Bob -
Here are the documents, web links, and answers from QRZ Q&A. http://forums.qrz.com/showthread.php?290978-3SK121-FT-726R-70cm-module-Q01
AMSAT-BB -- December 23, 2001 (Joe Leikhim, K4SAT) http://www.amsat.org/amsat/archive/amsat-bb/200112/msg00609.html
Toshiba 3SK121 -- TOSHIBA TRANSISTOR Dual-Gate, UHF, 10V, Idss>20mA, Up<4V Datasheet (largely in Japanese). http://www.datasheetcatalog.org/data.../499109_DS.pdf
The Icom mast-mounted pre-amplifiers (AG-25, AG-35) use the dual gate 3SK121 Dual Gate FET. The 2 schematics/manuals for the Icom AG-25 and AG-35 units are at QRZ page.
You will see Internet recommendations for the 3SK121 replacement on AMSAT and VHF/UHF DX discussion boards based on this usage by Icom. These two distributors indicated they had inventory of this Toshiba Dual-Gate FET.
XS Micro http://www.xsmicro.com/rfq.php?pn=3S...&ref=octoparts
and Express Electronics (UK) http://www.express-elect.com/
I have seen one Eastern Asia exporter (eBay Seller id: my_mkchan) based in Hong Kong offer a variety of Yaesu parts, including some hard to find (no longer mfg.) transistors.
I have seen the European CF-739 or BF981 listed as a suitable substitute. When you substitute check Noise Figures and Gain for your application.
BEWARE of Counterfeit (Fake) Semiconductor Parts from Asia ..... http://sound.westhost.com/counterfeit.htm
=== w9gb
----- Original Message ----
From: Bob- W7LRD [email protected] To: [email protected] Sent: Wed, January 9, 2013 4:05:35 PM Subject: [amsat-bb] here's a good one!
Getting ready for a AO-7A pass, started keying the transmitter, I noticed the computer monitor was blinking very nicely in time with the cw, also the az and el indicators on the G5500 control unit were dancing
around in tune with the cw.
In fact they danced in tune even with the power off. Tipped over satellite tower, got out ohm meter, direct open through the 2M Icom AG-25 preamp. Jumped around the now removed preamp and we're back in business. Question...The relay contacts seem to be suspect. Should I get parts and repair the AG-25 or get a better preamp, as I am going to scratch some EME efforts off my bucket list. If you have a better 2M preamp
"laying " around let me know.
as always 73 Bob W7LRD