The VEA MW 1812 High Performance Inductive loop Antenna

Review by Werner Funkenhauser

DXers have long known the advantages of loop antennas to help counter noisy (QRN) conditions. Perhaps of even greater importance, are the directional properties, which allow loops to be aimed towards a signal and to be peaked on a signal. Loops are  magnetic devices, which respond best to frequencies to which they're tuned and to signals which appear from directions along the plane of the loop (the direction of windings.) In this condition loops are known as peaked to a signal. They are less sensitive to signals from other directions, resulting in reduced QRM from co-channel and adjacent channel stations, which are not in line with the received signal. This is known as nulling. DXers who own radios without provision for external antenna connections will often use inductive loops to enhance their radios' performance. Such loops may be homebrewed or they may be commercial products, like the Select-a-Tenna. As their name implies, signals are induced from the loop into the radio's built in antenna. The action is similar to induction that takes place when one coil is wound on the same form as another, and there is no need for direct connection between loop and receiver.

A well-constructed loop will show a noticeably peaked signal when correctly tuned and properly aimed toward the signal. When the loop is turned 180 degrees so its "other" side presents itself to the same signal, a peak of equal intensity will also occur. As the loop swings through 90 degrees to the signal, there will be a null or reduction in signal level. Joe Carr a recognized authority and author on the subject of antennae writes, "The construction and uniformity of a loop are primary factors in sharpness and depth of the null." A properly built, uniformly constructed loop needs only be swung through 90 degrees to either peak or to null target signals. Performance of homebrew loops is often unsatisfactory because of shoddy construction. It makes the term "sloppy loop" quite relevant. Such loops will often have reception patterns that are skewed (unequal peaks) and will also exhibit shallow nulls. Invariably they look like homebrew projects too!

A loop antenna is not a signal amplifier but its peaking effect on signals can be striking especially during daytime listening when only ground wave signal is present. At night both ground and sky wave arrive together tend to make a loop somewhat trickier to tune and to aim for peaks and/or nulls. At such times, patient tuning and even more patient aiming needs to be used, but that can pay off in elusive DX. Statements on the Internet questioning loops' usefulness at night because "all signals are already too strong already" show the writer has probably never DXed when auroral conditions make almost all signals weak. It's doubtful also, that the same writer has ever used a loop to peak a Trans-Atlantic split, a station like Portugal's R. Nacional on 1035 kHz, whose frequency lies between two powerful North American stations, WBZ-1030 and WHO-1040.

Inductive loops may only marginally impact the performance of radios already provided with good internal loops, for example, receivers like the GE SuperRadio. I found that to be the case in some of my tests with a  SuperRadio II. Having said that, I'll also state that I've seen many a long haul catch reported by DXers who use the same receiver and an inductive loop.

For efficient induction to take place, wires of both inductive and ferrite loops must run in the same direction. The position of most radio internal ferrite loop cores is along the length of the radio. The loop wires are wound upon these cores. That means the radio must be aligned broadside to the inductive loop's wires, in other words at 90 degrees to the inductive loop wires. Though the radio is broadside to signal, the internal ferrite loop wires and also the inductive loop wires are in a line with the signal when the inductive loop is correctly aimed towards the signal. The inductive loop's wires should also be physically as close as possible to the ferrite coil loop wires so that optimum coupling takes place. If there is room inside the frame of the loop, the radio may be placed inside it (providing the two loops remain at 90 degrees to each other) and this usually further enhances coupling. A small solid loop like the Select-a-Tenna, doesn't give the DXer that choice but an 18 inch box loop does. Regardless, for best signal peak and/or maximum null, loop and radio must be re-aimed when tuning to another station that isn't in line with the first. During a typical DX session, both radio and loop are continually being moved about, or repositioned for best reception. Long ago DXers found a Rubbermaid Lazy Susan or a home built turntable with both radio and loop placed atop makes all this aiming and re-aiming much simpler.

The VEA MW 1812 High Performance Inductive Loop

The VEA MW 1812 inductive loop is a relative newcomer to the field of inductive loops. It is the outcome of several years of experiments and research on the subject by "Van" K6QGH (E.C. Van der Ecken) of VEA. Van and his partner Eric Force are the "V" and "E" behind the company. Their design appears to be carefully thought out, and integrates a number of desirable features among inductive loops, features sometimes lacking in other designs. They include physical and electrical balance, excellent signal coupling, very good sensitivity, operating convenience, and yes! to a degree, even aesthetics.

My unit came shipped in a large cardboard box with antenna and Rubbermaid Lazy Susan base carefully padded with newspaper wadding. All I needed to get started was to place the turntable base on my desk, to lay the antenna upon the base, then to place the radio upon a lower deck inside the antenna frame. After that, it was ready for use! Shipped complete with a color coordinated standard Rubbermaid Lazy Susan, the two parts look like an integral unit.

The loop wires are drawn on a sturdy frame (W 12 in. H 24 in. D 6 in.) constructed of type 40 white PVC plumbing tubes complete with elbows and joints of the same material. There are a few screws to hold the joints, but I suspect there is PVC solvent (of which there were no spills) inside the joints to add to the frame rigidity. I gave the frame some pretty hefty pulls and twists, but couldn't weaken it nor did the loop wires become bent or misshapen. The loop is made of 16 carefully located turns of #20 AWG enameled wire, stretched and saddled inside indented shoulders which are securely fastened to the frame corners. You'll never have to use Popsicle sticks to take up loop coil slack nor is there a fear that the wire coils of the antenna will ever unravel. The enameled antenna wires make a nice contrast against the white frame.

It is a true inductive loop without provisions to couple output directly to a receiver's antenna and ground terminals. I experimented to see how easily this feature might be added so that I could use it with my Icom R71A. I used several techniques, the simplest being to tape a single turn of hookup wire inside the frame. The wire was brought out at the bottom center as a twisted pair. I notified Van that I was doing these experiments, and since then received word that direct coupling is in the works for future versions.

VEA advertising describes their product as having a "small footprint" and indeed this is correct. Even with a receiver mounted on its deck, the antenna occupies little more than a foot square area of the shack desk. Differently shaped loops respond differently to ground wave and sky wave signals. The circular shape, like that of the Select-a-Tenna, is claimed by some to be the most efficient capture form. Spiral loops have their devotees too. The late Ken Cornell who was a low and medium frequency DXer and hardware guru, preferred large loops built in a diamond shape, maintaining that this form presented a larger aperture to incoming DX, greater than the more conventional box shape, hence greater sensitivity. Inductive coupling is most easily accomplished with a loop of a square or rectangular shape. For stability, rectangular loops are almost always built with the long side as a base, so that the shorter side(s) face the signal, as is the case with my Maartens regenerative loop. I suppose the MW 1812's configuration is kind of a compromise among all of these. It stands on its narrower 12 inch side, with 24 inches facing the DX,
so it would be classed as having a larger aperture.

It is also designed to optimize signal coupling with the receiver positioned inside the loop at the optimum 90 degrees to the inductive loop's coils and near the loop wires. The frame depth is about 6 inches and supports a felt covered deck upon which all but the largest of portable radios may be placed (i.e. it will hold a Super Radio II). With the radio situated that way, wires in both loops are in the same plane. The deck is deep enough to allow the radio to be moved from side to side a bit, which may allow you to find a sweet spot where best signal transfer or coupling occurs. Although standing on its shorter side, this antenna is very stable. I used a Radio Shack DX 400, Sony SW 77, Grundig YB 400 PE and GE SR II and had no problems with placement or of imbalance in the loop such that it would have a tendency to tip. Its integrated Lazy Susan base make directional rotation a snap and it is easy to peak or to null signals. Though the nylon coasters of the Lazy Susan have a slight backlash, this is not a serious problem.

A variable tuning capacitor, whose range covers the mediumwave band is fastened exposed in a bottom corner on the felt covered deck. The capacitor is protected from being inadvertently touched by a sub-frame made of  PVC pipe, a T, and an elbow.  To use the antenna position radio on the deck, tune in the station, tune the capacitor for maximum signal, then rotate the loop in the direction of the station for yet more signal. If two stations are on the same frequency but at different compass points, tune the antenna for maximum desired signal, then carefully rotate the base to find the most reduced QRM from the unwanted station, or you may reverse that sequence. This procedure may have to be repeated with patience while listening at night. When tuning the antenna, it's best to shunt the receiver's DX/local switch to local or the receiver AGC action may mask   improvements. In my receptions with a portable, I always left the DX/local switch on local. It made tuning easier and for the most part the MW 1812's peaked signals negated attenuation. It also helped to counter excessive AGC action (pumping). AGC pumping may further be subdued by slightly de-tuning the antenna. De-tuning should not be in the direction of a strong local! In a couple of instances, my careless tuning caused resulted in the  appearance of a strong local station on  frequencies other than its own. I had peaked the antenna to the local instead of to the DX frequency.

For my Proceedings Kiwa Loop Review, I first tested the Kiwa outside of the house, during the day, and away from wiring that might have upset its reception pattern. I did the same with the MW 1812, out in my side yard, using it with my wife's trusty little YB 400 PE. Operating the YB 'barefoot' I tuned WHAM-1180, just barely heard. Adjusting the antenna correctly immediately gave me a good signal, well heard above any noise. As far as I could tell, equal peaks occurred when I rotated the loop through 180 degrees. A properly balanced loop has a bi-directional receiving pattern and this one is no exception. There was a good null at 90 degrees to maximum, subduing but not completely nulling WHAM. That night, I tried it with a DX 400 tuned to 1000 kHz. WMVP was audible in a westerly direction. When I turned the assembly south, I was able to hear 15 Kw HJAQ the RCN station in Cartagena, Colombia. Once more, there wasn't a complete null of WMVP. To be fair to the DX 400/MW 1812 combination, I also couldn't null WMVP for HJAQ completely with my GE Super Radio II.

WMVP on 1000 kHz appeared more than once with CFLP Rimouski PQ on all the test receivers (YB 400, SW 77, DX 400, GE-SR II). Another instance showed that the MW 1812 nulling capability wasn't non-existent. With the YB 400 PE tuned to 730 kHz,  I was able to null CKAC and XEQ sufficiently well to hear CJNR Blind River ON (1 Kw), albeit poorly. One night when conditions to the south were favorable, I tuned CKLW-800 which is heard fairly well during the evenings, and nulled it in favor of PJB Bonaire in The Netherlands Antilles. CKLW is to the west of me, while PJB is to the south. Not too bad for a YB 400! Admittedly, the poor thing with extremely weak AGC action had a most difficult time delivering a steady signal while the DX 400 and SW 77 fared better. Very little improvements were noted in the GE when placed on the deck. Despite the GE's outstanding sensitivity and sharp nulls, I could never seriously DX with it because of its sloppy string-driven tuning setup and barn-door-wide selectivity.

The following table shows some of the stations that I heard during auroral conditions in February of 1999. Most of the receptions were made with the YB 400 PE, which I've already stated is not an outstanding mediumwave receiver.

Date    Freq.    UTC    Call/Slogan    Location    Notes
====    =====    ====   ===========    ========    =====
2/18    840      0513   CMHW Dobleve   Cuba        WHAS almost completely nulled
2/20    940      0435   CMKD R. Reloj  Cuba        with XEQ & HJTL (t)
2/20    760 770  0442   HJAJ, HJJX RCN Colombia    Bogota & Barranquilla parallel 1000
2/20    700      0447   RJR            Jamaica     WLW at equal level
2/20    530      0510   R. Vision      So. Caicos  poor under semi-local CIAO
2/20    630      0604   WSKN           Puerto Rico San Juan-good 'La Super Cadena'
2/21   1180      0647   unkn.Rebelde   Cuba        WHAM nulled, parallel 5025
2/22    670      2225   WWFE           Miami FL    easily separated from local 680 slop
2/27   1690      0410   KDDZ           Arvada CO   //1560 with WMDM nulled

Each of the station reported here was also heard in parallel on either a Drake R8B or Icom R71A connected to a highly directional low noise terminated K9AY triangular loops system with 30 foot sides or to my Kiwa Loop. This was done as much for identification purposes as to see how well the MW 1812/simple sets fared against high powered equipment. As it turned out, they fared  pretty well. Predictably, performance of the communications receivers and Kiwa/K9AY loops combinations was always better than with the simpler portables and inductive loop, but that's comparing apples and oranges.

I noted a couple of minor problems and one more serious problem, but these are for the most part surmountable.

1. Optimum radio placement is against the deck's far side where frequency is most easy to read. This requires the somewhat stiff capacitor to be tuned with the left hand, a bit of a trick. It is easy to overshoot. Vernier (fine) tuning would help, but might add to the cost.
2. The tuning range in my unit was from about 480 kHz to just under the X-Band high frequency. I managed to squeeze in the top end by adjusting the split vanes in the outside plates of the capacitor's rotor. This is an easy fix but must be done with care.
3. Hand-capacity effects especially near the top end of the band caused de-tuning after I adjusted the capacitor and removed my hand. This makes precise tuning a bit of a chore with fadey signals. The solution might be to turn the capacitor 180 degrees on its base with an extended insulated shaft running the full width of the deck. The hand would not be as close to the capacitor, and would cause less de-tuning though some effect would still be noticed with the hand near the loop.

I communicated these faults to VEA,  and very shortly after they advised me of pending redesigns to address these issues. The proposed upgrades include the following fixes:

1. standardized capacitor designed to permit uniform 530-1710 kHz coverage in all future MW 1812s
2. a higher quality capacitor with smoother tuning action
3. vernier tuning incorporating a long insulated shaft to reduce hand capacity effects
4. the option of mounting the tuning capacitor for either right or left hand operation
5. provisions for direct coupling to receivers having antenna and ground connections

It's clear that the fellows at VEA are not going to let any grass grow under their feet!

After using the MW 1812, I will state that it is a very good choice for the mediumwave DXer wanting to enhance the DX performance of a portable receiver. It is also for the guy who wants consistent reception of favorite stations a couple of hundred miles away. If I were a  beginning DXer using a better grade portable radio, a Sony 2010 or 7600G for example, the VEA MW 1812 would be my choice for an add-on antenna. That setup would allow some serious DXing and it would be a long time before I could exhaust the capabilities of such a combination and have to move up to a Kiwa. The MW 1812 is reasonably priced compared to competing brands, and it's offered with a no-quibble money-back-guarantee. Performance is very good, operational features are good, and it doesn't even look bad. In fact, it's a highly capable piece of gear, and while it's no Kiwa, it doesn't cost nearly as much. Minor operating annoyance aside, it is worthy of consideration by anyone contemplating the purchase or construction of an inductive loop antenna. Or, if prepared to modify it with a pickup winding as I did, a DXer could have a pretty good loop for use with a tabletop receiver.

When I first saw a picture of it, the term plumber's dream immediately came to mind. Now that term isn't always negative, and certainly not in the case of this unit. With it's attractive white framework and reddish enameled wire strands, it looks like a loop antenna, not like a hula hoop or some kind of wheel, and definitely not a homebrew kluge, but that's only my own opinion. I'd say that Van and Eric have themselves a winner. I'll give them two thumbs up!

How I came to write this review

I don't generally DX with portable receivers and loop antennae, inductive or otherwise. Over the years I've built a number of inductive loops as experiments. I've also used the commercial products a few times while on DXpeditions. They all behaved somewhat the same and I won't say the VEA product rates any better than this brand or that design. However, I will say of this type of antenna, the MW 1812 is the one to beat. I may as well add that I've never been fully satisfied with limitations that such antennae impose. The design is for use with simpler receivers which are unsatisfactory for my DX interests, the foreign longwave and mediumwave variety. Such DXing dictates using communications receivers with more sophisticated antennae -- larger loops, including The Kiwa, phased longwires, terminated loop systems, and when possible, beverages.

I've been meaning to write an essay on the subject of inductive loops for awhile. There's always hype and interest in the subject, sometimes even outrageous claims about how such antennae convert the simplest of radios into honking great DX machines. There's even a dealer claim on the Web that a certain kind of commercial inductive loop and a $10 radio will outperform $1000 set. It's ad hype that should be taken with a grain of salt. Will the MW 1812 (or other inductive loop) make my 6-transistor pocket radio perform better than my Icom? Only if the Icom has no antenna attached!

A while back, I surfed over to "Van's Think Tank", a web page to which I had links from my own antenna pages. It led me to "Van & Eric's Mediumwave DXing Page" and to this antenna. I expressed an interest to Van about writing a review in my ODXA column "Mediumwave Notebook". After a couple of e-mail exchanges, Van and Eric offered to provide me with a free unit to review the product. On condition that I could write objectively and that I could present my findings as I saw them, I agreed. It's exactly what the lads at VEA wanted! Since I'm not connected with the company I've had free rein to present what I hope is an objective personal review.

It has been a while since I wrote any sort of antenna review or other such article. I hope this one is interesting and will serve useful. I must say, I had fun using the thing, and writing this piece. The next time I head up to my cottage on Georgian Bay, the MW 1812 and my SW 77 and DX 400 will come along and I'll DX only with that combination, not worrying about porcupines chewing up my beverages or having to lug along a heavy Drake R8B. Not! I'll try them out together, but more than likely I'll continue to DX up there with the big sets, and those 1200 foot long terminated beverage antennas. <Hi!>
 

Addendum August 1999

Shortly after completing my the MW 1812 High Performance Loop review, and noting some of its minor shortcomings, I received a second one, which VEA called the MW-1812VE model. Physically it was almost the same but there were important differences that made short work of my earlier quibbles about problems. In addition, there was a 30+ page user's manual with detailed user instructions, loop antenna theory of operation, propagation, target frequency lists (based on my WHAMLOG 50 Kw list) , and much more.
 
This second generation, the  MW-1812VE  incorporated each of my recommendations to overcome the minor problems which I noted in my earlier review.
 
Problem - Stiff capacitor action and the need to tune with the left hand, lack of ability to tune with the right hand.

Solution - The new antenna was equipped with a 4:1 vernier mechanism. A small driver gear is located on a long shaft which extends the width of the table and  through PVC elbows which act as supports. The shaft is capped with tuning knobs on both ends. Ergo! Left, right, or both-handed tuning. The primary gear mates with a secondary gear which is fitted on the tuning capacitor shaft. The gear face is calibrated from 0-100 and looks like an ordinary dial except that its circumference has teeth, which mesh with the primary gear's teeth. A small fixed pointer attached above the dial allows settings to be remembered. With a gear ratio of 4:1, two complete revolutions of a tuning knob are required to cause the capacitor's plates to traverse 180 degrees. The ability to tune spot-on is now much easier and stiff capacitor action is not noticeable. The vernier action is smooth with little or no backlash.
 
Problem  - Hand capacity effects when tuning the capacitor because the hand is close to the tuning mechanism.

Solution - The location of tuning knobs controlled through the added vernier mechanism makes this a non-issue. Hand location is no closer than three inches from the capacitor during tuning.
 

Problem - Uniform coverage of the mediumwave band from 530 kHz to 1700 kHz.

Solution - The new MW-1812VE has a dual section capacitor, just like the old one, but also comes equipped with a "high/low" range switch. In the "on" position, both sections of the capacitor are used and provide a tuning range of approximately 500-1650 kHz. When in the "off" position, only one section is employed and the tuning ranges is now approximately 900-1730 kHz. High-band tuning is considerably easier with a combination of vernier action (as explained above) and because the higher end of the band is now spread out (or "bandspread") over the 180 degree capacitor shaft rotation.

Bonus - The MW-1812VE is equipped with a built-in coupling or pickup-loop (which VEA calls and "InductoCoupler"). Direct connection to a receiver's antenna and ground terminals is possible. There is no evidence of the  InductoCoupler which is cleverly hidden within the PVC framework. It's output is an RCA jack located on the bottom rung of the frame and requires the lead wire to the receiver to be equipped with an RCA plug (and an appropriate plug/connector at the receiver end if no screw terminals are present on the radio). The direct-connection will be a welcome addition to those DXers who have tabletop receivers, and who may wish to use this fine loop antenna as I did with my Icom and Drake receivers.
 
In all other respects, both versions are identical. However, performance expectations should be the same for both. The enhancements are just that. They add measurably to  more convenient operation of a unit that has already proven to have good, even excellent performance. As I wrote earlier, if I were a beginning DXer, I would couple this loop to one of the higher-end digital portables. It would be a DX combination hard to beat.
 

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