Simple HF Regenerative Receiver

A step towards an ultra-simple QRP HF CW transceiver (see

FETer

page)

Updated 24.10.08

40M OR 80M REGENERATIVE RECEIVER

The regen receiver is an amazing piece of electronics. If you have never tried to build anything
ever this is something you have to try! Various circuits are available on the internet (see links on
the left) but I offer you my own humble version based heavily on similar circuits that have been
published over the last 30 years or more.

The circuit described may not be the answer to the purist: it will radiate a little RF on the
frequency to which it is tuned so avoid using one when you have nearby hams trying to work DX.
Having said that it works well, is sensitive and produces decent level signals on SSB and CW into
a small crystal earpiece.

WHAT RESULTS CAN BE ACHIEVED WITH 9 PARTS?

With the circuit shown the receiver can pull in SSB/CW stations well from all over Europe on 40m
(or 80m) with ease. It will be overloaded if there are strong AM stations nearby e.g. in the 41m
broadcast band at night. If run from a 12-14V supply and R2 is increased to 5k6 or 6k8 the
output will be louder and sensitivity close to -100dBm (about 2uV).

DESIGN

L1 is a small T50-2 (red) toroid with around 18-20 turns (40m) or 35-40t (80m) on the main
winding connected to the FET with a single turn coupling loop for the antenna connection. The tap

HF Regen Receivers

http://homepage.ntlworld.com/lapthorn/regen2

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2015-06-12 03:21

is about 20% up the main winding. C1 is adjusted to set the radio into the 40m band and C2 then
acts as a fine tune within the band. You can check the frequency by listening to the frequency
radiated when the stage is in oscillation. By changing L1 and C1/2 other HF bands like 80, 30 or
20m can be covered. Experiment! C4 is adjusted to get the circuit to just regenerate. There are
no decouplers: these did not seem to matter, so were left out for simplicity. Increasing the drain
resistor to 5k6 and running from a 12-14V supply will increase audio output.

MAKING IT TRANSCEIVE?

This is where the REAL fun
starts! By switching the same
MPF102 FET across to a few
more parts (as was done by
W2UW) this can be made into a
single FET transceiver, albiet
with very low power around
10-20mW. W2UW has worked
2 Canadian provinces and 17
US states with such a rig.

For the FETer, an even
simpler G3XBM 80m version
of this transceiver, see the

FETer page

. So far the best

day;ight DX with the FETer is
18kms.

W2UW's circuit (copied from GQRP SPRAT magazine)

LINKS

Simple homebuilt radio projects

W2UW's site
GQRP Club and SPRAT

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HF Regen Receivers

http://homepage.ntlworld.com/lapthorn/regen2

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2015-06-12 03:21