Thursday, March 11, 2021

Tuning a DX Contest With the Knight SpanMaster--a REAL adventure

 After using first line receivers for DX Contests for years,  it might seem strange for someone to use a very basic, simple receiver to hunt for DX in one.  The idea came as I thought back to the days when I operated my first contests using a National NC-88,  a single conversion radio with no filters and very broad selectivity.  I remember the frustration at trying to pick signals out of the seemingly hip-deep pile of stations from one end of the dial to the other,  and when some could be copied they were only the strongest stateside stations.

But those were the first couple years as a licensed ham before I knew much about the strategy of working contests and before I had developed " DX-er's Ears" or the ability to discern between different stations by pitch or developed tuning techniques that helped and the sense of rhythm that can be used to copy weak stations during the breaks in transmissions of the strong ones.

I had wanted a SpanMaster for some time.  In fact it was one of the first receivers I had wanted when still just a listener.  Allied Radio had three regenerative receivers that could be called " budget radios" then,  the Ocean Hopper,  Space Spanner and SpanMaster.  As it turned out,  I never got my wishes,  but did end up with a National SW-54 for my first "factory built" short wave radio.  I thought at the time that it was pretty good,  but it was, in fact,  little more than an AllAmerican Five AC/DC radio that happened to cover the short wave bands.

The idea was to see if my listening skills developed over the years would allow me to hear things I could not seem to hear then, and beyond that as a challenge. There was also the thought that hams back in the 20's and 30's used these simple receivers and were certainly hearing and working DX.

There are a few things to consider that are different in using a simple receiver and something like my R-75 or FT-950. Beyond the very obvious lesser apparent selectivity and sensitivity there is the absence of what used  to be called " single signal reception."  The term has not had to be used for a long time because virtually every receiver of any note made in the last fifty years ( except the consumer portables) already have it. It refers to a cw signal being heard on only one side of the zero beat as you tune across it. 

In older or wider selectivity receivers,  as you tune up to and past a cw signal,  you hear it first at a high pitch,  then as you get closer and closer to the actual frequency,  the pitch goes lower and lower until it actually goes through zero, of"zero-beat".  Then as you tune further onto the other side of the signal,  it becomes audible again and goes to a higher and higher pitch until you get far enough away from it that its finally disappears.  The tighter the selectivity,  the less that distance is.  What you are hearing is the beat of the signal against the Beat Frequency Oscillator, without which the unmodulated on-and-off keying of the cw carrier would not be heard,  or at most would sound like a series of thumps.  The pitch depends on the difference in frequency between the BFO and the desired signal as it sweeps through the IF of the radio.  

In front line radios,  the BFO is permanently set at one side of the passband and the narrow "doorway" for the desired signal is adjacent.  The signal is audible on one side of the BFO,  but as it is swept across it and out of the passband,  by the time it would reach the point where you would hear it go up in pitch again, it is either attenuated to the point that it is inaudible altogether or at the very least way down in level from what it was when tuned for peak signal strength.

But in a regenerative receiver there is no IF stage.  You are listening on the actual frequency. There is no filter and therefore no way to create single signal reception.  The only selectivity you have is that which is created by the detector oscillating. True,  in a well designed regenerative receiver this can be pretty tight,  but there is no way to get the single signal effect.  There are a couple of techniques in tuning that can sometimes help that situation out a bit in a crowded band,  but more on that later.

The other condition that must be dealt with is the fact that a regenerative receiver must actually be in oscillation for the cw signals to be heard.  There is no Beat Frequency Oscillator.  The radio is actually oscillating on-frequency with that signal beating against the incoming signal. If a signal is weak,  this is not a problem,  but if a signal is strong,  it might overpower the internal oscillation,  requiring the amount of feedback or regeneration to be increased. In some designs,  this might cause a shift in frequency. And the incoming signal itself might "pull" the detector off-frequency.

You can see that with all of this going on,  tuning of one of these little jewels to copy a weak signal next to a much stronger one can become bit of an art,  or perhaps better described as a juggling act.

Then there is plain old drift.  These radios are not the most stable of things under the best of conditions. You might be listening to a signal,  waiting for an ID or to copy other information, and notice the pitch slowly, slowly ( or sometimes not so slowly) shifting up or down. One does not take one's hand off the tuning knob of these things.  And the other hand might need to be on the regeneration control.  What does this leave you with to write callsigns on a scratch pad or even put them in the log? Its best to be able to copy in your head and just remember the information until you can let go and write it in the log. Sometimes one hand might be free for a few seconds to write the callsign and other info directly in the log.  This might explain why log entries made using these things are not quite as pretty as they might otherwise be!!

So, again,  why do this? Well, it is a challenge, it is a throwback to younger days during which one can be transported back to see " what might have been" in those days.

( As an aside, some of the stability problems and lack of single signal reception along with overload were some of the same problems I had to deal with in using the old National SW-54!)

All of these conditions might seem enough to deal with in trying to copy cw with this receiver on the best of days with good  band conditions and not much crowding.But then add in the wall-to-wall signal situation you find with a DX contest and mix in the gonzo signals or the big gun DX contest stations running full legal power into huge beams,  and this might seem like total insanity!

After playing with the radio for a few days,  I decided that the best band to try would be forty meters. There would be a very good chance of good DX signals plus the radio was more stable there than on twenty meters. Also the antenna to be used was my 44 foot vertical which is pretty good on forty meters where a quarter wave is 33 feet, but not so good on 80 meters, where the stability of the radio might be better but the antenna is a bit short ( quarter wave on 80 meters is 66 feet and at least a quarter wave is needed to give the lower angle response needed for real DX) The vertical is made of pieced together scrap aluminum,  but RF doesn't care about that. And the vertical does set on a field of 60 radials,  so the little rig will be given a fighting chance.

So here it was, Friday afternoon, nearing 0000 GMT, contest starting time. The SpanMaster had been warming up for an hour,  I had might light early supper and snacks and  "Ham Radio Dad" coffee cup strategically placed around the desk. My usual preparations for tuning through a DX test were all in place,  extra note pads, lots of extra pens, but of course a work-related phone call came just before start up time. But by 0020 that little crisis had been dealt with and my aviation headset was on my head and tuning began.

Whoa! There were a lot of signals on the band!  It was not dark here in Central Texas yet so I was not sure how soon I might find some DX,  so I logged a few domestic stations since I was receiving only.

KU8E and K3ZO were boiling in and fell into the category of those needing to have extra regeneration to copy. At 0030 I heard a weak station and could tell in his report to stations worked he was not giving a state,  but something else.  This told me that he was a DX station because US and Canadian stations give signal report and state in this contest and all others give signal report and their power.

It was going to be difficult to copy him through the heavy stateside qrm,  but I used one of the tricks I had learned years ago. The strong interfering station was above him in frequency,  so I tuned down through zero beat and onto the other side of him,  accenting the difference in pitch.  That helped some, but there were portions of this transmissions that were still being blocked. However, by listening through several contacts,  his callsign and information became readable when they landed at a time when the interfering station was listening rather than transmitting.  This became a bit of the norm during this whole adventure and resulted in sometimes two or three minutes needed to get all the information. So much for logging two a minute as was usual with the R-75 or FT-950!

Finally at 0030 GMT, I copied his callsign: EA3F  Spain!  There was hope this would not be a waste of time!

Even at that the DX did not flood into the log. It was four minutes later before I identified my next "target" and it was a Canadian, VA2UR at 0034.  Five minutes later I copied NP2K in the Virgin Islands, it was six minutes later that I pulled out PJ2T Curacao, but then only two minutes later NP4DX followed by NP4Z, both Puerto Rico.

( Another aside here: Has anyone else noticed that sometimes two stations in the same country will be almost on top of each other? I have noticed this several times over the years.  In this case,  both Puerto Rican stations were audible at the same dial setting and simply separated by the difference in pitch method)

One more Caribbean station was logged before another European call made it. ZF1A in the Caymans was super strong,  up there with the big gun stateside stations.

It was a tough several minutes after that, but at 0113 another station from Spain, EA4W, was logged.
Then three minutes later CR6X from Portugal ( don't get overwhelmed by this high logging rate now!!)

It was eight minutes after that when LZ9W from Bulgaria was pulled out.

And that was kind of how it went into the evening...sometimes three or four minutes between loggings,  sometimes more.

A sample with times followed by callsigns and locations: 0137 OK4Z Czech Republic; 0143 IR2C Italy; 0154 KP4AA ; 0155 EA2W Spain; 0157 IR2Q Italy; 0200 II9P Italy.

Just when it seemed like things were going better there was a gap of fifteen minutes spent trying to identify a weak station that kept getting clobbered.  I could hear the reports he was giving and he was listing his power as a kw, but everytime he gave his callsign,  another station picked that time to call "CQ TEST":  Finally he got a break and gave his call in the clear: 4O4T Montgenegro.

I could see this was going to be a pull. Almost as a gift,  the next one pulled out was only two minutes later: S51YI Slovenia.

It went on like that, sometimes a minute or two,  sometimes as much as 20 minutes before a station could be pulled out. There were a few that I felt noteworthy for some reason: 0244 LU7HY Argentina; 0257 YL7TX Latvia; 0312 IT9ESW Sicily; 0326 KL7RA Alaska; 0327 9A9A Croatia; 0338 EA8RM Canary Islands; 0352 CT1GFK Portgugal.

There were of course,  others in between.  Like I said,  not setting the world on fire in the great scheme of things but satisfying in its own way to log them with a little two-tube radio.

I shut down at 0400 with the plan to get up the next morning to see if any Asians could be heard.

I started the next morning Texas time at 1130 GMT and the start was once again slow:  1149 NP4G Puerto Rico; 1147 P44W Aruba; 1150 CO6RD Cuba. What was this? Was I only going to hear Caribbean stations after getting up early?

Things changed drastically after that. I spent nine minutes trying to pull out the callsign of a station that was listing power as 200 watts.  Over and over his call slipped by me...but it turned out to be a really good one: FK8IK New Caledonia!  That would have been good on any radio!

Minutes later at 1201 GMY an old friend KH6LC from Hawaii showed up. Two minutes after that JE1NHD should up listing a kw; at 1212 GMT a very satisfying ( though also very familiar) ZM1A New Zealand. Then a ten minute gap before another old friend, JH8YOH Japan showed up. Then what I thought would be the prize of the morning at 1228 GMT, VK2IA  Australia. 

It was beginning to seem like it had been worth the effort.  The sun was coming up,  and I knew there might not be much time left,  but there was time to get JK2GRX, JH4UYB, JA6JCE and JH4JNG in the log. 

There was another good one to be had at 1306 GMT with the sun up as ZM4T came in. But to show you the rule about waiting one more bit before shutting down really paid off with the " oh wow" of the morning at 1312 GMT when YB8RW Indonesia came in.

I shouldn't have been too surprised,  because Indonesia always comes in on forty meters a bit after sunrise,  but I really did not expect it on the SpanMaster.

I shut it down after that, very pleased with the results.  Of course nothing like the usual two to three a minute that can be pulled in with the R-75 with two back to back 250Hz filters or the FT-950 tightened down all the way.  But very pleasing all the same.

It raised questions about my early days, however.  How did I miss all this stuff with the NC-88 which even such that it was should still have stood shoulders above the SpanMaster?  I guess the answer is in skills learning to copy through QRM through the years or something.  My horizontal antennas back then were not very high,  but I did have a vertical then too ( though it was a Mosley V-4-6 trap)  Who knows?

But whatever it was,  this was a great adventure of its own and won't be the last time I hunt for DX with the SpanMaster.  

There have also been other nights that I have spent time listening with the Hallicrafters SX-71 and SX-96 which both do very well on cw DX...and also the somewhat simpler Hallicrafters S-118.  For some reason using them has brought back some of the real electric excitement to the hobby....almost like back in the days when an 11-year-old boy went running through the house yelling, " Hey Daddy, hey Mom, come look what I heard!!!" 

Its a great hobby.  And I never know what might show up when I tell my wife as my old late friend Earl Sterling used to say, " I think I'm going for a short walk around the world."

1 comment:

  1. It seems I heard most of the same stations as you did. But it sure does seem like my 7300/6BTV favors South America. I worked the NP/KP4 stations and a KH and nothing in Europe/Asia. I did hear FY5KE but never could return transmission.

    Only worked 20 stations but still had fun nonetheless.

    I will try to post my contest log here or on Facebook.

    de kc5ngx