Monday, 23 September 2019

Recent BCB Loop DX / Upcoming CLE248

This past week has seen a welcome return to better band conditions on the lower frequencies.

I’ve had my 10' x 20' loop and Perseus SDR combination running a few overnight recordings on the AM broadcast band ... two mornings pointing at Asia and two overnights looking for domestic signals from the east.

The Asian signals have often been very strong, with many signals reaching S9 or higher. I’ve chosen some of the better ones below. Unlike those situated right on the west coast, my location here on Mayne Island gives me a nice shot towards Japan albeit not directly over the ocean, but close enough, as the path crosses islands to my north and then over northern Vancouver Island.

Looking towards eastern North America is a different story, with an unobstructed ocean view from due north to the south east.

As is often the case with overnight recordings, I did not get nearly enough time to thoroughly check them out but one catch caught my attention. It was from WPTX in Lexington Park, Maryland, on 1690kHz. This station supposedly runs 1kW at night and 10kW during the day but on this night (Sept 16), I heard their top-of-hour ID for three consecutive hours! I wonder if someone ‘forgot’ to switch to nightime power or if conditions were just really good? I have heard them again since with two TOH IDs but much weaker and sounding more like a 1kW station should sound!

JOAK - 594kHz in Shobu, Japan (13:30 UTC Sept 20)

JOUB - 774kHz in Akita, Japan (14:00 UTC Sept 20)
(with English lessons)

HLAZ - 1566kHz in Cheju, South Korea (13:30 UTC Sept 20)
(broadcasting in Japanese in this time slot)

Voice of America (VOA) - 1575kHz in Ban Phachi, Thailand (13:30 UTC Sept 20)
(listen for "This is the Voice of America" ID and then into "Yankee-Doodle-Dandy")


Hunting For NDBs In CLE248

Yes! Another month has passed and it's CLE time once again.

This time the hunting grounds will be: 275 kHz - 425 kHz.   

For those unfamiliar with this monthly activity, a 'CLE' is a 'Co-ordinated Listening Event', as NDB DXers around the world focus their listening time on one small slice of the NDB spectrum.

If you've been meaning to participate in  CLE, then maybe this weekend is a fine time to try! Lately, we've had a lot of first time submissions so you won't be alone!

As well, if you're trying to learn CW, copying NDBs is perfect practice, as the identifier speed is generally slow and the letters are repeated again every few seconds!

At this time of the season, summer lightning storms should be starting to wane and propagation can often be as good as mid-winter if the lightning cooperates.

When tuning for NDBs, put your receiver in the CW mode and listen for the NDB's CW identifier, repeated every few seconds. Listen for U.S. NDB identifiers approximately 1 kHz higher or lower than the published transmitted frequency since these beacons are modulated with a 1020 Hz tone approximately.

For example, 'AA' near Fargo, ND, transmits on 365 kHz and its upper sideband CW identifier is tuned at 366.025 kHz while its lower sideband CW ident can be tuned at 363.946 kHz. Its USB tone is actually 1025 Hz while its LSB tone is 1054 Hz.

Often, one sideband will be much stronger than the other so if you don't hear the first one, try listening on the other sideband.

Canadian NDBs normally have an USB tone only, usually very close to 400 Hz. They also have a long dash (keydown) following the CW identifier.

All NDBs heard in North America will be listed in the RNA database (updated daily) while those heard in Europe may be found in the REU database. Beacons heard outside of these regions will be found in the RWW database.

From CLE organizer Brian Keyte, G3SIA, comes the details:

Hi all

Our 248th Listening Event just squeezes into the last weekend of this month.
Worth waiting for because it is a 'Special', our fifth 'Channels Challenge'.
It's a simple idea, but one that we always seem to enjoy:

    Days:      Friday 27 September - Monday 30 September
    Times:     Start and end at midday, your LOCAL time
    Range:     275 kHz - 425 kHz   (see below)
    Target:    Try to log ANY ONE NDB in each channel

The 'channel' means the NDB's nominal (published) frequency.
EITHER  321.0  OR  321.5 kHz would be OK for channel 321, etc.

So it means a possible maximum of 151 loggings in all, though that would
probably be miraculous, even for the best placed of us!

All the NDBs must be 'normal' ones (no DGPS, Amateur, etc.) and
no UNIDs in your main list.   Yes, it does include those more
challenging frequencies in the DGPS range.

If you want to add extra interest you could also choose to:
    Maximise the number of radio countries you hear    or
    Maximise the total distance to the NDBs you hear    or
    Maximise the number of 'midday' loggings - i.e. NDBs logged
      within 2 hours of midday by your local winter clock time.

It will be extra tough for North American listeners, with their many 'empty'
channels. Southern Hemisphere and Europe listeners should be more lucky.

Our last 'Channels Challenge' was CLE231 in April 2018.
Please look out for the 'Final Details' a few days before the start.

From:   Brian Keyte G3SIA               (CLE coordinator)

These listening events serve several purposes. They:
  • determine, worldwide, which beacons are actually in service and on-the-air so the online database can be kept up-to-date
  • determine, worldwide, which beacons are out-of-service or have gone silent since the last CLE covering this range
  • will indicate the state of propagation conditions at the various participant locations
  • will give you an indication of how well your LF/MF receiving system is working
  • give participants a fun yet challenging activity to keep their listening skills honed

The NDB List Group is a great place to learn more about the 'Art of NDB DXing' or to meet other listeners in your region. There is a lot of good information available there and new members are always very welcome. As well, you can follow the results of other CLE participants from night to night as propagation is always an active topic of discussion.

You need not be an NDB List member to participate in the CLEs and all reports, no matter how small, are of much value to the organizers. 

Remember - 'First-time' logs are always VERY welcome!

Reports may be sent to the NDB List Group or e-mailed to CLE co-ordinator, Brian Keyte (G3SIA), whose address appears above. If you are a member of the group, all final results will also be e-mailed and posted there.

Please ... give the CLE a try ... then let us know what NDB's can be heard from your location! Your report can then be added to the worldwide database to help keep it up-to-date.

Have fun and good hunting!

Tuesday, 10 September 2019

DXing With The Heathkit CR-1 Crystal Radio

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.

Larry's gift!

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, inductively 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. Many 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 of 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 peaked for maximum signal. I also used a 100 microamp meter in series with the headphones to help peak 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, 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 a 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


Although the antenna system connected to my CR-1 is not nearly as impressive as an FLR-9 array, it is very capable on the broadcast band. I’m using my 630m inverted-L, bypassing the tuning and 50-ohm impedance matching system, essentially feeding it as a top-loaded vertical wire. The (somewhat slanted) vertical wire is approximately 70’ which is then attached to a 3-wire 100’ long tophat. The antenna is very close to the ocean and parallel with the beach. The CR-1 ground system consists of about 60 buried radials, varying in length from 30-60’. The basic antenna is self-resonant at around 1200kHz.

Over about two weeks of evening listening, mostly between 9:30 and 10:30PM,  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!

Designing and building a crystal radio capable of hearing DX is a wonderful way to learn about circuit losses as each tiny system improvement can be quickly noticed. There has recently (2021) been interest in renewing the once very popular "Crystal Radio DX Contests" that ran a few years ago over a one week period. Perhaps it's a challenge you might like to investigate as well.