UHF radios

Fab,

The fact that most people haven't got 80 channels is EXACTLY why I like it.

My friends and I have it and guess what. No Sh*&'s or F#$ks or music being played, or inane drivel on the top 40 channels. Just clear airwaves that we can use to communincate even with the kids present, even near big cities.

I hope everyone takes your adivce for a long time though.

Some great advice there. The only thing I would add in when selecting an aerial, try and get one that unscrews from the mounting base. Some have the cable permanetly wired in and if you break the antenea, you have to replace the wiring as part of the replacement.

I recently upgraded my GME to an 80 channel unit, have yet to hear a single converstaion on any of the extra channels while the original 40 channels are as crowded as ever. If you have mate/s with the 80 channels, you will have it to yourself, well until everyone catches up :(

Cheers

Captain

X2 and agree 120% re antennas and gain.

Icom and GME tend to be a bit better quality then Uniden and some other cheaper brands.

We have had issues of using our 80 channel in a group of 40 channel radios, poor receive audio, poor range and people using the 40 channel radios find out transmit audio to be low.

We have since over come this problem by reprogramming our UHF to operate on 1-40 wide band and 41-80 narrow band.

As far as audio volume and therefore signal to noise, you are at a definite disadvantage running the 80 channel band plan in 40 channel company.

Because the deviations don't match up your audio send will be half as loud as the 40 channel units.....and this is in a radio system where people don't seem to concern themselves with modulating well.

Unfortunatly I not all units can be programmed with different deviations.

I'll be sticking with my 40 channel unit for a while yet.

AND there are thousands and thousands of 40 channel units in use that wont be replaced any time soon.

cheers

As for the permanently terminated antennas.

There are realy two issues.

The durability and exclusivity of the plugs used to demount the non permanently wired antennas.

And the fact that some can easily be reterminated at the aerial.

All the elivated feed base antennas can be reterminated at the base, and you would have to be trying realy hard to break the elivated feed unit.

The whip can just be screwed of and a new one fitted.

Besides...replacing the whole lenght of coax is not a major problem most of the time.
Some people just over state the problem.

As for breakage....running a light aerial like one of the elivated feed types on a knock down mount will see the vast majority of the breakages illiminated.

A knock down mount can easily be made from a pair of angle brackets, a few bolts and some friction material.

cheers

Sorry but the gain V terain diagrames on the GME site are way out of scale and grossly exagerated.

Remember these guys want to sell you two antennas.

If you look at actual polar plots, even worst case, the reality does not resemble the marketing.

Then you find people playing with this whole gain v terian argument..AND mounting their aerial on the bullbar.

If the aerial was mounted high on the roofrack, they would gain an extra 3 feet in height and probaly get the same results with a smaller antenna.

The over riding factor in UHF is that it is pretty well LINE OF SIGHT, and that is not from the tip of the antenna.

On UHF, HEIGHT beats GAIN in so many situations, and in vertical sticks GAIN beats RADIATION PATTERN 99% of time.

cheers

Interesting you comment on the gain v terrain being overstated, then discuss placing the antenna on the roof (Good luck for 90% of people who don't want to have to remove the antenna every time they go into a car park.. or their shed, or put it back on every time they want to use the radio) yet you make no mention of ground plane/ground plane independent antenna's (Which given the usual location antennas are mounted probably has a more credible argument)

As said above, speak to a local specialist. You should get a fairly good idea straight away about the level of knowledge.

Check out what most people seem to be using, most likely there is a reason for it, might be the sales pitch but could also be a good reason for it.

If you travel on corrugations a thicker antenna (eg cane style) will remain more upright and serve you better at highway speeds (likewise a stainless style whip if bar mounted tend to vibrate and fatigue quickly dissapearing)

There are so many variables, every outcome will be a compromise, the best way is to speak to someone about those compromise and what will suit your needs best.

firstly the vast majority of UHF aerials sold are ground independent....In particular the elivated feed units mentioned.

At UHF particularly ground independednt, the ground plane plays a far less significant role than it would on VHF....so much so that it is praticaly irrelivent.

There is a reason why 6 dB elivated feed aerials like the one mentioned are used in volume in commercial UHF two way, and why almost every manufacturer makes an almost identical unit for UHF CB...because this is where all the factors converge to give the most effective unit for the size and price.

As far as mounting high.......the importance of mounting high for UHF can not be over emphasised...it is gives a significant and profound advantage to keep the whole radiating portion of the antenna high and unobstructed.

There is realy no problem making and fitting a knock down mount..and besides lots of people remove their bullbar mounted Big White Sticks arround town.

One reason so many people run Big White Sticks, is because they look tuff.

The claim that stanless whips fall appart on bullbars is simply overstated, my neices husband has had an elivated feed aerial like the one I mention on his bull bar now for over 10 years and it is still just fine and it has done plenty of rough road work.

There are plenty of reports of Big White Sticks falling to bits, braking off at the base and other downfalls....in many cases it is the size and mass that is their downfall..... vibtarion will kill anything eventually.

That brings another very good reason to get the blasted aerial off the bullbar.....the bullbar is rigidly attached to the chasis, and thus the worst of the vibration is transmitted to anything mounted there.
The cab on all relativly moden 4wds is rubber mounted to isolate vibration from the occupants.....this reduction in vibration is good for the antenna too.

As for stanless whips laying over at speed & so forth..if that worries you, opt for an elivated feed unit with a fibreglass whip and a stiff base spring instead of the stanless whip......functionaly identical, but stiffer and only marginally more expensive.

Again the highway speed thing in my opinion is over stated....this is UHF and is very limited in range........line of sight........any effect will be slight, besides if you are trying for long distance communication on any radio, if you are wise you pull up and get a good position.....the electromagnetic noise generated by the vehicle running will be far more of an impediment than any slight bend in the antenna.


Like so many things, people get preoccupied with minor details and fail to achieve in the simple basics.

and the simple basics of UHF aerials are.

Get it high and unobstructed.....it is UHF and is line of sight

Get an areial with a fair amont of gain....arround 6db is fair, easy and economical, more than that gets expensive and technicaly harder at UHF, less than that realy gets no cheaper.

Do the terminations properly.

Fail to do the above and you are simply wasting time and money.

cheers

Perhaps it would pay to go back through your post and edit it... you contradict yourself.

Height is important, it is line of sight, as UHF is "very limited" in it's range, an antenna that is leaning over at 45 degrees or more from upright is irrelevant? Plenty of evidence of White Kane style antenna's falling apart, but you know of 1 stainless whip that hasn't? (A quick check on metalurgy will quickly explain why stainless fails)



This is the problem with forums, lot's of "opinion" offered as fact.

The biggest limiting factor to range is that the units are legally restricted to a maximum output of 5 watts.

An upright antenna will work better in all directions (unless shielded by something) than an antenna on a 45 degree or worse lean

Stainless will fatigue quicker than a cane antenna, with or without a spring base to reduce the effects

The middle of the roof might be "ideal" but is rarely practical.

Line of sight while "theoretically" correct is oversimplifying things, anyone who has used a UHF in hilly terrain, between sand dunes etc will know that as a fact.

Bullbars aren't the best place, but often the most practical. If the antenna and mounting are matched to the intended use they are very reliable and give little trouble in thousands of km's of travel over even corrugations.

Something around 6db gain, 1-1.5m in height, preferably with a fiberglass whip and spring base will suit most people.

If your main use is in open country and especially if corrugations are a factor a thicker cane antenna around 1.8m will serve you well

If you use it in very hilly country or built up areas (eg a city) then a low db gain, ideally 0 will suit you best. (There is a reason taxi trucks, taxi's, emergency services etc use this style of antenna in city based vehicles)

Oh come on an antenna at 45 degrees...how fast do ya recon you are going.

I remember seeing roof mounted 9 foot stanless whips at 100Kmh pluss back in the days of 27 meg CB and even then THEY diddn't lay over at 45 degrees.

This laying over of aerials at speed is another one of those commonly over stated issues.

As long as the aerial is proplery mounted very few of the commercially available UHF whips are going to lay over far enough to present any issue at legal highway speeds....the stanless whip, 6db ish elivated feed item certainly does not lay over significantly at speed..they quite stiff little items.

It is almost unknown for commercial UHF installations on vehicles to use less than a 4.5db aerial...still technicaly a high gain aerial.

The next most popular and universal aerial to the 6db ish elivated feed aerial is the 4.5db rubber ducky......( everybody makes one)...the reason that are very popular is that they can be mounted high on the vehicle and they are very hard to break ( the whip is usually rubber coated steel cable)..they don't get knocked off in car parks..........gain V terain is not a consideration.

AND these guys running commercial UHF may have 25 watts up the stick on both the mobles and the base stations......AND the base stations will be located very high indeed...

On CB we have a legal 5 watt output and mostly work car to car. getting the whole of the radiating portion of the aerial another 3 feet higher makes a significant advantage.


As for the middle of the roof...on UHF particularly a ground independent aerial, there is no advantage to mounting in the middle of the roof.......ground plane influence is insignificant.........any where high and unobstructed will do.

Serioulsy do you know what a unity gain aerial looks like on UHF.
And to run a unity gain antenna you have to do a thru hole installation in the middle of the roof and that is simply impractical for most 4wds.

So ya spend a couple of hundred $$$$ on a 9db big white stick then hobble it to the tune of 3db by sticking it 3 feet lower and obstructed to the rear on the bullbar.

I just gota shake my head and chuckle.

cheers

Once again you contradict yourself, and don't bother/incapable of comprehending what I wrote, no one said anything about mounting a large cane style antenna in the middle of the roof. Not wasting anymore time with an armchair expert

To the OP there is little benefit at the moment in changing your radio unless your mates already have 80 channel units, or there are other reasons you wish to change.

Qualified technician 25 years of experience.....no armchair required.

Then you ought to have more brains

I have enough brains to rely on the strength of my argument and not personal insults to make my point.

cheers