Posts Tagged ‘crystal radio’
The first time I was involved with a crystal radio DX contest was about 20 years ago when I built a well-performing crystal receiver for the Yahoo Crystal Radio Group's annual DX contest. It was a great learning experience and taught me much about circuit losses and how to overcome them. I originally built several sets but was unable to hear anything other than local stations until I eventually figured things out ... the system was only as good as its weakest link or links!
Fast forward to more recently when I obtained and wrote about the Heathkit CR-1 Crystal Radio, a simple but very well-designed tuner that has become popular with collectors. Using the CR-1 re-kindled my interest in the DX contest activity of years ago and when talking with two other amateurs that had an interest as well (one had also been in the earlier contests sponsored by the Alabama Crystal Radio Group), we decided to bring the contest back once again. The Facebook Crystal Radio DX Contest Group was formed last fall, a set of rules drawn up and the contest date set for the first week of January of this year. This gave interested participants plenty of time to build something they could use in the contest.
I spent all of December designing and constructing a new contest radio, hopefully one with enough selectivity to get around the 15 local flamethrowers (10-50kW S9++ signals) that plague the band for me and eventually drove me from crystal radio activities.
The new radio makes use of several 'traps' to null strong signals ... two are in the antenna line while one is loosely coupled inductively to the detector tank circuit. The two inline trap coils are wound with Litz wire on ferrite toroids (R40C1) while the third is a basket-wound Litz coil (660/46) on a 4" diameter form.
The antenna tuning stage also uses the same ferrite material but in the rod / bar form. I wound a low-end as well as a high-end coil for the tuner using the same high-count Litz as on the big trap coil. The low-end coil is wound on a bundle of three rods while the high-end coil uses a single rod.
The detector stage uses another Litz coil with this one being solenoid-wound on a 4" diameter form. Both the antenna tuner and the detector use excellent quality hi-Q ceramic insulated air variable capacitors (18-360 pfd). All components that handle RF are insulated from the plywood bases in order to reduce losses. Moving a capacitor from the plywood to the insulated standoffs makes a noticeable difference, something learned the hard way years ago but actually measured while using the new radio.
The detector also has provisions for comparing various diodes as not all diodes are created equal ... not even all diodes with the same number! When testing and comparing diodes of the same type such as the popular 1N34 germanium, every once in awhile one of them will turn out to be noticeably more sensitive than the others. In my built-in B-A-C diode test module, the hottest diode is always mounted in middle-position A, making it easy to quickly compare by switching to the left for B or to the right for C. So far the best one I have found is the vintage Russian D18 germanium diode but an old 1N34 removed years ago from a 1950s-era Heathkit has given it a good run for the money! I've still several hundreds of early germanium diodes, pulled from old diode matrix boards years ago, to test against the D18 as well as numerous Schottky diodes.
Also on board the detector module is a Selectivity Enhancement Circuit (SEC) that increases selectivity by unloading some of the diode's effect on the detector coil, similarly to tapping the diode further down the tank coil. It uses a small butterfly capacitor seen to the right of the main tuning capacitor in the photo above. I found it extremely effective when needed and is well worth the addition to a high-performance tuner.
The detector stage is followed by an impedance-matching transformer for the sound-powered headphones. This stage also houses a 50uA meter to measure diode current / signal strength levels.
The meter can be switch-bypassed to prevent needle-bounce on stronger signals. It is particularly helpful when using the traps to null a signal to the minimum level.
The three traps utilized have been very effective in eliminating what I had originally perceived as an impossible DXing situation.
Here are the daytime-power signal strengths of my 15 line-of-site blowtorch stations that, without trapping, very effectively block most sections of the band. Anything over 50uA is ear shattering and problematic, usually requiring the use of all 3 traps:
KVRI 1600 50uA
KRPI 1550 100uA
CJVB 1470 40uA
CFTE 1410 350uA
CHMB 1320 100uA
CJRJ 1200 400uA
CKWX 1130 300uA
CKST 1040 90uA
CKNW 980 150uA
KGMI 790 100uA
CHMJ 730 450uA
CBU 690 650uA
CISL 650 200uA
CJWW 600 100uA
KARI 550 100uA
Overall I was very pleased and surprised at the good performance of the new radio. During the contest period I identified and logged 92 unique stations in 16 states / provinces. More than one station was logged on 9 different frequencies as the propagation varied from night to night.
Highlights of the DX Contest were hearing WHAS in Kentucky (2,007 miles), WJR in Michigan (1,970 miles), KXEL in Iowa (1,556 miles), WCCO in Minnesota (1,423 miles) and CBW-990 in Winnipeg, smack up beside local blowtorch CKNW-980! Additionally, hearing Washington state 250 watter KFLD-870 and 250 watt KWBY-940 in Oregon were great surprises.
I found the use of a spotter radio (Sony ICF-2010) to be very useful in locating signals to target and to zero-beat with an RF signal generator. The generator’s tone-modulated signal can then be tuned in and the xtal radio and antenna / detector stages optimized.
From here, any pest signals are then tuned to and individually nulled using the traps while watching the signal meter. Antenna and detector stages are then re-tweaked before disabling the generator and listening for the desired signal.
Often it is heard immediately following the above tuning procedures but if not, monitoring the frequency for several minutes often allows time for the weak signal to fade up to audible levels.
Comparing programming audio with what is heard on the spotter radio will confirm hearing the correct signal as will comparing audio to the station’s own live-feed on the internet.
Due to the larger and much better antenna (inverted-L 70’ x 100’) on the crystal radio, I would often hear good audible signals on it and not on the spotter (something that I found surprising) so often times it was productive to just tune around the band on the crystal radio, tweaking stages as required.
I’m looking forward to further improvements of the tuner as well as to the next DX Contest whenever that will be scheduled ... hopefully you can join in as well!
FREQ UTC STN LOCATION MI
550 1:04 KARI Blaine, WA 25
560 1:30 KPQ Wenatchee, WA 168
570 3:45 KVI Seattle, WA 107
580 3:42 KIDO Nampa, ID 492
600 1:17 CKSP Vancouver, BC 32
610 4:15 KONA Kennewick, WA 271
620 1:22 KPOJ Portland, OR 241
630 3:40 CHED Edmonton, AB 530
630 21:10 KCIS Edmonds, WA 87
650 1:05 CISL Richmond, BC 24
660 3:30 CFFR Calgary, AB 693
660 21:23 KAPS Mt. Vernon, WA 52
670 3:25 KBOI Boise, ID 807
690 1:06 CBU Vancouver, BC 19
710 3:21 KIRO Seattle, WA 108
730 1:02 CHMJ Vancouver, BC 22
750 3:55 KXTG Portland, OR 243
760 4:01 WJR Detroit, MI 1970
770 3:17 KATL Miles City, MT 831
780 4:00 KKOH Reno, NV 658
790 1:07 KGMI Bellingham, WA 39
810 4:05 KGO San Francisco, CA 786
820 1:59 KGNW Seattle, WA 106
830 2:20 WCCO Minneapolis, MN 1423
840 4:10 CFCW Camrose, AB 530
840 4:00 WHAS Louisville, KY 2007
850 4:20 KOA Denver, CO 1118
850 1:12 KHHO Seattle, WA 121
860 3:48 CBKF Saskatoon, SK 758
860 1:04 KPAM Troutdale, OR 226
870 4:30 KFLD Pasco, WA 266
880 1:17 KIXI Seattle, WA 102
890 4:35 CJDC Dawson Creek, BC 494
900 4:38 CKBI Prince Albert, SK 810
910 4:40 CKDQ Drumheller, AB 468
920 4:42 KXLY Spokane, WA 285
930 1:50 KBAI Bellingham, WA 37
940 4:45 CJGX Yorkton, SK 940
940 0:58 KWBY Woodburn, OR 256
950 4:50 KJR Seattle, WA 106
960 4:52 CFAC Calgary, AB 444
970 4:55 KBUL Billings, MT 722
980 1:08 CKNW New Westminster, BC 32
990 4:58 CBW Winnipeg, MB 1156
1000 3:45 KOMO Seattle, WA 105
1010 4:59 CBR Calgary, AB 453
1020 0:54 KWIQ Moses Lake, WA 216
1030 5:06 KTWO Casper, WY 918
1040 1:09 CKST Vancouver, BC 23
1050 5:10 CJNB N Battleford, SK 707
1060 5:07 CKMX Calgary, AB 441
1070 5:10 cfax Victoria, BC 33
1080 0:33 KFXX Portland, OR 232
1090 1:40 KFNQ Seattle, WA 109
1100 3:55 KFAX San Francisco, CA 779
1110 5:15 KRPA Oak Harbor, WA 48
1120 0:48 KPNW Eugene, OR 340
1130 1:10 CKWX Vancouver, BC 22
1140 5:20 CHRB High River, AB 443
1150 5:50 CKFR Kelowna, BC 185
1160 5:53 KSL Salt Lake Cty, UT 781
1170 1:11 KPUG Bellingham, WA 39
1180 5:09 KOFI Kalispell, MT 416
1190 5:55 KEX Portland, OR 241
1200 1:12 CJRJ Vancouver, BC 23
1260 5:58 CFRN Edmonton, AB 522
1290 6:00 KUMA Pendleton, OR 306
1290 6:00 KGVO Missoula, MT 449
1320 1:13 CHMB Vancouver, BC 23
1360 6:12 KKMO Tacoma, WA 115
1370 4:32 KXTL Butte, MT 535
1380 6:16 KRKO Everett, WA 88
1410 1:14 CFTE Vancouver, BC 22
1460 1:55 KUTI Yakima, WA 207
1470 1:15 CJVB Vancouver, BC 25
1480 1:20 KBMS Vancouver, WA 227
1520 1:05 KKXA Snohomish, WA 88
1520 1:13 KQRR Oregon City, OR 241
1530 4:30 KFBK Sacramento, CA 698
1540 1:50 KXPA Bellvue, WA 102
1540 4:46 KXEL Waterloo, IA 1556
1550 1:16 KRPI Ferndale, WA 31
1560 1:14 KVAN Burbank, WA 272
1580 6:25 KGAL Lebanon, OR 297
1590 1:22 KLFE Seattle, WA 91
1600 1:00 KVRI Blaine, WA 25
1620 1:30 KYIZ Renton, WA 111
1640 6:45 KDZR Lake Oswego, OR 239
1660 0:56 KBRE Merced, CA 812
1680 1:35 KNTS Seattle, WA 91
1690 0:53 KFSG Roseville, CA 705
|BCB Ferrite Loopstick|
Regular blog readers may recall my two previous blogs, on the Heathkit CR-1 crystal radio receiver.
This very much sought-after radio is a well engineered ‘double-tuned’ set utilizing a series-tuned antenna tank circuit coupled to a parallel-tuned detector tank.
Both coils are wound on the same 1/4” diameter tubular form containing two ferrite slugs ... one for the antenna coil and one for the detector coil. The coils have been pre-wound and fixed on the form, about 20mm apart while the slugs have been waxed in place to set each inductance to the desired value.
|courtesy: Scott's Crystal Radios|
I do wish that I'd had enough sense when I was a kid to buy myself a CR-1 as it seemed like they were dirt-cheap.
The $7.95 even included a set of headphones! Of course, $7.95 to a 12 year old was probably a lot of money, being about $70 in today’s currency!
My previous experience with homebrew DX crystal radios (ones that can hear stations other than strong locals) had taught me that they required large coils and ‘hot’ diodes. The CR-1 has neither of these yet it performed exceptionally well during the few weeks of evening tests a few months ago. I was able to log 50 stations, as described in the earlier blog ... and began to see that, just maybe, requirements may not be as rigid as I had always thought, when it comes to building DX sets!
When I discovered several ‘new-in-the bag’ broadcast band ferrite loopsticks in my junk box, I realized there might be an opportunity to allow me to make something very similar to the CR-1 circuit.
These are the same loopsticks used in the crystal ‘Rocket Radio’ of the 50s or in various transistor radios of the day.
I breadboard-mounted the two loopsticks so that the distance between the antenna coil and the detector coil could be adjusted, allowing some control over coupling and selectivity ... something not available with the stationary CR-1 coils.
Using the same antenna, headphones and external wavetraps, proved once again the excellent performance available from a very small and simple hi-Q coil system ... a DX machine without huge coils and expensive Litz! A total of 51 stations were logged over a two-week period, one more than was heard with the CR-1 and with a few ‘almost’ heards still waiting for one of those really good propagation nights. Having the ability to adjust the coupling was very helpful and made some of the weaker stations a little easier to detect. Stations in RED are local strong signals while those in BLUE are skywave propagated DX signals:
Mounting one of my old HRO 'PN' vernier dials on the main tuning capacitor provided plenty of bandspread, with each dial division corresponding to ~ 2kHz. It was very easy to locate any given frequency within the broadcast band once the dial was calibrated.
Soon after, I ran across a post by Zoltan Pap on Facebook’s ‘Crystal Set Radio Group’, describing his unique use of an old 455kHz I.F. transformer in a crystal tuner. I thought this was a rather brilliant idea and dug out an old I.F. can from the junkbox to see what it might offer.
The old I.F. can had two litz-wound (10 strand) tank coils, fixed in place over two adjustable ferrite slug cores ... in reality, something very similar to the, now very difficult to find, ferrite loopsticks used above.
The two inductors measured out at ~ 700uH - 1.1mH as the slugs were tuned from one end to the other. I was aiming for something close to the inductance used in the two CR-1 tank coils ... approximately 380uH.
A sufficient number of turns were removed from both coils to yield the needed inductance and both coils on the CR-1 breadboard clone were replaced with the old I.F. can coils.
In just a few minutes of tuning through the band, it was very easy to hear and separate all 16 local stations (RED in the above log). A few hours after sunset (on a not-so-good night) yielded quick copy of KPOJ (620kHz) in Portland, Oregon (231 miles) as well as CHED (630kHz) in Edmonton, Alberta (534 miles), demonstrating that even this old 1940's I.F. can could be turned into a crystal radio DX machine!
I don't believe the 'Q' of this pair of coils is very high, compared with the smaller loopstick, as its selectivity appears to drop off above 1000kHz. I'll try separating the form into two halves so that the coupling can be adjusted. The experiment is still under way but if you want to play and can't lay your hands on the pricey loopsticks, old I.F. cans are often much easier to find and probably a lot cheaper.
If you’re a regular blog reader, you will likely recall my description of “The Enigmatic Heathkit CR-1 Crystal Radio” a few weeks ago.
Back then I mentioned that I was ‘eager to get my mitts on one’ and that I had arranged to borrow a CR-1 from another VE7 who was fortunate enough to own one.
A few weeks after posting the blog, I received an e-mail from Larry, WB5OFD, in Texas.
"Reading thru your blogs the other night ... discovered your article on Crystal Radio reception reports. I am in the process of disposing of a lot of radio gear I have collected over the past sixty years and in that pile is a Heathkit CR-1. Yours for free if you would like to have it."
Needless to say I was overjoyed, both at the opportunity to actually own a CR-1 myself and at Larry's exceptional generosity!
Larry went on to explain that he had been in the Air Force and his little CR-1 had been all around the world with him, from Alaska to Turkey ... but from its fine appearance, you would never know it.
He was happy to pass it on knowing that it was going to a good home. I am most appreciative of this kind gesture from a fellow radio amateur, knowing that these things are not too easy to find ... and are somewhat pricey!
As can be seen in the schematic diagram above, the CR-1 is a simple double-tuned crystal receiver, utilizing a series-tuned tank circuit for antenna-tuning, coupled into the detector tank circuit. The detector diode, a 50’s-era 1N34, is tapped down on the tank for headphone impedance-matching and to reduce circuit loading. Reducing the load on the tank circuit improves selectivity but diminishes sensitivity. Crystal radio design is always a trade-off between these two critical characteristics.
Although I had heard good things about the CR-1, I must admit that I was somewhat skeptical ... just how good could an unmodified CR-1’s simple double-tuned design really be? I was about to find out.
My listening location, on the eastern shoreline of Mayne Island, puts me directly across several miles of saltwater from sixteen exceptionally loud 'blowtorch' signals whose antennas are located near the water on the other side of Georgia Strait. Six of these stations run 50kW ... 24/7. All of these signals are wide and strong, being well-over S9. It is a difficult location for crystal radio DXing as separating weak DX signals from the blowtorches can be challenging.
My previous experience with crystal radio DX is well-documented on my website here. Back then, I quickly adopted the standard protocols to help hear DX. This included the use if a separate ‘spotter’ radio to first find signals that might possibly be strong enough to be heard on the crystal detector. I also used an RF signal generator that let me temporarily put a weak tone-modulated carrier on the frequency of a station that I was trying to hear. Using the tone, the antenna tuning as well as the detector circuit can be optimized for maximum signal. I also used a 100 microamp meter in series with the headphones to make peaking these circuits accurately. The same protocol was used for my CR-1 DXing as well.
Since there are so many very strong signals here, I have added two inline L-C traps on the antenna lead.
My first trap was made from a ferrite bar loopstick inductor salvaged from an old transistor radio.
The second trap is made with a ferrite toroid and Litz wire and produces deeper nulls than the ferrite bar. The bar will soon be replaced by a second toroid trap.
The traps allow me to significantly null any strong signals that could be covering up a nearby weaker signal. For nulling, I set the signal generator on the frequency of the pest signal and then tune the trap for a null while watching the meter. Once everything has been tuned, I’ll often just sit and wait for the desired signal to fade up to a detectable level on the crystal radio and then confirm its audio match to what can be heard on the spotter radio. Very often, a signal initially too weak to be detected, will quickly pop up in signal strength to an easy-copy level for several minutes, before dropping below the threshold of diode detection level once again.
I am presently using a pair of RCA WWII sound-powered ('Big Cans') phones, impedance matched to the CR-1’s output with a multi-tap audio transformer. I have also used a nice set of extremely sensitive Western Electric 509Ws, manufactured in the late 20s. These are also impedance-matched to the CR-1's output. On weak signal tone tests, I can see only a very tiny improvement with the RCAs versus the old 509Ws as both are very sensitive.
There is a large variation in propagation quality on the broadcast band, especially this far north on the southern edge of the auroral zone. The difference from one night to the next can often be quite dramatic. On most nights the band favors the north-south path while on geomagnetically quieter nights it’s the east-west path that dominates. The band needs to be in good shape for any worthwhile hope of DX on a crystal radio.
On one of the recent better nights, of which there have been very few of lately, one of the stations in Alberta was so strong that it needed trapping! This was something I saw quite often with my previous DX set but I didn't expect to see it with the CR-1.
For crystal radio DX, propagation is the best helper. Small incremental improvements (in terms of db losses) can be made in any part of crystal radio's systems but on nights of good propagation, tens of db improvement will magically appear, thanks to Mother Nature!
When in Turkey, Larry had the opportunity to connect the CR-1 to the large FLR-9 circular antenna array used during the cold war for HF direction-finding of targeted signals. Covering 1.5MHz to 30MHz, the FLR-9 consisted of ninety-six 120' towers, suspending 1056 vertical elements ... all over a 1500' diameter ground screen! His notes show that he logged the BBC, Italy and West Germany on the CR-1 while using the array!
|The FLR-9 array in Augsburg, Germany|
Over the past few weeks, I have been spending a few nights patrolling the band between 9:30 and 10:30PM, to see what might be heard with the CR-1. So far, I've logged 50 different stations ... far more than I had expected to hear.
The log below shows all of the stations heard. The stations in red are all local line-of-sight transmitters and are extremely strong ... all are well over S9 on my Sony spotter radio. The stations shown in blue are all ‘DX’, with the furthest so far being KOA in Denver, at 1100 miles.
The log illustrates just how much the blowtorch signals prevent weak-signal detection, even with traps! The stations logged on 1510 and 1530 were only possible when the 1550 blowtorch lost their audio for about five minutes one evening! Selectivity becomes increasingly more difficult towards the top end of the band and, unfortunately, there is a larger concentration of strong locals (who seem to delight in over modulation and splatter), making reception up there extremely challenging.
There are still some lower-band signals that I have yet to log and they have been gradually growing stronger as the nights get longer. As well, the region above 1600kHz may still provide a few opportunities over the next few weeks, if the loud local on 1600 can be sufficiently trapped ... the next few weeks will tell if there’s anything left in the CR-1’s tank!
When it comes to crystal radios, there is nothing revolutionary regarding the CR-1’s basic circuitry but for some odd reason, it has achieved cult-like status as well as high dollar value.
|courtesy: Scotts Crystal Radios|
The article that piqued my interest appears on 'Scott's Crystal Radios' website and makes for an inspirational read, eventually revealing the inside core arrangement of the ferrite-loaded tuned circuits via an actual X-ray of the device! By the way, if you are looking for a nice set of older headphones, Scott's website is the place to visit!
|courtesy: Scott's Crystal Radios|
Scott was eventually able to achieve performance equal to that of his borrowed CR-1, with his own slightly modified versions, all in a similar-sized footprint. Perhaps this is one reason why the CR-1 is so much sought-after, as good performance in a very small package is not the norm when it comes to crystal radios. It's usually a case of ‘the bigger, the better’ when it comes to performance.
A recent search of my junque box revealed several NIB ferrite loopsticks that would allow a potntial reproduction of this interesting circuit.
Several years ago I spent an eye-opening winter learning about DX crystal radios as up to that time I had always believed it would be impossible to hear anything other than strong local signals on a crystal radio. I quickly discovered that there was a very large Crystal Radio Yahoo Group where menbers were working at the leading edge of crystal radio design. I also found that the group sponsored an annual Crystal Radio DX Contest which inspired me to dig deeper.
It wasn’t too long before I decided to join the fun and attempt to build a crystal radio DX-machine but I was in for a few surprises and a long learning curve ... it seemed that hearing broadcast band ‘DX’ on a crystal radio (anything other than loud locals) was not going to be an easy task!
Over the course of several months I tried many types of variable capacitors, tank coil configurations and antenna tuning circuits. I even erected a dedicated antenna system for the various experimental circuits I was putting together ... an 'Inverted-L', 50’ straight up and 70’ horizontal, along with a ground rod connected to several buried radials.
I quickly learned about something I normally didn’t have to worry about when working with ‘active’ devices and that was overcoming system and component losses. In critical crystal radio design, it’s all about minimizing the losses in every stage and every component in the system since there are no amplifiers to help overcome these losses. Your system is only as good as the weakest link. In true crystal radio DXing, no active devices are permitted ... it’s just your crystal radio and the energy generated at some, hopefully far away, transmitter site!
After several months, I eventually ended up with a well-performing triple-tuned set that used lots of 'trapping' because of all of the very strong nearby signals here ... eight 50kW locals!
A description of the learning curve, with several do's and dont's to help new builders, can be found on my website here.
Back then, 80 stations were logged (from my location on Mayne Island in SW British Columbia) over the one-week Crystal Radio DX Contest.
SAN FRANCISCO, CA
100 MILE HOUSE, BC
MERCER ISLAND, WA
DAWSON CREEK, BC
NEW WESTMINSTER, BC
SALT LAKE CITY, UT
SAN ANTONIO, TX
ST. MARIES, ID
MEDICINE HAT, AB
TWIN FALLS, ID
LAKE OSWEGO, OR
ST. PAUL, AB
OREGON CITY, OR
SAN JOSE, CA
LAKE OSWEGO, OR
BRIGHAM CITY, UT
Old notes indicate that there were 14 stations at S9 or higher, requiring heavy trapping to hear anything close to their frequencies.
|My recent interest made me wonder what the situation is today when it comes to the number of strong local ‘blowtorch’ signals, surely the bane of all crystal radio DXers? Although there have been a few changes over the years, a quick scan of the band during the prime DX evening hours found that although one of the blowtorch signals (at 600kHz) was now gone, another had appeared at 1200kHz ... sadly no net difference.|
The top end of the band, always a prime area for good skywave DX, is unfortunately still dominated by a huge signal from KVRI just across the water near the Canadian / U.S. border. If KVRI were silent, the top end would be a wonderfully quiet hunting-ground for new catches. The new local blowtorch (CJRJ) on 1200 kHz will now cause problems for the middle of the band, which was always a good region for DX.
So it seems overall, there hasn’t been a huge change here other than in the middle of the band. It looks as though there are still some good watering-holes to be had but several traps will still be needed in any new system.
Once my present radio-bench project is finished (a '36 RK-39 crystal power oscillator) I’m looking forward to more research and design of a couple of new systems, starting with something similar to the CR-1 as well as some experimentation with toroidal coils. I always find the research and planning phase of any new project more interesting and fulfilling than the actual construction and implementation! Hopefully I’ll have something ready for the fall DX season!
Thanks to VA7MM, I will also have the loan of an original CR-1 next winter to make comparisons to any clone that I might build!
If building a DX-crystal radio is something that might interest you, there are several great websites offering inspiration and helpful info. The links for these may be found at the bottom of my own crystal radio page. As well, there are two active crystal radio groups on Facebook, where daily two-way discussion can be had.
Perhaps, with enough new interest, we can even revive the annual Crystal Radio DX Contest!