Monday, May 18, 2020

Can real DX Be Heard on a Regenerative Receiver

In an earlier episode,  I told about the somewhat unplanned project to build a regenerative receiver.
It was done out of a desire to see how such a radio would have performed if I had had one when I was a young kid.

The project had a regenerative detector and two stages of audio and included bandspread tuning and was expected to tune about 6-18 mhz.

The first night it was finished,  I tuned through the dial just to make sure it was working and to get some idea what frequency range it actually tuned.

It ended up being a couple of days before I was able to get back to the little radio,  with things coming up at work and household projects that had to be taken care of.

The first test run had shown that the radio worked and a couple maritime cw stations along with a broadcast station or two and time signal station WWV were heard.

A couple days later,  I sat down in front of the rig with it actually set up on the desk as it would be used,  rather than turned on its side with test leads connected and tools and such scattered all over the place.

The first step  taken was to get a better idea of what was where on the dial,  which was only calibrated 0-100.  I had already found where 10 MHz was because of WWV and where 9420 was from finding the very well known Greek broadcast station. It was decided to use my ham transceiver to get a few more calibration points.

I put my Icom 720 on a dummy load and had the drive turned all the way down to provide the test signals.  Then calibration points were found for the bottom and top of the 40, 30 and 20 meter ham bands.  Tuning up from the mark for the top of 20 meters had me running into the 15 MHz WWV which gave another calibration point.

Going down the other way, the radio did not tune down far enough to reach the 5 MHz WWV.  In fact,  the bottom of the 40 meter band just did make it within the tuning range of the radio,  and the 49 meter shortwave broadcast band didn't quite make it at all at first.  By turning the tuning slug all the way in on the input coil,  only a portion of it could be reached.

I spent a little time getting the feel of the controls tuning through the 20 meter cw band.  It seemed that the most stable point for copying cw without overloading the radio was with the regeneration control set just barely past the point of oscillation.

It being early summer,  twenty meters was still open with lots of signals even at just before sundown.
It was obvious that the selectivity was not going to be as good as the Icom or my FT-101 with its 200 Hz cw filter.  It might prove difficult to pull out weak signals from DX stations in a crowd.

But then,  it must be possible,  because in the early days of hamming,  regenerative receivers were all many ops had....and they did work DX.  But were the bands as crowded as today? No way to know.

So it was down to tuning. Starting high in the cw portion of the band,  I immediately ran across a strong station that could only be one thing from the was an ARRL bulletin.  It seemed somewhat appropriate that one of the first ham stations in the log from the little receiver would be the ARRL Club Station, W1AW !!!

Going on down the band netted a number of US stations,  but there was still hope for some DX.  The little rig did not disappoint.  It took some very careful juggling of regeneration and bandspread controls,  but soon I had confirmed an ID for OA4CWA from Peru!

I was pretty happy with that,  but there would be a few more.  Within the next half hour I had logged OM3KFF from the Slovak Republic,  IK3HZK from Italy  and F1MCC from France.  Not rare DX by any stretch of the imagination in the eyes of big time DX-ers,  but I felt it was pretty good for the little regen rig.

A quick run down to 40 meters did not yield quite as spectacular results.  Stateside signals were much stronger and it was early in the evening.  I did identify K4DMT, W0RFN and KA9KWR. I was anxious to try a run through the maritime cw band at 8 MHz,  but did stop on one last station that could be considered DX I suppose,  KP4/W8HNI from Puerto Rico.

The maritime cw band was a real bit of an adventure,  but in some ways was a little easier,  first from the standpoint that the stations generally ran more power than hams,  and also because they were not piled on top of each other helter skelter and were easier to separate.  In about 45 minutes I was able to put several of them in the log. Those pulled out included the following:
PJC Netherlands Antilles
FLBA ( being a four letter call apparently a ship as opposed to a shore station)
WNU Slidell, Louisiana
FUF  Guadalupe Island
WNU-33 Slidell
WCC Chatham, Mass.  ( probably the best known of the shore stations of the day)
ZSC Capetown, South Africa
VCS  Halifax
FFL St Lys Radio,  France
DAN  Norddeich Radio, Germany
OST4  Ostend Radio, Belgium
HPP  Panama
CLA  Cuba

Not bad stuff for a junk box regen radio.

( And another good reason for keeping logs.  Then and now I log virtually everything I hear each time I hear it and have kept logs going back to 1957)

Over the next few days,  I played around with some things trying to overcome the overload and pulling that occurred with some stations.  I ended up putting a 100 pF variable capacitor in series with the hot lead of the antenna to provide a little decoupling at times.

It may seem perhaps sacrilege but at one point I brought out a little MFJ tuned preselector and put in front of the input.  It was not so much as to provide gain for weak signals,  as there was really no need for that.  It did seem to provide a little " cushion " between the antenna and the detector and let it see a more stable load on the grid circuit.  Most of the time the gain control on the preamp was kept very low.  The additional selectivity did seem to help.

It is unfortunate that other things got in the way of spending much more time on the little rig.  Field Day was coming up and a local group was planning to operate at a nearby park and attention got diverted from it.

After Field Day,  pieces for a 10-meter beam were picked up and the design and construction of the yagi got my attention,  working out the details of maximum gain,  optimum wide spacing of the elements,  then getting it on top of the 40 feet of Rohn 45G that had grown outside the shack at my folks house ( my dad,  who is now a silent key and I had a joint shack for a time when I lived in an apartment and before I moved to my current location across town with my own real yard and future antenna  farm)

After that it was more projects,  overtime at work, and other things and the little radio got put on the shelf.  Now almost thirty years later, it sits dust covered in my back yard shop.  Perhaps its time to dust it off, re cap the power supply and bring it into the indoor shack and give it a chance to pull in some more DX.

Thinking about it still brings back the says of yearning for a Knight Ocean Hopper or Span Master.  It  would be nice to find one and spend some time twirling the dials,  but unfortunately they are not great in number any more and the collectors seem to snap them up and put them on a shelf,  not leaving many to be found by us old geezers who would just like to spend some time with them finding adventure.

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