Passive Repeater

[Project25_MASTR]

Trying to modernize my University club's repeater system. (I say modernize loosely)

Essentially I have come into possession of surplus VHF and UHF Micor systems as well as the club has gained access to the tallest building on campus. The plan was to go with a crossband system using a spare controller at the new location. Unfortunately we tend to hang out a lot in the basement of one of the buildings on campus and have trouble making it out to the repeater. We thought about doing a simplex link but then one of the Doc's asked if we had looked into a passive repeater...so I'm looking into it and now asking y'all, any thoughts?

 

[AK9R]

Not sure exactly what you have in mind, but I will pass along that I've heard good reports about the Argent Data Simplex Repeater.

 

[trlrdrdave]

Point a yagi at the repeater outside. Run cable to the basement and put a quarterwave mag mount some where and try it. I have seen this work very well at times.

 

[majoco]

Many years ago I installed a passive repeater for a family living in a valley - TV reception was terrible. On a fence post on the hill I mounted two yagis one pointed at the TV transmitter and one at the farmhouse - a bit of coax in between. Worked a treat.

 

[zz0468]

Done right, a passive repeater can make a noticeable difference. Use a high gain antenna aimed toward the donor site, make sure the path length to the donor site is pretty short. On campus, is more than perfect. Use low loss line between the donor antenna and the antenna in the basement, and keep your expectations reasonably low. It should work decently in a room. The whole basement may be asking too much.

Passive repeaters have been used in the microwave bands for decades. Designed properly, they work quite well.

 

[Project25_MASTR]

Done right, a passive repeater can make a noticeable difference. Use a high gain antenna aimed toward the donor site, make sure the path length to the donor site is pretty short. On campus, is more than perfect. Use low loss line between the donor antenna and the antenna in the basement, and keep your expectations reasonably low. It should work decently in a room. The whole basement may be asking too much.

Passive repeaters have been used in the microwave bands for decades. Designed properly, they work quite well.

The only hopes I'm having is for most of the ht users in the basement to be understandable from the basement. Right now, it's can key the repeater, they just can't get the audio through to the repeater.

 

[WA0CBW]

Is this a problem with the repeater? Squelch set too tight? Repeater de-sense? Is the audio weak or noisy? No audio? Inquiring minds want to know!
BB

 

[zz0468]

The only hopes I'm having is for most of the ht users in the basement to be understandable from the basement. Right now, it's can key the repeater, they just can't get the audio through to the repeater.

Before you do anything else, try to find out why they can key the repeater, but no audio gets through. That's not right. I would be looking for a desense problem.

 

[zz0468]

Is this a problem with the repeater? Squelch set too tight? Repeater de-sense? Is the audio weak or noisy? No audio? Inquiring minds want to know!
BB

Good questions. Now you have me wondering.

 

[Project25_MASTR]

It could be. I have not actually been granted an audience with the current repeater, I know it's a hack job done with some mobiles (what kind, I'm not sure), a NHRC 3 controller, and DB420. The repeater's overall performance is just poor in general. Though it's installed on one of the taller buildings on campus, it can't compete with a lot of the lower powered repeaters around town on the RX side. Eventually, it's getting replaced with Moto repeaters (I just have to have some crystals manufactured and whatnot). It transmits fine into the basement, just can't get out to it. Might be that a building or two are in it's way (one being the taller building that the new system will be installed in). My understanding is that this repeater uses some 70cm radios that were set up once upon a time ago (my repeater experience deals completely with commercial repeaters and the lower power commercial radio based repeaters put together with Moto and Icom radios).

 

[DisasterGuy]

I would also look into the duplexer that is supporting this system. Since it sounds like may not have been that well engineered to begin with, the duplexer would have been a prime spot for someone to have cut a corner. Make sure the duplexer is appropriate for the application and is properly tuned. In improperly spec'ed or tuned duplexer could be cause for desense (as mentioned above) or attenuation on the receive.

 

[KB3KBR]

what is a passive repeater?

 

[WA0CBW]

A passive repeater is just 2 antennas connected together. A high gain antenna is placed outside the building and the other is placed inside. The theory is the one outside collects RF and sends it down the coax to the other antenna which is inside. The inside antenna then takes that signal and re-radiates the RF from the inside antenna. In certain situations with very short runs of coax it can provide limited coverage very near the inside antenna. In most instances however it doesn't work.
BB

 

[popnokick]

Wirelessly posted (Mozilla/5.0 (iPhone; CPU iPhone OS 7_0 like Mac OS X) AppleWebKit/537.51.1 (KHTML, like Gecko) Version/7.0 Mobile/11A465 Safari/9537.53)

Agree.., duplexer. Although I did have a problem that I thought was duplexer on my repeater.... But turned out to be bad lightning arrestor. Plug in it had opened up... Maybe nearby strike. Switched to Alpha-Delta and no prob in 4 years now. Lots of t-storms, too.