Steve and Katie Dold's web site


Generate Amplifier for the IFR 1200-series

Note: I've temporarily stopped building amplifiers because everything is packed away for a move. If you've already bought one and need to have it repaired, send me an email at stevedold1960 followed by the "at" symbol, then gmail, followed by dot com.

I designed and built these amplifiers to be used with the IFR 500, 1200, 1200A, 1200S and 1200 Super-S service monitors to amplify the -20 dBm generate level to +10 dBm or more. They are similar to IFR's “Option 5” 30 dB Generate Amplifier, which was a very useful amplifier but is becoming hard to find. This amplifier does not have the internal relay and receiver port connection of the Option 5 factory amplifier, which was used to connect the amplifier output port to the monitor's receiver port during receive mode operation. It is a straight generate amplifier that will allow you to key and test distant repeaters using an outside antenna. It is also useful for tuning filters, especially deep notch filters that require more than the standard generator provides.

Like IFR's Option 5, it plugs into the generate output port (the “T/R” connector) and power jack on the service monitor and amplifies the generated signal by about 32 dB, giving an output of approximately +10 to +12 dBm from 10 MHz to 1000 MHz (See "S21" gain plot in the pictures).

It uses two off-the-shelf microwave gain block amplifier ICs that, like all of the parts, are easily replaceable with minimal SMD soldering skills. The DC power input has a self-resetting fuse to protect the service monitor from damage in the event of an internal failure of the amplifier. The housing is rugged aluminum that is gold Alodined.

Full documentation is included, including parts list. Schematic and parts list are included, and all parts are available from Digi-Key and other sources.

Note to IFR 1500, A7550 and A8000 owners: This amp is not a good fit because the spacing between the DC power pin and the RF input connector is not the same as on the 1200. Also, those units already put out 0 dBm, so the full gain of this amp would not be realized since its 1 dB compression point is only +17 dBm.

Warranty: I will repair or replace any defective units at no charge within 1 year of purchase if you call or email me first before shipping the amp to me. For non-warranty repairs (keyed-into, etc) I will be happy to repair the amplifier for a flat fee of $20 plus return shipping.

Even if the unit is not defective, I will be happy to buy it back for any reason if you return it to me within 30 days, even if you simply decide you didn't need it after all or that it doesn't do what you wanted. I want you to be happy with your purchase.


  • Supply: 11-13VDC at about 110 mA
  • Gain: about 32 dB, see S21 (gain) plot below
  • P1dB: 17 dBm (the point at which the output goes 1 dB into compression)
  • Freq. Range: 10-1000 MHz

Price if ordered direct from me is $89 which includes USPS Priority Mail shipping in the U.S.
Outside the U.S. the price is $99 USD plus shipping.
I can take a check or Paypal (please call or email me for the paypal payment address)

Contact info:

Steve Dold (W6KCS)
705 Wiegand Way
Dixon, CA  95620
(916) 273-4451
w6kcs (at) stevedold (dot) com (If your email bounces or I don't answer within a day or so, please try again. My server is somewhat unreliable.)

Click on the following links for more images and network analyzer plots from a sample unit:

Gain plot

Input return loss

Output return loss

Input (S11) and output (S22) smith chart plots

Interior view