uhf radio transmitting range

[wombat50]

I have a GME tx3350 which I brought as a kit including the Gme Ae4018k3 Hi Gain 6.6dbi Uhf Antenna. I don't seem to get the range I was expecting to get when it was installed. I have the antenna mounted on top of the nudge bar and with the overall height it is about 10cm below the roof line. How can the range be increased. Ive read that the top of antenna should be approx. 10cm above the roof line or would a bigger antenna be a better idea. I was looking at one of those 7.5dbi fiberglass ones. To make the current antenna higher I was going to mount it on one of those brackets that fix to the inside of the front guard under the hood.
All suggestions welcomed.
Ross

[Keithyv]

How far is the range? - How long is piece of string?

A major issue such as a grounding problem or broken wire in the antenna coax will affect the range dramatically. Antenna placement WILL affect things but nowhere near as dramatically.

With an antenna mounted on the front of a vehicle coverage will be better behind you.

Just how bad is the range?
What type of unit is at the other end?

There is nothing definite in radio, all sorts of things can affect range. Rain, mountains and a million other things.

Check the basics first.
i.e. is the antenna mounted properly (grounded) and all connections secure and solid?

[geopaj]

How much range are you getting? What is the terrain (remember UHF is considered for’line of sight’)? What is the receiving UHF your using for testing?

[spot01]

UHF is usually only useful over a relatively short range, unless you, the other radio or the repeater have significant elevation. Repeaters are needed for longer range use.



Some UHF radios have a high/low power setting - if so, check it is on high. Make sure the squelch is adjusted as low as possible. If you are in a built up area or near power lines, the background noise will significantly limit it.



With the antenna mounted there, it will be quite directional. As mentioned, UHF is very much "line of sight". Some antennas need a "ground plane" (flat metal underneath, eg, roof) & others have an inbuilt design that doesn't need one. Even a short "rubber ducky" antenna on the roof may outperform a high gain one on the nudge bar.


Where is the car when you are using it? Needs to be in a clear area away from buildings, obstructions, low land areas, etc. to properly test it.



Do you know anyone with a similar set up to compare it with side by side?

[wombat50]

maybe '' range'' isent the right word. when going on the highway I don't seem to be getting good reception. there seems to be a fair amount of interference and not very clear. the radio was installed by a auto elect. and all seems the be tight and nothing loose

[spot01]

maybe '' range'' isent the right word. when going on the highway I don't seem to be getting good reception. there seems to be a fair amount of interference and not very clear. the radio was installed by a auto elect. and all seems the be tight and nothing loose

Quite normal on a busy highway if quite a few people are using the channel, eg, the road channel. I find UHF quite frustrating when it is busy.
Try using a quiet channel to see if it improves when talking to another person some distance away.
Also, make sure you have a list of what each channel is for. If using a repeater, it must be set to "duplex".

[nj swb]

Check the coax connectors. Despite the "common wisdom" of the internet, you can't cut corners with these things.

RF transmitters are designed to transmit into a specific "characteristic impedance" - if the connectors have a poor connection somewhere the impedance seen by the transmitter won't be correct, you'll get poor performance, and worst case can damage your transmitter.

The centre conductor must be crimped or soldered to the centre pin, to ensure a joint of negligible impedance - you can't just stick it in there and expect the electrons to jump properly.

The insulator on the centre conductor must extend as far as you can make it extend inside the connector. The insulator is also a dielectric, affecting the capacitance between centre and outer conductors. No dielectric affects the capacitance, which affects the RF impedance - maybe not by much, but every little bit adds up.

The outer conductor (hopefully braided, not a foil) should have good 360 degree electrical connection to the shell of the connector, and no part of the braid / foil can be allowed to come near, much less touch, the centre conductor.

If you want good performance from your system "rough enough" isn't good enough. Make sure your connections are good before you worry about antenna location.

[nj swb]

maybe '' range'' isent the right word. when going on the highway I don't seem to be getting good reception. there seems to be a fair amount of interference and not very clear. the radio was installed by a auto elect. and all seems the be tight and nothing loose

Posted while I was posting.

I had this problem when I bought my NT. The UHF was only 40 channel, so I decided to simply start again with an all new system. When I pulled the old system out, the connector at the back of the radio hadn't been crimped or soldered, and the braid wasn't done too well either.