Using UV5R HTs. Will i lose receiving range by attaching coaxial cable to put my antenna remotely as well as higher?

Question

Using beofeng UV5R HTs. Changed antennas to retevis whips. Will adding coaxial cable to HT & antenna for height reduce or increase reception. As i'm in a valley. I receive only. As i'm still studying for my licence. Gratitude in advance for any help. As i'm very new to this world.

Answer 1

The answer is that it depends, although in my experience increasing height will always improve range. Height matters a lot in most VHF propagation. For your UV5R HT, antenna height will generally trump any loss in the coaxial cable. A few dB makes very little difference. I recently raised my antenna from 24' to 50' and I've seen 20dB or more improvement from signals 20-50 miles away That's many times more improvement than you would lose from an extra 26' of coax.

Answer 2

You have to be pretty high up in frequency (basically in GHz instead of MHz) where the coax loss becomes more of a factor than the gain you'll benefit from getting an antenna that much further away from the ground.

The further you get an antenna away from the ground, you get:

1. dramatically increased line-of-sight distance
2. somewhat less signal losses to the soil
3. possibly less local noise (?)

And especially when receiving, any coax loss really isn't a problem. See e.g. https://ham.stackexchange.com/a/17922/1362 for more details, but basically:

for reception quality we're interested in signal-to-noise ratio

Your receiver can usually add the gain back it needs to compensate for any coax loss (which should attenuate both the signal and the noise ± equally anyway). So usually far better to give a good antenna a better "bird's eye view" — out of the valley, away from all the phone chargers and LED transformers and whatnot in your house with a little bit of coax loss, than to use a stubby antenna down by the ground.

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All that said though, one important caveat! What I said is all good in theory but in practice sometimes especially the more cost-effective receivers end up doing worse with a better antenna: Why do Baofeng radios have such poor reception reliability?

With my Baofeng's I often find:

1. poor reception with stock antenna
2. no reception with a good antenna (!!!)
3. good reception with a good antenna and a filter to block 88–108 MHz which is the FM broadcast band here in the USA (quite strong signals from good towers for commercial music/news programs/advertisements)

Basically the receiver could amplify a weak signal however much it needs. But if there's also really strong out-of-band signals those throw a wrench in that idea, because in the real world the amplifier itself ends up distorting on the strong signals and making hash of everything, before it can get the weaker signals up to their proper level.

Answer 3

You've received some good answers here saying height means everything.

The exception to that is if part of the coax has a long horizontal run.

For example, this chart asserts that there's 1.7dB loss per 100m of RG8 type cable at 146MHz. So if you're running 100m of RG8, then you'll want a signal gain of at least 1.7dB to break even in terms of receiving a particular repeater or station.

And it may be worth it regardless if the new height gives new line of sight to signals you're missing completely today.

Answer 4

Adding coax will reduce power. A common mistake is to think that power and range (or even antenna and range) have anything to do with each other. It is possible to hear and contact a satellite in orbit with 1/2 watt of power, and that's a lot further away than you are likely to be attempting. The key is that it has to be in your line of sight.

Power helps overcome noise. For receiving, this only matters if your coax acts like an antenna and receives noise that buries the signal.

As others have said, raising the antenna will help range more than any other factor.

Coax might make the signal weaker, but it won't reduce the range. However, a very long poorly shielded high loss coax might reduce the signal and increase the noise to the point where there is little signal left. Higher quality coax would help this. If the coax is very long (100ft or more?), then adding an LNA (amplifier) at the antenna would overcome this easily.