Tactical antenna prototype number 3: 445 MHz whip body antenna

One of my projects is to overcome some of the horrific (radio wise) terrain we have a our sites where we play. Well, not only at our sites but the whole country. We unfortunately don't have the opportunity to select our frequency ourselves and carry around HF equipment. We are limited to 444 and 446 MHz which propagates a line of sight, which mean it doesn't help much to throw a bigger punch of power. Besides we are limited to 0.5 W RMS transmit power.

So what can we do?

One things, is that we can make antennas with high sensitivity and try to relocate them higher on our body as well as relocating to higher ground.

A future project to test might be a duplex or simplex reciever located on the high ground, but more on that another time.

My first project is a tactical antenna for the back of the tactical vest. Here is prototype three.

Basically, this is a whip antenna with a 3 winding coil just before connection. It is a half wave antenna of the 444 and 446 MHz (meaning it is tuned for 445 MHz). Contruction is pretty simple. 1 piece of rugged single core RG-58 Coax, tape, glue, a BNC connector and BNC to SMA extension cord.

I don't think the antenna is bad, it is probably just as good as the original whip antenna on my teams radios. However I do not have the numbers to show at the moment. I did a field test where it had slight better audible reception than the original antenna. The original antenna is a whip designed for both VHF and UHF. I think i have to get a SWR meter to get some actual numbers, it might improve the design as well.

I'll get back to you on the design thoughts later.

The contruction is very simple. Slice open the RG58 coax and remove mesh coating and foil. Give it a layer of electrical tape instead of the mesh and foil. Remove a part of the the coating all the way to the core, this is vere you'd like to make a coil on the antenna. I gave the antenna 3 windings, it should probably have 5 instead (have not read theory on this yet though). After I made the coil with a needle-nose plier I re-applied the outer rubber coating of the RG58 and gave it a good spin with the electrical tape. And the final step is to apply the BNC connector.

I think I'll find out how to measure the performance of this a proper way.