Electronic Circuits and Projects Forum

UHF isn't simple to build, nor cheap - by far the most effective method would be to use a better aerial - a decent size Yagi will give you 10dB gain on both transmit AND receive, and at UHF frequencies you can get higher gain than that quite easily, because of their small size.

However, you may need to check the legality of it?, often you are limited in what you can do.

Amateur radio operators buy or build UHF amplifiers with pre-amplifier. The power is increased on transmit by the amplifier - when not seeing a transmitted signal it switches to the receive mode and amplifies the incoming signal.

The schematic diagram for the amplifier or preamplifier will appear quite simple but as Nigel suggests, it won't be easy for a beginner.

You need to be licensed for the band/mode/power. You also need to know that amplifiers can amplify the stuff you want and stuff you don't want. They can also generate out of band emissions. All stuff that you must manage.

I'd recommend you heed Nigel's advice - taking it a bit further. Take a close look at the whole system to see if you are suffering any losses that can be addressed such as a lossy cable, mismatch, etc.

Also bear in mind that UHF is 'line of sight', so range is fairly low unless you are on the top of a hill.

No, there's no problem increasing the receive sensitivity - you need a suitable preamp that's automatically bypassed when you transmit, either by pin diodes or relays.

However, at VHF and UHF frequencies the limiting factor is the noise of the front end devices, unless your existing front end is particularly noisy it's unlikely a preamp will make very much difference. You also tend to get the problem that you can hear them, but they can't hear you - it's important to try and keep both transmit and receive reasonably balanced.

But such a device isn't simple to build, UHF is very tricky - I would suggest trying looking round for a commercial unit you could buy?.

If it's any help?, here's a UHF (432MHz) preamp from the '1976 RSGB UHF/VHF Manual' - if you're serious about wanting to try and built one, I would suggest getting a copy of either the RSGB or ARRL Manuals.

You don't want a receiving amplifier that boosts a wide range of frequencies unless you are very far away from civilization. All the high power TV stations and cell phone towers will overload it.