Hi Mark, N8MH I have seen the pictures of your Landwehr 70 cm preamplifier and I know very well the model of coax relays used in it.
They are 50 ohm coax relays Tohtsu CX 120 P for printed circuits and can handle 150 watt pep at 500 MHz with an insertion loss of 0.2 dB and a crosstallk (insulation) of 35 dB with a VSWR of 1,08 at 1 GHz don't worry about to clean the contacts because they are very large silver contacts and you just need to remove the side cover with your fingers and spry a contact cleaner over it. I use four of them in my switching four polarizations switcher on a 70 cm crossed yagi as you can read into the AMSAT Journal March/April and May/June 2007 Have fun 73" de i8CVS Domenico ----- Original Message ----- From: "Mark L. Hammond" <marklhamm...@gmail.com> To: "i8cvs" <domenico.i8...@tin.it>; "Amsat - BBs" <amsat-bb@amsat.org> Cc: "Vince Fiscus, KB7ADL" <vlfis...@mcn.net>; "K5OE" <k...@aol.com> Sent: Thursday, June 02, 2011 3:33 AM Subject: Re: Fixed! Re: Landwehr 70cm preamp device question? > Hello Domenico I8CVS, > > I did take pictures while I had the cover off :) You can see and download them here: > > https://sites.google.com/site/marklhammond/hamradio > > Indeed, they are labeled "COAXIAL RELAYS" as you suspected. > > You can also see the "little white button" on the relays that I mentioned previously. > > 73! > > Mark N8MH > > At 02:42 AM 6/2/2011 +0200, i8cvs wrote: > >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 > >applications. > > > >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. > > > >Tanks > > > >73" de > > > >i8CVS Domenico > > > >----- Original Message ----- > >From: "Mark L. Hammond" <marklhamm...@gmail.com> > >To: "Amsat - BBs" <amsat-bb@amsat.org> > >Cc: "i8cvs" <domenico.i8...@tin.it>; "Vince Fiscus, KB7ADL" > ><vlfis...@mcn.net>; "K5OE" <k...@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 > >they?!? > >> > >> 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" <marklhamm...@gmail.com> > >> >>To: "Amsat - BBs" <amsat-bb@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] > >> > _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
