[amsat-bb] Re: Fixed! Re: Landwehr 70cm preamp device question?

i8cvs domenico.i8cvs at tin.it
Wed Jun 1 17:42:57 PDT 2011

Hi Mark, N8MH and All guys on the list.

I am very happy that you solved the problem on your preamplifier and since
you took the cover off I would like to know if the relays are or not
"COAXIAL RELAYS" or just non constant impedance relays for AC or DC

Can you take a picture on the inside of preamplifier and send it to me by
email ?

I remember that the owner of Landwehr was a 432 MHz EME'r in the early 1973
and I worked him off the moon but actually I don't remember his call letter
from Sweden.

I believe that he dismitted the production of the above preamplifiers many
years ago.


73" de

i8CVS Domenico

----- Original Message -----
From: "Mark L. Hammond" <marklhammond at gmail.com>
To: "Amsat - BBs" <amsat-bb at amsat.org>
Cc: "i8cvs" <domenico.i8cvs at tin.it>; "Vince Fiscus, KB7ADL"
<vlfiscus at mcn.net>; "K5OE" <k5oe at aol.com>
Sent: Thursday, June 02, 2011 1:44 AM
Subject: Fixed! Re: Landwehr 70cm preamp device question?

> Hello All,
> You gotta love a happy ending ;)
> Thanks to I8CVS, Domenico; Vince, KB7ADL; and Jerry, K5OE for the advice
and coaching with troubleshooting my Landwehr 70 cm preamp.
> I took the cover off and applied 12V, and the two relays closed----or did
> One side looked good, while the other side didn't quite push the "little
white button" enough to make the contacts meet.  It was stuck--just a gentle
push with the finger, and I could tell it had become "unstuck."  Inserted
back in line, and bingo!  It's working just fine.
> I have resisted my urges to spray something down in there...figure I can
unstick it the same way another time, should it happen.  Looks like the
preamp was made in 1990, based on the dates of the relays.
> What I was seeing seemed like it might be a relay issue on one side (could
hear a rise in noise, so the relay at the output side (rig) was working--but
the relay on the input side (antenna) wasn't.  So, when powered, the input
relay didn't switch over correctly--what I was seeing now makes sense!
> Anyhow, it wasn't the GaAsFET after all.
> Thanks again for the help, guys.
> 73,
> Mark N8MH
> >>----- Original Message -----
> >>From: "Mark L. Hammond" <marklhammond at gmail.com>
> >>To: "Amsat - BBs" <amsat-bb at amsat.org>
> >>Sent: Tuesday, May 31, 2011 8:00 PM
> >>Subject: [amsat-bb] Landwehr 70cm preamp device question?
> >>
> >>> Hello All,
> >>>
> >>> I have an old Landwehr preamp that apparently uses the MGF1402 device
> >>> (does that sound right?).  It's not working so I presume it's the
> >>> GaAsFET.
> >>>
> >>> Can the MGF1302 be substituted for the original MGF1402?  Or can
> >>> anybody recommend another device for the 70 cm Landwehr?
> >>>
> >>> I need to do something...
> >>>
> >>> Thanks in advance!
> >>>
> >>> --
> >>> Mark L. Hammond [N8MH]

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