VHF/UHF OMNI ANTENNA FOR SOTA USE 17 JUNE 2019 by BOB K0NR

For Summits On The Air (SOTA), I’ve been using just the VHF/UHF ham bands, with the 2m band being the most popular. For most activations, I use a 3-element Arrow II yagi antenna that has a gain of about 6 dBd. Sometimes that extra gain makes the difference between completing a contact or not.

Omnidirectional Antenna

The RH770 Dualband Antenna with BNC Connector

But it is also handy to have an omnidirectional antenna that is easy to deploy. Sometimes I’d rather just call or monitor using an omni without having to point the antenna. “Easy and good enough” can be an effective strategy for SOTA.

A key advantage to an omnidirectional antenna is that it is always pointed in the right direction.

I usually carry one of the TWAYRDIO RH770 VHF/UHF antennasfor use with my 2m/70cm handheld transceiver. Despite its low cost, I have found that its performance to be quite good. That antenna is offered with a variety of connectors, including a BNC.

This led me to the idea of putting together a simple antenna mount with a BNC on it, attach an RH770 antenna to it and support it using some kind of pole. I have several monopod devices (intended for use as a camera support) that use the standard 1/4-20 thread. I also have a trekking pole that has the same camera mounting thread. Another option is to use an actual camera tripod which is a bit bulky but may work for some SOTA activations.

After a short visit to the hardware store, I selected crossbar for mounting a light fixture that was about the right size and shape. I happened to have a bulkhead-mount BNC-to-BNC connector which I inserted into the large hole in the crossbar. That hole was not quite large enough for the connector, but a few minutes work with a round file solved that problem.

After some filing to expand the hole, the bulkhead BNC connector (female-to-female) was inserted into the main hole in the crossbar.

The crossbar was originally flat but I bent one one end of it 90 degrees, with the idea that this might offer other mounting configurations in the future. For example, I might be able to strap or tape the 90 degree angle member to a pole or support.

The monopole support is inserted into one of the slots of the crossbar. Again, some filing was required to make the slot big enough for the 1/4-inch thread.

The other end of the crossbar has a large slot that accommodated the 1/4-20 mounting stud. Actually, the slot was not quite wide enough, so some addition work with a round file opened it up. I secured the 1/4-20 thread using a nylon wing nut.

A nylon wing nut (1/4-20 thread) is used to attach the crossbar mount to the monopod.

I’ve used this setup on one SOTA activation and was pleased with the results. I carried the crossbar mount attached to the monopod in my pack. On the summit, I simply installed the RH770 antenna onto the top BNC and extended the monopod. On this summit, I found the perfect pile of rocks that made a good support for the monopod. Then I used a short length of RG-8X coax between the bottom BNC and the 2m/70cm transceiver.

The antenna support in use: the RH770 antenna attaches to top BNC connector, the crossbar mount attaches to the monopole which jammed into a pile of rocks on the summit. An RG-8X coaxial cable feeds the antenna through the bottom BNC connector.

Although my primary interest was with the 2 meter band, it was really convenient to have both 2m and 70cm on the same antenna. I am pleased with operation of the antenna and the ability to deploy it quickly. I expect to carry this on most of my SOTA activations.

73 Bob K0NR