Repeater Assistance in Michigan.

kfd29 · Post by **kfd29** » Thu Jan 05, 2006 3:27 pm

Looking for assistance w/ a new repeater system in GR, Michigan... Could use a hand in finding out why we can not pick-up 5watt handheld's only 5 miles out, maybe we missed something in setup? If anyone is knowledgable in troubleshooting repeaters or in the GR area, please contact me! Small business that can't quite afford the $70/hr charge for a tech right now lol. Thanks!

DJP126 · Post by **DJP126** » Thu Jan 05, 2006 5:53 pm

I'm definately no expert when it comes to repeaters but the first things I would look at are:

Receiver sensitivity?
Antenna problems (corrosion etc)?
Losses in the coax?
Duplexer tuning?

Just a few to get you started. I'm sure others will have ideas also.

HLA · Post by **HLA** » Thu Jan 05, 2006 5:59 pm

how high is the antennae for the repeater? is this a one way problem, can the portables hear the base and the base not hear the portables? i've also had a couple times people program the portables the same as the repeater, they need to be opposite.

kfd29 · Post by **kfd29** » Thu Jan 05, 2006 8:12 pm

Receiver Sensitivity according to the manufactor is .25uV @ 12 dB SINAD. I'm not sure if the duplexer changes this or not.

Antenna is a 5/8 over 5/8 vertical right now as a fill-in until our Antenex FG1523, 3dB Fiberglass Omni, comes in.

Coax is RG8, asked for 9913 but I'm not sure, no markings on the coax when it came back from the shop.

Duplexer is a Sinclair MR256B*2, Mobile type, Tuned by shop

------------------------

Antenna height is 27.0m, rooftop tripod mount. 16.4m HAAT

At about 3-5 Miles south (about level terrain), I lose both Rx and Tx from the portables.
At about 3 Miles north (the terrain goes down), I lose Tx but can still hear the repeater... a couple more miles and I lose both.
In my mobile setup in my truck, I can Tx and Rx with great audio quality even at 10 miles.

Freq's are programmed as should be

DJP126 · Post by **DJP126** » Thu Jan 05, 2006 8:47 pm

At about 3-5 Miles south (about level terrain), I lose both Rx and Tx from the portables.
At about 3 Miles north (the terrain goes down), I lose Tx but can still hear the repeater... a couple more miles and I lose both.

Freq Range? (low band, vhf-high, uhf, 800?)
Only your portable or all user portables?

In my mobile setup in my truck, I can Tx and Rx with great audio quality even at 10 miles.

You are comparing apples and oranges here. Totally different antenna systems and tx power.

440roadrunner · Post by **440roadrunner** » Thu Jan 05, 2006 9:15 pm

When DJP126 said

Receiver sensitivity?
Antenna problems (corrosion etc)?
Losses in the coax?
Duplexer tuning?

He did NOT mean what it says in the manufacturer's advertisment, he meant can you actually measure it? This is what, by the way, the $70.00/hr shops do

Frankly, there are so many variables, here, that it's hard to find a place to start.

You actually need to measure the RX sensitivity, both at the receiver, and at the antenna port at the duplexer, or else pin down the "shop" who tuned the duplexer if they did and what that reading was.

Wherever this is located, could have high "noise floor"---what else is around the repeater?

The coax could be very lossy, (how long is the feedline) and since there are no numbers on the coax, you don't know WHAT it is. You need, at the very least, a good wattmeter, a dummy load, and access to both ends of the cable to measure it.

(Did anyone check the installed coax/antenna for SWR/ power output?)

Heck, at this point, it could be something as simple as a poor connection in the antenna/feedline.

What is around this site? Trees? buildings? Is the antenna "in the clear" of surrounding obstacles?

Will · Post by **Will** » Fri Jan 06, 2006 1:17 am

" Antenna is a 5/8 over 5/8 vertical right now as a fill-in until our Antenex FG1523, 3dB Fiberglass Omni, comes in. "

Well there is TWO problems, the antenna you have now is not a good choice for a repeater that is duplexed.

The Antenex FG series antennas are a VERY poor duplex antenna. They just have a 18 gauge copper coated steal wire with a few "curlie cues" hidden in a plastic pipe. This is NOT a base or fixed station design, just a overgrown mobile whip in a tube.

Get a quality antenna designed for duplex operation, your terrain and AAT.

440roadrunner · Post by **440roadrunner** » Fri Jan 06, 2006 8:34 am

Some light reading:

http://www.dalek.org/srg/Desense_testing.html

http://www.repeater-builder.com/rbtip/

http://www.repeater-builder.com/rbtip/gtm.html

http://www.seits.org/repeater/tuneup.htm

http://www.seits.org/repeater/tuneup2.htm

http://www.seits.org/repeater/tuneup3.htm

http://www.seits.org/repeater/tuneup4.htm

Will · Post by **Will** » Thu Jan 12, 2006 2:26 pm

This is a VHF system.

Here is a short up date:

The local Motorola shop mounted a mobile antenna on a ground plane/base adaptor and called that a base antenna. It is an AS 5/8 mobile type with an aluminum rod instead of the steal whip.

The realy bad part is the 'shop' mounted the antenna one half way down the mast, guess they could not reach high enough so the antenna cleared the mast.

Then to make matters worse, the aluminum rod fell off onto the roof......

Then there is the cheeeeep RG8 cable...

apco25 · Post by **apco25** » Thu Jan 12, 2006 7:31 pm

Poorly tuned duplexer

Excessive line loss from RG8 cable. Replace it at least with an LMR type cable or Andrew Heliax 1/2 inch or larger. 7/8 would be nice.

Get a real antenna from AS or DB.

mike m · Post by **mike m** » Sat Jan 14, 2006 9:22 am

Also another consideration is I can't remember how many times I have seen a duplexer hooked up wrong. RX to the tx port and vice versa.

Dan562 · Post by **Dan562** » Tue Jan 17, 2006 11:06 am

kfd29 provided that the repeater antenna is 90' above ground level, the HAAT is at 50' and he's experiencing an In-Bound Talk-In RF coverage problem.

I think there may have been a verbal communications disconnect right from the start between the equipment supplier and kfd29. Someone in the original supplier / customer conversation could have made the system coverage indication of 10 air miles radius from the base station repeater location based on mobiles using 25~30 watts output. Unfortunately the handheld portables only have 5 watts output which presents a -6~7 dBm Path Loss compared to the 25~30 watt mobiles and in the real world drops the RF coverage by 60~65% resulting in a 3.5~4 air mile radius for portables.

I still haven't seen a manufacture's name and/or model numbers for the Base Station Repeater, the Mobiles and the Portables. Any RF Power Ouput Levels (in Watts) for the Repeater and Mobiles? Where the Repeater site is located in downtown Grand Rapids or the surrounding part of town. I haven't been upto GR in several years but I seem to remember there's a gentle roll in land elevation of 40~60', Medium Pine Trees and 40~60 Floor Buildings in the downtown area which will produce RF Path Losses.

You should have specified at least 1/2" if not 7/8" Andrews Heliax feedline and connectors. A RFS/Celwave, DB Products/Andrews or Sinclair Products +5~6 dB Gain Base Station Antenna.