[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

RE: LO startup problem on DEMI 2400-144RX



Just for the record I had the same problem with my DEMI downconverter. If I
applied 12 volts directly 90 percent of the time the LO was off or on the
wrong freq. For a while I solved this by powering it from a Radio Shack
power cube with multiple voltages out. I would start at 3 volts then switch
through the ranges up to 12 volts and it started every time. Once it was
started it stayed on.

I ultimately solved the problem by putting in an ADIC down converter and the
DEMI is on the shelf.

Gary Gonnella W6RYO
http://www.w6ryo.com


> -----Original Message-----
> From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
> Behalf Of Scott Townley
> Sent: Sunday, June 29, 2003 6:31 PM
> To: amsat-bb@AMSAT.Org
> Subject: Re: [amsat-bb] 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
> >
> >----
> >Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> >Not an AMSAT member? Join now to support the amateur satellite program!
> >To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>
> Scott Townley NX7U
> Gilbert, AZ  DM43di
> http://members.cox.net/nx7u
>
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home