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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.

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.

73
  Brian
-------------------------------------------------------------------------
From:   Brian Keyte G3SIA               (CLE coordinator)
ndbcle'at'gmail.com
-------------------------------------------------------------------------
These listening events serve several purposes. They:

courtesy: americanradiohistory.com

The new 'loop' is not really loop-shaped but is rectangular (10' x 20') and more like a Flag antenna shape. I considered a Flag but really don't need any back-end nulling capability since I'm mainly interested in listening to the east and to the north.


The main boom section is composed of two sections of 1" PVC thick-wall (Schedule 40) pipe joined at the center and reinforced with a 10' section of 2" x 2" Douglas Fir. In addition, the boom has a truss of 1/4" Dacron to take out any end-loading sag. The vertical end sections are 3/4" Schedule 40 PVC pipe, fastened with a T at the boom end. The center mast is made of 2" Schedule 40 ABS pipe with a long section of 1 1/2" ABS nested inside that telescopes upward to anchor the truss ropes and give some additional rigidity to the mast.

Main boom and mast construction

This type of construction would lend itself well to anyone interested in a rotating Flag antenna for the BCB / LF or 160m. The costs are very low, the structure is lightweight and the materials are readily available at most hardware outlets.



Looping E/W

Although the preamp is completely sealed and weatherproofed, I still decided to mount it inside a container. The container also provided a convenient anchor to terminate the loop end wires (PVC-coated #18 stranded) without putting any tension on the soldered terminals.

Although I have not had much time to listen, and conditions are still in 'recovery' mode from earlier disturbances, initial indications are that everything is performing as well, if not better, than expected. It certainly outperforms my 10' active shielded loop by a large margin. I have yet to do any serious S/N comparisons between it and my primary LF receive antenna, a large inverted L, which must be tuned to resonance for the desired listening range. I believe that the very quiet loop / Wellbrook combination will provide an overall S/N improvement.

I have always believed that smaller loops provide deeper and sharper front-to-side nulls so I was pleasantly surprised to measure (using Perseus) null depths from 25-30db, on various groundwave signals ... more than expected. Skywave signals also deliver sharp deep nulls in the order of 22 - 25db ... again surprising, but I'll take them!

A brief listen while pointing S-E last evening turned up good signals from 1 kW'ers KYHN (1650kHz) in Fort Smith, Arkansas and KKGM (1630kHz) in Fort Worth, Texas. An early morning listen revealed good audio from JOIK (567kHz) Sapporo, Japan and JOAK (595kHz) in Shobu. Down in the ndb band, little 25-watter 'IP' on 210kHz was an all-time new catch from Mobile, Arizona.

There is still much to learn from this new antenna system but the biggest challenge will be keeping it up all winter. I did lose one of my 10' loops after several years, due to wind, when the main (un-reinforced) PVC mast eventually failed from flexing fatigue. I will tie the ends of the new antenna down when the winds get strong to reduce as much mast flexing as possible. I could however, run the risk of violating another long-standing radio adage ..."if your antenna stays up all winter, it's not big enough". I just can't win.

Part 3 - Loop Listen 

As Murphy would have it, and in spite of the low amount of solar activity, LF/MF propagation has been very poor since getting my new 10' x 20' loop in place. The few front-to-side nulling checks that I have done, have produced results varying from around 20db to 30db, depending upon the signal. I suspect the depth of null is also affected by the signal's arrival angle but there is still more to learn. The pattern seems to be very close to that of a typical circular loop...the classic figure-8 pattern illustrated below as shown on the Wellbrook data that came with my ALA100LN preamp.

Courtesy: http://www.wellbrook.uk.com

More typically, the null is around 21-22 db as shown on this test while listening to the ground wave carrier of the 'YZA' NDB (236kHz) located in Ashcroft, B.C., about 150 miles to the NE. As expected, the null is fairly sharp and the front / rear lobe, fairly broad.



One short check at dusk produced nice signals from  CJBC, the French-language station in Toronto. The past few nights it has been very strong but with a strong echo effect. I wonder if there is more than one CBC outlet here (860kHz), such as a low-power repeater, causing the echo.



At the same time, while still fairly light outside, WCCO in Minneapolis had a nice signal just before sunset.



No matter how poor conditions become, it seems that the Hinchinbrook (Alaska) NDB, 'ALJ' (233kHz), is always strong ... looping north.

Courtesy: https://www.google.ca/maps

My apologies for the video quality. If you know of any software available for making full-screen Perseus video captures so that I might improve my technique, please let me know. Presently I am just capturing them on my I-Pad which leaves a lot of room for improvement.

(Since originally posting the above, I have been using the Tiny Take free screen capturing software, to produce better quality catures of my Perseus recordings. It's also probable that my new iPhone would produce a high quality video of my computer screen compared to the older iPad used for these ones, but it's something yet to be tried.)

Hopefully conditions will only get better as the season progresses and I am able to give the loop a good workout ... before it gets too windy!

Ionosphere:  source

One of the Broadcast Band’s (BCB) six ‘graveyard’ frequencies is 1240 KHz.




These frequencies (1230, 1240, 1340, 1400, 1450 and 1490 KHz) are assigned to smaller stations running non-directional antennas and up to 1000 watts of power. In North America, there are typically about 150 stations assigned to each frequency.

The origin of this spooky name is often a source of debate. Some suggest that it comes from the cacophony of strange howls and sounds that can be heard on these frequencies at night, as multiple fading signals fight it out to be heard, while others relate it to the similarity of the jam-packed headstones in a typical graveyard. Whatever the true reason, it's a fascinating part of the BCB to explore.

Most BCB DXers enjoy the challenge of tackling the graveyard frequencies as they're often so busy. New stations will fade in for a brief period only to be replaced by a totally different one a few moments later ... and then a different one soon after. It gets even better if the fade-ups coincide with a local ad or a ‘top-of-hour’ ID, putting a new catch in the log!

Several days ago I reactivated my 10’ x 20’ loop and Wellbrook ALA100N preamp, that I use for NDB and BCB DXing, by adding a new buried coax line from the shack.





I had previously re-appropriated the loop’s coax for a nearby HF wire antenna and had been without the loop all winter.


After BCB DXer Mike Cherry (VE7SKA) on Salt Spring Island, the next island to the west of me, described some of the European action that he had experienced last winter, I am determined to not miss out during the next winter's BCB DX season!

10' x 20' Loop & Wellbrook ALA100N Preamp

Once getting the loop powered-up in mid-afternoon, I decided to give it a test by making a ‘deep-search’ on 1240 KHz.

At 1500 hours local time, I wasn’t hearing any audio on 1240 but a weak carrier could be detected audibly. Using my Perseus SDR’s waterfall in its narrowest possible window, produces an extremely narrow passband, effectively increasing the sensitivity by a huge factor. This allows the waterfall to display weak signals that are presently being propagated to my location but far too weak to be heard by ear. I’m estimating that in this narrow bandwidth, it can dig about 30 dB or more into the noise, but there is a price to be paid for this extra gain .... time!

If you're used to watching your receiver’s waterfall scroll along quickly, this mode is just the opposite. It moves in very slow increments, allowing the weaker signals to build up enough to be visible before taking the next deep look. The screen capture shown below is a result of a three-hour listening period, from 1500-1800 hours local time. The entire waterfall is 25 Hz wide, with each tick representing 1Hz.

3-Hour Daylight Deep Search

Although no signals were clearly audible during this period, my deep-search revealed the carriers of ~28 different stations being received here in south-west British Columbia ... in the middle of a summer afternoon! It’s interesting to note that few of these signals are 100% stable and several can be seen really struggling to maintain their exact assigned frequency. In this highly narrow bandwidth view, even the worst drift amounts to no more than a Hertz, well within the required tolerance of +/- 20Hz.

Using the always-reliable MWLIST, the locations of the most likely candidates for these 28 signals are plotted below. These are the 28 nearest stations and with my loop pointing east, a definite east / south-east flavour is evident.


At mid afternoon, one might expect to see only groundwave-propagated signals on the broadcast band. Midday groundwave on the broadcast band can easily travel a few hundred kilometers, gradually growing weaker over the longer paths. Perhaps all of these signals are arriving via this mode as they are at least 20-30dB into the noise. I initially thought that some of the further-out signals were being reflected from a strong daytime D-layer, although most of the energy would be absorbed. Further reading shows detectable groundwave up to 1200km is possible which coincides nicely with the distances observed. Most likely what I'm seeing is a combination of extended groundwave and D-layer refraction on the furthest signals.

The second screen capture shows the same frequency for another three hours, starting about an hour before local sunset. Some of the weaker signals seen earlier now begin to grow in strength as the D-later absorption starts to decay and reveal the higher E-layer. By the end of the third hour, an additional 41 stations have appeared for a total of 69 carriers cantered on 1240 KHz. (note that my Perseus calibration is off by a few Hz)

3-Hour Sunset Deep Search

The next 41 closest stations are now plotted below in yellow, showing the most likely source of these signals. The distances illustrated are in-line with single and double-hop E-layer or possibly lower F-layer refraction.



This view shows the directional pattern of the front of the loop while pointing east, with its very broad circular lobe. In this direction, the narrow null is only seen along the coast.



It will be interesting to do a mid-winter follow-up on 1240 and compare the present summer propagation to the much better winter conditions. I expect that a some point, propagation via the higher F-layer will be present and extend skip distances out to the east coast or to South America.

In the meantime, things are almost ready for some pre-sunrise looks to the west and some overnight top-of-hour recordings ... as soon as I re-calibrate Perseus!

Have you ever wondered where those odd stations found at the ends of the AM broadcast band might be located and what they're all about? These are 'Traveller Information Stations' or 'TIS's and, 'Highway Advisory Radio' (HAR) stations. Because of their low power (100mw - 10W), they make challenging DX targets if you can catch the ID on their continually- repeated audio loop.

These stations are located throughout Canada and the USA at places such as highway intersections, border crossings, ferry terminals, airports and parks ... just about any place that needs to advise travellers (vehicles) with up-to-date directions or information. From here on Mayne Island, the farthest TIS I have been able to identify was WPTC509, located in Carbon County, Wyoming.

courtesy: https://www.google.ca/maps

Thanks to the International Radio Club of America's (IRCA) Phil Bytheway, an up-to-date list (58 pages) of all known stations is available for download or, if you choose, as a purchased hard copy.

 IRCA TIS/HAR LIST (Winter 2016)

The IRCA TIS/HAR LIST lists all US and Canadian TIS/HAR stations, by frequency, including call letters, state (province,) city, county, licensee, address, coordinates, expiration date and dates of DXM/DXN reports/sources. It has been updated with FCC data, DXM, DXN and DXer reports, and on-line listings through March 1 2016.
The 2016 IRCA TIS/HAR LIST is posted on the IRCA website for all to download. The link is: http://www.ircaonline.org/TIS_2016.pdf.
For those preferring a hard copy, one can be ordered from the IRCA.
 
As well, this page on regulations, permitted content and TIS history has some interesting info.

IRCA is one of the oldest clubs dedicated to DXing the broadcast bands and members receive a monthly journal of members loggings as well as other relevant articles. A trip to the IRCA website might get you hooked on this part of the radio hobby as it's probably the way that most amateurs discovered the 'magic of radio', on late winter nights! Just in case you need it,  the mwlist will help you identify any stations heard in the AM broadcast band, worldwide.

Conditions towards the east on LF as well as on the broadcast band (BCB) have taken a positive leap forward over the past few days. Last night, 160m was open to Europe from here, the first opening of the season as far as I am aware. I also spent some time listening to a dozen or more TA (Trans-Atlantic) carriers on the broadcast band, signalling good conditions over the pole finally.The polar skip also extended down into the LF band, as it did the previous night.

In the afternoon hours I started watching for Europe1 on 183kHz, transmitting from western Germany, and was able to see its weak carrier on the Perseus SDR's waterfall display several hours before sunset. Twilight here brought a dramatic improvement in signal strength as shown below.



As daylight approached the transmitter site in Germany, the 183kHz signal provided a good visual example of 'dawn-enhancement', with the signal showing a dramatic flare on the waterfall indicating its build-up in strength.




Once dawn arrived, it was interesting to see that the signal was able to hang-on for over an hour with reasonable strength before fading out rather quickly. Even though the transmitter site was in full daylight, the dark skies to the west were able to sustain propagation for some time before it all came crashing down.

Of late, the pre-dawn hours here have also been providing some exceptionally strong signals from Asia on the BCB. These are often enhanced at sunrise as well, as the strength often takes a short fast peak, before fading out for the day.

One of the loudest this week was from JOAK (NHK1) in Tokyo on 594 kHz ... listen ...

This was heard on the Perseus SDR and inverted-L antenna. The LF polar signals shown above, were recorded with the 10' X 20' loop and Wellbrook preamp while looping towards Europe at 030 degrees.

With the DST going positive, hopefully these good conditions will continue to build over the next few weeks. October is often one of the best months of the year for LF/MF DX.

courtesy: http://wdc.kugi.kyoto-u.ac.jp/dst_realtime/presentmonth/index.html