09/06/2020

A long time ago I bought at a hamfest a preamplifier from DX-Engineering the RPA-1.

The problem with this amp is that it is 50 Ohm and the hole RX  system will be 75 Ohm.

Some time ago I replaced the F connectors to BNC connectors so I have to reverse that again.

At my controller inside the shack I will make a switch so I can switch it on and off if needed.

Some info of the manual of YCCC

12.1.1 DX Engineering RPA-1
The RPA-1 provides exceptional dynamic range performance of 110 dB or greater (IM3 at 500 Hz BW) and a +43 dBm third-order intercept. It has 16 dB gain and is nominally a 50-ohm preamp, but its input impedance varies with the load impedance on its output port. If the output is terminated in a 50-ohm load, then the input impedance is very close to 50 ohms. This 50-ohm input can be stepped up to 75 ohms by means of the broadband transformer on a Fair-Rite 2873000202 core.
50 ohms 4 turns to 75 ohms 5 turns

19/08/2020

I made that transformer and tested it with my analyser and a 75 Ohm resister .

All looks fine at this point.