[amsat-bb] Mast mounted low noise amps

[Gregory Beat]

Bill -

The Icom AG-series of mast mounted pre-amplifiers for weak-signal and satellite work are now legacy (I believe Icom has discontinued recently).  A lower noise figure of the active device (FET, MMIC) is important for satellite work (sky), than weak-signal work (noisy terrain/earth).
High noise-levels with the AG-series are often attributed to a Failed FET or an improper FET replacement by an earlier owner.

Newer FETs have ESD / static protection, while older designs — DID NOT !
Nearby lightning strikes can damaged the FET on the AG-series pre-amps.

Central States VHF Society annually performed Noise Figure tests on a variety of devices.
This may be useful, as you examine modern devices or recent surplus.
https://csvhfs.org/index.php/vhf-101/24-csvhfs-history/noise-figure-results

The Icom mast-mounted pre-amplifiers (AG-25, AG-35) used the dual-gate Toshiba 3SK121 Dual Gare FET (discontinued).  Schematics and manuals for the Icom AG-series are available via the Internet.
http://www.radiomanual.info/schemi/ACC_preampl/Icom_AG-35_user_IW2HEU.pdf
MODS.DK has the parts list and hand-drawn schematic for AG-35 (1999),
the othe file AG-25 etc. Instructions has schematic for AG-25 (last page).

Toshiba 3SK211 — GaAs MES FET, Dual-Gate, UHF, 10V, Idss>20mA, Up<4V
http://pdf.datasheetcatalog.com/datasheets/134/499109_DS.pdf

Icom AG-series (brochure)
https://www.icom.co.jp/world/support/download/manual/disp_down.php?SWT=&ID=20010101248&GNR=Options&TYPE=I&PDNM=IC-AG1/IC-AG25/IC-AG30/IC-AG35/IC-AG1200&INQWORDSWT=No&INQWORD=

In 2012 and 2013, Earl Andrews, VE3AB (Netty Electronics) 
http://www.nettyelectronics.com/
did comparison testing of various Dual Gate FETs, used by Icom, Yeasu, and Kenwood since the late 1970s.
http://www.earlandrews.com/dgshootout.html

Earl also noted Eastern Asian counterfeit products (various FETs), largely from China.
The Phillips/NXP BF981 being a common bad Chinese export (March 2014 & June 2015)
http://www.earlandrews.com/dgmosbadagn1.html

http://www.earlandrews.com/dgbadagn.html
—
RF Parts — Low Noise FETs
https://www.rfparts.com/rftransistors/transistor-misc/transistor-misc-lownoise.html
===
As far as a MMIC swap, I have not seen anything posted (YouTube, Icom boards, amsat-bb reflector), BUT that does not mean it has not be attempted or accomplished.
—
Beginning this month — Corey Abercrombie, N4NGZ, acquired the exclusive rights to manufacture, sell and repair the existing DownEast Microwave, Inc. (DEMI) VHF/UHF Transverter product line and all past VHF/UHF transverter products. 
https://www.downeastmicrowave.com/
Q5 Signal, LLC
17704 County Road 455
Montverde, FL 34756

Sales:  sales at q5signal.com

Support:  support at q5signal.com


Corey may be a source for current production UHF/Microwave devices, now or in future.
==
Jay Rusgrove, W1VD owner of Advanced Receiver Research (ARR) has a number of excellent Gallium Arsenide low-noise preamplifiers (LNA’s).
The ARR MSP144VDG-160 and MSP432VDG-160 models are often recommended for fixed satellite earth stations.

High Performance, 160 Watt Mast Mounted, Amateur Radio Preamplifiers
http://www.advancedreceiver.com/page10.html

Greg, w9gb
== 
From: Bill Acito <w1pa at hotmail.com>

What's the opinion/consensus of the older ICOM AG series, as an 
economical alternative? Can they be updated, with say, a different MMIC?

Bill W1PA