Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Counterpoise on HT?  (Read 3651 times)
KE2KB
Member

Posts: 653




Ignore
« on: December 26, 2016, 03:49:00 PM »

Hi;
I just ran a simple test and am astounded at the result.
I wanted to know what the SWR of my Diamond RH77CA 1/4 wave antenna would be when attached to my Yaesu VX-150 HT.
I couldn't exactly measure the SWR with the antenna screwed into the SMA (using a SMA to BNC adapter) connector on the HT, so I rigged my SWR meter to "act as" the HT for this test. My SWR meter is the Swan SWR-1A.

I connected the HT to the Swan using a 24" length of RG58A/U cable (and a UHF to BNC adapter).
I attached the RH77CA to the Antenna connector on the Swan (using a UHF to BNC adapter).
I set the radio to 147.450Mhz (it just happened to be there, and that is a simplex frequency), and set the output power to "low", which, on this radio is less than 1W.

My location for this test was my shack, which is on the 2nd floor of my home, about 12ft above the ground.

I held the Swan in such a way that the antenna was pointed upwards, and I could read the meters.
I keyed the HT (announcing my call, and "testing") and adjusted the Swan to read the SWR.
The reading I got was at least halfway through the red zone of the scale, indicating that the SWR was somewhere between 3:1 and infinity.

I couldn't believe the result, so I checked every connection, and tried different positions of the Swan/antenna, but it only increased or decreased the SWR slightly.
Still wanting to check the Swan meter, I connected my outdoor Ringo Ranger ARX-2B to its output.
The SWR at the same frequency read about 1.4:1, which is about what I got yesterday when I checked the Ringo.
So the Swan, and my cable/adapter was working properly.

For the next test, I attached a 20" length of #16AWG wire to a screw near the antenna connector on the Swan. I positioned the Swan and the new counterpoise so that the antenna pointed up, and the counterpoise pointed down.

The SWR reading with the counterpoise was somewhere around 2:1, and it depended somewhat on the angle I positioned the antenna (the Swan meter) and the counterpoise, with the best result when the counterpoise was pointing as straight as possible towards the ground with the antenna pointing straight up.

After running these tests, I did a Google search and found this interesting article:
https://kc4lmd.wordpress.com/2015/08/04/what-happened-when-i-added-a-counterpoise-to-my-ht/

So now I'm thinking that perhaps adding the counterpoise to the HT is a bit more complicated than it appears. My tests showed the counterpoise to drastically reduce SWR, but this was while standing more than 1/4 wave above the ground. My next tests will be:
1) Run the SWR comparison while standing on the ground - trying different locations; dry concrete, wet earth, etc.
2) Set up my SDRPlay to receive and record my signal as I walk through my neighbourhood, announcing my call at various points, and making a mental note on where I was at each call.

I'm considering purchasing an antenna analyzer (I am looking at the RigExpert AA-170), which I intend to use mainly for building HF antennas, but this counterpoise thing looks interesting, and I might be able to get some useful info from an analyzer. I could set it up as the "rig" instead of using my HT, or I could rig up a setup that would simulate using the rig with and without the counterpoise, where the HT actually performs the function of interfacing my body to the antenna with and without the counterpoise. I saw this done in another ham's blog; the coaxial cable from the analyzer was terminated at the HT's antenna connector in such a way that only the shield of the coax made connection to the shield of the HT's connector, while the center conductor of the coax went to another connector onto which the antenna was attached. I am not sure whether the antenna's BNC or SMA "shield" was connected to the radio's shield or not, but I can examine that if and when I get the analyzer.

I guess everyone's antenna situation is unique in some way, and should be analyzed as such.

Your thoughts?

Thanks
Frank - KE2KB
Logged
N8EKT
Member

Posts: 593




Ignore
« Reply #1 on: December 26, 2016, 04:48:27 PM »

Hand held radio antennas are designed with being hand held in mind so you and the radio become part of the antenna.

A counterpoise wire 1/4 wavelength long is a good addition when you use 1/4 wave or 5/8 wave designs.

That's why I always use 1/2 wave ht antennas.

They don't need the counterpoise to work well.

I think the AEA isopole ht antenna was likely the best 2 meter ht antenna I've ever tested.

Sad that they quit making them but MFJ makes a 1714 that looks similar
Logged
KE2KB
Member

Posts: 653




Ignore
« Reply #2 on: December 26, 2016, 05:28:56 PM »

Hand held radio antennas are designed with being hand held in mind so you and the radio become part of the antenna.

A counterpoise wire 1/4 wavelength long is a good addition when you use 1/4 wave or 5/8 wave designs.

That's why I always use 1/2 wave ht antennas.

They don't need the counterpoise to work well.

I think the AEA isopole ht antenna was likely the best 2 meter ht antenna I've ever tested.

Sad that they quit making them but MFJ makes a 1714 that looks similar
I'm  about to do some more experimenting with the counterpoise. I will take my 2m HT (VX-150) out with me when I walk my dog over the next few days, and from various points I will call on one of the 2m simplex frequencies, all the while my SDRPlay/SDRUno is recording what it hears from home.
I should be able to see the difference in the signal, assuming I am standing in exactly the same location and position for both tests. I don't usually go very far from my home QTH while walking the dog, but using the VX-150 on low power and the SDRPlay with a random-wire HF antenna I set up, may provide enough attenuation so I can get some data from the testing. If that fails to produce results, I'll take my HT with me on my next long run, when I go sometimes 10-20 miles from my QTH.
If I get into a QSO with another station, then all the better.

I do plan to buy the MFJ-1714S, but with HRO shipping on the $16 antenna is almost $10, so I'm waiting to see whether or not I decide to buy the Rigexpert AA-170 (which will get my order free shipping) before I buy the antenna. Otherwise, I'll have to wait for the next hamfest to buy one.
In any case, this is helping to relieve the drab winter blues I have right now.
Logged
WB6BYU
Member

Posts: 17192




Ignore
« Reply #3 on: December 27, 2016, 11:19:44 AM »

Measuring the SWR on a HT antenna isn't as trivial as it might sound.  That's because the body of the
HT is part of the antenna, and anything else you mount the antenna on that isn't exactly the same
can shift the resonant frequency.

In your case, the "ground plane" for the antenna is the SWR meter plus the outside of 24" of
coax plus the HT at the other end of the cable.  That's longer than 1/4 wavelength, while the
dimensions of the original HT case by itself is less than 1/4 wavelength.  Sometimes manufacturers
will tailor the antenna characteristics so they work best with the specific HT size they are made
for.  Of course, sometimes they just use any sort of antenna that is vaguely close in frequency
because so few hams can actually measure their antennas.  Assuming that your SWR meter is close
in size to your HT, you would get a better reading if you could add some sort of decoupling (perhaps
a stack of suitable ferrite beads) over the coax jumper where it connects to the SWR meter to
isolate the rest of the equipment from the measurement.

Once you add the counterpoise, much of the antenna current will flow on it rather than the attached
equipment, so your results will be more consistent.



As far as the actual process of measuring the effect of adding the counterpoise, I've done that
several times, with varying results.  My recommendations:

1) if your radio has an S-meter, the easiest approach is to find a distant repeater or other signal source
that is on much of the time and see how much difference adding the radial makes.

2) reflections cause great confusion in measurements at VHF and UHF.  The measurements will be most
accurate done outdoors in a clear area (for both the transmitter and receiver) and with the antenna
at least head high, or otherwise above or away from your body so reflections off of you don't affect
the measurement.

3) The location of the equipment at both ends must be very repeatable.  In one case I used some
sort of sign post or stand having a low wall around the edge:  I could place the HT snuggly in the same
corner of the wall each time to within 1/4".

4) The end-fed wire on the receiver will have multiple lobes and nulls in the pattern, and respond to
different polarizations in different ways.  I'd recommend making a cheap ground plane or other such
antenna to use with it that has a more predictable pattern:  this will reduce the opportunities for
variation in measurements, especially when the HT location isn't exactly the same every time.

Another option for measurements would be a simple Field Strength Meter driving a digital multimeter:
it may have to be fairly close to the transmitter, and you'll have to convert the readings to relative
power, but it can give a reasonable resolution.


For the particular equipment you are working with, an improved procedure might be to select a few
different measurement locations, and at each provide some sort of repeatable location for your HT.
It might be a chalk rectangle drawn on the top of a fence post, or a tripod or other stand that you
carry with your on which the HT and antenna can be mounted securely.  Then, at each location,
take multiple measurements, perhaps a total of 10, alternating with the radial on and off.  That
allows you to see how repeatable your measurements are for the same condition, and you can
take the difference of the averages to get a nominal increase (or decrease) in signal strength.

You end up with multiple measurements from several sites to give you a better overall indication
of performance, because any one location (or more, of course) might be adversely affected by a
particular case of reflections or blockages.  If the variation in measurements for a single condition is
greater than the difference between the two conditions, you need to improve you methodology
to get an accurate indication of the difference.

One method I've seen for testing convenience is to attach the radial wire to an alligator clip that
can be easily attached or removed from the ground on the antenna connector.  I generally just
twist the bare end of the wire into a loop that fits around the BNC jack and plug the ducky on top
of it, but that assumes a thinner wire.  (A large lug also works.)  The minimum that you need to
disturb the setup to add or remove the wire, the more repeatable your results will be.


Oh, and the halfwave AEA antenna was called the HotRod.  The Isopole was a different design with
metal cones for a base station antenna.
Logged
KE2KB
Member

Posts: 653




Ignore
« Reply #4 on: December 27, 2016, 02:10:23 PM »

Last night when I went out, I left the HF (horizontal wire) antenna connected to the SDRPlay. Signal attenuation at 146.520Mhz from the 1/4 wave (vertically polarized) antenna on the HT was higher than I had anticipated. When I was only about 1/4 mile away from the receiving antenna, the signal started to drop way down. I had the HT set for low power, which is only about 500mW. After that, I didn't get any signal at all.
This morning I went out again, but had the Ringo Ranger connected to the SDRPlay. Results were more usable, but as you (WB6BYU) stated about doing multiple tests at the same location, and getting the HT into exactly the same spot, the results were inconclusive.
But in all of my tests over a route that took me about 1.5 miles in a loop, adding the counterpoise never made the signal worse.

I do believe that in that blog I mentioned for testing the 1/4 wave whip with the antenna analyzer, there was a choke at the antenna end of the connecting coax. I had completely forgotten that detail when I did my SWR testing. He also used the HT itself as the ground plane, so that would produce more useful results to start with.

I am planning to purchase a 1/2 wave antenna for the HT. The MFJ-1717S. I also had the AEA "Hot Rod" 1/2 wave telescoping whip. It was a very heavy antenna, but I was using it on an FT-530, which has a BNC and is very well built, so there was no damage caused by the weight of the antenna. The VX-150 and FT-60 on the other hand use SMA connectors, so I'm not sure how well those radios will handle the weight of the MFJ-1717S, but for $16, I'll try it out. I would expect that, so long as the antenna is kept vertical all of the time, it won't put too much strain on the radio's connector.

For the continued testing of the counterpoise, I will see what I can rig up for getting the radio into a precise location for the entire test at each location. I also plan to put more distance between transmitter and receiver. I'll also check out some distant repeaters, and also try to contact some stations who can hear me either way, and have an s-meter on their rigs. The VX-150 and FT-60 have a rudimentary s-meter, but it's not nearly as accurate as a true s-meter would be. The SDRPlay displays everything, so on its end, I can get a very accurate signal report.

For testing receive, I have used the NOAA weather stations, but either they are too far away, and band conditions are unpredictable from one minute (or second) to the next, and/or the transmitter is too strong to show any difference. Besides that, they are at 162.500 Mhz, which is so far out of the amateur band that the antenna gain may be starting to fall off.
Perhaps, placing an antenna analyzer with a loop antenna tuned to the frequency being used and set up at some specific-fixed distance from the HT with its 1/4 wave whip would be a better method of testing the effect of the counterpoise for receive.

Wouldn't it be great if there were a tool that could measure, and display visually, the radiational pattern of an antenna.
Logged
WB6BYU
Member

Posts: 17192




Ignore
« Reply #5 on: December 27, 2016, 05:05:54 PM »

Quote from: KE2KB

Wouldn't it be great if there were a tool that could measure, and display visually, the radiational pattern of an antenna.




You mean something like this?  That's done by rotating the antenna (in this case a beam on a mast sticking out the
top of his van) and plotting the S-meter reading vs. angle on a 'scope with a long persistence phosphor.  
There are other methods that digitize the process.

One other thing you can try doing is trimming the length of the radial for maximum signal strength.  It may vary from
one radio or antenna to the next.
Logged
KE2KB
Member

Posts: 653




Ignore
« Reply #6 on: December 28, 2016, 07:59:02 AM »

Quote from: KE2KB

Wouldn't it be great if there were a tool that could measure, and display visually, the radiational pattern of an antenna.




You mean something like this?  That's done by rotating the antenna (in this case a beam on a mast sticking out the
top of his van) and plotting the S-meter reading vs. angle on a 'scope with a long persistence phosphor.  
There are other methods that digitize the process.

One other thing you can try doing is trimming the length of the radial for maximum signal strength.  It may vary from
one radio or antenna to the next.
Is that used for transmitter hunting? When I used to do that, I used a simple 5-element yagi, but others used something called "dopplerscant" which was a circle of 8 antennas mounted at compass points on a plate, then to the roof of the car, fed to a phase detecting circuit and displayed by LED's also in a circle of 8, indicating the direction to the strongest signal.
Logged
WB6BYU
Member

Posts: 17192




Ignore
« Reply #7 on: December 28, 2016, 09:15:59 AM »

That's one of a number of methods of rotating a beam and displaying the resulting pattern for
transmitter hunting.  It allows one to see all the peaks and nulls, both due to the antenna as
well as those due to reflections, blockages, etc.  This particular unit includes a compass so
the display is always centered on North, even when the car is pointing some other direction.
Logged
KM3F
Member

Posts: 794




Ignore
« Reply #8 on: December 28, 2016, 12:00:52 PM »

We just used a Kenwood THF-6 for interference hunting using a dual band hand held beam.
The interference was all the way up beyond the 70cm band.
The HT is wide band receive all the way to 1300 mhz. so the 5 element beam worked very well on 70cm.
On AM mode at 70cm, the interference was finally found coming from a power pole out in a pasture where the lines run more than a mile way from the QTH..
Used Binoculars to see the pole  number for reporting to the power company..
.
Next, I did extensive testing and building for this same HT.
Using a COMET Ca500 Mkii, it's metal case takes the place of the HT for testing antenna SWR.
A back up test with an small SWR meter rated for the frequency attached to the HT and directly to the antennas verified the same reading on the HT  under power.
I found virtually no multiband Duck  antenna was even close  for SWR match on bands above 2m as supplied from the factory.
With a Duck antenna, the use if a flying wire about 20 inches long for 2m does affect the performance when using a Duck  antenna.
I have built very light weight 3/4 and full wave antennas with tuned L networks at the feed point that are insensitive to  hand capacity on the HT or the analyzer.
These antennas perform way above a Duck if you can accept the whip length and needs no extra flying lead.
They are also as sensitive to polarization  and direction as a beam would be and seen by doing long distance direction tests. I monitored a QSO at close to 40 miles over the mountains and ask if the stations were running beams horizontal. They were, as found by holding the HT horizontal with special antenna the same and broad side to their direction for max signal.

Believe it or not, this THF-6 outputs a full 5 watts on all three bands 2m, 222 and 70cm into a dummy load.
I also use it as a monitor for my home brewed 222 all mode transmitter that is capable of running 180 watts.
Good luck.

Logged
K8AXW
Member

Posts: 6378




Ignore
« Reply #9 on: December 30, 2016, 09:13:01 AM »

Adding a counterpoise to an HT (called a Tiger Tail) has been going on for a very long time.  The results are mixed or varied depending on who did the experimenting.

From all I've read, it's pretty much a waste of time and effort.  As one pointed out, the radio and our body is the "other half" of the antenna. 

I have found that longer whips (duckies) do better than the shorter antennas sometimes supplied by the manufacturer.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!