Notes on the Crystal Set DX Contest
The Crystal Radio DX contest, held from 16 to 26 April 1999, was an interesting experiment. All business was conducted in cyberspace, on the web, except for some snail mail forwarding of entries. Ten entries were received after the contest; not as many as we were hoping for, but enough to get a good feel for the possible, what works, and what really works. Here is my analysis based on a review of all the entries submitted.
Results: Bottom line.
Stations heard ran from 6 (then the antenna broke) to 59.
The top score was over 78,000 points (Larry Pizzella), based on each station counting the maximum of either 25 points or 10 x distance (km) divided by power in kw. You can read all about it in his account in the Sep 99 XSS newsletter.
Seven entrants reported receipt of dx stations, and three reported only locals.
The top 5 scorers heard over 50 stations each. The remainder heard from 6 to 17 stations.
The break in performance appeared to be between #5 and #6 - 17,392 vs 2271 points (for 55 and 15 stations, respectively.
The point spreads in the high station count entries were heavily influenced by a few low power/distant stations; one such station accounted for over 40,000 points.
The top 5 all used decent outside antennas, from 65 to 200 feet of wire in the air.
The top 5 used antenna tuning. Of the remainder, one used a tuner, but with a short indoor antenna. One other entrant used a set with a capacitor in the ground circuit for antenna tuning.
Attention to coupling, impedance matching and circuit Q was an important factor.
The top 3 used big (3 inch diameter and larger) coils and big gage wire like #16 space wound or basket wound).
Number 4 used toroid coils for Q and efficiency (and elimination of out of band "ghosts").
Selectivity when you needed it; this included the judicious use of wave traps, hi Q circuits, and variable coupling between tuned circuits.
What didn't work as well:
Indoor and short antennas, single-tuned sets, lower Q circuits, and using "classic" coupling methods, such as direct coupling antenna to top of tank circuit, direct coupling antenna to tank circuit anywhere, and tapping detector to top of tank circuit (unless you did it as Al Klase did by using a 100k transformer after the detector)
What didn't matter as much as we thought it might?:
Headphones/earplugs - pretty much everything worked as long as it had good sensitivity and was properly matched - crystal earplugs, antique Baldwins, sound powered phones, low impedance "walkman" phones.
Detectors - everything was used, and seemed to work pretty well - 1N34 diodes and galena detectors were the industry standards. Diodes in parallel, double diodes feeding separate earphones, razor blade and flame detectors (when the signals were strong - get a point multiplier for them and rocks), and biased transistor b-e junctions.
Location - winner was given unofficial crying towel award due to his moaning about how the strong locals would shut him down, before the contest, that is. #2 (Dave Cripe) lives in the boonies with no strong stations nearby; didn't bother using a wave trap 'cuz he didn't need it, while #1 used 3; two in the antenna line and one inductively coupled to the tuning coil. Actually, I suspect there are some problems with location, but we had a small data base, and don't know about the ones that couldn't hear much and didn't enter. However, of the three entrants that didn't get any dx, one used a small indoor loop for his antenna and tuning coil, one had an indoor antenna, and the third had a short (28 foot total) antenna. Also, some people put a bunch more time in than others, I suspect.
What we didn't learn:
Antennas- each entrant seemed to use the same antenna throughout, so I don't have any comparison info from high scoring entrants, such as a vertical sometimes outperformed a flat top in the same location. No one reported specialty dx antennas, such as rhombics or beverages.
Tricks of the pros:
Listen throughout the day and night. New stations were heard during times when you don't expect anything new, such as at mid day or late afternoon. Stations that change power, or sign off and on during their broadcasting day offer opportunities, such as unmasking that small guy on or close to their frequency. Another profitable time for me was about an hour either side of sunrise, when some medium distance low power stations were starting their broadcast day.
Patience and slow tuning. During casual listening, we often pass right over stations that are there all the time, but have a weak signal.
Keep the ambient (room) noise level down. Dave Cripe used a pair of Mouser earplugs under shooter's earmuffs, and Larry Pizzella used muffs over his walkman earbuds.
All the top scorers used both ears to listen.
Believe that if you can hear them on your superhet, you can hear them on your crystal set. Larry Pizzella used his signal generator to spot the crystal set on a station's frequency, and then waited for the station to come in.
Use "tuning aids": At a minimum, this is a reasonably well calibrated superhet to check frequency and screen out stations already heard. You can also use a sig gen to put the xtal set on frequency, and can use an unmodulated rf signal from your sig gen to inject a carrier into your set on a frequency you are watching; it can bring in a station sooner, and then you can turn your injected carrier off to listen barefooted. It is a truism that once you pick up a station, by any method, that you can often continue to hear it well even if you shift to a different detector, different phones, or while you fiddle with the antenna tuner or coupling.
Determine your optimum set configuration, but feel free to fiddle. Use different phones, particularly if they "sound" different (different frequency response), and different detectors. Play with your coupling and your traps.
When a strongish dx station shows some fading, wait around to see if it is masking another station. A corollary to this is to revisit old haunts from time to time. If you are periodically bedevilled by out of band ghosts, as I am, be patient; they are subject to fading as well. Mine tended to show up around sundown and hang around for several hours.
Check on your weaker "band marker" stations periodically during a long contest. If you don't receive them as well as you expect, your rig might have developed a problem, such as a loose connection (or a blown down antenna).
When searching a specific part of the band, use a weak station you can hear to peak up your rig's settings.
Be kind to your spouse. Nothing distracts like a feeling of impending doom or a nagging reminder that the trash needs to go out.
A#1 - Larry Pizzella's monster rig (operating manual not included). Larry says he is going to send in specs on his rig to the Xtal Set Society newsletter; another good reason to join if you haven't already. This is a triple tuned rig with 3 traps; for professional use only.
Another big radio, used by Richard O'Neill (#3 in the contest). Tuggle Circuit with Hi-Q coils
Al Klase's (#4 in the contest) modernized blast from the past (antique parts with toroid coils), with operating instructions: Go here
Final Comments: The results in the contest were simply great, by everybody that participated. A year or so ago, I myself felt that getting a few local stations, like two or three was doing well. And, for many set owners, using short antennas and simple sets, a couple of stations is about all they should expect. We tend to forget that these so called "toy's", as many people regard crystal sets, were once the industry standard, taken seriously because there were no other options for radio communications. When the vacuum tube was perfected, the crystal set and a body of technology was dumped in favor of tube rigs, and we are slowly resurrecting lessons learned several generations ago, and applying new technology to make even better these radios that work for free.
My contest log ( I was the #5 guy)