Trying not to start a flame fest, but done right... this sounds like a job for one of those cheap "flat-pack" mobile duplexers if you bring the power down a bit. Then use hardline to feed the cellwave and forget about the 1/4 wave altogether.
30W is WAY overkill for a "neighborhood". At 40' most HT's won't be able to talk to it where you can hear it, so it'll be a slight "alligator" anyway... if all you're attempting to cover is a "neighborhood". Also be aware of the other "typical" problem for those of us operating anything like a repeater or link at home... if you regularly use other nearby UHF frequencies, say like listening to other repeater's via your HT... the HT's going to get clobbered by desense with a 40W transmitter right above the house, making your regular operation on UHF, something you won't enjoy as much anymore. GMRS is enough MHz away from the Amateur spectrum, that it might not be a problem for ya... but just a thought. If you're into any kind of VHF/UHF weak signal stuff you'll end up VERY annoyed with the link/ repeater co-located with your other antennas... and you'll find yourself creating "mystery outages" of the thing (you turned the power switch off) so you could operate the other VHF/UHF portions of the hobby that you enjoy... I try to keep links and/or repeaters for the "backyard" down to very low power levels and put their antennas away from (or utilize vertical separation where I can) the other antennas for that band or anything where a 3rd harmonic would be annoying. Nate WY0X On Jun 27, 2009, at 3:13 PM, Chuck Kelsey wrote: > > > If it were me, I'd mount the Celwave on top and use the Heliax on that > antenna. The top antenna being your receive antenna. > > The 1/4 wave antenna would be for transmit. I assume it has a ground > plane > kit (sounded like you were using a mobile antenna). Feed that with > something > other than 9913 or LMR-type cable. If you can't use Heliax, use some > RG213. > You'll need a side mount bracket and consider weatherproofing and > hanging it > upside down. > > Now, that all said, 40 feet is not a lot of tower real estate to try > to get > enough isolation. You may not be able to accomplish that, especially > running > 30 watts. You may need to drop your transmit power considerably to > avoid > desense. All you can do is try. But don't be surprised if it doesn't > work. > > Chuck > WB2EDV > > ----- Original Message ----- > From: "agrimm0034" <[email protected]> > To: <[email protected]> > Sent: Saturday, June 27, 2009 5:01 PM > Subject: [Repeater-Builder] Where to install my repeater antennas > > > This isn't the most difficult question to answer, and I figure it > can be > > answered relatively easily. I currently over the past few weeks > > constructed a GMRS repeater for my neighbor hood to use. It is > constructed > > of 2 maxtrac radios one set at just 30 watts tx. I plan to use 2 > antenna's > > so no duplexer is needed with some good Heliax cable running at > least to > > the TX antenna. I have 40 ft of tower that I plan to mount the > antennas > > on. One antenna is a Celwave (RFS) 6db gain antenna. And the other > is just > > a plain 1/4 wave NMO style mount antenna. Which is the best way to > install > > these antennas on my repeater? Celwave on the transmit end and at > the top, > > or 1/4 wave on the Transmit and celwave on the receive? Also which > antenna > > should be mounted on top of the tower? > > > > > > > > ------------------------------------ > > > > > > > > Yahoo! Groups Links > > > > > > > > > -- Nate Duehr [email protected] http://facebook.com/denverpilot http://twitter.com/denverpilot ------------------------------------ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) <*> To change settings via email: mailto:[email protected] mailto:[email protected] <*> To unsubscribe from this group, send an email to: [email protected] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
