Batboard

Need a little help with one or two ideas. We have a repeater system located on a tower site just outside of town. This works well EXCEPT in the immediate downtown area inside buildings, etc. What I'm hoping for is something "cheap" that would work without changing channels, etc. I don't know if they make an "in-building" system that can rx/tx the signals out of the basement of a particular building,etc. Or if you can put an "in-town" repeater that works in the "area" of the immediate downtown. I suppose it would be like a 'voting' system, but that sounds/seems to expensive. I didn't know if there were "special" repeaters for local areas. Thanks

Can you hear the repeater inside the downtown buildings, but are just not able to get out on a handheld? If so, then you have more options for solving your problem. If you can not hear the repeater, then you have fewer and more expensive options to consider.

IF the problem is in a small number of buildings to which you have access, you may be able to use a passive repeater to fill the holes.

Place one reasonably high-gain antenna for the frequencies of interest on the outside of the buidling.

Place one antenna inside the building, near the trouble spots.

Connect the two with coax.

The external antenna will receive the repeater's outbound channel, and it will be re-radiated by the antenna on the inside. The antenna on the inside will receive the HT signal, and the outside antenna will rebroadcast it to the repeater.

No power needed, no tuning.

wowbagger, what kind of antenna would you use for the inside one?

is there any chance of heterodyning or any other problems with that set-up if the portable is reaching the real repeater by itself *AND* being rebroadcast by the passive repeater?

I'd try to use a nice directional Yagi for the outside antenna.

For the inside - depends upon the job. If it is one dead spot, put a single quarter-wave at that point. If it is a long skinny dead corridor, run a wire down it.

Since the system is entirely passive, there are no issues with mixing (unless you get some corrosion on the connectors acting as a point-contact diode, but even then you are not dealing with strong signals - the mix products will be down at the thermal noise level).

Regarding the issues, its especially bad in two buildings in particular, though its basically a somewhat big area with a couple of rooms. The option of putting an antenna on the inside and outside; it may work. I'm guessing it would not only "pickup" the portable transmissions and "link" them to the outside, but it would probably work the other way too, right? The portable would "rx" better because of this method.

wowbagger, what kind of signal strength loss are you talking on a passive repeater? (not looking for -dB or anything that specific) but what kind of reasonable degradation of signal strength would you get on a system like that? 50-60%?

Had one of those passive antenna systems in one of our substations. Used two 1/4 antennas
Worked like a charm

Fowler

i might have to give this a try too.

do you need to run a hardline or can you use some regular cable?

Does anyone know where I can find a BDA for UHF ? THANKS

We talked in the past about 75 ohm leaky feeder cable.
It works super great.We have run miles of it in
tunnels and the signal is 5-5.

Another option, I guess would be to put in a "satellite receiver" deal between the "main tower" and a remote rx signal (voting system) I suppose. Does anyone know about something like this (on a small scale) cost and where I could begin to look for something like this.

Gigs wrote: What I'm hoping for is something "cheap" that would work without changing channels, etc. I don't know if they make an "in-building" system that can rx/tx the signals out of the basement of a particular building,etc. I suppose it would be like a 'voting' system, but that sounds/seems to expensive. Thanks

If you're still looking for a voting system / satellite reciever after reading the above passage, cheap must mean "more than 5 or 10k". Cheap for me means REALLY trying and setting up the passive repeater w/ 2 antennas & coax like Wowbagger said. If you're looking cheap (even w/ used parts) you're gonna spend a HELLUVA lot more going to voting or a satellite setup than you are with a passive set up.

To put Da' Fish's statement in perspective for you:

JPS SNV-12 Voter with 2 line cards: ~$6,000
Receiver, power supply, etc: ~$1,000 at least
Antenna: $30-$200

Then you have to find a way to get that remote receiver's audio back to the voter and transmitter. You'll either need leased telephone pairs (Lots of $$), or setup an RF link with two Yagis. If you do the RF link, you'll need a link transmitter and a link receiver. If you want the link fully supervised, you'll need the link transmitter to be continious duty.

Ready to try the passive repeater now?

Might be a lot easier, better and more cost effective to use your NexTel phones in the private radio dead spots, like inside buildings. Craig McCaw has predicted that his systems will eventually supplant private 2-Way radio systems. He might be right!

Larry

ASTROMODAT wrote:Might be a lot easier, better and more cost effective to use your NexTel phones in the private radio dead spots, like inside buildings. Craig McCaw has predicted that his systems will eventually supplant private 2-Way radio systems. He might be right!

Larry

If this is a public safety system, then that statement is very bad idea.

Regarding the Passive Repeater conversations that is going on, I'm finding this interesting to try too for one of my projects. To hook this this kind of repeater, can you explain a little better, plus this might help the other person asking. Does you use "leaky" cable or radiating cable, etc.

One method that I am most familar with is with two antennas rather than leaky cable.

You have a yagi on the outside pointing at the main site. You need all the gain you can get with this thing so don't buy some piece of junk.

On the inside, you have another antenna appropriate for the area it is covering. A 1/4 wave whip or even one of those stealth antennas would be idea for omnidirectional coverage.

Connect them both together with the lowest loss cable that you can afford. Radio Shack RG-58 is not what you want.make sure your connections are tight, sealed, soldered, and good quality. Make it as short a run as possible but still with the antenna where they need to be.

If you want to get fancy, you can throw a Bi-Directional amplified in the middle of this coax. This may or may not help depending on how much RF is actually reaching the thing to begin with. A BDA is not cheap either. Try it without first.

The passive repeater works better than most folks realize.

Like Matt sez, use the best shielded, lowest loss cable you can get, and it is surprising how well the system will work.

Case in point:

My 900 MHz pager is useless at my home. Stuck a 7 element yagi on my tower fed with about 40 ft. of 1/2 hardline. Connected to a 900MHz quarter wave spike hung upside down in a hallway..

pager works great, work bothers me all the time... probably was better off when the pager didnt hear!

73

Mike in CT
KM1R

We had the problem with a pager not working in
a home so we took the pager and placed it in the
car charger.We pluged a BABY monitor into
the car and the person has the other half
of the monitor in the house.The Price
Was Super Cheap And Has Worked For
Four Years.
Talk about CHEAP.

What the mind can do when we say CHEAP.