New indoor passive loop antenna for shortwave

Many thanks to SWLing Post contributor, Dave Zantow (N9EWO), who notes:

Here is an interesting looking indoor passive HF loop antenna [photo above] that Randy McIntosh just started selling in the US. Made in Greece. Model TLA500C. Sorry it’s not for MW.

Here’ are the specifications/description from the eBay page:

This sale is for an HF magnetic loop antenna that should be attractive to anyone living in an apartment, residence, or other location where it is not possible to erect an outside dipole antenna. If you can erect an outside antenna, this is always the best solution for reception as no inside antenna can compete with a good outside antenna for the very best signal reception. But erecting an outside antenna is not always possible for many people desiring to listen to amateur radio or shortwave signals. Thus, this antenna offers a solution to such hobbyists handicapped by personal physical limitations to mount an outside antenna, minimal yard space to erect such an antenna, apartment living, or HOA restrictions.

This antenna spans a tuning range spanning 3.5 MHz through 40 MHz and thus covers 80 – 10 meters on the amateur radio bands, all international shortwave bands plus the 11 meter CB bands. The antenna comes with a 3′ coaxial cable to attach the antenna BNC output to a SO-259/PL-259 input of your receiver (most receivers).

Simple assembly directions are also included and you may be view this information in the last picture at the top of this listing. If you have a different input on your receiver other than the PL-259, you will need to acquire the proper interconnect cable from another Ebay seller. Assembly takes 5-10 minutes using only a proper sized Phillips head screwdriver and the antenna can be disassembled to transport to a remote DX location or for convenience in your travel luggage…..or as our picture shows, located permanently at your home listening room or bedside. Depending upon your preference and the dimensions of your receiver, the antenna can be set on top of or next to your receiver (see pictures at the top of this listing) during operation. Please remember that this is a “receive only” antenna and cannot be used to transmit signals.

Features:

  • non amplified….no batteries required
  • works on wide variety of communications receivers both stationary or portable
  • light weight aluminum construction weighs about 1 lb with the interconnect cable
  • portable – can be disassembled and folded into a low stature for compact transport
  • sharp tuning helps filter strong non-desired out-of-band signals
  • low noise loop design helps filter RF noise often found inside a home or apartment from lighting or appliances
  • tuning range of 3.5 MHz – 40 MHz
  • small loop antenna assembles to 18″ diameter at the broadest point
  • great alternative for signal reception when an outside antenna is not possible
  • very easy set up and connection

Thanks for the tip, Dave! This looks like a practical design for portable and low-profile operation.

Since it is passive antenna design, I image you would have to re-tune the antenna for peak performance each time you shift frequencies. It looks like the control panel would make this a pretty simple process.

Click here to view this antenna on eBay (partner link).

Post readers: If anyone has used this antenna, please comment with your impressions or contact me with your review.

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8 thoughts on “New indoor passive loop antenna for shortwave

  1. Mark

    I was interested in this loop antenna until I saw the price. Stick with my PK loop for indoor dxing. Very disappointed.

    Reply
  2. Edward

    “no inside antenna can compete with a good outside antenna” Can anyone direct me to a side by side comparison with hard numbers ( dBm or s-units)? It is consistent with my experience but I don’t have the precision RF equipment to do it. Any articles in QST, etc?

    Reply
    1. 13dka

      Of course this a very generalized statement that lives in a spectrum of possibilities in which there may be extremes (an ideal “house” like a big, high, grid-installation and plumbing-free barn out in the woods, that can house full-size wire antennas etc. in an appropriate height) where the statement turns false (because you have a “good outside antenna” within a structure that allows it, but probably only until it starts to rain). Any deviation from this ideal “inside” and the conditions are back in the part of the spectrum where the statement is true again. The major contributors to the universal truth of that statement are A) noise, B) signal attenuation, C) size restrictions and D) disturbance of the antenna function by parts of the house structure close to the antenna (pipes, wires, girders, roof tiles…). Given the same antenna can be used indoors and outdoors, A), B), and D) still make a difference.

      Here’s a comparison of a TX antenna:

      https://www.sotabeams.co.uk/blog/indoor-hf-antennas-does-it-make-much-difference/

      Since this compares the antenna only for TX, the “hard” data has only a partial relevance to an RX antenna, since it doesn’t account for A), which is the main source of trouble for listeners. It describes only the general signal loss, at that specific QTH, for that specific antenna that is, which is 6-7dB. Because this depends so much on the individual situation, any “hard data” is practically meaningless for you, your location and your opportunities to install antennas, and you still have to add any “indoor vs. outdoor” difference in noise level to the disadvantage of the indoor antenna. That “a *good* outside antenna” beats any contraption you may use inside is pretty obvious, backed up by theory and the practial experience of experimenters since radio was invented.

      A few years ago I made some experiment too: the following link hopefully leads to an image showing 2 spectra, the top one shows an improvised indoor SML, the lower one a short OCF dipole strung up in the same room:

      http://www.sdrplay.com/community/download/file.php?id=116&sid=5cfa32065bdc9fcb3811e7ae9bd0ab3a

      The following spectrum shows the same dipole strung up at the same height outdoors:

      http://www.sdrplay.com/community/download/file.php?id=117&sid=5cfa32065bdc9fcb3811e7ae9bd0ab3a

      As you can hopefully deduct from the picture, the indoor loop beats the indoor dipole, and the outdoor dipole beats both. But that’s not hard evidence either, just a result of many variables, half of which are set by the location and other individual circumstances.

      Some words on topic: I think the properties of all kinds of small loops are getting highly overrated and misunderstood on a regular basis, and there’s a lot of hype connected with these usually quite pricy antennas. That hype leads to people buying expensive active SMLs and mounting them in the backyard, in front of the tree where they could’ve hidden 60ft of wire forming a bigger loop that outperforms any $400 active SML anytime – for $40, because it’s easy, because they think a $400 antenna must be better than a passive wire contraption and because they didn’t think through their options. SMLs are only really great when size really matters, when there’s absolutely no other way to escape local QRM or no good way to support some wires, when it’s essential that the antenna can be rotated, or when you’re all thumbs. Making a killer active wideband SML with crossed loops and electronically steerable nulls (using the LZ1AQ amplifier) for inside or outside could be had for less money than any ready-made loop, active or passive.

      Reply
  3. DL4NO

    I think, too, that the price is a quite steep. In my view this is a nice little weekend job with parts from a good junk box. Besides what you see in the photo you need a variable capacitor and any of the well-known coupling systems. Google is your friend. I would add a larger base to prevent the antenna to tilt.

    Such antennas are *very* selective. You will need to re-tune if you listen across the 31 m band. For in-house reception this is more of an advantage than a disadvantage: On a wideband antenna you would pick up lots of noise that might overload your radio. A magnetic antenna is much better than any electrostatic antenna like a telescopic whip, as most near-field signals are electrostatic. And magnetic fields can enter buildings better.

    This holds true if the antenna is for reception only. Even with a low-power transmitter you can measure voltages of several 100 V across the capacitor and currents of several 10 A. This is why those antennas are quite expensive, especially if they can be tuned remotely.

    Reply
    1. RonF

      I agree; I’ve argued before that most commercial loops – particularly amplified loops – are far too expensive for what they are. That said, it (a) is collapsible & semi portable, so can be hidden away & set up quickly, (b) looks tidy and presentable, so keeps the other half happy, and (c) isn’t asking US300+ for an amplified loop built on a scrap of vero from near-obsolete parts, so there’s that to it. And, while I think that following instructions to build one should be well within the abilities of anyone who can tune a radio, fact is I guess not everyone is in a position to do that…

      On the downside, I’ve never been a fan of auxiliary loop coupling for receive antennas – optimal coupling is somewhat frequency-dependent, and impedance matching too is frequency-dependent (although the latter arguably doesn’t matter on RX antennas, signal levels from loops are so low to start with that it’s worth paying some attention to). But the plus side to that is it’s difficult to make them _too_ selective – which isn’t hard to do with, say, transformer-coupled loops.

      As with all antennas, it really pays to get them away from noise sources (even if loops are relatively insensitive to near-field noise). To my mind, that means getting them outside, or at least out of reach of the receiver – which means remote tuning.

      Be interesting to see if somebody real reviews it. This one’s been around for a while, but I’m yet to see/read a decent review.

      Reply
  4. Pingback: New indoor passive loop antenna for shortwave – dxradio.de

  5. Peat

    Hopefully someone can offer a review. I’m interested, but $179 and no returns accepted seems pretty risky.

    Reply

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