[HiDARG-MEMBERS] Folding HT antenna

Sat Jul 13 12:26:18 EDT 2019

Good stuff….

The goal is to figure out if these foldable flat antennas have better performance over the stock duck or aftermarket verticals…

It would be interesting to see the actual pattern however.

..Max

From: HiDARG-Members [mailto:hidarg-members-bounces at hidarg.org] On Behalf Of Doug Miller
Sent: Saturday, July 13, 2019 08:18
To: HiDARG Members
Subject: Re: [HiDARG-MEMBERS] Folding HT antenna

 It’s probably obvious, but instead of taking measurements around a circular path, an alternative is to rotate the antenna And record field strength with each antenna orientation.  I’ve done this before with a tripod using 10 or 15 degree increments. This is easy to set up and execute, and also helps eliminate the influences of terrain and surrounding objects.  

 With these types of tests in the military and aerospace environment I’ve seen labs typically trying to ensure they are taking measurements at least 3 to 5 times the Fraunhofer distance, which is considered the boundary of the radiating near field. For a typical 2 meter antenna this is much less than 100 feet. 

https://en.m.wikipedia.org/wiki/Fraunhofer_distance

Doug

W7ZV

Sisters

On Sat, Jul 13, 2019 at 7:59 AM Max Vaughan bb <maxv at bendbroadband.com> wrote:

Extracted from various sources….

You should not need more than 100ft circle with no nearby metal or reflective surfaces.

Normally used to determine antenna directional patterns, in an ideal setting.

Walk around the circle get various readings, and draw on grid paper…. that gives you the pattern.

But that is not what you’re doing here…. your comparing signal strength over a set distance.

Actual distance is less important than getting a relative reading at a set distance and comparing that same 

exact setting and reading with the same power and a different antenna, again the number you get is not important

the difference in the reading from the same exact positon of the units being held and their settings etc is what you are after.

Any change in the sensitivity controls between one antenna and another will not be valid.

Use the sensitivity control to adjust the reading to get at least half scale, if too far away then get closer….

Once set don’t change sensitivity while comparing….

Also how close a person is to the transmitter, and meter is important as well.

Don’t change the way you hold each unit between each antenna your testing.

Arms length, straight out away from body is easier to do and track.

Distance from body and height above ground should be keep the same between antennas.

Don’t change who holds radio and transmits and who is holding meter between antennas under test.

Ideally, you would want a tripod to hold the antenna, and an extension cable to the HT, and the operator

opposite the FS meter side.

IE the goal is to minimize all variables between two antennas you are comparing.

If you want to test the actual pattern of an antenna, you have to have a set circle.

Transmitter / antenna can’t move position, FS meter rotates around the circle at various points logging reading.

From: HiDARG-Members [mailto:hidarg-members-bounces at hidarg.org] On Behalf Of Mike Williams
Sent: Saturday, July 13, 2019 00:31
To: HiDARG Members
Subject: Re: [HiDARG-MEMBERS] Folding HT antenna

I wonder if any articles in QST or that experimenters journal about antenna testing this way?

On Fri, Jul 12, 2019, 11:27 PM Jeff Moore <tnetcenter at gmail.com> wrote:

I think an area like a football or soccer field would work great for this or a large open park.   100 feet may not be far enough to get good readings.  A 5 watt HT can throw out a signal that can reach miles depending on terrain.  I'm pretty certain at this point that 10 or 20 feet is way too close!  100 - 300 ft may even be too close.  We'll have to try it out and see what we get.   Like I said before  "play with our radios"!

Jeff Moore  --  KE7ACY

On Fri, Jul 12, 2019 at 11:01 PM Mike Williams <kb7klt at gmail.com> wrote:

Ya.. I've been camping and doing more for a bit..then I'll be around to try that...The weekend of the 20th and the 27th looks good too...

How big an area would we need?  5/10 acre grass fields? bigger? dunno 

de Mike KB7KLT

On Fri, Jul 12, 2019, 7:38 PM Jeff Moore <tnetcenter at gmail.com> wrote:

I don't know how "scientific" any of this will be but I will document it as best I can and share that with everyone.

Hey Joe Barry,  you want to bring your antenna analyzer down and play with us???

Jeff  Moore  --  KE7ACY

On Fri, Jul 12, 2019 at 7:31 PM Steven Fletcher <srfletcher at gmail.com> wrote:

Jeff

I'd love to see this documented even if the science of it is not perfect.

It is something I have thought of doing

BTW last night on our UHF simplex net (446.575) I did a shoot out between the $20 guaranteed for life antenna and the $10 titanium Chinese antenna

the $10 antenna won 

not scientific but somewhat indicative

steve

Steve Fletcher

Phone: 541-699-1909

Grant County ARES Emergency Coordinator

K7AA  

 <http://drawingforth.org> My Blog 

------ Original Message ------

From: "Jeff Moore" <tnetcenter at gmail.com>

To: "HiDARG Members" <hidarg-members at hidarg.org>

Sent: 7/12/2019 7:19:41 PM

Subject: Re: [HiDARG-MEMBERS] Folding HT antenna

Hi Mike,

I got a digital field strength meter from Kent at the meeting last night - one of the QRPGuys kits.   Playing around with it last night in my room was somewhat inconclusive - likely because I was way too close to get meaningful readings from it ( 10 feet).  So I suspect that to do realistic tests I need at least 100 feet of separation between the ht/antenna and the meter.  I'll need help to do it.  It looks like I have access to a couple of other Field Strength meters (one a military surplus unit and one that looks like it could be homebrew with John Ogden's name on it).  I have no idea if any of them actually work, the QRPGuys unit- seems to work but, I haven't tested the other two units. 

So, do you want to get together with a bunch of HTs and antennas and see what we can figure out???  We can go to a local park (open the invitation to the entire club) and set up an ad hoc antenna test range and play radio!  Or . . . .?

Jeff Moore  --  KE7ACY

On Fri, Jul 12, 2019 at 1:31 PM Mike Williams <kb7klt at gmail.com> wrote:

I would be interested in comparing my cushcraft 4-ele too...also have other homebrews to look at.

de Mike KB7KLT

On Wed, Jul 10, 2019 at 3:38 PM Jeff Moore <tnetcenter at gmail.com> wrote:

Hi Everyone,

I figured there would be some interest in this antenna.  I have the 28.3-inch version, there is one longer version and two shorter versions.  Note that the ad on Amazon also includes a couple of different length extension cables, so be sure you're ordering the antenna not one of the cables(unless you want one fo the cables:-)! 

I'm still testing this antenna, but so far it's at least as good as the antennas I have and I think the longer (42-inch) version will work really well with a GO BOX that has VHF/UHF capability.  It's also available with both a female SMA connector and a male SMA connector so it will fit on a lot of radios (provided you get the correct connector).

Anyway, for the price - hard to beat!!!   here's the link:

https://www.amazon.com/gp/product/B07RRPC8VQ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8 <https://www.amazon.com/gp/product/B07RRPC8VQ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1> &psc=1

These are ham band antennas so be aware that they will probably not work very well outside the bands - I noted a reviewer who was complaining that the antenna didn't seem to work at 150 MHz or 466MHz (both outside the ham bands).   Testing these antennas (or most HT antennas) with an antenna analyzer can be tricky since the chassis of the ht is often used as a pseudo-ground-plane and inserting the analyzer between the antenna and the radio may not give you a good reading.  A better testing method is to use a field strength meter at a set distance from the antenna/radio being tested.

Does anyone have a field strength meter???  We could set up a quick and dirty antenna test range that would reveal just how effective a particular antenna is based on actual RF output!  I've heard that the results of such testing can be very revealing.   

Enjoy!!!

7  3

Jeff Moore  --  KE7ACY

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-- 

DOUG MILLER
dougmiller72 at gmail.com

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