Looking for some power on the 3400 MHz ham band?

Toshiba UM2683B 3.5 GHz power amplifiers are available on eBay from AECI South, that become a plug & play solution for 3.4 GHz.

Buy it now price ~ AUD$200 (+/- exchange rate) + postage (approx. AUD$40 +/-), so you’re looking at ~ AUD$240 shipped to you.

Compare this to the 13W Kuhne PA KU PA340360-13A for €250 (AUD$360 +/-) + postage, as quoted to me in July 2013.

Toshiba UM2683B at a glance
Class-A linear amplifier
20W out
1mW drive
+12v @ 10.5A

It came with an Inspection Data Sheet, which lists these parameters for my particular unit;

  • Linear Gain min
  • Linear Gain max
  • Gain Ripple
  • Linearity
  • Return Loss in
  • Return Loss out
  • DC Current
  • “Shutdown”
  • “Alarm Functions”

It comes packaged in the original manufacturer’s sealed anti-static bag, and looking at the date, 1999, we can determine these are “NOS” New Old Stock.



You will most likely need to pad back your drive, to suit the 1mW 0dBm input requirement.




DB15HD Pinout by DL7YC

1: +13.8 volts
2. +13.8 volts
3: Ground
4: High Output Alarm (1-38dBm = +5volts / >42dBm = 0volts)
5: VSWR Alarm (>12dB return loss = +5V /
6: Might be FORWARD Pwr (measured at the “cold end” of a stub at the PA`s collector)
7: Ground
8: Low Output Alarm
9: Enable (Open = Stand By / Closed to ground = TX ON)
10: Ground
11: Ground
12: +13.8 volts
13: +13.8 volts
14: Might be REFLECTED Pwr (measured at the termination leg of the o/p circulator)
15: LED via 820 Ω resistor to monitor internal +5volts



You will need a heatsink!

Power Output Mod
The UM2683 “B” variant can also be tricked up to run 60W output, with a simple bias mod.

Found on the DB6NT web site, is a 13 Mb pdf by Manfred Ploetz DL7YC.

  For a Few Dollars – 40 More Watts at 3400 MHz


Manfred points out

All modifications are easy and cheap because they are made in the DC/bias part of the amplifiers only. No changes to the RF part are necessary.

Manfred also describes how two of these amplifiers can generate 125 Watts.
That’s serious EME power!

John Jaminet, W3HMS, also provides information about these UM2683B amps, found here.