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New to GMRS. Setting Up a UHF Repeater

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#1 brandon962

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Posted 02 April 2017 - 06:44 PM

Hi All - I am fairly new to GMRS. I've worked in a shop and have done minor tuning, programming, installs and surface mount repairs on portables and mobiles over the years. I have limited experience with repeaters. I am attempting to setup a home repeater in Dutchess County, New York.

 

Equipment I have:

2 CDM1250 UHF Radios (40 Tx Watts / 25 Rx)

1 Dual power supply

1 ID O Matic 4 IV controller

1 Duplexer (properly tuned to Hi and Lo)

 

Can somebody make recommendations on the remaining equipment? (10 foot coax run....type of cable...N connectors.....antenna). I can not get onto the roof, so I will be running a pole/pvc out of the highest window of the house....extending it to roof level. 

 

Thank you for your help!

 

Brandon, WQYZ962



#2 ldcarson

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Posted 02 April 2017 - 07:23 PM

I would tune the radios down to 20 or 25 watts...they will last longer. It's a short run on coax so rg8x or some 213 will be fine with n connectors. I use dcp, vice ctcss. Try and go up as high as you can. Height will be ur friend. Lastly, make sure you have a good power supply to run the mobiles on. This k about a battery back up for when u have power failure. What type of antenna? I use a jpole, it works great.

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#3 brandon962

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Posted 03 April 2017 - 02:04 PM

I would tune the radios down to 20 or 25 watts...they will last longer. It's a short run on coax so rg8x or some 213 will be fine with n connectors. I use dcp, vice ctcss. Try and go up as high as you can. Height will be ur friend. Lastly, make sure you have a good power supply to run the mobiles on. This k about a battery back up for when u have power failure. What type of antenna? I use a jpole, it works great.

Sent from my SM-T357T using Tapatalk

 

Thank you! Couldn't a duplexer fed grounded UHF NMO mobile antenna suffice at bare minimum? 



#4 ldcarson

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Posted 03 April 2017 - 02:51 PM

Yes it could work, but remember your feed line AND antenna are critical components to a repeater. Make sure you use quality. Checkout repeater builder website for good info.

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#5 n4gix

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Posted 04 April 2017 - 09:02 AM

The single most critical part of any repeater is the antenna system!

 

Keep in mind that a repeater can only "repeat" what it can hear. Additionally, UHF frequencies are mostly limited to line-of-sight (LOS), so an antenna that's very limited in height will not really provide much of an advantage over simplex operations.


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#6 quarterwave

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Posted 04 April 2017 - 10:21 AM

I ditto on turning the power down. 20/25 will do as well as 40 in most cases, as the higher the tx power the more chance of drowning your input, even with dupexor (unless you are spending $3,000 on it, and even then I have turned them down to necessary power only. 

 

When I worked for M we had a customer that used a 25 watt mobile for 2 way and phone interconnect, and 2 HT600 portables, but her repeater antenna was on a 500 foot tower she owned. We had the repeater all rigged up blowing A/C directly into it, as she liked to use that phone for 20-30 minutes at a time, and it was an R100 repeater! We had it set down to get about 2 watts out the antenna, and it had great coverage, more than she needed.

 

Input path to the repeater will determine the usability in most cases not power out. Too many guys have CB mentality, not what you need.  


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#7 Sasquatch

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Posted 04 April 2017 - 01:11 PM

I ditto on turning the power down. 20/25 will do as well as 40 in most cases, as the higher the tx power the more chance of drowning your input, even with dupexor (unless you are spending $3,000 on it, and even then I have turned them down to necessary power only. 

 

When I worked for M we had a customer that used a 25 watt mobile for 2 way and phone interconnect, and 2 HT600 portables, but her repeater antenna was on a 500 foot tower she owned. We had the repeater all rigged up blowing A/C directly into it, as she liked to use that phone for 20-30 minutes at a time, and it was an R100 repeater! We had it set down to get about 2 watts out the antenna, and it had great coverage, more than she needed.

 

Input path to the repeater will determine the usability in most cases not power out. Too many guys have CB mentality, not what you need.  

 

 

Interesting information. I have an 1100 foot mountain within 3 air miles from the house (but no AC power), and although we now have a great 30 watt repeater in the area, it might be fun to build a very low power (8 watts) solar machine just to see how it does. 


De Oppresso Liber


#8 kb2ztx

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Posted 05 April 2017 - 12:08 PM

Interesting information. I have an 1100 foot mountain within 3 air miles from the house (but no AC power), and although we now have a great 30 watt repeater in the area, it might be fun to build a very low power (8 watts) solar machine just to see how it does. 

 

So it really depends on the location and the subscribers being used. I actually have a low power GR1225 GMRS repeater in my motorhome. I hit the antenna at 5 watts. Being this is run on batteries for days while on the road I can't draw alot of power. When I use this system i am only using 4 watt portables, so if i can't talk in there is no reason to have the repeater transmitting 25 watts. Back when i worked at a MSS this was one of the ways we would balance radio systems in factories and buildings also. You could reuse the frequencies in an area as alot of times the channel would not make it outside of the building. Every repeater should be balanced. 

 

I tried to explain this to a local ham club who is a "i need 100 watts out" when all they have is HT's ...... 



#9 n4gix

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Posted 06 April 2017 - 10:12 AM

I tried to explain this to a local ham club who is a "i need 100 watts out" when all they have is HT's ......

I've found the simplest way to explain this is this one simple fact:
"A repeater can only repeat what it can hear."

#10 brandon962

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Posted 06 April 2017 - 02:41 PM

Thanks all. Was looking for an easy way out. Don't really want to get up on a ladder :)







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