Two repeaters one antenna 11MHz apart

[W5DMH]

I have a tower with a single antenna on it and I want to put two UHF repeaters on that one antenna.
Each repeater currently has its own notch duplexer supporting 80db of isolation.

Repeater 1 is GMRS
RX : 467.600
TX : 462.600
45w output (before duplexer)

Repeater 2 is Commercial DMR
RX : 456.025
TX : 451.025
40w output (before duplexer)

I am looking for equipment suggestions for doing this to allow safe simultaneous operation of both repeaters .

 

[buddrousa]

It can be done but will cost more than adding a 2nd Antenna and 7/8 Andrews Hardline plus it will introduce more loss.
The 2nd Antenna and line is by far the best option.

 

[lenk911]

two UHF repeaters on that one antenna

You should combine with a filtered combining system with circulators. The notch duplexer is worry some. All filtering should have band pass band reject properties. In a multi-station facility notch duplexers should not be used.

 

[Firebuff66]

You are looking at going with a combiner 2Ch Combiners can be had for $2k-$30K depending on a lot of factors
Here are a few I found

HC450-2 UHF TX Combiner

HC450-2 series is a UHF TX hybrid combiner with single or dual isolators used for combining 2 UHF transmitters into one antenna with close frequency spacing.

www.scan-antenna.com

Combiners | Low Profile, Compact, Channel & Multi-Band Combiners

Browse Tessco's industry-leading inventory of multicouplers & accessories. View UHF & VHF combiners, along with multiband, hybrid & channel combiners.

www.tessco.com

 

[W5DMH]

Yikes, it seems a second antenna is the most cost effective method, and here I thought that would be a very expensive alternative.

 

[lenk911]

You are looking at going with a combiner 2Ch Combiners can be had for $2k-$30K depending on a lot of factors
Here are a few I found

If you ever see your combiner system growing beyond 2, use a T-Pass combiner system. Let the vendor design it for you. It has the least insertion loss can be expanded and adjusted as the need arises. The original vendor will re-engineer it for you. It will cost more!
Many of the low cost combiners are one and done solutions which may be valid if the potential of your site is limited.

 

[prcguy]

You can do it with two good Bp/Br duplexers, a Tee and two critical lengths of cable between the Tee and duplexers. Its not going to work with notch only duplexers. You will also need isolators on each transmitter if you don't have them already.

 

[freddaniel]

As everyone suggests, with enough time and money, you can make the two repeaters work on a single antenna. HOWEVER, if you add a second antenna and make one a master receive and the other a common transmit, you can easily place those two repeaters and likely add more repeaters with little investment and time involved.

 

[prcguy]

As everyone suggests, with enough time and money, you can make the two repeaters work on a single antenna. HOWEVER, if you add a second antenna and make one a master receive and the other a common transmit, you can easily place those two repeaters and likely add more repeaters with little investment and time involved.

Master receive is great but you need vertical separation and tower hardware to accommodate that. Then a front end preselector, preamp and power dividers for the receivers. Then a good cavity filter for each transmitter and preferably a dual isolator for each transmitter and a hybrid combiner. That's a lot of $$ in hardware to support multiple repeaters on a split antenna system. Once you have it you can easily add more in the future but that first step is going to be expensive.

Edit: for 11MHz spaced transmitters you don't need a hybrid combiner, just a Tee adapter or star depending on how many transmitters and of course the cavity filter and isolator. If the transmitters are very close spaced like 1MHz or less then you need the hybrid combiner and say goodbye to more than half your power.

 

[kayn1n32008]

The main site, of the club that I belong to, has 6 UHF repeaters, using master Rx and Tx antennas, vertically spaced. Rx antenna is a SRL310-C4. Tx antenna is a SRL 310-C8

This has P25, 2x DMR, Fusion, D-Star and Analogue. 1x 440.xxxx, 1x 441.xxxx, 1x 442.xxxx, 1x 443.xxx, 2x 444.xxx. Each channel has a dual circulator.

The receive multicoupler is an 8 port, it's past life was in the 400-430MHz band. 2 ports are currently unused, and terminated. We recently added a GPS-DO

 

[AM909]

The main site, of the club that I belong to, has 6 UHF repeaters...

Wow. That's a pretty-well-funded ham club.

 

[kayn1n32008]

Wow. That's a pretty-well-funded ham club.

VERY. They own two tower sites with one of them having a major cellular carrier an anchor/preferred tenant, weather radio, and 2 LMR tenants, the other owned site has a WISP, and weather radio. Most of the multicouplers in the photo were donated by companies/PS agency upgrades. They also have a healthy amount of VHF gear. Not shown is 4 racked VHF, 4 cavity multicouplers.

The main site tower, containing the equipment in the photo, was built by the cellular tenant, and after a 25 year long contract for the use of the club land, turned ownership over for $1, at which time the carrier started paying to be there.

There is still lots of work to upgrade all the interconnecti cables to eliminate some LMR400 we have found at the site. Our aim is to be using superflex between all cavities and repeaters, and between cavities and feedlines.

Grounding also needs to be upgraded, as it's really unknown what actually is a system ground, and we need to tie, properly, into the tower ground system.

All in all, there was a lot of neglect over the last bunch of years, with a lot of poor quality work done by well meaning people, that have no business touching it.

We already have taken dozens of feet of LMR400, and more adaptors than I care to count out of the various RF chains at the site.

There is still a single VHF MSR2000(to be replaced by a MTR200, that was had a preamp, feeding a second preamp.

It's been eye opening experience working through cleaning up this site. We went from 9 multicouplers(4x VHF and 5x UHF) sitting on the floor, to being racked properly. We have added P25 and started moving gear around to minimize feedline length.

 

[kayn1n32008]

Edit: for 11MHz spaced transmitters you don't need a hybrid combiner, just a Tee adapter or star depending on how many transmitters and of course the cavity filter and isolator. If the transmitters are very close spaced like 1MHz or less then you need the hybrid combiner and say goodbye to more than half your power.

I think Sinclair specs their hybrid combiner for minimum of 6dB of loss at as little as 0.0MHz separation. Multicoupler with minimum 350kHz separation, is minimum 3dB loss. We are currently seeing 20w to the feedline from the weather radio transmitting at 68w out of the PA. The weather radio, APRS and a VHF 147MHz Tx/146MHz RX using 4x 4cavity Sinclair multicouplers.

 

[Echo4Thirty]

I think Sinclair specs their hybrid combiner for minimum of 6dB of loss at as little as 0.0MHz separation. Multicoupler with minimum 350kHz separation, is minimum 3dB loss. We are currently seeing 20w to the feedline from the weather radio transmitting at 68w out of the PA. The weather radio, APRS and a VHF 147MHz Tx/146MHz RX using 4x 4cavity Sinclair multicouplers.

the NOAA transmitter is only putting out 68w TXPO? Around these parts they are at least a kilowatt or more. I didnt realize they had sites with such low TXPO.

 

[prcguy]

the NOAA transmitter is only putting out 68w TXPO? Around these parts they are at least a kilowatt or more. I didnt realize they had sites with such low TXPO.

Can't be an NOAA transmitter, they would not share a transmitter combiner with commercial or amateur and the power is usually much higher as mentioned.

Edit, forgot that is in Canada, eh, no NOAA. Plus they do some things a bit different up there. For all I know they could have neighborhood weather captains, each with their own weather transmitter broadcasting to the public.

 

[Echo4Thirty]

Can't be an NOAA transmitter, they would not share a transmitter combiner with commercial or amateur and the power is usually much higher as mentioned.

I missed the part where it was combined. You are correct, they do not combine on to any one else's stuff and own everything from the rack to the antenna.

 

[kayn1n32008]

the NOAA transmitter is only putting out 68w TXPO?

It's an Environment Canada weather radio transmitter.