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What does a trunked antenna look like?

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b52hbuff

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Let's start very simple. If I have a 10 channel Motorola trunked radio system (e.g. a single site). How many antennas come out of the trunking controller?

Is it 10? One per input/output pair?
Or is it 20? One antenna per input and per output?

Just how much can a single antenna 'share'?
 
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N_Jay

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b52hbuff said:
Let's start very simple. If I have a 10 channel Motorola trunked radio system (e.g. a single site). How many antennas come out of the trunking controller?

Is it 10? One per input/output pair?
Or is it 20? One antenna per input and per output?

Just how much can a single antenna 'share'?

It has nothing to do with trunking.

Antenna systems can be designed with one antenna per station,
one antenna per site,
one RX and one TX antenna per site,
one RX and several TX antenna per site,
even 2 antennas for each station (but no one is that crazy).
 

b52hbuff

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N_Jay said:
It has nothing to do with trunking.

Antenna systems can be designed with one antenna per station,
one antenna per site,
one RX and one TX antenna per site,
one RX and several TX antenna per site,
even 2 antennas for each station (but no one is that crazy).

Ok, so to clarify. You could have a 10 channel trunked system be supported by a single antenna?

How do you handle the issues of simultaneous transmit & receive? If you have a constant transmitter (e.g. CC), then how can you receive on that antenna?
 

mam1081

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The same way that a repeater works - it's TXing and RXing at the same time. "Cans" or duplexors allow this. Basically, they are "band-pass" or another one that limits (I forgot the name!). They are really good filters that only allow the RX freq (and anything very close to it) into the repeater. The TX can go on the same antenna. A combiner will help you combine multiple stations into one antenna. I know one SO that has 3 channels (3 RX and 3 TX) all on one antenna - and that's VHF...Generally, you loose signal when you go through these devices, both on TX and RX.
 

N4DES

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Typicially the sites use a sigle antenna for receive. The transmission line goes thru a tower-top amp (if it's 800 or UHF) then to a multi-coupler that connects to all of the receivers.

On the transmit side, it ususlly depends on the spacing between the frequencies and how many. My system has 28 channels and uses 4 antennas for transmit (7 channels per antenna). All of the transmitters connect to a combiner network that "combines" the 7 transmitters to 1 feed line that goes up to one of the antennas.

In total a 28 channel system uses 5 antennas (1 RX & 5TX). A 10 channel system can use either 2 antennas (1RX & 1TX) or 3 (1RX and 2TX) depending on the channle/frequency spacing.

Hope this helps.
 
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portsmouth

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Hi. We have a ten channel trunking system. We have ten transmitters that feed into a combiner. It is about half the size of a 55 gallon drum. The combiner (usually factory tuned) combines all ten transmitting frequencies and has one output to the transmitting antenna. Thus one transmitting antenna for ten transmitters.

We have one receiving antenna with a tower top amplifier and comes down into the site where we have filters that only passes the receive band of freqs. This is then connected to a multicoupler with 12 output ports. Each receiver is connected to a port on the multicoupler. Thus one receiving antenna and 10 receivers connected to it. The other two ports are spares.
Every trunking system works like this.
You can also do the same with conventional (none trunking system) systems in the VHF and UHF bands.
The other respones to your question were correct also. I am just trying to keep it simple.
Regards. Joe
 
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