[DSP-10] Transverter high-side conversion

[Bob Larkin]

Hi Jess and All,

(This is Re: [DSP-10] EZ Lite CPU Replacement )

As you suggest, on the 432 transverter, the usual low-side conversion with a
288 MHz LO will not work.

To solve this problem, the DSP-10 UHFA.CFG configuration file has a field in
the transverter description, sb, which is -1 for most transverters, but 1
for a "high-side conversion." The note from the readme16.txt file talks
about this: "The sb field is -1 for most transverter cases.  Sometimes,
however, it is
undesireable to use "low-side" conversion.  For instance, if a 432 converter
uses a 288 MHz LO, there is an unwanted response at 2x288-144=432 MHz.  This
can be avoided by using a 576 MHz LO and "high side" conversion.  If this is
done the sb field should be set to 1 and the software will flip the numbers
over so that the dial tunes in the correct direction, frequency readouts are
correct and the USB/LSB selection is correct."

I need to mention, that I have never tested this!! If anyone has, please let
us know if there were problems. The most likely problem is some frequency
control being backwards---maybe EME Doppler correction or something like
that. If everything is working OK, all frequency indications should be
exactly the same as if a 288 MHz LO was being used.

Good luck on the transverter project! And congratulations on the 2181
replacement!! It sound exciting!

73,
Bob W7PUA


At 04:56 PM 8/25/02 EDT, W4mvb@cs.com wrote:
>Good Evening To the Group,
>
>Thanks to the info from the users manual that Paul, HB9OMQ sent to me and to 
>the advice and encouragement I received from Dave, WB9OWN, I was able to 
>diagnose and replace the failed CPU in my original EZ Lite unit.
>
>I have about half the parts necessary to build another unit.  The LMX1501AM 
>is no longer available from Digi Key.  Is there sub for this part or another 
>source perhaps?
>
>Since 432 is included in the software as a possible transverter is anyone 
>using (planning to use) a DSP-10 for that purpose?  If so, what frequency  
>conversion scheme is anticipated (or used)?  It seems to me that the obvious 
>harmonically related 144/288/432  scheme would be a no-no.
>
>One more question if I may?  I have used the 90 mhz oscillator circuit from 
>the no tune transverter designs for several units and I have always bought my 
>crystals from Down East Microwave since they use the same oscillator circuit 
>in their transverters.  I went to the DEM website last week looking for a 
>93.6667 mhz crystal for an AO-40 L Band transmit converter and was surprised 
>to find that DEM has apparently replaced all their 90 mhz crystals with 180 
>mhz units.  Has there been a circuit for these crystals published anywhere?  
>I would guess that the basic circuit is the same but with some changed values 
>for components in the oscillator circuit.
>
>Thanks for all the help.
>
>73 de Jess - W4MVB
>
>
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