Domenico,

Thank you very much for your advice and the data sheets. I had compared the two data sheets and could not see why a substitution was a bad idea.

I appreciate the other part numbers and source recommendation, too!

73,

Mark N8MH

At 09:49 PM 5/31/2011 +0200, i8cvs wrote:

----- Original Message ----- From: "Mark L. Hammond" marklhammond@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]

Hi Mark, N8MH

The MGF 14......types are MIL versions (Hi-Rel) of the MGF 13..... and MGF 19..... and so "apparently" the MGF 1402 can be repleced by a MGF 1302 with minor current adjustement for the lowest Noise Figure

By the way the MGF 1402 can be directly replaced by a ATF 26550 or MGF 1412 available at 9,30 Euro's from

http://www.rfmicrowave.it/catalogue.php?lang=eng

Look at the Catalog and then click over GaAsFET and FET

If you contact Franco Rota of the above rfmicrowave company I am sure that he has few MGF 1402 at stock

You can pay it with credit card and get the GaAsFET in a few days by regular post.

73" de

i8CVS Domenico

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" marklhammond@gmail.com To: "Amsat - BBs" amsat-bb@amsat.org Cc: "i8cvs" domenico.i8cvs@tin.it; "Vince Fiscus, KB7ADL" vlfiscus@mcn.net; "K5OE" k5oe@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" marklhammond@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]

One more update: the relays can be purchased here!

http://radiodan.com/ted_stuff/tohtsu.htm

73,

Mark N8MH

At 09:33 PM 6/1/2011 -0400, Mark L. Hammond wrote:

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" marklhammond@gmail.com To: "Amsat - BBs" amsat-bb@amsat.org Cc: "i8cvs" domenico.i8cvs@tin.it; "Vince Fiscus, KB7ADL" vlfiscus@mcn.net; "K5OE" k5oe@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" marklhammond@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

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" marklhammond@gmail.com To: "i8cvs" domenico.i8cvs@tin.it; "Amsat - BBs" amsat-bb@amsat.org Cc: "Vince Fiscus, KB7ADL" vlfiscus@mcn.net; "K5OE" k5oe@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" marklhammond@gmail.com To: "Amsat - BBs" amsat-bb@amsat.org Cc: "i8cvs" domenico.i8cvs@tin.it; "Vince Fiscus, KB7ADL" vlfiscus@mcn.net; "K5OE" k5oe@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" marklhammond@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]

AO-51 solid signals in ZL. AOS (0459 UT) about five minutes after it came out of eclipse.

Alan ZL2BX

Hi Mark,

Well I can finally confirm that AO-51 is loud and clear over ZL in full eclipse. AOS 1435 UTC. Solid signals from the transponder.

Alan ZL2BX

-----Original Message----- From: Mark L. Hammond [mailto:marklhammond@gmail.com] Sent: Friday, 3 June 2011 09:32 To: Alan Cresswell Cc: amsat-bb@amsat.org Subject: Re: [amsat-bb] AO-51over ZL

Thanks, Alan! Keep the reports coming.

73,

Mark N8MH

On Fri, Jun 3, 2011 at 1:16 AM, Alan Cresswell alancresswell@xtra.co.nz wrote:

AO-51 solid signals in ZL.   AOS (0459 UT) about five minutes after it

came

out of eclipse.

Alan ZL2BX

---

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