Antenna range testing between multiband mobile antennas

prcguy

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I was going to add more to this package of information like a diagram of the setup, but I may never get to that so here its is as-is. I've been wanting to do an antenna range comparison of multi-band mobile antennas for some time and the recent purchase of a COMPACtenna LMR-1 compelled me to put this test together.

I've had most of the antennas tested for some time and all are in new or as new condition. mmckenna was kind enough to loan me a Larsen Tri-Band new version and an EM Wave Tri-band for this test. I also added a few dual band amateur and single band UHF gain types as I have always been curious about their performance and once everything is setup and calibrated its easy to test additional antennas.

The test vehicle was my Jeep Gladiator pickup with a trunk lip NMO mount on the front hood. Its all I had available and not everyone has the luxury of putting their mobile antennas on top of a large van roof anyway. The hood mount ground plane is not perfect and may have contributed some to the overall performance, but it should affect all antennas in a similar way on radiation pattern. VSWR, especially on VHF may not be ideal for some antennas tested and as mentioned, not everyone has a perfect ground plane available.

The test environment was on the So Cal coast with large hills blocking nearly all reception except out towards the ocean. The noise floor was very low and signal to noise ratio of my test signals were close to 60dB above the noise floor, which is extremely good. The test instrument was an Agilent FieldFox vector network analyzer in S21 mode feeding a broad band amplifier producing around 20dBm or a half watt. The exciter antenna was a Racal log periodic covering 100MHz to 1GHz continuous with about 6dBi gain placed off the front of the vehicle 35ft from the vehicle antennas under test and pointed at the test antennas. The test antenna mount had the entire length of the vehicle hood as a ground plane in line with the exciter antenna. The vehicle NMO mount had about 17ft of RG-58 coax terminated with a 6dB attenuator pad for matching to the test instrument.

The reference antennas were a 1/4 wave whip on each band with the VHF being a Sti-Co brand, the UHF being a Tram and the 800 being a Laird. These are simple 1/4 wave NMO whips tuned to roughly the center of each band and the FieldFox was calibrated with the band specific antenna on each band where the 0dB reference in the instrument became the normalized response of the 1/4 wave whip which the antennas under test were compared to. If the antenna under test showed + or - gain over the 0dB reference, that was the exact amount of gain that antenna had over a 1/4 wave whip.

Attached are the plots arranged by band, VHF 136-174MHz, UHF 400-500MHz and 800-950MHz. Also attached is a picture of the Racal log periodic exciter antenna and the test setup inside the test vehicle. After testing I discovered we made a mistake on the UHF and higher band limits which should have been 380-512MHz and 760-960MHz but we did get most of that.

You will notice some ripple in the measurements mostly on the higher bands. Depending on the antenna it could be a characteristic of the antenna or multipath in the test area or VSWR related. It is what it is and antennas in the real world on your car or mine will be different than calculated on paper. Some interesting conclusions from this test are the popular Larsen, EM Wave and Laird Tri-band antennas compared to the COMPACtenna Scan III and LMR-1 antennas. The VHF plots between these are within about 3dB favoring Larsen, EM Wave and Laird but on the UHF and 800 bands things reverse with the COMPACtennas looking very good. Its interesting to see an 11.5" long antenna even compete with others in the 16 to 19" length range and even outperform the others over some frequency ranges.

Another interesting test was using the VHF 1/4 wave reference antenna on the UHF band where it did surprisingly well at roughly 2dB down from the UHF reference 1/4 wave whip. I intended to test the VHF whip at 800MHz but got sidetracked and forgot. The Larsen dual band amateur performed about as expected as did the Maxrad and Motorola single band UHF gain types.

So, hopefully these plots will answer some questions about the different antennas tested like which one might work better here or there, or why does mine not do so well on certain bands. I don't think this should be taken as the end all answer of what antenna is best overall as a more comprehensive test using more vehicles and mounting locations would be needed. But these tests do point out some good and maybe not so good characteristics between the antennas tested.

Many thanks to teotwaki for the loan of the FieldFox VNA and assistance during testing and mmckenna for the antenna loan.

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  • Multiband Antenna Shootout 9-21-22.pdf
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JPSan

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Thank you very much for doing this comparison testing. Even tho you took the time and effort some will not pay attention and ask the same questions over and over about which antenna performs how.

This old 1st Class with radar endorsement. John
 

paulears

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Mobile wise on my van, the quarter waves are cut for marine band. They are perfectly usable on ham band VHf and UHF and my business band radios. Compromises, of course, but the slightly less range doesn’t matter. The larger flat roof of the vehicle making them higher and more effective.
 

K4EET

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Very good on your efforts and analysis @prcguy! Hopefully your efforts can be referenced in future threads about antennas although what @JPSan said above about folks still asking the same old questions, well, some things never change. 🤣

On the COMPACtenna of which I have two, one being the tri-band ham variety for 146 MHz, 220 MHz and 440 MHz; it does perform very well as noted in your UHF testing. At times, I have even used mine for communications with the International Space Station’s (ISS’s) ham repeater. I have used the COMPACtenna on the downlink since the signal changes phase to some extent as it passes through the Earth’s atmosphere and the COMPACtenna handles that nicely due to its unique design.

One other attribute that the COMPACtenna is known for, as documented by a federal agency, is its ability to pull signals out of the “mud” where others cannot. There is a signal strength plot used in several YouTube videos of Dr. Jack Nilsson that illustrate that ability in a moving environment. I’ll see if I can find one such video and reference it to this post.

As you noted, the COMPACtenna does not always come out ahead on a dB to dB amount of gain comparison but it does work astonishingly well for a short antenna. It can definitely hold its ground in any antenna “shootout” and especially where a short antenna is required.

Thanks again for your analysis @prcguy! It will be very helpful in answering future antenna questions.
 

Ubbe

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It's obvious that you cannot make a broadbanded antenna. The narrowband 1/4 are still the best single band antenna. A broadband antenna would show a U shaped diagram but those who do that now have the bottom of the U show way lower signal than what the 1/4 produce. An antenna like Larsen 2/70 show 1-2dB gain in the 440-480MHz range, but it has two stacked 5/8 in that band so should be better than a 1/4 wave but are now not near the >4db one would expect.

But as Dave K4EET mentioned there could be other aspects as well. The signal levels are measured coming from a source at a horizontal level. If an antennas directional pattern also receives signals at a high gain from a higher angle it would receive cellular towers, and other transmitter close by on towers or buildings, at high signal levels that could decrease the sensitivity in a receiver making it receive less. There are antennas that are classified as low-noise, meaning that they have less side lobs that pick up unwanted signals, the direction pattern are more focused to where the signals comes from. Then it's a lesser risk to receive interferences.

The more narrow filters in a receiver, that only pass the frequency you monitor, the better the receiver will operate. The same for antennas but you still want them to work over the same range as the frequencies you monitor.

So in real life use it might show that you receive more using an antenna that produce less signals that could desense a receiver. The combination of antenna and receiver quality and the RF environment you usually travel in could be important for the end result.

/Ubbe
 

cbehr91

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The results of that SSB-224 are interesting. I get that it's three or so elements phased together, but if I'm reading the results correctly, despite also being a 1/4 wave on 2m it's around 1dB better through most of the VHF band than the reference antenna.
 

prcguy

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With the elements being about 12" for the bottom and 16" for the top, the SSB-224 could be a 5/8 over 1/2 wave on UHF and maybe 5/8 overall on VHF. The Larsen, Laird and EM wave multibands don't appear to be a stacked colinear type on any band and probably 1/4 wave on VHF.

The results of that SSB-224 are interesting. I get that it's three or so elements phased together, but if I'm reading the results correctly, despite also being a 1/4 wave on 2m it's around 1dB better through most of the VHF band than the reference antenna.
 

vagrant

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@prcguy I am unfamiliar with the COMPACtenna Scan Multiband. Is that a model no longer made as there is now a Scan III model?
 

prcguy

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I don't know its official name but it was an early VHF/UHF/800 version that is about 7.5" tall. The newer Scan III is about 9.5" tall. You can see by the plots that VHF is much improved on the newer Scan III.

@prcguy I am unfamiliar with the COMPACtenna Scan Multiband. Is that a model no longer made as there is now a Scan III model?
 

K4EET

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In my Post #4 above, I mentioned a government agency that did a test with the COMPACTenna and was able to pull signals out of the mud. Here is the resulting plot:

7110DDA9-FA86-46AE-8550-C52E65335193.jpeg

As you can see, the COMPACTenna was able to pull weak signals out of the mud. While the strong signals were easily readable, four (4) low level signals were heard using the COMPACtenna versus the 17 foot Monopole at HF frequencies. The small COMPACtenna therefore would be ideal for use in a clandestine environment.

Another interesting attribute of the COMPACtenna is decreased flutter/fades in a mobile environment. Referring to the following hand-drawn slide:
A5A2F988-1111-4F8E-A762-2CF15F06EB17.png
You can see the improvement over a typical vehicular antenna. The overall advantage here is where information would be lost in a deep fade, the COMPACtenna mitigates that deep fade and no information is lost. This could be replicated by using two UHF mobiles on a ham repeater and observing dropouts on one receiver but not the other.

I wish I could still drive because I would like to be out in the field testing various antennas. This is a fascinating subject that I very much enjoy. 😃
 

K4EET

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I might further add some additional knowledge that I have gained by having one-on-one conversations with Dr. Jack Nilsson, the man behind the COMPACtenna technology. He is a true inventor that has taken basic antenna and magnetic field theory to the next level in compact antenna design. I hope that the following is conveyed in understandable language.

It’s amazing how well the COMPACtenna did compared with antennas 4 times it’s height. The outdoor range testing was well done, but the COMPACtenna has a benefit that the other antennas do not have, and this benefit was not measured in the outdoor range testing, as I understand it from discussions with Dr. Nilsson.

The range test was done in the vertical polarization plane. The COMPACtenna is elliptically polarized, so there’s an additional 2 dB (roughly) of signal in the horizontal polarization plane that was not measured during the testing and subsequent analysis. And that is part of the reason that the COMPACtenna does so well in the multipath environment where signal fades are to be expected, capturing signals that change in polarization and phase that the other antennas do not capture. That is what reduces flutter and increases reliable range with the COMPACtenna.
 

k7ng

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@prcguy, I'm in your debt (again).
I have a hat full of different applications for mobile antennas and your test data helps a lot.
The Comet/NCG SBB224 is one I've been eyeballing for personal use and you really helped me out on that one too. I'm going to put one into service with an A320 amplifier driving it.
 

prcguy

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Too bad there is no reasonably sized antenna to take full advantage of your A-320 amp. I have three of those, three RAMP-25s and a TCR-MBA-75.

@prcguy, I'm in your debt (again).
I have a hat full of different applications for mobile antennas and your test data helps a lot.
The Comet/NCG SBB224 is one I've been eyeballing for personal use and you really helped me out on that one too. I'm going to put one into service with an A320 amplifier driving it.
 

tweiss3

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@prcguy you seem to speak highly of the LMR-1, would you be able to provide an SWR sweep on each band of that antenna? I'm giving it a second look, but I can't seem to find someone who has one to sweep it.
 

osborne605

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I'm trying the Mobile Mark A55136TBS triband antenna as it has some gain over the Motorola, EM Wave and Larsen ones in the 3 areas it covers.
 

prcguy

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The Mobile Mark can't have any noticeable gain over the Motorola, EM Wave, Larsen or most others as its the same physical size. You would need to more than double its length to get any useable gain. The gain is in their marketing strategy.


I'm trying the Mobile Mark A55136TBS triband antenna as it has some gain over the Motorola, EM Wave and Larsen ones in the 3 areas it covers.
 
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