What Antenna Configuration Would You Recommend?

[Floridarailfanning]

I'm working on planning/pricing a Capacity Plus system but I'm not sure what antenna configuration would make the most sense. The system will be VHF and the sites will have 2 channels/4 slots each with 50W output.

Since there will only be 2 repeaters per site it seems like the best option would be running 2 antennas (with the appropriate separation) and 2 duplexers.

Now, I know a lot of larger systems where there are 5 or 6 channels per site would use a dedicated RX antenna and a dedicated TX antenna, but would this configuration with "master antennas" be overkill for just 2 channels?

Any recommendations would be appreciated, thanks.

(I think this should go without saying. No purchasing decisions will be made solely from the info provided here, I'm just looking for some preliminary recommendations.)

 

[jeepsandradios]

I would use a combiner for TX. IF not you may find places one channel may work differently than being assigned to the other channel. Its still two antenna's on the tower. Small receive multicoupler with filters. I'd get one that allows expandability.

 

[Project25_MASTR]

The better question, are you ever going to expand your system?

VHF is an absolute pain to deal with receive multicouplers on due to the non-standardization of splits. This means that the pre-selectors have to be channelized (window filters for a specific frequency) as you can't use simple band pass pre-selectors to pass 455-460 MHz and 465-470 MHz like you can with UHF. If you are building a two channel per site system and leaving it a two channel per site system, I would honestly just go with dual BP/BR duplexers with an extra notch filter on the RX side of each.

For antennas, it really depends on what you want to cover...I'm fond of just using something like stacked Telewave ANT150D's on a common mast.

 

[Ubbe]

The easiest way are to use seperate duplexers and antennas. But it depends of the cost of installation, antennas and coaxes.

In some cases it's less work and cost with a TX combiner and an active RX multicoupler and a single antenna and coax.

/Ubbe

 

[Floridarailfanning]

Thanks for the insight guys. At this point, I'm not anticipating expansion beyond 2 channels since this will be a small commercial/SMR type system so I'm thinking separate duplexers and antennas would be my best bet from a cost and simplicity perspective.

 

[WB9YBM]

Some sites also require repeaters to have circulators/isolator (check out Isolator (microwave) - Wikipedia ).