By Jock Elliott, KB2GOM
It was the survey that Thomas, our Maximum Leader, conducted that got me to thinking about this.
The survey revealed that portable radios were used 38.6% of the time by SWLing Post readers as their “daily driver.” I like portable radios, too, and use them frequently. Hold that thought for a moment.
I also like medium wave DXing (content DXing, really, I enjoy tuning around for unusual programs) because, as Gary DeBock once put it: “It’s a target-rich environment.” With that in mind, I was exploring the CCrane website and found a couple of items – the Terk AM Advantage and the Twin Coil Ferrite® AM Antenna Signal Booster that looked like they might help portable radio listeners who want to pull in medium-wave signals better. I asked the CCrane folks if they would like to review both products, and they sent them to me without charge.
Bottom line: they both work for boosting reception of medium-wave signals.
The Terk AM Advantage is a nine-inch tunable loop encased in plastic, and it requires no power supply. Simply place it near your portable receiver and just the dial to the desired frequency, and you could get up to a 20 dB gain in the signal you want to hear. The loop of the Terk AM Advantage inductively couples with the ferrite antenna inside your portable radio, although the unit comes with a direct wire connector that can be used with some radios.
I tried the Terk AM Advantage with my CCrane Skywave SSB on an AM that was coming in with a lot of static at my location. Without the AM Advantage, I had 3 bars of signal strength. As soon as I placed the AM Advantage close to the Skywave and adjusted the tuning knob, the signal strength increase to 5 bars, and the audio was much easier to hear with less noise.
With my Tecsun PL-880, which has a numerical signal strength meter, signal strength was 11 without the AM Advantage, but with the AM Advantage, signal strength increased to 14, and it was much easier to hear. The Terk AM Advantage definitely provides a modest boost in signal strength and clarity, is easy to use, and requires no batteries or external power supply.
The Twin Coil Ferrite® AM Antenna Signal Booster is more complicated. It consists of an antenna element that measures 8.5″ W x 2.5″ H x 1.25″D, a tuner unit that measures 3.25″ W x 4.25″ H x 1.25″ D, a small ferrite stick, and some patch cords. It comes with an AC adaptor and can also be powered by a 9-volt battery. For radios with external antenna connectors, package also includes a RCA female patch cord to two bare wire ends.
Set up is pretty easy: connect the tuner unit to the antenna element with a patch cord; connect the tune to the ferrite stick with another patch, and provide power through either the AC adaptor or 9-volt battery. (I used a battery).
Here are C.Crane’s directions for how to use The Twin Coil Ferrite® AM Antenna Signal Booster with a portable radio:
- Place the Tuner Control in a comfortable location relative to your radio. Place the Antenna Element a few feet away. If the Antenna Element is placed too close to the radio, it will cause noise on your radio.
- Place the Ferrite Stick on top of the radio near the center. Placement will vary depending on where the internal AM antenna of the radio is located.
- For testing purposes, tune your radio to any weak AM station. It is important that the station be weak so you can clearly detect the improvement in reception.
- Rotate the Fine Tune control, it will click on and the red LED indicator light will come on. Turn the Coarse Tune control knob slowly and you will likely notice a change in reception at some point on the dial. Adjust the control knob until you notice the most improvement on your signal. Now you can use the Fine Tune control for further refinement.
- Move the Ferrite Stick around the radio to find the position that affects the signal the most. This position is the “sweet spot”, or the best position. Again, adjust the Fine Tune on the Tuner Control for the best reception possible. (I used rubber band to hold the Ferrite Stick in place, but the unit comes with some double-stick foam tape to hold it in place.)
- Now you can orientate the Antenna Element for best reception. In most cases, the Antenna Element does not have to be adjusted again. When radio noise is a problem, try rotating the Antenna Element in the direction which reduces noise to a minimum.
And The Twin Coil Ferrite® AM Antenna Signal Booster works like crazy! With same station on my CCrane Skywave SSB, it boosted signal strength from 3 bars to full scale. With my Tecsun PL-880, it increased signal strength from 11 to 38.
In my view, although The Twin Coil Ferrite® AM Antenna Signal Booster costs twice as much as the Terk AM Advantage and is more complicated to use, it is more than twice as effective in boosting medium-wave signals.
Thank you Jock for another pair of fine reviews and well written article.
I would highly recommend those using or considering purchasing passive tunable loop antennas to read Kevin Schanilec’s very well written tips and technical explanations on placement, spacing and tuning loops to get best effects of signal boosting, selectivity effects, and cancelling interference:
After reading Kevin’s tips and explanations
you may want to buy 2 loops,
Another rare but highly effective AM and SW small loop is the amplified Kiwa Pocket Loop:
I wish Craig at Kiwa would allow someone to start making those again.
I have one and have always been impressed with it. It provides so much RF gain that you need to off tune most signals as a type of RF gain control. The built in “noise bridge” helps exact tuning.
Years ago I owned a Palomar Engineers LA-1 electrostaticaly shielded 5-15 Megahertz SW loop. I did not own the MW ferrite rod antenna for it. It was so “peaky” to tune I replaced the simple knob with a 4:1 vernier. I sold it at a DX meeting in Greensboro NC 30 years or so ago because gain was weak, although S/N usually improved. Clem Small reviews it several articles down here:
I have two older Selec-A-Tennas that have held up over 40 years.
I bought 2 Tecsun AN-100 years ago when they were $18 each. I later bought a 3rd for $5 at a yard sale.
I think the old high quality made in USA air core variable capacitors in the Selec-A-Tennas have higher “Q” which makes them tune sharper peaks and are superior to the much cheaper made variable capacitors in the Tecsun AN-100s.
Here’s a web link to a guy who cut open his Selec-A-Tenna and took pictures:
Thanks for the kind words.
I will check out those links you provided.
I love my Select-a-Tenna. It’s amazing. CCrane used to sell them. They’re no longer made, but available on ebay. My Sony AN-1 helped on SW but no help on AM/MW.
DIY Option — Wind 22AWG around a wood dowel (1.5in diam) over 8 inches and place that in parallel with the loopstick.
The am medium and long wave transmitters are being switched off so me receiver will be obsolete I used to listen to absolute on my collection of vintage radios but they switched their medium wavectrabsmitter off so I refuse to listen to absolute radio and listen to planet rock and greatest hits radio on my chinese dab radios the chine roberts radio is very good
I made my own using the plans in this YouTube video. https://youtu.be/3sDtmmRHzZc
It works very well with my Tecsun PL-680.
I think I agree with your review of the Twin-coil antenna right down the line, although it doesn’t help me as much as I had hoped. I will need to move it outside to use it to best effect with my SDRplay RSPDX, as it picks up a ton of RFI from my laptop monitor. It works beautifully as an antenna for my Denon AV receiver which has no AM antenna. I expect it will be best used in that service since I have a few old HiFi tuners located away from my outdoor wire. It sure is fun to tune on the SDR, as you can easily see the frequency peak as you adjust it. Don’t forget the excellent customer service that C. Crane is known for… second to none in my opinion.
Thanks for your comments . . . and I agree about C.Crane’s customer service!
Thanks Jock for your excellent, informative and helpful article
I’d love to try the CCrane active twin ferrite…
Some more info on Mag Loops…
1. RDF 501 / NavMar 121
You mentioned the RDF 501 ad on eBay – thank you for that, an interesting radio, here’s some more infor on it
At page 237 of the July 1982 Double Issue of ‘Cruising World’ – a yachting magazine – there’s a brief contemporary review of the NavMar 121 / RDF 501
Here’s a link:
2. Tecsun S-2000
The Tecsun S-2000 / Grundig 750 features a modest detachable rotatable MW AM ferrite bar
For SWLingers who hanker after a radio with an analogue meter, knobs and dials like the old Sony ICF 6700 or 6800 this should satisfy that urge.
We have one and I’ve read many reviews.
It’s fun. It’s quite capable. But it’s not my go to radio.
3. A few compact indoor Mag Loops
I’ve searched long and hard for the ideal indoor receiving antenna for years and tried several passive and active Mag Loops
I haven’t (yet) found it, but here’s a bit of information on a few of the loops I’ve tried:
a) Tecsun AN100 and AN200
In my experience the passive Tecsun AN 100 / AN 200 – as far as I can tell essentially the same antenna but with different stands – works well and at US$24.99 each from Anon Co is worth the price
Both the AN100 and the AN200 are still available
b) Tecsun AN48x
The tiny, portable and easily set up Tecsun active Mag Loop AN48x powered by 2xAAA batteries that seem to last a long long time works but at US$27.99 don’t expect miracles
One nice thing about the AN48x are the included accessories that include a range of connectors from a small inductive loop ferrite rod, and various connectors for various types of antenna plug and the telescoping spacer for making a mag loop using a piece of flexible wire
The AN48x works in both passive and active modes
Note: What does ‘x’ / ‘X’ mean in Tecsun?
By the way ‘x’ / ‘X’ in Tecsun parlance indicates ‘export version’ which typically means the manual and radio info are in English
c) AOR LA400
The compact expensive and possibly no longer manufactured AOR LA400 is an excellent indoor active magnetic loop that also works as a passive loop when not powered. It features a 30cm aluminum mag loop.
I have no connection to Anon Co – other than having corresponded with them
And I have no connection with Tecsun and or AOR other than having bought their antennas and radios and communicating with them.
To be clear I’ve always bought my radios and accessories, so far I’ve never received a free review radio or antenna.
Thanks for the kind words, the info on the RDF radio, and the detailed comments on loops.
Youtube video with quite a lot about the RDF501 and NewMar NAV-121 radios
How does the Terk compare to the AN-100 or AN-200 AM antennas from Tecsun?
My guess is they should be about the same. They both have the same 9″ coil diameter, and probably about the same number of turns. For air-core loops, those having a greater NA product (i.e, number of turns times area) will grab more magnetic field. For me, I like having the tuning cap out to the side. After that, it’s just cost and nits.
I got my first portable radio, an RCA Victor model 8B41, in 1949 (guess that comments on my age), a small (for the 1940s) four-tube set with excellent sensitivity and selectivity, but limited audio volume. In 1951, I became hooked on DX, when I heard KFI-640 from Los Angeles, whilst visting relatives in Brookline, Massachusetts (near Boston). I still have that radio, but I rarely use it because it devours batteries. In 1961, I bought a Zenith Royal 500H transistor set, to “retire” the RCA, and I still use that one, although the sensistivity is not quite as “hot” as that of the RCA. From my location between Albany and Utica, New York, WBZ from Boston is quite clear at midday on the tube set, but a bit hissy on the Zenith; WABC from New York is almost clear on the Zenith, but sounds “local” on the RCA. Some years ago, I bought a Select-A-Tenna, which responded oddly with the tube set (which has a wire loop antenna, not a ferrife rod), but transformed the sensitivity on the Zenith! My problem lately, though, is severe R.F.I. from everyone’s use of L.E.D. lamps. It is so evil, that I must go out to the country in the open, away from buildings, homes, and overhead wires, to get decent reception! I’d like to try the C.C. Crane unit — but where could I use it indoors? I have a stockpile of incandescent light-bulbs, but the power-lines themselves bring me the R.F.I. from neighbours’ L.E.D.s, computers, and flat-screen televisions! My own television-set is a Zenith Chromacolor console from 50 years ago — but the R.F.I. that it generates vanishes when I shut it off. I very much appreciate any tips on M.W. DXing, and I thank you for your informative review! By the way, while the zenith tunes from 525 to 1620 kcs., the RCA Victor tube set goes from 515 kcs. to 1715 kcs.! So, it is good for the extended broadcast band. I would LOVE to know who plays endless hours of “adult standards” on 1620 kcs. with never any I.D.: — some “pirate” in my age-group? I’ll go listen to my 78s.?
Here’s a review that compares the Terk to the Selec-A-Tenna:
In my experience the Tecsun AN-100 provides useful gain or nulling,
but the Selec-A-Tenna tunes to sharper peak gains, or deeper nulls.
I first bought two Tecsun AN-100 loops because I thought it would be “extra good” to place a small radio inside the hollow loops. This did not turn out to be true in practice.
I own both the Terk AM Advantage and Twin Coil Ferrite Antenna, they have been useful for many years and have both been great little AMDX tools. The Terk can be fed directly into a radio with an external antenna hookup or a random wire tuner to radio. I use a mono 1/8th cable directly into radio or tuner when possible. I find it’s more convenient and works better in my environment. I DX from indoors, in an apartment in Dallas, TX. Another cool use for the Terk was inductive coupling, sitting next to a Sangean PR-D5, on top of an old record album so that both could be turned at the same time. I remember hearing WBZ for the first time with this configuration, it was like local copy of traffic and weather. As I recall the proper distance between the D5 and Terk was was key to boosting the D5.
The Twin Coil is lots of fun too. To be honest it sat in a closet for years, it was difficult to use due to inexperienced operator and apartment RFI at that time. Now I have the Twin Coil running underneath MLA-30+ and switch them out for comparison in the Eton Elite 750. Great topic!
Thanks for the kind words. I like the idea of using an old record album as a turntable for rotating the radio and antenna at the same time. One of the posters on Radio Reference forum suggested using a cake turntable for the same purpose.
My experience is with the Tecsun AN-200, which is very similar to the Terk antenna. The AN-200 has also been marketed under names such as Grundig and Kaito and was preceded by an AN-100 model. Being a passive, inductively-coupled antenna it will not introduce any noise or other artifacts of amplification. Most appealing to those not inclined to construction, these antennas can be used right out of the box with no connection to the portable radio.
Besides inductive coupling, the AN-200 can be connected to the radio’s external antenna phone jack with an included cable. First of all, be advised that not all portable radios are designed to connect by cable to external long or medium-wave antennas, and one should investigate this before wasting a lot of time. Second, I have never been successful using the AN-200 cable connection with any radio. Having built my own loop antennas for over 40 years and being cursed with an insatiable curiosity about how things work, I took the thing apart to find out what was going on. In short, the visible outer coil is in series with a tunable capacitor in the usual fashion to resonate and tune through the medium-wave band. The cable is connected to a 2-turn secondary coil mounted directly under the center of the primary coil. My experience has always been that mounting a secondary coil too close to a resonant primary circuit tends to overcouple the device, drastically lower the Q, and generally degrading performance. Obviously, my untutored mind is missing something here, possibly some strange impedance value, so I have always stuck with inductive coupling, in which case the AN-200 works just fine. You can always use the cable for a patch cord on something else.
Finally, keep in mind that whichever antenna you are using in the inductively-coupled mode, you are rearranging the magnetic dipoles of two different loops, causing the wave phases to support or counter one another. The internal ferrite antenna does not stop working; it merely reacts to the field of the external antenna. Like playing a musical instrument, you need practice.
Thanks for taking apart an AN-200 and letting us know how the plug connector is coupled. Like you, I’ve never had any luck using that either, even when running it into my base ham radio. Of course, the inductive coupling works great; in fact, I’m using it right now to listen to a dinky little AM station ~300 miles away over the Gulf of Mexico.
I use a a very well traveled “select-a-tenna” that I purchased from CCRane decades ago. I also have a Twin Coil Ferrite® AM Antenna Signal Booster that I bought off e-bay for $30 which is a steal IMHO. In case anyone is wondering the 9V battery lasts for hundreds of hours. I have many RF quiet areas in the mountains nearby that I like to DX from. I bring a CC Skywave a few extra batteries and a paper logbook and disappear in radio-land for a while.
“I have many RF quiet areas in the mountains nearby that I like to DX from. I bring a CC Skywave a few extra batteries and a paper logbook and disappear in radio-land for a while.”
That sounds like great fun!
Pure amplification has no benefit of its own, especially on the AM band where atmospheric noise is quite high. The only thing that matters is the signal-to-noise ratio.
I see four ways such signal boosters can improve reception:
* The radio has design problems, for example a very small ferrite rod and a noisy front end.
* Poor preselection. Modern, digital radios quite often have none at all.
* The radio collects noise, for example through its power supply.
* The large coil without all the radio around it has a better directional diagram. You can better null out other stations at the same frequency or strong stations.
The most important feature of these signal boosters obviously is preselection. Old, analog, radios always had some. They needed it to suppress image reception, a unavoidable problem of “superhet” receivers.
An attenuator might also be helpful so local stations do not overload the receiver front end.
Unfortunately the Twin Coil Booster cannot be used without the 9V power amp. It would be much improved if there was an method to bypass the powered amplifier and use similar to the tunable loop.
It seems to me that without the 9V power amp, the Twin Coil Booster would not be as effective as I found it to be.
Great article as usual Jock, thanks much. I’ve used the AM radio loop antenna by Kaito (maybe it was Antron?) a few years back for radios I’ve owned that had built-in ferrite bar antennas and it definitely made a difference.
The best of both worlds would be a radio that comes with rotatable bar antenna like the Panasonic RF-2200 or the CountyComm GP-7. It seems that rotatable antennas on portables were more popular years ago. As a matter of fact there was an article on this website a few years back about radios with swiveling antennas.
If one really is serious about AM DXing, look into a RDF (Radio Direction Finder) radio. These were very popular with the maritime crowd in the ’40’s to the early ’80’s to navigate at sea using the many nautical radio beacons that were present at the time. These radios had a very substantial rotatable antenna with a heading compass to triangulate and included the LF (150 – 520 kHz) and most times the AM broadcast band. Unfortunately these radios can only be found on the used market in all varieties of physical condition. I’ve had a few of these in the past and they are superb for AM BCB DXing. Many are battery operated for portable too.
Thanks again for helping us dyed-in-the-wool AM radio DXers who are constantly spinning the dial for the next distant prey hihi.
Thank you for the kind words.
Is this what you had in mind for an RDF radio?