Boosting Inexpencive 2 ways (UHF)

[John39466]

Hi Im John, I joined your forum to quickly and effectively get a few questions answered. Besides this intro, I will be brief, as a guy thats not "into" radios, Im a guest in your house, and will try to be "in and out" quickly.

I want to (if possible) take a two way radio to produce a Manned Relay station. Mobility will not be a factor. I understand a new antenna is one way to boost gain(?) Again Mobility not being a factor antenna length is not a concern. (assuming running copper wire can act as an antenna extension/or a salvaged antenna is an option) Also If more power is need that wont be a concern. Im only limited by 2 things, Money and FCC.

So in short, is it possible under these conditions to take 1 two way UHF handheld radio, and increase its effecting sending and receiving range by x2 to x5, If so how.

Thanks Much, John

[mmckenna]

I think I understand what you are asking, correct me if I'm wrong.

You have a UHF radio.

You want to be able to transmit and receive farther.

You are asking if you used a better antenna in place of the stock one, would it greatly improve coverage.

Does that sound right?

So, short answer YES.

Longer answer:

There could be some legality issues here. If you are using an FRS or GMRS/FRS radio, then removing the antenna would run afoul of the FCC. FCC says FRS radios that have been tampered with are no longer approved for use. Removing the antenna would be considered tampering.

If it's not an FRS radio, or maybe it is...
The stock flexible antennas are usually poor radiators of RF power. They are designed for convenience first, function second.
If your radio has a removable antenna, then removing it and installing a better external antenna would GREATLY improve your coverage. I wouldn't venture how much, because there are too many variables.
If the radio has a removable antenna, then you can remove it and if you know the connector type, it's usually pretty easy to find adapters. Using the adapter and some coaxial cable, you can connect to an external antenna and get some great results.

There are a couple of things here:
The antenna needs to be specifically designed for the frequencies you are transmitting on. As a tuning fork vibrates at a specific audio frequency, or as a piano wire makes a specific note, an antenna will work best when it is a specific length. There is some math involved here that I'll bypass, but using a random length of copper wire isn't going to necessarily work well. A properly "tuned" antenna will allow your radio to transmit with proper efficiency.
Antenna height is the other thing. The higher you can get your antenna up, the farther it will "see". Since UHF tends to work line of sight, the more it can "see", the better it's going to work.

So, find the correct adapter for your radio. Get some decent coaxial cable and a proper antenna. Get the antenna up high as you can and you will see a lot better coverage, both transmitting and receiving.

Good luck!

[UPMan]

An enhancement to the above: There are two factors that generally affect range the most. These are (in order of importance):

1) The height of the transmitting and receiving antennas are the biggest factors in determining reliable communications range. Radio signals will not pass through hills, terrain, or solid structures (but most structures are not entirely solid as far as RF is concerned). Radio signals are basically "line-of-sight" meaning that if there is not a clear path between the transmitting antenna and the receiving antenna, reception is not going to be reliable (if possible at all). On "flat" terrain, two handheld radios will have no more than about a 6-mile line-of-sight (and you'd pretty much need to be out on a glacier to have that much open area with no obstructions).

2) The transmit power being used. Higher power will not punch through a hill, but might provide more complete coverage in an environment which might have buildings. You will get some reflection off of structures (or land masses) that could also improve performance within the visual area of the antenna. Power alone will not extend the "horizon" of your radio coverage. Consider that you can talk to a satellite orbiting 17,000 miles away with just 10-20 watts (power is small, but the antenna height is superb).

More minor considerations are the receive sensitivity of the receiving radio, the presence of other radio systems operating on near frequencies, and other things you cannot really have much control over.