Getting a signal out of a building that won't....

nmfire10 · Post by **nmfire10** » Thu Sep 26, 2002 6:55 pm

Our PD building is made of metal studs etc etc and is a total RF hole. The UHF portables can not reach out of this building to hit the voting repeaters. It is kinda sad that police radios don't work in their own station. My question is, would a "passive repeater" work here? Put a little antenna in the dispatch room and a yagi on the roof?

jcobb · Post by **jcobb** » Thu Sep 26, 2002 7:17 pm

Or see if they'll put a voting receiver to the nearest repeater. If they put the antenna for it up on a pole just outside the PD, would it also get signals from the donut shoppe? A little FD humor..........

nmfire10 · Post by **nmfire10** » Thu Sep 26, 2002 7:44 pm

I don't work for this Dept. Just want to make a recomendation to an Lt that is wondering. The passive would be much less $$ than a voter and not dependent on power or wireline or anything.

jcobb · Post by **jcobb** » Thu Sep 26, 2002 10:36 pm

Matt,

I have a friend that swears he has made them work. He also said that if you could use a TPL-type amplifier and feed it with the inside antenna (with as short of a coax run to it as possible), it would put a strong enough signal up to the roof antenna.

The killer on passive is the coax run since you are getting so little signal into the rec antenna. And use good coax.

I know it needs power, but is that worth pursuing?

Sorry about the donut joke - I have GOT to find something to do at nite besides mess around on the computer!

Jack

Will · Post by **Will** » Fri Sep 27, 2002 12:08 am

I think the donut statement is valid, there are other places in town with simmular problems too!!!
A directional yagi on the roof pointed at the strongest repeater and a preamimum hard line to a small antenna in the "day room" in the station is deffenitly a step in the right direction, we have done this, passive antenna, in several "RF sink-holes" with good results.

Jaqx · Post by **Jaqx** » Fri Sep 27, 2002 5:51 am

Will,

What if............ You want to do a passive setup with VHF (Primary two-way), 800 (Cellular) and UHF (Paging.)

I'm dealing with an ex-fallout shelter building that does a great job of protecting occupants from all the harmful RF.

All three of these signals come from a mountain behind the building. One directional antenna will point generally at all of them.

Could you use some kind of directional scanner antenna on top of the building linked to something like a VHF quarter wave mounted inside above the ceiling tiles.

Any benefit?

Of course I would be dealing with low to no budget on this. An in building repeater is far, far out of the question.

Basically the goal is to talk on portables, get pages, and make and receive cell phone calls, all at a bargain price.

Tks,
Jaqx

jjmcrowell · Post by **jjmcrowell** » Fri Sep 27, 2002 9:40 am

We had the same problem, I beleive they used a PAC-rt unit mounted up in the ceiling....when we are in the station, we use a diffent channel to transmit and receive. And so if we forget to swith back, when we leave.....the channel is in the scan list, along with our primary channel, so even if we don't swith back, we will here dispatches. The audio will have that chopping sound as it checks the priority channel (our priority channel is whatever the channel selector is on).

This is a quick fix till we switch over to a digital 800mhz system, hopefully this will work better.

Hope that helps you.

N4SZS · Post by **N4SZS** » Fri Sep 27, 2002 12:42 pm

I had the same problem with a UHF paging system. The problem was overcome by using a yagi directional mounted outside. The rf feedline went to one of those low-buck preamps on their frequency range.this was powered by a 12v wall wart. the output of the preamp went to a magnetic antenna mounted in the center of the building. Basically they were flooding the interior with the full range of frequencies that the preamp would pass, but It worked! trouble is that it is only one-way-into the building.just something to consider. good luck

A10382 · Post by **A10382** » Fri Sep 27, 2002 3:09 pm

Howse about a BDA (Bi-Directional Amp). It would then allow both your radios systems and cell phones to work....

Not free.. but in the name of safety, could be sold.

You could always invoke the words that put fear into the minds of anyone responsible for public safety....... HOMELAND SECURITY..

Jim202 · Post by **Jim202** » Fri Sep 27, 2002 3:48 pm

If it is a true UHF repeater system that the PD uses, then like the above, a "bi directional amp" is a good consideration. The best way would to include the needed filtering. This way, you don't have to worry about what is outside your operating channel.

A regular duplexer would work, only 2 amps are required and 2 antennas required. Some what of a cable change from a normal duplex configuration. The filters would work as a pass filter for each of the 5 mhz. channels, (input and output) of the normal repeater.

Jim

Nand · Post by **Nand** » Fri Sep 27, 2002 6:27 pm

perthcom · Post by **perthcom** » Fri Sep 27, 2002 7:50 pm

We had a large pig operation who had their own UHF repeater on top of a silo.
The barns were built double layer steel siding inside and out and concrete..
at a barn one mile from the repeater, full quieting from outside the barn, walk inside and close the door.. nothing.. So we tried a 5 element yagi pointing at the repeater (less than a mile away) and a half wave inside. Well it worked for about 2 feet from the antenna inside. I think we had no more than 4 feet of cable between the outer and inner antennas.

Systems like this work.. but you need bi-directional amps.

Nand · Post by **Nand** » Mon Sep 30, 2002 2:38 pm

n8uhn · Post by **n8uhn** » Wed Oct 02, 2002 4:59 pm

Reminds me of a tunnel (conveyer) below ground at the local cement plant.

i installed a (vhf) 5 element yagi at one end of the tunnel pointing down the tunnel and ran about 50 ft of 3/4 inch hardline out of an airshaft and up to a catwalk about 10 ft above ground to a 5 element folded dipole array type of vertical.

it worked great, but this was vhf.

iv'e also used two 5/8 wave cell antennas coupled together with a barrel connector at thier coaxes for semi trailer type class rooms.

USPSS · Post by **USPSS** » Wed Oct 02, 2002 6:23 pm

If the passive repeater does not work an inexpensive bi-directional amp could be installed inline and that might do the trick.

KitN1MCC · Post by **KitN1MCC** » Thu Oct 03, 2002 3:26 pm

How about a Wire line Extension from the Dispatch console. with a t-1600 or other in the room