Which Aerial works best will UHF?

[MotoNut]

As title says, which aerial will work best and give better range on a UHF CP for outdoor work?

I currently have UHF Stubby antennas NAE6522 (7.5cm).

Will I see gains on changing to a Stubby (9cm) or a Whip antenna NAE6483A?

Also is a 9cm Stubby I'm seeing for VHF only or can you get VHF and UHF 9cm? Are these same and compatible with each band as well as a GP series fitting a CP?

TIA

[bw18]

General rule of the thumb is the longer the aerial the better. Also the higher the aerial/antenna the better.

You might see a small increase in your coverage with a whip aerial, but nothing amazing. I use stubby aerials most of the time, purely for the fact they don't get in the way as much. If I need wide area coverage I fire the repeater up, which regardless of what aerial I am using I know I am going to get out a decent distance.

GP/CP series share the same fitting for aerials, however VHF and UHF are totally different and should not be mixed (I.e. using a VHF aerial on a UHF radio). There is the potential to cause damage to the radio if you do this.

Unfortunately without using a repeater your coverage will remain around the same regardless of the aerial, the only real way to make a substantial improvement is to incorporate a repeater into your system. If I use my TRBO units at the office back-to-back we are lucky to get coverage half a mile away... If I use one of our repeaters I can easily get 10+ miles (as the crow flies). This is partly thanks to our elevation and being able to get the aerial nice and high on the building. It's even more exciting when we go and do an event and use the I.P site connect facility. This allows us to talk to the office hundreds of miles away using VoIP! Fascinating stuff!!

BW

[MotoNut]

Thanks BW again for the time to post a reply.

OK. The stubby I can see if favoured as it smaller and won't get in the way as much.

Right, Repeaters:
How do these work? Do they have to to synced each of the radios you are to be using with them and how big are these? Haven't a clue what they look like either! What sort of range do you get, do each one vary?

Are they the weight and size of a brick or do you have to have a trailer to tow the fooker!? lol


Cheers,

[emsgeorge]

type 'uhf repeater' into fleabay to get an idea of prices.

If you think of a repeater as 2 radios, one listening, whilst the other transmits the signal at 25 w or more, then you wont go far wrong.

There are some things to think about: new repeaters cost upwards of a grand or 2 each. Thus, ones you see on fleabay at £99.99 are either so old nobody supports them any more, or you will have to run the software on a very very old machine (or like our old repeater, the freqs were on eeprom chips, and nobody could program them).

You will also need a decent aerial, duplexer (you dont need a duplexer, although if you dont, you need 2 aerials, and to separate them by a few meters, or it becomes deaf), and some decent cable.

Best thing you need, is height !. The higher you can get the repeater aerial, the bigger range you will have. If you happen to live on top of a hill, then all the better (you might even get away with putting it outside your window !)

We had one once, in Swansea, where one of the subbies lived on top of the surrounding hill (plasmarl for those who know the area). We got most of swansea on hand helds, with a tripod in his back garden. 10 min install job !.

[bw18]

Think George has nailed that one!

Size wise they vary. Motorola are 19" rack size 4U. Not a huge piece of kit and nice and easy to install in a rack. I have 2 TRBO repeaters both of which are installed in mobile flight cased racks. This way I can throw them in the back of the car with an aerial and, again, as George stated 10 mins and your up and running.

There is no 'syncing' the radios as such. With analogue, such as the CP's, aslong as you have the correct TX and RX frequencies as well as the CTCSS tone you can open the repeater. With digital you need the correct colour code (and TX/RX frequencies)... This is a slight problem with TRBO as other users can piggy back on your repeater by using different group codes... Very annoying! But that's a whole different story!

For a brand new DR3000 repeater (capable of digital and analogue) you are looking at £2000+!

Other manufacturers make smaller, thinner repeaters... But hey why would you want anything apart from Motorola

Also... You're looking at a different license to operate a repeater. Purely for the fact you operating across a further range and area, thus you are more likely to interfere with other users! If the prop is right, you're up high you could easily be covering 20-50 miles or even further! 25watts is a lot of power when everything is located and set-up correctly!

Ben.

[MotoNut]

TVM Ben. Right no syncing them up as such. So if I bump into a repeater somewhere, what happens then? Could I be accidentally feeding off someone else's repeater and convieniently be boosted by 25w??

10mins to set up? Not just a case of plugging into the mains and away you go?
Do some of these have built in aerials or do you have to position them correctly? and how do you know when they are in the best location possible?

This one any good?

http://www.ebay.co.uk/itm/Motorola-Eurobase-UHF-Repeater-Two-Way-Radio-/200605371056?pt=UK_ConsumerElectronics_SpecialistRadioEquipment_SM&hash=item2eb5030ab0#ht_500wt_677

[emsgeorge]

The eurobase ones are reliable - nice find on ebay!.

You will still need either 2 aerials or a duplexer and one aerial, some decent cable (RG174), and a power cable.

Aerials can be up to £500 for the aerial alone if you want a decent one, although panarama stuff is good.

Get some ali scaffold pole and brackets, and get it up as high as you can. The higher the better. If you have a mate who lives on a hill, all the better !.

Re program your radios to the repeater, and voila, you have much better range (assuming the aerial is up nice and high).

[bw18]

Technically yes IF you piggy back off someone's repeater you will increase your range... HOWEVER, I do not advise this or by any means agree with it. If you jump on an analogue repeater every user on the system will be able to hear you... There is also a very good possibility the license holder will lodge a complaint with Ofcom. I'm sure you would'nt do this after reading my advice!

10 mins... Probably 2 mins to plug into the mains and plug/screw the antenna(s) in and 8 minutes to put the antenna up (depending how you mount them).

Antenna positioning really is an art- but not difficult. There are so many different sorts and solutions you could use. I have a few to choose from, mainly though I use a collinear or stacked dipole. I also use a duplexer, I cant be bothered with fiddling with 2 antennas... Sometimes one is enough hard work. The best way to rig an antenna is at the highest possible point, and in my opinion, central to your operation. Exactly the reason why George suggests scaff poles, high as you can! 

I can hear a TRBO system nearly 15 miles away from my office using a handheld radio (its a citywide system, that branches out into the county), even then I am getting a really good clear signal (2-3 bars on the signal strength indicator). I often do work with that particular council, hence why I have access to their system. They have a dipole stack at the top of the local broadcast tower, so it just shows how important height is! This system only runs at 25watts, so no nuclear reactors needed to power it for massive coverage!

I recently worked on an event at an old mansion... I put the collinear on the roof of the mansion (probably 40ft from ground level) and we were getting out for miles (and miles and miles) around. Bearing in mind that the mansion was surronded by woodland and hills this really was a great sucess and showed the power of a well positioned antenna! I think if we were using VHF we would have been going even further. As I left the site for the evening I could still hear the main event group/channel a good 10-12 miles away (as the crow flies).

It's all good fun!

Ben

[MotoNut]

Many thanks for both your replys. I get a better picture on what's required and how it works with what to expect out of one.

My only other query regards a repeater is... How the radios work in relation to location with repeaters.

Say I set up the repeater on a hotel rooftop successfully and program 2 radios to it as required and say range with repeater gives radios a range of 20miles.
How does it work in terms of range?

Basically what I mean is does the signal now go through the repeater and not the radios. So if you are out of range of the repeater (20miles in this case for example) will both radios still work if both radios are say 200 metres from one another?

Another way of maybe answering is say one radio is 20miles North of repeater and the other 20miles South of repeater will both radios function?

[bw18]

Good questions!

Easy one first... If you are out of range of the repeater the radios will not talk to each other 2 feet away, let alone 200 metres because you are using 2 separate frequencies (one for TX and one for RX). However, if you enable 'Talkaround' mode for the channel and set a button definition to activate it you turn the radios into simplex... In other words they TX and RX on the same frequency, rather than using a repeater shift frequency. So, aslong as you can identify that you are out of range of the repeater you hit the button and you are back to simplex mode!

Range... This depends on the location and how built up the area is. In theory you could achieve 20 mile coverage radiating in a circular pattern from the antenna. This is when you would need something such as a stacked dipole antenna which radiates 360 degrees, or, North, East, South and West. As we have all said, the higher the aerial the better. Power does play a role in how far you 'get out', however, you can pump 100 watts into an antenna and it will struggle to get out a mile if it is surrounded by concrete and has no elevation.

In theory, and for arguments sake, you might achieve 15-20 miles coverage North and East, but only 5-10 miles South and West. There could be hills in the way, raised ground elevation etc etc. it's also worth bearing in mind 20 miles is a massive coverage area... We are not talking about 20 'driven miles', we are talking as the crow flies. So effectively 20 square miles, which is bloody huge, and would take a serious antenna in a well positioned and efficient place... By no means impossible though!

If you look back at the old analogue Police system this easily covered 20+ miles (not without blackspots though). They often had sites at the tops of hills and high ground elevation. I know the repeaters for my local force were at the top of a large hill on a very large tower! The VHF system used for county communications did exactly that... Covered the WHOLE county! This was by using connected repeater sites, not just one repeater bashing out 3 million watts lol.

My personal advice would be to buy a 'cheap' second hand repeater and have a play. Duplexing is the way to go as you only need 1 antenna. Two things to remember... 1, Your aerial and duplexer needs to be tuned to your frequencies (you won't be able to do it yourself unless you have the knowledge and equipment). 2, You will need a 'Technically Assigned' license to operate a repeater and start covering larger areas. Mr. ofcom won't be to happy if you start flooding 449 with 25+ watts of power! Maybe for a VERY short time to test, but thats it... Don't take the risk!

Hope that answers your questions.

Ben.

[MotoNut]

Ta Ben. I did wonder this, in terms of if the radios would work outside the repeaters range as it would be running through the repeater. I only used the 20miles simply for example. I had/ have no idea what range could be capable, but as you say, it depends on area and equipment involved which I guess would play a massive role.
 
I shall do a little research on 'Duplexing', no idea what this is and will have a deeper look into the whole repeater set up. I most probably wont go this route as its not idea for my use. My asking was mainly curiosity or possible future intentions.

If a simple aerial change would have shown immediate results, I would have possibly given it a go, hence the original Post. However it seems I wont benefit greatly and with the increased aerial size it may make things a little less practical for my use. Maybe still worth a go?

Can I ask, would any UHF aerial work or do they have to be specific to UHF frequencies. I have a report if you are interested to know anything about them. Doesnt mean too much to me.

Cheers again.

[bw18]

Yes it's worth a go, any longer aerial will improve performance, even if it is only marginal.

Some aerials are tuned to specific frequencies, some you can use an ATU (used very often for HAM radio who use a specific aerial, but it's important that they have the aerial tuned as accurately as possible). I personally use aerials that cover the whole band (400-470MHz)- or at least the part of the band I use most!

Businesses who have set frequencies that are not going to be changed on a regular basis may well have had their antenna tuned by the install company. Some companies dont, some do! If they are using a duplexer (which I imagine 90% do) the duplexer will be tuned to the frequency.

It all sounds complicated, but once you have everything set-up it just ticks over in the background. Designing and purchasing the infrastructure is the longest and most expensive part.

[MotoNut]

Cheers BW.

My frequency range (MHz) is: 438.000000 - 470.000000

I have found some here very cheap I was thinking? (assuming Genuine Motorola 9cm aerials): PMAE4003A - £5.36 + VAT

http://www.roadphone.co.uk/Motorola%20Accessories.htm#Antennas%20Analogue%20Portable

What is the break in the middle part of the Aerial for? Is this purely aesthetic or? Most radios I have seen with this 9cm aerial, its never straight and always seems to be bend. Do they have a tendency to do this or is this down to bad handling and easily done and does it affect its performance?

Also ref Freq. Is this built into the radio from day of manufacture or is this fully adjustable? Does this affect range in any way?

Sorry for the flooding of questions.

[bw18]

The break is normal, not quite sure why they do it. I doubt it has anything to do with the coil inside, probably just to make an aerial look more modern (and save rubber!!) knowing Motorola. Personally I would go for a whip aerial (NAE6483AR UHF whip Antenna), the 9cm is not going to be any better than what you currently use.

All aerials have a tendancy to bend, when they rub against people or through heavy use and bad handling. There is no real damage caused apart from extra strain on the connection... To be fair I have never seen a radio damaged by an aerial... I'm guessing it is possible though.

Not quite understanding your frequency question... If you mean is the radio tuned, then yes it is. Using software and measuring equipment... Not something you want to mess about with unless you know exactly what you are doing. You will notice the aerial description states what frequency the aerial is capable of, most OEM aerials provide full band coverage. However, you do sometimes find aerials which cover specific frequency ranges. 

Ben

[MotoNut]

Your prob right about upgrading to a whip if any at all but they just look crap don't they! lol
The 9cm stubby I see as still being subtle but also with a small increase in length.

Re Freqs. I am aware there are different ones you can choice from. Im not even entirely sure what the Freq does tbh. I suppose knowing this will answer my own questions? 

Ta Ben