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Re: LO startup problem on DEMI 2400-144RX



More...
The LO is "on" but the multiplier stage "U2", a Minicircuits ERA-2, is 
flaky.  If I touch the output of the device with anything (an oscope probe, 
VOM probe, my finger) it takes off and suddenly the IF shows up.  Power 
off, power on, and no IF until I touch the ERA-2 output with something.
So the add'l capacitance is doing something.  But since the ERA-2 feeds the 
multiplied LO BPF, it doesn't seem right to put a piece of foil to increase 
the capacitance there (hose up the BPF response).
Those with more experience with these MMIC-thingys...is this a 
parts-replacement fix?  Again, it worked fine before being idled.
PS it's not heat...it worked fine all last summer here in Phoenix, and just 
to be sure I refrigerated it before testing with no change in response.



At 04:57 2003-06-29, you wrote:
>Don't know if anyone else has seen this...
>I have a DEMI 2400-144RX downconverter for AO-40 which has always worked 
>perfectly.
>Now after being out of service for about four months, the LO doesn't want 
>to start up.  If I leave it on the bench with an RF source and DC power, 
>eventually (like after 10 minutes) it will suddenly start 
>"downconverting", having just sat there until that point.  Of course, when 
>I put it back on the antenna it chooses not to start up at all (d*** 
>Murphy...).
>Any clues?  I seem to recall reading about an adjustment in the LO on this 
>device some time ago but can't recall exactly what it was...
>TIA,
>
>Scott Townley NX7U
>Gilbert, AZ  DM43di
>
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Scott Townley NX7U
Gilbert, AZ  DM43di
http://members.cox.net/nx7u

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