hi everyone
just like to hear peoples thoughts
on Scout camps that have activities such as biking and orieentering i split kids up into groups giving them 1 or 2 477 uhf radios per group to communticate keep in touch and for safety. kids can end up 10 plus km away.
me and other leaders have 5 watt handheld and 5 watt base units in 4wds
but as no’s of kids have growen ild like to get more hand held radios.
if i brought sets of 0.5watt radios linking with the 5 watts would we still be able to communicate to 10km as 0.5wats usaully go 1-3km, but im hoping the 5 watts will pick it up and be able to send to the 0.5s
i no this is affected by terrain etc but in general terms ild like to know
dont want to use reapeters as no one wants to hear us take over the airway
just trying to keep costs down if could as can get 4 packs of uniden 0.5 radios for just over $100, so not a major if kids break loose them etc
otherwise ill have to go more powerfull.
thanks
Low power equipment will have less range than high power, but not by as much as you expect. What happens is that things work well when the signal strength at the receiver is enough to produce a workable signal to noise ration. Radio signals get attenuated by things in the path - some things attenuate the signal very little - glass for example, while other things are much worse - trees that have sap in them, for example. Some things are essentially impenetrable - like the ground, or mountains. VHF and UHF are usually considered line of sight - so your low power radios on the top of two mountains will work perfectly well as there’s nothing between. Valley to valley is going to simply not work. The other issue with mixing powers is that your high power radios may well have enough output to overcome the obstructions, and emerge from the speaker the other end - but you won’t hear their reply. They will find it very annoying to hear you, but not be able to speak back, In a mixed power system, the practical area is the area covered by the lower power units.
If you have the funds, and for most countries, licenses, you could install a battery powered repeater on high ground in the centre, and then anyone within it’s operational area could communicate with anyone else - which could improve the coverage greatly - IF - the topography works for you.
yea, all the experiance i have had with uhf radios but spec low powed ones they definatly **** unless linked to a repeater for longer distance conversations, i no i really need to go to 2watts to acheive what ild like over the terrain we typically would visit but just trying to avoid the cost of doing so.
i managed to find a old article in a old aus4wd mag that i had all along just forgot about it, explains alot and just happend they tested uhf handhelds over different watts over different terrain etc to find there ranges and abilties comparing against base units different ariels etc so thats been very helpfull,
and their conclusion was what?
wrtiten for 4wding but same applies,
basics of it was that 1watt helds over flat terrain average max over flat terrain is 4km mountain terrain 800m,
5 watt held helds 13km and 5.5km
5w in car base units went from 30km to 5km depending on ariel db
so basically to what we are trying to do is unless everyone is running 5w hand helds we are best to link into a repeater if one is available.
i tested use of repeaters yest using a 0.5 hand held and it still manages to get onto a repeater even tho its 20plus km away from the repeater then comunicate to me on my radios,
but the big butt for us is we arnt always in range of a repeater for our activites and with nz rules its not straight forward to just use our own portable repeater.
so our conclusion is almost make sure our remote activities are in range of a repeater, then any radio can be used and the cheap easy to obtain 0.5w radios for the kids are as good as our larger ones.
There is some random element in those figures - I suspect their tests were a little, er, non-technical.
The repeater thing is confusing me a bit. So you can’t in NZ license your own portable repeater, but you can access other people’s? Are there repeaters in the places you want to be that you can get access to? That seems a bit unusual - but maybe the situation is different.
.5W to 5W is a decent power increase. However, the performance of a repeater with low power radios depends far more on the repeater end equipment than the transmitter. If the aerial system the other end is not high enough or is obstructed then the low power portables suffer exactly the same problem - not enough grunt. Radio to radio is twice as bad of course, weak on the way out, and weak on the return.
Here in the UK you can license a temporary repeater if you hire it - there’s a specific license that covers this and is not location specific. Is there something like this available in NZ? Could be cost effective too as repeaters are expensive, so for short periods, hire could actually be cheaper.
I also think those figures are a bit “suspect.” The problem is that UHF is line of sight, and at 13 kilometres, even assuming two handheld radios being held above your head, the antennas would still be below the horizon.
I have to agree with paul. Although power is one factor in range, it will have far less effect than you would think. Obstructions, terrain, foliage and antenna height all have far more effect on range.
Given a good quality half-watt radio with a decent receiver and the antenna held high, you should be able to get nearly the same range as an average 5-watt radio on a belt.
This is why no one can give you an easy answer. It all depends on terrain, etc. and will vary a lot, sometimes in only a few meters back and forth. NZ uses what is called UHF CB in the 477MHz band, and you are allowed up to 5-watts on a handheld, so consider it is similar to FRS and GMRS here in Canada and the U.S.
In Canada, we are limited to 2-watts in GMRS (but don’t need a licence) but in actual practice, I have seen little difference between .5-watt FRS and 2-watt (or even 5-watt) GMRS.
That’s why I would be inclined to get the best quality UHF CB 477 radios you can afford and don’t worry so much about power. Cheap 1/2-watt to 1-watt ones for the kids because they will be hard on radios and you will need to throw away a few every year, and better quality 5-watt ones for yourselves.
Until you can get a repeater system, they will need to learn the limitations of two way radios, and the fact that anything over 1 to 2 km in average terrain should be considered a bonus.
Also, be sure you are not relying on 477 radios in an emergency.
yea be actual in use testing, obviosly dont know the terrain factor so only consider a rough guide at best.
in nz we can licence to have our own repeater but at the cost of licene and cost of repeater thats why its out of our leage,
the uhf 477mhz channel system being 80 channels in aus and nz is public
anyone can use these channels so tho the repeaters are private the channels are not and everyone can access them.
a very highly used system just google it.
This is why they are inexpensive. You share the channels with everyone.
Short of having everyone get their HAM ticket, or getting a business licence and a system of repeaters, there simply is no solution.
One can’t refute the laws of physics. FRS, GMRS, PMR446 and UHF CB 477 radios are ALL designed for very short range communication
Get the kids some inexpensive radios, let them have some fun with them; never rely on them for emergencies, and basically consider anything over 1 km to be a bonus.
Give the problem to the kids. Tell them they have a week (or two weeks, or three days, or whatever) to devise a simple system of communication between two groups 20 kilometers apart in rough terrain. Without batteries or electricity, they need to devise a system where there is one question (are you okay?) and two possible responses (yes or no.) Let them figure it out.
Are these US Boy Scouts?
If so, there is a radio merit badge that the scouts can obtain and if they go on and get their US amateur radio license, there is a tab they can wear on their uniforms.
This might be a way to get them interested in ham radio, with the added benefit that you can have better communications in your other activities.
The OP is in New Zealand. I know in Australia, there are CB repeaters… but by regulation they MUST be open repeaters. No private systems at all.
I’m unsure about the NZ regulations and how they apply to this. I do believe their UHF CB services are identical though.
nz and aus pretty much run a identical system for uhf
nz scouts ill look into what if any badges they have for radio communication.