.

	73 Brian

	KF6C/G3ZVC

	-----Original Message-----
	From: premium-rx-bounces at ml.skirrow.org [mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of Michael O'Beirne
	Sent: Friday, February 11, 2005 1:49 PM
	To: Premium-Radio
	Subject: [Premium-Rx] Clean LOs

	Dear All,

	One quick idea to see what a really clean LO can do for a receiver might be to disable the internal synthesiser and feed in some RF from a good HP8640B genie or similar from R&S.  G3OSS (Angus McKenzie) did this at VHF with a professional VHF receiver and was much impressed.

	73s

	Michael

	G8MOB

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