Tag Archives: Bob Colegrove

A File Worth Having: Bob’s guide to building an Electrically Small Resonant Loop Antenna for Mediumwave Reception

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This post is short and sweet.

If you click here–Electrically Small Resonant Loop Antenna for Mediumwave Reception (PDF)–you can download a copy of Bob Colegrove’s excellent paper on the Electrically Small Resonant Loop Antenna for Mediumwave Reception.

He has actually built this antenna; it works; and he uses it often. Perhaps you might want to build one for yourself. As an added bonus, Bob is an excellent writer (in my not-so-humble opinion). What’s not to like?

— Jock Elliott, KB2GOM

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Bob’s 1968 Radio Tirana QSL Card

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Many thanks to SWLing Post contributor Bob Colegrove, who writes:

Kudos to Don Moore for his excellently crafted article on Albanian radio.

[…]Perhaps some might be interested to see a 1968 QSL from R.
Tirana.

Regards,

Bob Colegrove

Thank you for sharing this excellent Radio Tirana QSL card, Bob!

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Channel 6 FM Radio Stations

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Many thanks to SWLing Post contributor, Bob Colegrove, who shares the following guest post:

Channel 6 Radio Stations

By Bob Colegrove

Even after all these years, I still find occasional surprises while playing with radios. How did I miss this one? I recently did what I thought was a definitive audit of the available FM stations in my area. Then, just the other day I happened to tune down below 88.1 (FM Channel 201). At 87.7 MHz I came across some delightful Latin music in clear stereo and proceeded to park the tuning knob there for a listen. At first, I thought I might simply have some intermodulation from a strong local station, but the stereo signal was much too clear. So, I resorted to the internet to determine what was going on. Turns out, according to their website, I was listening to DC 88.7FM in Fairfax, Virginia – no call letters, just “DC 88.7FM.”

Further investigation indicated that the station is officially WDCN-LD a low-power operator, but you won’t find it listed on the FCC FM Query site. That’s because it is something of a legacy station, a carryover from analog TV days when the audio for Channel 6 was broadcast with the carrier centered on 87.75 MHz, within the range of most FM receivers. Having discovered this, I retuned the radio slightly to 87.75 MHz and found the signal strength peaked. Wikipedia describes the history of WDCN-LD at https://en.wikipedia.org/wiki/WDCN-LD.

Of further interest is the history of so-called “Channel 6 FM radio stations.” The evolution of present-day stations is long and involved. Over several years, the FCC formed committees, requested comments, held hearings, wrote reports, published proposals, rendered rulings, and ultimately granted waivers. For the full story, see https://en.wikipedia.org/wiki/Channel_6_radio_stations_in_the_United_States. What resulted are legacy stations dating back to analog TV days which continue to operate sans video as de facto FM stations. For all practical purposes, we have a modest extension of the FM band. There are, in fact, 14 such stations currently spread across the lower 48 states. It is unlikely that the circumstances which created these stations will ever result in more stations being added. As of July 20, 2023, an FCC report and order restricted these stations to those already licensed and current licenses untransferable.

Do you live near a Channel 6 FM radio station?

Just to complete the picture, there is also officially an FM Channel 200 at 87.9 MHz, which was established in 1978, but to my knowledge is not used. Does anyone have any information on FM Channel 200?

As an historical aside, the present-day FM band, 88 to 108 MHz, is located directly between analog TV Channels 6 and 7. In 1958, to foster FM use, Regency Electronics, Inc. marketed a converter, Model RC-103, in a handsome Bakelite case, which could be attached between the antenna (generally “rabbit ears”) and the TV set. The converter contained a single transistor and was powered by three AA batteries. By tuning the TV to Channel 6, turning on the TeleVerter to FM, and rotating its dial, one effectively detuned the Channel 6 audio frequency upward, and could listen to the entire FM band. As this converter was manufactured prior to the advent of stereo broadcasting, the sound was in mono, and fidelity was limited to the audio quality of the TV. My dad bought one of these. It was connected to our Arvin 12”, B/W tabletop TV, and it served as our first FM radio for a few years. There were only a few stations at that time, mostly classical as I recall. Thus “FM” came to stand for “fine music.”

Source: Sams Photofact Folder, Set 397, Folder 11, Regency Model RC-103, May, 1958.

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Bob asks: “What’s Your Favorite Corner of the Dial?”

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Many thanks to SWLing Post contributor, Bob Colegrove, who shares the following guest post:

What’s Your Favorite Corner of the Dial?

As asked by Bob Colegrove

Let’s suppose you’ve been listening to radio for a while. Consciously or not, you’ve probably favored a range of AM, SW, or FM frequencies. These are areas where you go to DX or just listen to your favorite stations. One area I seem to keep returning to is the very bottom of the medium wave band, roughly 530 kHz to 600 kHz. With the convenience of today’s digital radios, I have consciously pushed the envelope somewhat lower.

The main reason for specializing in that frequency range is the challenge. In the very beginning there didn’t seem to be much at the extreme lower end of the AM broadcast band. Growing up in Indianapolis in the ‘50s, the local stations were all at the upper end of the mediumwave dial. WXLW held down 950 kHz – lower than that nothing. I would say the stator plates on the variable capacitor got very dusty, never being closed any further than that on many radios.

Another challenge was sensitivity. In analog times, the sensitivity of a tuned circuit had some falloff as the inductance/capacitance (L/C) ratio decreased. Sensitivity is highest with the variable cap open at the high end of the band. As you tune lower by increasing capacitance (inductance remaining constant), the Q and consequently sensitivity drop off – not dramatically, but somewhat.

Finally, not all old analog radios tuned to 530 kHz; some were even challenged to tune 540 kHz. By performing a little mischief with the alignment, I could sometimes venture into unknown territory.

This was all part of the challenge. So, what could I do to coax some activity out of the bottom of the band? I spent many hours poring over Bill Orr’s Better Shortwave Reception (Radio Publications, Inc., Wilton, CT, First Edition, 1957) and tweaking caps and coils trying to squeeze the last few kilohertz and microvolts out of my radios. This exercise fascinated me and became a hobby within a hobby. If I may be allowed a self-deprecating aside here, the first time I took a radio out of the cabinet, I just assumed that all these alignment screws were loose, and dutifully torqued them down. The alignment problem is not comparatively complex with today’s digital receivers. Note, I didn’t say it was unimportant.

I still tend to favor the bottom of the medium wave band. Below is a list of my catches over the past couple of years. It’s just a sample of what one might hear by casual listening over time. Highlighted stations are heard during daylight hours. This is NOT intended to impress anyone, rather it is hopefully a stimulus for your own efforts.

As another attraction of the lower mediumwave band, you will find a potpourri of stations. Besides regular North American broadcasting stations, one might possibly hear an occasional high-powered trans-Atlantic station which is not synchronized with the 10 kHz spacing. 530 kHz is interesting. It is not used in the US by commercial broadcast stations. Instead, stations from Canada and Cuba at roughly orthogonal directions from me are regularly audible at night on this frequency. Thus, the radio is tuned by simply rotating the antenna. 530 kHz is also home to several Travelers’ Information Stations (TIS) throughout the country. Question: How will this long-time service fare if travelers don’t have AM radios in their new cars? Finally, the very bottom of the frequency range still contains a few holdouts of non-directional beacons.

Frequencies below 530 kHz probably put a strain on the medium wave bands of old radios, but they are likely no problem on most digital radios having both LW and MW coverage. As mentioned, there are a few non-directional beacons down there. They are Morse coded using amplitude modulation. I have found placing the receiver in SSB mode makes detection much easier, as the heterodyne from the carrier can be heard well before the signal is strong enough to produce any audio. These beacons generally fade in for brief periods of time and then fade out like passing comets.

My most recent catch was experimental station WI2XLQ, 486 kHz, during its annual Fessenden Event on Christmas Day and again on New Year’s Day. See https://swling.com/blog/?s=Fessenden+ . The experience was not the armchair listening quality one might expect from FM or the Internet. Instead, it was weak and fraught with atmospheric noise. The station came in periodically, then disappeared, in short, DXing to its highest degree of satisfaction.

The antenna is the key to good reception, and there is no exception to this rule at the lower end of the AM band. Many years ago, I switched to an indoor, resonant loop antenna. The selectivity, directional properties, and noise rejection of a loop antenna in this frequency range are superb. The figure below shows my 40-year-old loop antenna, which is still used in its original form. It tunes from ~485 kHz through ~1710 kHz in two bands. The antenna can rotate 360 degrees horizontally and 90 degrees vertically. Further, it is mechanically balanced to remain in any position without locking. For those not inclined to construction projects, the Tecsun AN-100, AN-200, and Terk Advantage will perform quite well through inductive coupling with a portable radio’s ferrite bar antenna.

As all experienced medium wave DXers know, for success you need to have patience, “set a spell,” and let the radio do its thing. Radios are living organisms, kind of like cats, very independent at times, and will let you hear only what they want you to hear. On many channels, stations will come and go over time. If you’re lucky, you might catch an ID; lacking that, you might be able to identify it by the format or network. You might try to compare the contents you hear on the radio with what you can hear online either over the station’s website or via streaming sites such as TuneIn, iHeart, or Radio Garden. There may be a delay between the Internet stream and the live signal.

When you feel you’ve exhausted the possibilities, there’s still more. Turn the antenna 90 degrees and start over. You’re only half finished with that frequency. Don’t forget a headset or earbuds.

What’s the next challenging rung on the limbo bar? Well, possibly the 633-meter ham band, 472 to 479 kHz. I’ll have to pad the old loop with a small capacitor to tune down there.

What’s your favorite corner of the dial? Why?

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Bob talks ergonomics and radio buttons…

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XHDATA D-808 on a 5” × 9” neoprene pad.

Ergonomics and Radio Buttons

By Bob Colegrove

Am I being too picky? Are the buttons on some newer portable radios hard to press? I’ve read many reviews and watched as many videos, but haven’t encountered many complaints about this. Perhaps it’s an age-related affliction.

The most succinct description of the problem was expressed in the review of the Tecsun PL-660 way back in the 2012 edition of the WRTH. In referring to the buttons, “All are in our view rather too small for comfort and have breakout forces which are out of all proportion to their size; the combination of this with excessively long travel and weak tactile feedback does not give much pleasure to the user.” The problem has only gotten worse with some newer portable radios.

I see two problems here. First, too much pressure is required; what the WRTH called “breakout force.” Designers may say, “that’s so you won’t accidentally turn the radio on and run down the battery.” Well, I reply, “isn’t that what the ubiquitous lock button is for? They all have one.”

If you’ve ever taken one of these radios apart, you’ve likely seen a pliable membrane between the buttons and the switches or traces on the PC board. This provides some spring action necessary to return the buttons to the upright position. Couldn’t this be thinner or more elastic?

Second, some radios have flat buttons that don’t protrude very far above the case. By the time the fleshy part of your finger bottoms out on the surface of the case, still more pressure and button travel is required to activate the function. Couldn’t the buttons be slightly higher?

The result, if you operate the radio on a desk or table and apply the requisite walnut-cracking pressure on a button, the radio might well rocket off its foundation.

Pads for Portables

A partial solution without violating the integrity of the radio is a stable foundation. In today’s euphemistic world the term counterpoise is use when referring to what we used to simply call an electrical ground. It seems some sort of mechanical counterpoise would be useful to better anchor a portable radio for operation.

Neoprene is a synthetic rubber developed by a DuPont scientist in 1930. It is tougher than natural rubber and relatively impervious to solvents. This stuff is virtually skidproof. There are perhaps other materials suitable for this application, which is simply to get the radio to stand its ground while you operate it. After some thought and experimentation, I bought a 1/16”-thick neoprene pad. A 12” × 12” pad is more than enough. Mine came from https://amzn.to/3XsmQDe [Note Affiliate link supports the SWLing Post]. I cut this into three smaller pads as follows:

7” × 12” for a Sony ICF-2010, which has nice easy-touch buttons and really doesn’t need a pad except to anchor the radio in place.

5” × 9” for a Tecsun PL-990 and many other similar size radios.

3” × 5”, the scrap piece can be used for a C.Crane Skywave, which already has nice raised buttons; a Tecsun PL-330, which needs a pad most of all; and an XHDATA D-220, which doesn’t even have buttons.

A Tecsun PL-330 lying flat covers a 3” × 5” pad. But that’s OK.

There are a couple of alternatives:

You can leave a large pad uncut to accommodate various sizes of radios; or
You can cut bits of neoprene and apply them as feet to the bottom rear corners of the radio and bottom of the stand. There might be some difficulty getting them to stay in place or allowing the stand to fully collapse. Some portables already have rubber feet.

It’s probably apparent that neoprene will adhere best to a smooth surface such as glass or Formica. However, I have tested it on a cloth-covered, memory foam chair cushion, and it works just fine. Pressing down the material will make it adhere to a surface even more. I would estimate that a lateral force of at least 10 or 15 pounds is required to make a small radio break loose from three or four points of contact with the material.

Besides holding the radio in place while you operate it, much like a large table radio, neoprene offers the radio some cosmetic protection against abrasion from rough surfaces. However, the material is so sticky it will pick up every bit of dust or dirt. This can somewhat compromise its adherence requiring an occasional rinse in water.

Admittedly, the neoprene pad isn’t going to be very useful while you’re sitting in a beach chair using the radio in the handheld posture. However, in the shack, a suitable pad has a purpose.

XHDATA D-220 sans buttons on a 3” × 5” pad.

Caps for Buttons

In the case of buttons which are too low, some additional help is desired. On the Tecsun PL-330, I glued plastic caps on top of the STEP and ETM buttons, which raises them about 1/16” and helps considerably. I am still looking for some transparent material to use as caps on the numbered buttons.

STEP and ETM buttons with caps on a Tecsun PL-330.

Further validated suggestions are solicited.

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U Twente WebSDR: New Tablet/Phone Interface Option

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Many thanks to SWLing Post contributor, Bob Colegrove, who shares the following guest post:

U. of Twenty Site for Phones and Tablets

by Bob Colegrove

I’m not sure if this is new. It may have been around for a while. Very recently, while accessing the WebSDR site at the University of Twente, it detected that I was on a tablet and offered redirection to an experimental version of their site: http://websdr.ewi.utwente.nl:8901/m.html.

Besides being an interesting site to surf radio stations, I use it regularly as a ‘spotter’ tool to see what’s on shortwave. Admittedly, it is more than 3,900 miles from my receiver, but I like to see how well my antennas are doing.

The experimental version was accessed using the Silk browser on a 7-inch Kindle Fire. It is slimmed down from the main version, and much easier to use with a phone or tablet, particularly the zoom in and out feature.

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A Band Aid for the XHDATA D-220

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Many thanks to SWLing Post contributor, Bob Colegrove, who shares the following guest post:

A Band Aid for the XHDATA D-220

By Bob Colegrove

In the olden days of analog radios, we would have generated a graph plotting frequency against a 0 to 100 linear bandspread scale. That permitted determination of a station’s frequency with varying degrees of accuracy.

The case of the charming little D-220 requires a simpler approach. The dial covers 5.6 MHz to 22 MHz in less than two inches. They could have cut off coverage at 18 MHz and gained a precious half inch of dial.

With the shortwave scale well below the pointer, I needed some additional guidance indicating where I was. Best not to get too fancy. I cut a strip off a sticky-back label and attached it to the dial right below the pointer. Using the left edge of the pointer as a guide, I marked off the location of each international broadcast band and a couple time stations. The width of each band isn’t much more than the point of a sharp No. 2 pencil. Any further resolution is hopeless, but at least you know what part of the spectrum you are in.

Red lettering is not part of the band aid.

Again, going by the old logarithmic analog dials you would expect the frequencies to be increasingly mashed together as you go higher. This is not the case with the D-220, nor do the increments appear to be very linear. At any rate, it is now relatively easy to tune from band to band.

The sensitivity and clarity of the D-220 is amazing. Perhaps it’s the green one.

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