Antenna Tech / Technical Articles

Part 9: How to Build Antennas from a Blind Ham’s Perspective (and if You’re Not Blind, You’ll Learn Something, Too!)

Editor’s Note: Over the next several months, OnAllBands will be featuring a series of articles from Harry “Trippy” Brown, AC8S, longtime amateur operator and antenna builder/tester who’s never let his visual impairment stop him from enjoying the hobby he loves. As the title of this series states, we hope these articles provide you with invaluable insights as you pursue your own successful antenna projects.

In our continuing look at antenna building, I’ll be offering a few more of my opinions on dipole/inverted-V combo antennas, coaxial cables, connectors, and mag mount antennas. To read the first eight entries in this series, just enter “Trippy” in the OnAllBands search box above.

Which antenna is better: a dipole, a vertical, a dipole/inverted-V combo, an inverted-L, or an end-fed?

From my perspective, the best antenna to use, by far, is a dipole/inverted-V combo. Here’s why:

  1. You don’t have to ground the antenna.
  2. You don’t have to use radials or any counterpoises.
  3. Verticals and inverted-Ls, which are a quarter-wave vertical bent to fit into the available vertical height, need a number of radials (32 radials, according to Joe, W1JR). For me, radials are not something I want to mess around with.

How can I make sure my SO-239 connectors stay free from any water or moisture damage?

This is a problem that all hams can avoid. Buy a Diamond Antenna Weather Cap for UHF, SO-239 Mounts from DX Engineering. I love this cap. It’s a waterproof screw-on type that covers the SO-239 connector and keeps water out.

As far as the coax connector is concerned, my coax is so short (it’s only 14 feet long), so I just bring it back inside the shack when I’m not using it. When I want to use it on a non-rainy or non-snowy day, I take it outside, unscrew the SO-239 cap, and connect the PL-259 connector to the SO-239 connector on the balun. In doing that, I never will have water in the coax, the coax connector, or the SO-239 connector.

How long should I make the dipole/inverted-V combo or end-fed?

As long as possible. Here’s why: The longer the antenna, the higher the wavelength you’ll get and the more dB gain. Also, on higher frequency bands, the same antenna of the same length will be a longer wavelength on those bands, giving you a higher dB gain. As an example, Bob, W7SX, notes that if you have a half-wave vertical, dipole/inverted-V combo or end-fed on 40 meters with a 1.6 dB gain, if you run the same antenna on 20 meters at the same length, it is now a 1 wavelength with a dB gain of 3.6!

Is there any fire danger when using antennas indoors or outdoors?

Yes. Outdoors, if you’re using 20 watts or more and copper wire for the antenna, do not let the antenna touch anything that is combustible. When you’re transmitting, the RF will catch things on fire if any of the antenna touches something combustible. If you’re using a dipole/inverted-V combo indoors, use insulated wire because there is no fire danger using insulated wire and no more than 20 watts.

What brand of coax should I buy for my antenna?

When you buy coax for the antenna, buy the better brands that are used and trusted by more hams, such as DX Engineering coaxial cable.

Should I have them custom make a piece of coax for me?

If possible, I prefer buying precut lengths, but if the length you need is not precut, then yes, you can have them custom make a piece of coax for you.

Can I use hard line instead of coax?

I take the advice of Joel Halis, W1ZR, who told me not to use hard line because it will break if you try to bend it.

What should I use to feed my antenna to my radio or external antenna tuner?

I only use RG-213 coaxial cable. I prefer using RG-213 coax over LMR-400 because it works well with PL-259 connectors and is only a ½ S unit less in signal strength when transmitting than LMR-400. I do not use ladder line (also called open wire line) because if it touches any metal, it will short out the antenna, and the SWR will go way up.

If I build an antenna by putting a piece of coax or wire inside PVC pipe, will it work?

According to Emmett, W0QH, who works with antennas, “No, it will not work. But you can put a piece of coax or a piece of wire inside an aluminum pipe, and it will radiate well because aluminum is a great radiator.” I personally tried using a piece of coax inside a PVC pipe and it did not work.

How long should my coax be to connect my radio to the antenna?

Buy the shortest precut length of coax you need, because the longer the piece of coax, the higher the line loss and the higher the SWR. However, don’t buy a length of coax that is so short that it pulls on the radio or antenna tuner that the coax is plugged into. Add three extra feet so it won’t pull.

What about using mag mount antennas for non-mobile use?

I use mag mount antennas for non-mobile use only for 10, 6, and 2 meters. They’ve never worked on any other band for me. The mag mount must be placed on galvanized steel or other metal. Now if you use a mag mount on a vehicle, they work perfectly on all HF bands plus 6 and 2 meters. You can put them on a cookie sheet, or on top of a refrigerator, metal filing cabinet, or tin roof. Any plane of metal is great, and it does not have to be grounded. A metal screen makes a great place for a mag mount as well, and your antenna will work fantastically on 10, 6, and 2 meters.

Stay tuned. More good stuff next week!

Leave a Reply