Batboard

This is probably a super dumb question. I have a 2 meter ham repeater currently using 7/8" hardline with a run of about 140' to the top of a water tower. I'm currently using the same antenna for transmit and receive. There are two more antennas of the same exact type on top of the water tower not being used. However they are on 1/2" hardline. Would there be any advantage to using the 7/8" for transmit and the 1/2" hardline for receive? I realize I'd still need to use the duplexer due to the distance of the antenna's being so close. When I purchased the repeater the seller checked the output and it was around 25 watts. I'm not totally happy with the coverage area of the repeater but the rent is free and the antenna/hardline were left behind by the sheriff's department. I know, I know - the antenna is tuned to 155 Mhz - I never checked the SWR because I'd probably be scared of what I saw. The site was free so I couldn't pass up the opportunity. Thanks in advance for any thoughts/ideas.

Hey, looks like you already answered most of your own questions. You outta really check that SWR and check to see if your antenna is wide/narrow, but I'm betting its either freq. centered or very narrow, as most commercial antennas are, hence your problem.

If it's a money thing, borrow yourself a mag-mount ham antenna, attach it on the end of your hardline and stick the antenna to the tower or current antenna bracket, you may be surprised at your coverage area.

peace,

You should run a return loss sweep of all three antenna and probably use the one that has the best match at your frequency.

If you are not happy with the coverage - I would guess that those antennas may be Celwave Stationmasters or similar. Those antennas exhibit pattern tilt off resonance. An exposed loop antenna like a DB224 will maintain better performance than a Stationmaster when operated off optimum frequency.

Well to answer your question on the feedline, go with the 7/8 for the receive and 1/2" for the transmitter. As single site systems are talk-back limited the receiver needs all the help it can get. The loss seen on the transmit side will never be seen.

As far as the duplexers, remember you will have to split the cans. When you do this you may have to re-calculate the harness length between the cans on the TX and RX side. The phasing harness connecting the cans together to connect to the antenna will no longer be used.

Sweep everything, especially if it hasn't been used in a long time.

Thanks for all the great info. The city won't let me climb the water tower or I would just go up there and change one of the antennas to a true ham antenna.

We always test first before starting up a system.

If you can not sweep it.
If you do not have an antenna tester.
Then do you have a watt meter to read
forward and REVERSE power?

That is the least
you Must do to fire up a system.

Get someone who has this gear.
1 hour of testing can save a lot of grief.