Repeater question

[Wayne]

Apologies in advance if this topic has been covered here previously. My question regards repeater functionality in general. In the FCC database, most licenses show a base station on a certain frequency with high power output (say 100 watts) and numerous mobile units on a separate frequency with say 4 watts output. So, it would appear the base station with 100 watts output is not transmitting on the input frequency to the repeater but rather direct on the repeater output frequency. Is this correct? I know the mobiles transmit on the repeater input frequency and then the transmission is rebroadcast on the repeater output. Thanks in advance for the insight!

Wayne

 

[LarrySC]

The mobiles do NOT transmit on the repeater freq. They transmit on the mobile freq that goes into the repeater and comes out on the output freq. The only time a mobile uses the repeater freq is to bypass the repeater for close range car to car. They can, however, still hear the repeater. 800 trunking works the same way.

 

[Wayne]

I was interested in particular how the dispatcher transmits. I am assuming the dispatcher is the base station with 100 watts in this case. When the dispatcher transmits, does it typically go thru a repeater or direct on the repeater output frequency?

Wayne

 

[Bucko]

In my county the sheriff dispatch for example is on the input side of the repeater, I can monitor the base on both input and output...............

 

[nexus]

I think you have that correct... Ive known several departments who transmitted SIMPLEX onto the REPEATER'S output frequency. So that would make sense....

Units transmit on 154.8900 and it goes out on the repeater on 155.7000
but dispatch transmits simplex on 155.7000 at 100 watts.

 

[motomeso]

I think you have that correct... Ive known several departments who transmitted SIMPLEX onto the REPEATER'S output frequency. So that would make sense....

Units transmit on 154.8900 and it goes out on the repeater on 155.7000
but dispatch transmits simplex on 155.7000 at 100 watts.

The dispatch is most likely direct wireline or RF link full duplex to the repeater so he/she can hear if they accidently talk over top of an officer and / or can get an emergency call out regardless of activity on the repeater.

 

[STiMULi]

I think you have that correct... Ive known several departments who transmitted SIMPLEX onto the REPEATER'S output frequency.

The Highway Patrol here sometimes think that no one else is listening.

 

[qball]

Wayne,

Here are some really basic things to follow when looking at a license to determine what kind of station it is.....

FB2 - repeater output

FB - base station greater 25' tall

MO - mobile

FX1 - fixed station with antenna less than 25'

Most of the time a license with a repeater will have the FB2, MO on the repeater input, MO on the repeater output, FX1 for each other small base/location.

 

[KC4ZEX]

Their are 2 or 3 variations especially on older systems. Most new systems now put the dispatcher on a low wattage input transmitter just like a mobile and they transmit into the repeater like mobiles. Meade co Ky got a new dual repeater system 2 yrs ago one located in west part of co one in east. they use same freq's but different pl to select which repeater you open. Its a Motorola high band system with 3 repeaters at each site. one for police one for EMS and one for fire. One of the sites has a telephone link to take the receive back to dispatch. The other goes back over the air direct.

 

[michaelsbus]

The 100W station is the repeater itself. The base station may simply be one of the mobile units, or it may be a direct control link to the repeater site. In that case, the FCC ULS will show it as a control point to the location of the repeater site. I've seen some licenses that show 2 or more control points; likely backup base station sites.

 

[rescuecomm]

Most public safety agencies license the base station to higher power in case the repeater goes down due to power failures, lightning, etc. With the higher power, mobile units can shift to the repeater output freq and have some coverage. The WT coverage will be limited. That what I did with the rescue squad repeater license. With the higher power, most of our pagers can be set off using the output freq if necessary. You just never know what might happen. You really don't need the higher power to hit the repeater though.

 

[kb2vxa]

Hi Wayne and all,

Sorry if these guys have you confused by now so here's my SIMPLE answer to your question.

"So, it would appear the base station with 100 watts output is not transmitting on the input frequency to the repeater but rather direct on the repeater output frequency. Is this correct?"

This is correct because the "!00W output" transmitter is the repeater itself. There may also be a low power base station transmitting on the input, this is the control point. There are several ways a control point may connect to a repeater, a telephone line, microwave link or direct radio link but they usually employ high gain highly directional beam antennas so it's unlikely you'll hear dispatch on the input in any case.

"I know the mobiles transmit on the repeater input frequency and then the transmission is rebroadcast on the repeater output."

You got that right.

There are a few additions usually, the mobiles may transmit on the output thus bypassing the repeater should the need arise such as in the case of repeater failure. This simply involves shifting the transmit channel while leaving the receiver alone so they may also hear the repeater. There may also be one or more mobile channels used direct car to car that are unrelated to the repeater.

It's rather silly to listen on a repeater input which is why the frequencies usually aren't listed in the various web site databases. The place to go for full information (except PL and DPL tones etc.) is the http://wireless2.fcc.gov/UlsApp/UlsSearch/searchAdvanced.jsp FCC ULS database search engine.

 

[bigcheez69]

It's rather silly to listen on a repeater input which is why the frequencies usually aren't listed in the various web site databases.

There is obviously two schools of thought on this. Infrequently there can be transmissions of intrest for one reason or another on an input frequency.

The place to go for full information (except PL and DPL tones etc.) is the http://wireless2.fcc.gov/UlsApp/UlsSearch/searchAdvanced.jsp FCC ULS database search engine.

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