A simple project capable of excellent results
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
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).
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 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)
GQRP Club and SPRAT