Wednesday, March 9, 2022

Is it a mag loop? Lets find out!

Kenwood TH-D74, Alinco DJ-MD5XTG, Lanch HG-UV98, APRS, VHF 2m loop antenna, HYS, HVDN, DMR, amateur radio SHTF

Here is a preliminary review of a recent antenna toy acquisition thanks to some spare Amazon points.

If this antenna proves to be a good option for MF waves instead of EF waves, this is likely going to become a popular product pretty quick. Let's dig in here, shall we?

MF, EF - What is it? A round antenna duck?

Here the antenna is on Amazon and it comes in BNC, SMA and SMA-J variants so it will pretty much work with most radios if you buy the right one.  

The vendor on Amazon does not call this a magnetic loop and I have not taken this antenna apart to see if a hidden capacitor is in that black bubble at the top of the loop but I suspect there is.

For me, I chose the BNC connector antenna version since using it with an adapter like the ones shown in the "Portable RF Connector Emergency Kit" are always on hand.

Kenwood TH-D74, Alinco DJ-MD5XTG, Lanch HG-UV98, APRS, VHF 2m loop antenna, HYS, HVDN, DMR, amateur radio SHTF
Where to find this?   Look on Amazon

How does this compare to the original factory antenna?

The radios tested with the HYS antenna pictured include the Alinco DJ-MD5XTG, the Kenwood TH-D74 and the Lanch HG-UV98 all using the original factory antennae.

A second round of testing was done with all three same radios but with the same aftermarket Diamond SRH320A tri-band antenna.

The test scenario was to communicate via a 2m repeater 30 miles away with all three different antenna options and at all available power levels for each radio. 

The results were from an audible report from different users on the repeater without telling them what I was doing over the span of a few hours on different days.

Kenwood TH-D74, Alinco DJ-MD5XTG, Lanch HG-UV98, APRS, VHF 2m loop antenna, HYS, HVDN, DMR, amateur radio SHTF

Results of Test: Non- Scientific you say?

Kenwood TH-D74, Alinco DJ-MD5XTG, Lanch HG-UV98, APRS, VHF 2m loop antenna, HYS, HVDN, DMR, amateur radio SHTF

The reason why I chose to use different radios is that different antennas will work differently based on the radio mass offered as the reflective or counterpoise part of the antenna system. What?   Here, look into counterpoise or "Tiger Tail" if you must learn more...

This test allows us to see more uniform tests in a real world environment instead of lab style results.

For each transmission, the radio was held the same way and at the same height.

Signal reports in green were all positive and as good as one could expect to come from an HT 30 miles from a repeater. Yellow reports included comments of fading or weak signal but still audible.  The red reports were scratchy or not very pleasant sounding.

At first pass, we can say that the HYS "Loop" antenna and stock antenna are all pretty much about the same results.  As expected, the longer and higher "gain" Diamond antenna worked the best.

Now with some baseline curiosity under control, lets do something more scientific in terms of radiation patterns and reception tests.

Is this an EM or RF antenna?

To test if the HYS functions in the "electro-magnetic" wave or the "electric" wave function,  I used a field strength meter to check radiation patterns of all three antennae at three distances outside in my backyard away from anything before it snowed this morning.

Kenwood TH-D74, Alinco DJ-MD5XTG, Lanch HG-UV98, APRS, VHF 2m loop antenna, HYS, HVDN, DMR, amateur radio SHTF

Based on the test data as expected, stronger signals from the stock and Diamond antenna were strongest when they were vertically oriented which matched the polarity of the sense antenna used with the field strength meter.   

When transmitting with the radio held horizontally, the field strength meter dropped to more than 70% less than what was shown in the vertical test.

Here is the interesting thing with the HYS antenna though. No matter which orientation (horizontal or vertical) the same signal strength was recorded at the field strength meter.

MATH TIME  (1005/146.500 MHz = 6.8 * 12 = 82.3 inches)

Rotating the HYS antenna to have the edge of the hoop or broadside of the hoop aimed in phase with the sense antenna did not show any major differences unless I moved to the furthest test location which was five full wavelengths  away from the sense antenna.  

At the one and three wavelength distance, there was no major difference with all three radios transmitting at highest power levels.

What does that mean?

I think it is safe to say that the polarization of the HYS antenna does not conform to the normal EF wave portions and this seems to function like a true magnetic loop when used for transmitting since its polarity and field strength are very different.

For reception, there is a very sharp null off the edge, but it is very sharp.  Testing this with an attenuator built in to the Kenwood TH-D74 while tuned to the local repeater or NOAA Weather station which are known locations was the only way I could tell there is a sharp null.

Magnetic waves work differently compared to electric waves.  When a true EM or MF antenna is used, signals received may be lower, but with less noise.  This means that the "signal to noise" radio is higher and better for reception usually.   This is what makes a true MF antenna interesting.

Kenwood TH-D74, Alinco DJ-MD5XTG, Lanch HG-UV98, APRS, VHF 2m loop antenna, HYS, HVDN, DMR, amateur radio SHTF

This  becomes important especially for HF frequencies where there is more man made noise than ever.  Even still, today more man made noise also happens in the VHF spectrum and this small loop might come in handy. 

If you want to learn about EM antenna, especially for HF, use your Google subscription to discover more about that. Many options exist, including overpriced commercial products and many DIY projects that are fun to look at if you are interested in this for HF spectrum communications.

Further Testing Needed

There are not many people local to me involved in casual non-contest 2m SSB or FT-8 activity to see how well this will work as a portable antenna for SOTA with the Icom IC-705, so that will have to wait.  

Some testing on APRS however has been interesting but will need to drive around with the antenna on the roof for more testing too.

Overall, I think this antenna is worth a purchase if you have some Amazon points or other disposable funds anxious to leave your ownership. 

Kenwood TH-D74, Alinco DJ-MD5XTG, Lanch HG-UV98, APRS, VHF 2m loop antenna, HYS, HVDN, DMR, amateur radio SHTF
Your mother told you NOT to stare, right?  Here are some of the things used during the test
(Source:  Steve Bossert K2GOG)


  1. I can't seem to find the BNC version of the antenna. Do you have a link for it?


    2. Look for "HYS antenna" on aliexpress. There is one for BNC and one for Baofeng. Both about 20USD. 73 de DL1AV

  2. Steve, did you measure the antenna with an SWR meter or analyzer? After some thoughts and considering that there is no real directional effect to monitor by you I think it is fake and just for the eye.
    We built those real loop-antennas for vhf-handhelds in the 80ies (made of copper stripes and a little tuning capacitor) and they were (as usual for magnetic loops) very narrow in bandwidth, just a few hundred khz. And not dualband.
    BTW: the loop must be all around on the top. Did you check if the loop is going completely through the plastic clip on the top?

    But it looks cool and I am not disappointed to have ordered one :)
    "Antennas for the eye" are not new. Even the infamous german manufacturer Bosch made one for a railways operator handheld during the sixties. It looked like a round clip to carry the handheld. Or like a directional quad antenna :)
    When I tested it these days, no directional or other effect was to measure. Performance-wise it was worse than the rubber ducky *ggg*
    73 de Stefan DL1AV

    1. Hi Steve DL1AV,

      I did SWR testing a few different ways and the results varied too much dependent on what radio or mount the antenna was used with, so I left that out of the review so focused instead on FS and RS measurements. I used an AA-500, SW-33 and the built in SWR plotting of the IC-705.

      Antenna connected directly to the IC-705: SWR was lowest at 1.2:1 at 147 MHz and 438 MHz and then increasing SWR around 148 and 445 MHz. Lower ends of both 2m and 70cm were very high.

      Antenna with 50cm diameter pizza pan with BNC bulk head in middle with length of RG-240 connected: SWR measured on IC-705 and AA-500 were about the same. SWR was lowest at 1.2:1 at 146 MHz and 435 MHz and then increasing SWR around 147 and 441 MHz. Lower ends of both 2m and 70cm were very high.

      Surecom SW-33 with antenna connected to 3 different HT in article: SWR was lowest at 1.2:1 at 149 MHz and 449 MHz and then increasing SWR around 151 and 452 MHz. Lower ends of both 2m and 70cm were very high but not higher than 1.6:1 at 144 and 430.

      I would need to disassemble the antenna to find out what is in the middle of the little black plastic and do not want to ruin it (yet) until I do more testing.

      -Steve K2GOG (Co-Founder, HVDN)

  3. Very interesting indeed. I wonder how this would fare with ISS reception or weather sat transmissions with an SDR?

  4. Finally I got mine :)
    First: It is very robust. It is made completely of metal. No plastics, nothing is getting loose or could be bent. That alone is worth the money.
    Performancewise: It is nice on uhf. Very good reception, better than an original Diamond on the handheld. No directional effects to monitor inside the building but that may be because of the reflections.
    On vhf it works, too, but it is too small to get a good reception (about 2inches diameter). Here the Diamond is better.
    Unfortunately all copper is coated with plastic spray so no measurements for connections in the loop are possible without destroying it. Maybe another day... :)

    I have a halo für 2m-vhf on the balcony which looks similiar to this antenna (besides the dimensions). It has a gamma-match and is open at the top.
    Something like that:
    This guy built something similiar and called it "magnetic loop" but I think it isn´t exactly one:

    The "real loop" we built in the eighties looked like that (besides we built it the other way round to have no capacitor on the top):

    Conclusion: Looks cool, robust as hell, on uhf it works better than the usual handheld antenna, no real function on vhf (simply too small for the wavelength)

    73 de Stefan DL1AV


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