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A word on antennas


berkinet
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When discussing antennas commenters often refer to their antenna as "working great."  However, while I am sure the observation is subjectively true, it is a whole different question as to how "great" the antenna is in objective terms.  In other words. Unless you test the antennas in a well equipped and controlled environment it is virtually impossible to draw any concrete conclusions.  

 

A big part of the difficulty in judging a UHF antenna's performance lies in the nature of how we observe them in use. It is pretty simple, do we get good connections to the stations we are communicating with? Given the nature of UHF, in most cases we are looking to contact stations relatively close to us and would probably succeed with a tuned coat-hanger.  A secondary problem, especially for people coming from CB is that FM reception behaves quite differently than AM. AM tends to fade all the way to the point where the noise over-comes the signal. However, FM tends to go from intelligible to non-existent very quickly. Thus, if we receive the signal at all, it tends to be good enough for conversation.

 

There are also a host of other issues, like bandwidth and propagation pattern that may be important in some applications and irrelevant in others. And, finally, there are the mechanical factors ((like corrosion) that are usually only observed after a period of a few months or years. 

 

All of which is to say, and this is strictly my own opinion: Unlike the ham low-bands where you can, and in some cased (low-power/QRP) must spend more on the antenna than the radio, for most GMRS uses, that is not the case.  The perfect GMRS antenna is probably gong to be the lowest priced antenna that meets your basic communication needs* and is built by someone you trust to make quality products. Unfortunately, in GMRS there is no magic perfect antenna.

 

 

* terrain (elevation changes), distance, mobil, fixed or portable, power, etc.

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How do the factories test them?

The factory most likely tests their antennas with a laboratory grade VNA.

Here is a photo I just took using a calibrated NanoVNA to check one of my 144-520MHz HT antennas. Not bad at all.

I can tell you that the results changed, but insignificantly, between holding the VNA vertical, horizontal, standing it on a table, laying it flat on a wooden table, laying it flat on wooden table with the antenna overhanging the edge of the table, and when touching and not touching the chassis ground of the VNA. 0118946f1562097adebd28bab0125786.jpg

When comparing HT antenna performance, the best comparison of antennas is not going to be it’s SWR, but relative difference in signal strength at some given far field distance using some given amount of input power.


Michael
WRHS965
KE8PLM
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14 hours ago, maddogrecurve said:

How do the factories test them?

Testing is an open-ended question depending on what parameter or characteristic you're validating and how rigorous it has to be done.

This is just one example test setup from FCC submitted test data by Harris.  Sometimes it's done inside an RF chamber, sometimes in a lab that happens to be quiet enough or even outside like this (to get away from sources inside, like computers). 

I've seen this set-up in other Harris reports so it must work fine for them.  It doesn't necessarily have to be absolutely radio silent as long as you can characterize the baseline with high confidence.

Test-Setup-Photos-35237.thumb.jpg.5f5dbedcd84863e4c9242b9370575e7f.jpgTest-Setup-Photos-35238.thumb.jpg.6b626c8b7be901ccdc4291e996b4ebbb.jpg

 

Edit To Add:  It occurs to me that this won't have answered your question because the fundamental question is still open.  "What are they actually testing?" 

The radio itself was analyzed in simulation so the real article tests are validating those analysis.  You don't necessarily have to re-test SWR at every level because if all the analysis was correct you can tell by the field strength and pattern that it radiates like you predicted.  If they were interested in SWR they'd probably measure at test points on the circuit board.

Whether they test the antenna as a stand-alone item depends.  Most of the basics are well understood so you don't have to keep reinventing the wheel.  But a novel antenna they would test using a mock-up of the device, like for highly integrated devices like cell phones because they have antennas folded within antennas integrated into the enclosure.

 

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Whole heartland agree with all the above. The more I look at antenna designs the more all the different designs in a particular category tend to look similar. There is no one better antenna.

 

A lot of manufacturing limitations do show up and effect the antenna. Type of materials used, how was everything soldered up etc. This seem to constitute a majority of price differences. Buy cheap get cheap, you don't do something for nothing neither does the manufacturer. The lower cost are usually due to no R&D (cloning), materials, lower labor cost and QA. Conversely, buying expensive doesn't assure you quality. Same with the name.

 

I am finding more and more it is about what you can get away such as 1/4 vs 1/2 vs 5/8ths wave. The installation choice (how it is installed) has a much greater impact. Mobile is already a compromise at best. If you jam a 1/4 mounted to roof rack or magnet mount, you have to be realistic with the overall performance of the package. You have take a compromise and added more compromises, small and easy. You effect gain and ground plane. Both work with a multitude of factors and add up. In the VHF being cheap (quality) with connector, cabling etc, are worse with the losses. Thankfully, not as bad on mobile vs a base. They add up to make your radio more and more deaf.

 

Sent from my SM-G975U using Tapatalk

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When discussing antennas ...

 

It occurred to me after posting the  above comment that there are some issues involved that may make the transition to GMRS from CB a bit harder to understand at first.  Unlike CB, being roughly 6" long, installation of a basic 1/4 wave ground-plane antenna is easily achieved on GMRS. Likewise "gain" antennas and even multi-band gain antennas are all achievable in designs that will not break every light in a parking garage.  This becomes even more straight-forward when you consider that (as noted previously) in the majority of cases, the basic 1/4 wave antenna will be more than adequate.

 

However, the situation in mobile CB is very different. In that case, at 102", mounting even the basic 1/4 wave antenna is a compromise, and all the options involve managing loss, not gain.  So, the choice of antenna design, mounting method and mounting location all become critical. This is especially true when you consider the maximum 4 watts of power out of the radio.

 

Anyway, I hope this helps newcomers to GMRS and VHF/UHF in general, ease the entry to the new environment.

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However, the situation in mobile CB is very different. In that case, at 102", mounting even the basic 1/4 wave antenna is a compromise, and all the options involve managing loss, not gain.  So, the choice of antenna design, mounting method and mounting location all become critical. This is especially true when you consider the maximum 4 watts of power out of the radio.

 

Anyway, I hope this helps newcomers to GMRS and VHF/UHF in general, ease the entry to the new environment.

 

Part of the reason  Marc  seams to dislikes the newer CB antennas. Even when they are at 102" he feels they are they are two short and make the radio even more deaf. He wish they were closer to 110" from what I gather. 

 

GMRS I would just suggest what ever you are going to install it. Make sure the antenna has no obstructions in it's line of sight. Even more so if it has a loading coil. The coil has to be above the roof rack, the windshield ect... I have seen significant noticeable differences just by clearing obstructions to the coil. Police cars can have the antennas about anywhere, from what I gather there are repeaters everywhere for them at least in an urban environment. 

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On 7/3/2020 at 4:13 AM, berkinet said:

When discussing antennas commenters often refer to their antenna as "working great."  However, while I am sure the observation is subjectively true, it is a whole different question as to how "great" the antenna is in objective terms.  In other words. Unless you test the antennas in a well equipped and controlled environment it is virtually impossible to draw any concrete conclusions.  

 

A big part of the difficulty in judging a UHF antenna's performance lies in the nature of how we observe them in use. It is pretty simple, do we get good connections to the stations we are communicating with? Given the nature of UHF, in most cases we are looking to contact stations relatively close to us and would probably succeed with a tuned coat-hanger.  A secondary problem, especially for people coming from CB is that FM reception behaves quite differently than AM. AM tends to fade all the way to the point where the noise over-comes the signal. However, FM tends to go from intelligible to non-existent very quickly. Thus, if we receive the signal at all, it tends to be good enough for conversation.

 

There are also a host of other issues, like bandwidth and propagation pattern that may be important in some applications and irrelevant in others. And, finally, there are the mechanical factors ((like corrosion) that are usually only observed after a period of a few months or years. 

 

All of which is to say, and this is strictly my own opinion: Unlike the ham low-bands where you can, and in some cased (low-power/QRP) must spend more on the antenna than the radio, for most GMRS uses, that is not the case.  The perfect GMRS antenna is probably gong to be the lowest priced antenna that meets your basic communication needs* and is built by someone you trust to make quality products. Unfortunately, in GMRS there is no magic perfect antenna.

 

 

* terrain (elevation changes), distance, mobil, fixed or portable, power, etc.

Very wise words my friend!  I love to test, test, test!  I am having issues getting trustworthy HT antenna test results with an SWR meter however.  I have to use a jumper between the antenna and the meter and from the HT to the meter which adds line length to the antenna, however I did hook up a super long foldable C.B HT antenna directly to the meter and tested it.  Not sure how trustworthy the results were, but the SWR was at a 1.9 on 1 and 40, so I feel "Okay" about using it.

My little UHF/FHF antennas do not give me consistant results though.  I have the two BF radios, one UV5R and one GMRS V1, and I purchased aftermarket "super long range" antennas for both of them prior to purchasing the radios....  Don't ask me why...

Now, where I live, I here FRS traffic all of the time, and I have no repeaters in my area, and only have made a few contacts.  So I do not have a means to real world test these antennas.  I did make a dipole for my shop "resonates on GMRS 467......" really well, but not well on FRS, and have two mobile antennas that I use.  Still not enough traffic to even really test the bigger antennas.  

 

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1 hour ago, maddogrecurve said:

Very wise words my friend!  I love to test, test, test!  I am having issues getting trustworthy HT antenna test results with an SWR meter however.  I have to use a jumper between the antenna and the meter and from the HT to the meter which adds line length to the antenna, however I did hook up a super long foldable C.B HT antenna directly to the meter and tested it. 

The main issue with testing HT antennas is duplicating the coupling between the radio and the users body. Yes, the users body is part of the antenna's ground plane, and it makes a huge difference.

I've done the experiments myself. Some of the antennas were screwed into a "SMA" magnet mount, yes they are around, then placed on a 30 to 40 inch square metal sheet for a ground plane.

On a few of the antennas tested the SWR was over 3 or 4 to 1. Removing the magnet mount from the metal sheet and placing it on the back of my hand reduced the SWR to under 2:1 in some cases.

The below links are what others have tried.

https://www.hamradio.me/antennas/ht-antenna-comparisons.html

https://reflector.sota.org.uk/t/antenna-testing-jig-swr/14791

https://www.ko4aje.com/ht_antenna_tests.html

https://kd9nrt.com/2020/07/09/antenna-comparison-test/

http://www.km4fmk.com/NewAntTesting.html

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On 7/20/2021 at 6:18 AM, Lscott said:

The main issue with testing HT antennas is duplicating the coupling between the radio and the users body. Yes, the users body is part of the antenna's ground plane, and it makes a huge difference.

I've done the experiments myself. Some of the antennas were screwed into a "SMA" magnet mount, yes they are around, then placed on a 30 to 40 inch square metal sheet for a ground plane.

On a few of the antennas tested the SWR was over 3 or 4 to 1. Removing the magnet mount from the metal sheet and placing it on the back of my hand reduced the SWR to under 2:1 in some cases.

The below links are what others have tried.

https://www.hamradio.me/antennas/ht-antenna-comparisons.html

https://reflector.sota.org.uk/t/antenna-testing-jig-swr/14791

https://www.ko4aje.com/ht_antenna_tests.html

https://kd9nrt.com/2020/07/09/antenna-comparison-test/

http://www.km4fmk.com/NewAntTesting.html

Thank you for your efforts!  I wish that there was a tried and true method of testing HT antennae!  I wonder how they test in the factory?  I am going to purchase an analyzer and see how that works with the little buggers....

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On 7/20/2021 at 6:18 AM, Lscott said:

The main issue with testing HT antennas is duplicating the coupling between the radio and the users body. Yes, the users body is part of the antenna's ground plane, and it makes a huge difference.

I've done the experiments myself. Some of the antennas were screwed into a "SMA" magnet mount, yes they are around, then placed on a 30 to 40 inch square metal sheet for a ground plane.

On a few of the antennas tested the SWR was over 3 or 4 to 1. Removing the magnet mount from the metal sheet and placing it on the back of my hand reduced the SWR to under 2:1 in some cases.

The below links are what others have tried.

https://www.hamradio.me/antennas/ht-antenna-comparisons.html

https://reflector.sota.org.uk/t/antenna-testing-jig-swr/14791

https://www.ko4aje.com/ht_antenna_tests.html

https://kd9nrt.com/2020/07/09/antenna-comparison-test/

http://www.km4fmk.com/NewAntTesting.html

I love that antenna test jig that the guy made!  I have been thinking of something like that myself but wondered how I would make it simulate an HT.  I guess that it would be difficult as the radios are designed to have us as the counterpoise.  I suppose that we could touch the jig while we test the antennas maybe?  When I have tested my antennas, I have laid them down onto plywood and tested them that way.  Some have good results, some poor, the best SWR's are from the TwayRdio foldable 2M/70 CM antenna on GMRS and 2M/70CM.  The stock antennas are horrid!  But like it has been stated before, there is no real way to accurately duplicate what is going on with an HT antenna while it is hooked to a radio.

 

Thanks again for sharing the links.

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21 hours ago, mbrun said:


The factory most likely tests their antennas with a laboratory grade VNA.

Here is a photo I just took using a calibrated NanoVNA to check one of my 144-520MHz HT antennas. Not bad at all.

I can tell you that the results changed, but insignificantly, between holding the VNA vertical, horizontal, standing it on a table, laying it flat on a wooden table, laying it flat on wooden table with the antenna overhanging the edge of the table, and when touching and not touching the chassis ground of the VNA. 0118946f1562097adebd28bab0125786.jpg

When comparing HT antenna performance, the best comparison of antennas is not going to be it’s SWR, but relative difference in signal strength at some given far field distance using some given amount of input power.


Michael
WRHS965
KE8PLM

Michael,

 

Very cool tool you have there!  I have one in my Amazon shopping cart, just waiting to pull the trigger!  Looks like you have the big one?

Anyhow, I do not have anyone to talk to, however I finally got the code to access a repeater so I have been testing my Nagoya magnet mount coming to and from work on the highway.  So far 23 miles on this little antenna and to be honest that is amazing because the terrain is not easy to navigate!  CB is blocked after about 10-15 even with my 102" whip and running my good radio.  This area is in a gorge, high mountains and a windy highway, so the signal has to maneuver around the mountains to go anywhere.

I will try to test my rubber duckies in the morning, though i do not have much faith.  For now I can reach the repeater from my office at work; I work in a food manufacturing plant and my office is upstairs, right in the middle of the building, I do have a window in my office, but not to the outside world, just to the open foyer area where the other windows are.

 

 

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