Radio and headset/earpiece

[Moose87]

Just to clarify a few thing after reading this subject.

Changing the power will boost a radio wave that is transmitted.

Changing the ANTENNA!!!! (radios do not use aerials) can increase the size of the radio wave transmitted and has no bearing on the freq used.

A larger antenna will produce a larger radio wave and will allow it to travel further before being absorbed by its surroundings.

 

[Baz JJ]

The increase in power will allow it to penetrate further and lengthening the aerial or antenna to specific lengths will increase the gain and therefore the useable range. This is why it is illegal to transmit more power or modify aerials in PMR446.

Another common misconception is that the sub-channels on PMR446 provide you with more than 8 channels. Its just an encoded squelch which means you cant hear unwanted traffic. They can still hear you.

I scan all eight channels and I hear everything in range.

 

[Moose87]

If your using a vertical radiating antenna on UHF then a roughly accurate size it good. the ones on a hand held radio are gonna be a 1/4 wave length so biggest its ever gonna need to be in 4 times.

Yer sub channels is more to do with fine tuning. fairly unnecessary for short wave comms

 

[Ian_Gere]

Wavelength and frequency are two ways of describing the same thing.

 

[Moose87]

well yes and no. you can adjust a wavelength without changing the freq, the freq dictates the type of wave length. a HF radio transmitting on 5Mhz will have a long wave length and a UHF radio transmitting on 400Mhz will have a very small wavelength. there are specific calculations to work out the length of an antenna depending on the freq and those calculations work in 1/4 wavelengths. the most optimal antenna size is one that transmits 3/4s of the full wave length. the antenna will also change in size depending on the material that you are using as an Antenna.

Trust me guys in know my stuff i came top of my class as an Communications Operator in the army. thats not being condescending to anyone and people may know more then me im just reassuring people of my credentials.

 

[Baz JJ]

deleted

 

[Moose87]

you miss understand what im saying, you are completely right. the actual wave is fixed but what i was trying to get across is that at 30mhz a wave length is 10m but if you build a 7.5m antenna it will only transmit 3/4s of the wave length. my original point of thinking is that if you cant up the power than you could try increasing the size of the antenna and therefore more of the wavelength will be transmitted

 

[Baz JJ]

Yes.

At 446 Mhz, the wavelength is about 67cm. All PMR446 radios come with a little stubby antenna which has an electrical length much less than 67cm. If you could increase the antenna length, then you would improve its antenna gain/efficiency and therefore its effective range. That is why they do not permit this to happen.

It is also why PMR446 is pretty rubbish in terms of range.

 

[jcheeseright]

most decent quality handheld radios allow for you to put a bigger antenna on them though, it's completely legal as long as you're not transmitting at greater than 0.5W. in real terms a bigger (or I should say more appropriately sized) antenna will help far more with reception than transmission.

 

[Baz JJ]

Initially OFCOM tried to insist on an integrated antenna so it couldn't be modded.

I think that has now been relaxed.

Many cheaper sets on the market still have the integral antenna. At 500mW output power, I don't think you will notice much of a range difference between the stubby and the largest whip or helical antenna you can fit and still maintain portability for Airsoft use.

 

[jcheeseright]

well no, but with a longer antenna you'll be able to RECEIVE signals from further away. if both parties have longer antennas then you're getting increased 2 way range.

 

[Ian_Gere]

While we're on the subject of modding handsets, can you get better reception via the black magic of earthing some part of the circuitry or case? I vaguely remember the CB craze back in the day and people did use to do some odd things...

Obviously "earth" and "portable" are usually mutually exclusive, but we're not talking about much in the way of voltage and even less current, so the human body would act as an earth.

 

[Baz JJ]

No because they work on a balanced output. CBs didnt. military field radios sometimes need an earth especially on HF frequencies which need a longer aerial due to the lower frequency.

 

[Moose87]

Ah HF radios are my fav. You can build some of the most random antennas for them. I remember one we managed to pick up something in eastern europe crazy.

 

[chris555]

If anyone feels confident on fabbing a new areal on a midlands g7 plwease post how to do this

 

[Baz JJ]

I dont think the aerials on the G7 come off. Looks like they are the integrated type mentioned earlier in the thread. I have similar on my Motorolas.