Batboard

Hey all,

Would this work for a repeater setup?:

Two Motorola mobile radios (both the same model), one programmed with RX, the other with TX,separate large mobile antennas and UHF Co-Ax cable attached to both. Both radios linked to a power supply. A cable such as the one on the link below for linking the TX and RX radios together. (The cable going from the plug on the back of the RX radio to the microphone jack on the front of the TX radio - have I got that right there)???
http://cgi.ebay.com.au/REPEATER-DELAY-c ... dZViewItem The antennas mounted with mounting brackets onto a high place, such as the roof of a building?

would all of this work to form a simple repeater or am I missing a few components?

Also, is it possible to repeat the signal if the RX and TX are the same (eg. RX = 470.111 / TX = 470.111), or would the signal just come through the RX antenna, go out the TX antenna and then back once again into the RX antenna, creating a giant circle, with the signal going nowhere? or does the TX/RX have to be different for the repeater to properly work???

And, with the two seperate mobile antennas, how far should they be mounted from each other on the roof? Finally, what is the best type of medium-large length mobile antenna to use for a base/repeater setup (keeping in mind that I will need range of approx. 6.5- 13 miles, or 10-20 kilometres over a medium-large sized city - and for this kind of range will 4-5 watt radios on the repeater do or would I need higher wattage, and if so, what wattage would you reccommend)?

If it helps, mostly Motorola portables will be used on this system, UHF, 2-4 Watts, and some mobiles too. All on conventional). I guess using portables across a medium-large sized city means I would need huge wattage from the repeater to make sure that there was at least decent coverage??? - I will only be using a single personal repeater, so I need to keep costs down, but I also have feelings that the portables will not have adequate range to make it from the outskirts of the city to the repeater? only about half of the quoted coverage area will be needed though, I just wanted some extra coverage incase).

Thanks to everyone in advance for the help.

I will add this to your info, UHF penetrates better than VHF (IMO). So going with UHF means it will help in the range. So you'll be good imo in range with a 4watt portable. As for the repeater setup, ill let someone else answer as I dont fool with repeaters yet.

You cannot run a repeater on a single frequency, no. Unless it's a time delay playback thing and I think those are no legal for Part 90 use.

Unless your two antennas are hundreds of feet apart horizontally or 40 feet or so one above the other, you will need a duplexer. Without a duplexer or enough physical isolation between the antennas, your transmitter will desense the receiver, meaning the signals to the repeater will have to be excessively strong to get in. The required isolation is less the farther apart your receive and transmit frequencies are, but with rare exceptions the split between them is fixed by FCC. For a repeater from 450-470MHz the split is 5 MHz, above 470 it's 3 MHz.

(You ARE going to license this thing, aren't you?)

The other thing to keeep in mind is your little two mobile repeater will not stand up to heavy use. For the transmitter to survive even a light duty operation will require the power to be reduced by about half. For heavy duty use this system simply will not hold up.

Good luck.

wa2zdy wrote:You cannot run a repeater on a single frequency, no. Unless it's a time delay playback thing and I think those are no legal for Part 90 use.

Unless your two antennas are hundreds of feet apart horizontally or 40 feet or so one above the other, you will need a duplexer. Without a duplexer or enough physical isolation between the antennas, your transmitter will desense the receiver, meaning the signals to the repeater will have to be excessively strong to get in. The required isolation is less the farther apart your receive and transmit frequencies are, but with rare exceptions the split between them is fixed by FCC. For a repeater from 450-470MHz the split is 5 MHz, above 470 it's 3 MHz.

(You ARE going to license this thing, aren't you?)

The other thing to keeep in mind is your little two mobile repeater will not stand up to heavy use. For the transmitter to survive even a light duty operation will require the power to be reduced by about half. For heavy duty use this system simply will not hold up.

Good luck.

If you're familiar with his background (from other posts) he's from Australia and is using their UHF CB freqeuencies.

-Josh

Here's a webpage to help you understand how a FM repeater operates.

http://www.repeater-builder.com/rbtip/repeater101.html

I do not know the current Australian Radio Frequency Laws as to how they read for Licensing UHF Repeaters on your Citizen Band Spectrum but this information can be acquired through your Government's Postal and Telecommunications Department.

Josh wrote:
If you're familiar with his background (from other posts) he's from Australia and is using their UHF CB freqeuencies.

-Josh

I should have seen that in his signature. I stand corrected.

The technical issues are unchanged however.

(You ARE going to license this thing, aren't you?)

Sure am (if i ended up building it that is). Thanks to all for the help. So basically the only thing im missing from the list at the moment is a duplexer?

more power isn't always going to be your key to better coverage either, the more height you can get out of you antennae the better. i think i'd take 5 watts 200 feet in the air over 100 watts on a vehicle roof.

losanglescop,

You better have real good UHF Duplexers because there's only a 700 kHz Split between your repeater's TX Output and RX Input Frequencies. Standard 5 MHz Split Duplexers will not provide enough isolation, you'll have the Transmit Frequency overloading the Receiver Frequency causing Desense. This narrow of a Split will create very expensive $$$$$$$$$ Duplexers.

losangelescop - where are you located in australia?

losangelescop - where are you located in australia?

Near Brisbane.

OK, there should be a few CB repeaters already operational up there....

lol, pretty much everywhere except in the Redcliffe/Caboolture area where I am. Everyone near us is covered except for us ourselves. haha

HLA wrote:more power isn't always going to be your key to better coverage either, the more height you can get out of you antennae the better. i think i'd take 5 watts 200 feet in the air over 100 watts on a vehicle roof.

FWIW, Australian CB regs limit everything to 5 watts, including repeaters. So if he wants to keep it legal, that's all he'll be running anyway.

Ditto on the $$$ for a 700kHz split-capable duplexer. I know there are guys down there who sell 5-7 dB-gain collinear base station antennas to those morons that put them on their "utes", so at least you won't have any problem locating a decent antenna.

HLA wrote:more power isn't always going to be your key to better coverage either, the more height you can get out of you antennae the better. i think i'd take 5 watts 200 feet in the air over 100 watts on a vehicle roof.

Ywp, invest in antenna quality then gain, and height. Those factors help your receive too while transmit amps do not. And they don't run up the electric bill either.