“Tiger Tail” or “Rat Tail” Counterpoise for UHF/VHF HT Antennas

[Aron Insinga]

[caption id="attachment_81054" align="aligncenter" width="402"] HT With A Counterpoise[/caption]

I noticed that the HTs used by some local rovers in Winter Field Day had an extra piece of wire sticking out from the base of the whip antenna.  I’ve heard of this use of a “counterpoise” (sometimes referred to as a “tiger tail” or “rat tail”) from instructors in the NARS licensing classes, so I finally decided to search for more information.

They really do greatly improve both transmit and receive performance.  Use an insulated wire cut to the length given in the articles below for your band.  On one end, strip the insulation and crimp on a ring connector that fits around the SMA connector on the HT.  It probably helps to solder the wire after crimping.  Cover the joint with heat-shrink tubing.  Slide a half-inch or so section of heat shrink tubing half-way onto the other end of the wire.  After shrinking this bit of tubing, while it is still hot, squeeze the end sticking out past the end of the wire with pliers, or otherwise seal it up by filling it with a small bit of something like “Liquid Electrical Tape” from a hardware store, or hot glue.  You just want to electrically insulate the end of the wire and also cover any sharp edges where you cut the wire.

There is a nice article at https://newhams.info/2018/12/11/ht-antenna-improvement/ with pictures showing how to mount the ring connector around the SMA connector.  It links to some other articles.

(And by the way, https://newhams.info/, which is maintained by Jim (AF5NP), looks like a good site.  Note that the blog entries are cross-referenced to the question pool for the licensing exam!  It’s great if you want to understand why the answer is what it is, or if it is just something that tickles your curiosity or seems useful to you.)

The page http://www.hamuniverse.com/htantennamod.html with sections by Edward (KE4SKY) and Dale (N6JSX) shows how to do this for an HT with a BNC antenna connector.  It references the PDF file http://www.hamuniverse.com/n6jsxEasy-HT_1.pdf  by Dale (N6JSX) which gives the diameter of the eye in the ring connector for each type of antenna connector and has a table of the lengths of the wire for a number of  VHF/UHF frequencies.

Mike (KM4FMK) did a test and posted the complete results at http://www.km4fmk.com/blog/counterpoise.html.  His bottom line was that it produced significant improvement for both transmitting and receiving.  He also found that, if you have an HT with multiple bands, you’ll want to switch counterpoises to have one of the appropriate lengths when you switch bands.  This was a single test in a particular environment, so of course, Your Mileage May Vary.

These articles also describe the size and type of wire.  The counterpoise wires used by the rovers in Winter Field Day for the much higher frequency bands were solid so that they could stay perpendicular to the antenna.

You don’t need a counterpoise with a mag-mount antenna on a vehicle because the roof of the vehicle is a great ground plane all by itself!

Use some caution to not put extra stress on the SMA connector because it (or its connection to the circuit board inside) can break, and to not poke yourself or anyone nearby with the end of the wire, and to make sure the tip of the wire is insulated for safety.  Don’t touch the antenna or the counterpoise when transmitting!

[Aron Insinga]

p.s. Do check that the ring terminal will fit over the antenna connector.  The ones I have on hand do not, so I have to go shopping tomorrow!

[Fred Kemmerer]

Hi Aron,

If you have a terminal that is close, a little work with a drill can get you there. Let me know if you can’t find terminals that will fit. I probably have some more that will work here.

 

[Aron Insinga]

Thanks, Fred.  I got larger terminals at an auto parts store and was able to finish the assembly for 2m and 70cm.  I need to look at the HT manual, or the data I used for chirp to program the HT, so that I can see which repeaters are 2m and which repeaters are 70cm, so that I know which counterpoise to use.

Soldering the wire to the crimp part of the connector is important, especially if the wire is thinner than the connector was designed for!

I took pictures during process and will add them here.

I have SMA-BNC/BNC-SMA adapters on the HT and the whip antenna and a mag-mount antenna so that I can do a quick BNC connect-disconnect to change antennas.  This let me add the counterpoise between the whip antenna and the SMA-BNC adapter, making adding and removing the counterpoise automatic when adding and removing the whip antenna; there’s no extra part to handle or store.

 

[Aron Insinga]

Here are pictures of:
* The 2m and 70cm counterpoises after removing ring terminal insulators, crimping, and soldering.
* Installing the 70cm counterpoise on a Yaesu FT-60R dual-band HT. Note the heat-shrink tubing covering the crimped-and-soldered connection.
* After installation of 70m counterpoise.
* After switching to the 2m counterpoise. Note the heat-shrink tubing on the end of the wire. The hole in the end of the tubing was sealed with a tiny drop of “Liquid Electrical Tape.”
(The SMA-BNC adapters I normally use with this xcvr were removed for clarity.)

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