Suppose I own a couple Motorola handheld GMRS/FRS radios in the 3-5 watt power range.

If I bought a 15+ watt mobile unit for the car, would I notice any appreciable range gain, or will I still be pretty much limited by the handheld's ability to transmit back?

Having a better antenna higher off the ground is likely to make more of a difference than the increase in power (and works for both transmit and receive, unlike extra TX power), but there isn't going to be a huge difference either way.

With a good directional antenna and a 5 watt handheld radio you can bounce a useable signal off the moon (really!).

In the frequency ranges we're talking about, emitted power is almost never really the limiting factor, it's all the stuff in between you and the person you're trying to talk to, the signal getting layered with tons of delayed repeats from bouncing off stuff, and other EM noise.

quote:

Originally posted by Aeteocles:
Suppose I own a couple Motorola handheld GMRS/FRS radios in the 3-5 watt power range.

If I bought a 15+ watt mobile unit for the car, would I notice any appreciable range gain, or will I still be pretty much limited by the handheld's ability to transmit back?

Yes, the handheld still only puts out 5w. The mobile unit's 15w are only good for transmit power. A gain antenna might help at both ends (good antenna - directional has more gain than non-directional antenna).

5W can travel 30 miles line of sight and hit a repeater for instance, but repeaters usually have high gain antenna 6-12 dB gain, transmit and receive.

If the GMRS handheld allows for a different antenna, get one for the frequency - I think GMRS in the 460 Mhz range so about about a 6 8/16 inch antenna for 1/4 wave vertical, for optimal radiation efficiency. So if you current GMRS handheld antenna is less in length, it is less efficient in send and receive.

5w could hit the moon, but you need very high gain antenna to hear the signal return as there is a huge signal loss upon hitting the moon.

But 5w will make it to the ISS with ease and back again too.

So, something like a 6 db gain antenna on the car would help with both the Tx/Rx with the handheld, regardless of the unit's power?

It doesn't help the handheld: the handheld only does what it can do; it has a weaker output and more limited range, and in any event, is still restricted to line of sight (same as a more powerful transmitter). What it does do is allow the car or base station to pick up more; the hand-held isn't enhanced, but the base station is.

Think of it more in terms of trying to hear someone across the room. If they don't change the volume of their voice, you may be able to cup your hand by your ear to enhance your ability to hear them. The speaker hasn't changed, but you've altered something that allows you to hear better. Increasing the gain, as it were.

Try turning it up to 11.

Thanks all. Went down a little bit of a rabbit hole learning about radios. Purely entertainment at this point, but I'll file it away in the back for the apocalypse.

A properly tuned anteanna SYSTEM accounts for 90 % of the radios performance be it handheld/vehicle mobile/home base station. What good is a high power transmitter if the reciever cannot hear a returning signal?? There are many ways to help enhance a signal. Anteanna height. Anteanna with a gain factor for signal strength. Multi-element beam vs omni directional. Quality feedline between radio and anteanna. .......... drill sgt./KL7JIU

yea but in the end you can't overcome the frequency characteristics and the power.

quote:

Originally posted by drill sgt:
A properly tuned anteanna SYSTEM accounts for 90 % of the radios performance be it handheld/vehicle mobile/home base station. What good is a high power transmitter if the reciever cannot hear a returning signal?? There are many ways to help enhance a signal. Anteanna height. Anteanna with a gain factor for signal strength. Multi-element beam vs omni directional. Quality feedline between radio and anteanna. .......... drill sgt./KL7JIU

Tell them about your setup.