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Setting up a Repeater - 2 stupid questions

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swen_out_west

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I am looking at setting up a GMRS repeater and see that most 8 pair setups for sale on Ebay always seem to have 141.3 as the PL Code. It also so happens that 3 of the 4 repeaters in the area are 141.3. Is there any reason why 141.3 seems to be the standard. I'm trying to see if the seller will program another pl code into the 8 pairs, is there any other preference other than 141.3,

Also I want to be able to switch pairs occasionally when needed so I really don't want to get a duplexor tuned every time I switch (I don't have the gear to do it myself), besides I'm basically using this to receive from a fixed point distance and transmit locally, so I'll be running a 13db YAGI as my receive antenna and a dipole as my transmit. Is there any problem using space isolation. If I run my yagi receive on one end of the house I'll be setting it up at and put my transmit omni on the other end I believe the spacing is 50 feet, is this fine?

I guess I have one other stupid question, when this all started I had obtained 2 things of cable. 1 25 foot and one 50 foot of LMR400, now that I have it, I have been running into posts about not using LMR400, Why and what should I be using?
 
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mmckenna

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I am looking at setting up a GMRS repeater and see that most 8 pair setups always seem to have 141.3 as the PL Code. It also so happens that 3 of the 4 repeaters in the area are 141.3. Is there any reason why 141.3 seems to be the standard. I'm trying to see if the seller will program another pl code into the 8 pairs, is there any other preference other than 141.3,
141.3 seems to be popular with the REACT groups. It's commonly used on 462.675/467.675 as a "travelers assistance" repeater. I think that has been pushed so long as an agreed upon "standard" that it has just sort of taken off on it's own, even though in many places REACT no longer exists.

You can use whatever you want, it's up to you.



Also I want to be able to switch pairs occasionally when needed so I really don't want to get a duplexor tuned every time I switch (I don't have the gear to do it myself). Is there any problem using space isolation. If I run my yagi receive on one end of the house I'll be setting it up at and put my transmit omni on the other end I believe the spacing is 50 feet, is this fine?
There are so many variables here I wouldn't even wager a guess. Horizontal separation between antennas requires a lot more space that vertical separation. There are tools on line that will help you figure it out, using power output, antenna gain, feed line loss, etc.

Usually you need quite a bit of spacing to not have desense issues. That usually requires a lot of low loss coax ($$$), two antennas, etc. Get to a point where a duplexer might be better/cheaper.

Lots of physical separation can be achieved by using a remote receiver at a distant location. Link it back to your repeater site by wireline, point to point radio outside the UHF band, internet link, etc.

Depending on what different pairs you want to use, you may be able to get away with a duplexer that is tuned near the middle of the bands. It may not be "perfect", but some duplexers are wide enough to handle the spread with acceptable results.
Plus, it saves you one antenna and a lot of feedline, or the remote receiving setup.

I guess I have one other stupid question, when this all started I had obtained 2 things of cable. 1 25 foot and one 50 foot of LMR400, now that I have it, I have been running into posts about not using LMR400, Why and what should I be using?
LMR-400 isn't the holy grail of coax cables. It's better than what most hobbyists use, but that's about it. It's REALLY easy to do better than LMR-400. LMR-400 is inexpensive and easy to work with. It's slightly better than the RG-8 that many hobbyists would buy at Radio Shack. It's popular in that aspect, but on the professional side, it's used for short cable runs in fixed installs.
There are also issues running repeaters through these types of coax, the type with a wire braid over a foil shield. The two different shield materials can cause some issues. These issues usually require some moisture in the cable to show up, but either way, it's not the right way to do it.

LMR-400 will have a considerable amount of loss at UHF. Getting around the loss and outer shield issue is really easy to do by using Heliax type coax that has a solid outer shield. Since you really do want low loss cable, 1/2 inch (LDF4-50) type Heliax would be the minimum I'd use, and then only if it was a short run between the duplexer and your antennas. Anything much over about 50 feet, and you'd probably want 7/8 or 1 1/4" heliax.
 

swen_out_west

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Usually you need quite a bit of spacing to not have desense issues. That usually requires a lot of low loss coax ($$$), two antennas, etc. Get to a point where a duplexer might be better/cheaper.
I don't want to turn this into I ask and you guys answer, so yes I have been researching a lot. I just want to bounce the questions off you experts to wrap it up in my head.

No matter how I do it I'll need two antennas since I'm using that yagi as my receive and want an omni at the transmit. Transmitting with the YAGI would have my effective power way too high.

Besides after finally losing my patience, I pushed the conversation last night and called the pirate Hams (yes they are licensed Amateurs but don't have their GMRS license, I looked them up) on the local FRS channels, idiots and how they are illegal with their 10 watt effective power out FRS simplex repeaters, not to mention non-type approved BaoFeng crap, So I really have to watch my back on effective power out. I'm basically being watched and am going to have to keep everything within limits and type approved. I actually just had to lower my antenna this morning because one idiot drove by my place yelling 'THAT ANTENNA IS TOO HIGH' so I dropped it from 30 to 20 feet.

Anyways, back to the Antenna, my drama of how I despise some licensed Hams who are idiots and how it grows by the day(and I repeat SOME, there's childish idiots in every group) is for bar talk.

I've looked up the isolation on a graph at 465 (the aprox center) over 50 feet and came up with -45db. This should be acceptable should it not. However, I am checking to see about your idea of range. I'll probably buy one of those 6 cavity duplexor's from ebay (Hong Kong) for $88 tuned to ch7 so I can also use it on 8. Then eventually buy another tuned to ch 4. I don't care about CH 1 or 2 because that's where frick and frack have their FRS repeater (FRS 1). At $88 it's cheaper to buy multiples than having the local guy tune it and especially cheaper than buying the required test equipment
 
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mmckenna

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Using an omni for the transmit and a yagi on the receive is likely going to give you lopsided coverage.

What is your reason for choosing that setup? Just want to understand what you are looking for in coverage.
 

mmckenna

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As for the guys running the illegal gear….

I know this isn't what you likely want to hear, but ignoring them is probably the best choice. They either are purposely ignoring the rules, or have zero understanding of the rules. It's very likely that you are not going to be able to get them to change their minds either way.

Sometimes ignorance is caused by lack of education.
Sometimes ignorance is caused by lack of willingness to understand.
Education can be provided, and that usually works.
Unfortunately you cannot force someone to understand something and accept it. They'll always pull up a reason why they are exempt from the rules, rules don't apply to them, they are special, or you are mistaken. Even when faced with enforcement of the rules, they'll still refuse to accept it. In other words, everyone is wrong, except them.
 

swen_out_west

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So for now that LMR400 will be fine. My calculator that I use is coming back that 50 has approx. 1.4db loss (I rounded up) As mentioned loss isn't an issue for now, I actually have a few watts effective power I need to shave off.
 

swen_out_west

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Using an omni for the transmit and a yagi on the receive is likely going to give you lopsided coverage.

What is your reason for choosing that setup? Just want to understand what you are looking for in coverage.
Lopsided is what I am looking for actually. I basically am trying to connect 2 neighborhoods 12 miles apart. On one end with all the buildings ( that is where the mobile operates out of ) that is where I'm setting up the repeater. I will then be linking to it with a 10 db yagi running at 5 watts to keep my effective power below 50 and that side is fixed.

Most communication will be inside that 12 mile route I can hear the truck just fine when in town off the yagi. I then switch to the repeater when the mobile is in town and they'll hear me fine So it will actaully be used as a one sided repeater.
 
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mmckenna

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GMRS rules allow 50 watts transmitter power out on the primary channels and repeaters. You can run more ERP than 50 watts.
 

jonwienke

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swen_out_west

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Maximum station power is 50 watts output (not ERP).

§ 95.135 Maximum authorized transmitting power.
(a) No station may transmit with more than 50 watts output power.

https://www.gpo.gov/fdsys/pkg/CFR-2009-title47-vol5/pdf/CFR-2009-title47-vol5-part95.pdf page 7 (labeled 533)
Yes but that's interpretation, and since everything else on part 95 is listed as ERP I just want to stay below 50 watts ERP until Frick and Frack stop stalking me.

Eventually I am going to swap yagi's. Then my transmit side will shoot to 99 ERP (over 80, I haven't calculated actual loss) when I switch sides. (I have 2 yagi's to work with a 10.5db and a 13db)

Honestly, that's low power if I really had to (wanted to) I can hit high power with 3 keystokes on the menu option and have over 200 watts ERP.
 
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swen_out_west

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Back on topic, as mentioned 50 watts ERP is what I want for now. That's it, I got all settings and antenna's calculated, just waiting on my UHF range power meter (As a former CB'r all my test equipment is 11 meters) for an actual check as to what the actual wattage going in to the antennas are.

Back to the repeater. As mentioned, it's basically a one way repeater. When the mobiles get in that area, I switch to repeater (a simple change the channel knob setting) and my transmit then becomes OMNI in that area. The mobiles would just stay simplex on that channel full time and since my receive side is still 462.xxx, I'll hear them on that yagi, like I say I want to switch yagi's so my receive is even better, but that's in a few months when last night's conversation (or argument I should say) has blown over (children tend to get bored harassing people eventually)

So the last thought that needs to be clarified is physical separation of the yagi and dipole. I guess I could go just dipole and run a duplexor. I just wanted a crystal clear connection between yagi's, or maybe I was over designing this thing. (I tend to overbuild/overdo things)
 
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jonwienke

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Yes but that's interpretation, and since everything else on part 95 is listed as ERP I just want to stay below 50 watts ERP until Frick and Frack stop stalking me.
It's not "interpretation", it's the plain language of the rule. ERP is specified as ERP, power output is specified as such.
 

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I've run quite a few repeaters at home with separate antennas, no duplexers and various types of radios as an experiment. If your using a very high end radio or repeater like a GE Master II with a receiver and transmitter that gets tuned to a specific frequency, you can probably make it work. If your using cheap broad band Chinese radios to cobble a repeater together then get ready for a lot of wasted time and frustration.
prcguy
 

swen_out_west

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The only transmitter that would even access the repeater at base 2 is the one at base 1. All other radios in the comm plan have no need to even access it.

The full scenario is 2 towns separated by 12 miles. Right now transmit and receive is fine except the mobiles have poor reception due to obstacles when in base 2's area. Not a problem around base 1 since it really is a 1 horse town.

I was just going to go with a simple dipole with duplexor but still like the idea of a yagi for the receive if I ever want to access it from a mobile around base 1 just to broadcast a simple 'Coming your way'.

So yes the coverage plan is oblong and not your typical repeater setup. Like I say it's only to re-transmit the one radio's signal due to obstacles.
 
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RFI-EMI-GUY

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The problem with having two antennas and no duplexer (or other filter) is that the receiver will get overloaded by the transmitter carrier and or noise. A duplexer has two rejection circuits.

1) On the low side 462.xxx MHz transmit, a rejection of transmitter noise at 467.xxx MHz..

2) On the high side 467.xxx MHz receive, a rejectection of the transmitter carrier at 462.xxx MHz.

A GOOD duplexer, not the silly Chinese ones, will also have a bandpass characteristic so that all forms of out of band noise and spurious responses don't mix into the receiver and/or transmitter. If your receiver isn't top notch it may have spurious reposes out of band. If the transmitter isn't top notch it may have spurious noise outside the UHF band.

Regardless of what you build, be prepared to make effective sensitivity and desense measurements to see if the repeater is "duplexed" properly. If it isn't it will always be noisy and may drop out and come back on at odd times.
 

swen_out_west

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Right now I decided to put this on hold. $600+ for a repeater setup isn't really worth it for the few places that the mobiles have bad reception. By the very nature of being mobile they can always move to a spot that has a better LOS.
 

RFI-EMI-GUY

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Maximum station power is 50 watts output (not ERP).

§ 95.135 Maximum authorized transmitting power.
(a) No station may transmit with more than 50 watts output power.

https://www.gpo.gov/fdsys/pkg/CFR-2009-title47-vol5/pdf/CFR-2009-title47-vol5-part95.pdf page 7 (labeled 533)
This too is subject to interpretation.

Does it mean 50 watts at the terminals of the PA? If there is a built in circulator or isolator panel (Like an MSF5000) can it be 50 watts at the circulator output port? What if there is a duplexer inside the cabinet with the isolator panel? Can it still be 50 watts? This is a common configuration and to meet 50 watts, might require 75 or 80 watts final output.

The effect is same, 50 watts station output. But with more built in protection.
 

RFI-EMI-GUY

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Right now I decided to put this on hold. $600+ for a repeater setup isn't really worth it for the few places that the mobiles have bad reception. By the very nature of being mobile they can always move to a spot that has a better LOS.
You can do this same thing with a simplex repeater:

Install a base station (50 watt mobile) at your QTH. Wire up a simplex repeater controller. Program one simplex channel in the station with duplex PL tones; Example Transmit 141.3 Hz (or your normal simplex PL), Receive 192.8 Hz).

Program a second simplex channel in your mobile with normal channel and receive tone (example 141.3 Hz) and transmit tone 192.8 Hz.

Now when your other mobile cannot hear you you can switch to this channel and your message re transmitted with a delay. The other mobile will only hear the re-transmission.

But the other mobile should program the same capability in the event you cannot hear him.
 

prcguy

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Its 50w at the PA output for GMRS. If the "repeater" comes with an internal isolator like an old Motorola Micom repeater then it would be 50w measured at the TX output of the box. If your using an external isolator it would be 50w out of the box and into the isolator leaving less than 50w out of the isolator and into the duplexer, etc.

I had this clarified when putting up my first GMRS repeater about 35yrs ago.
prcguy

This too is subject to interpretation.

Does it mean 50 watts at the terminals of the PA? If there is a built in circulator or isolator panel (Like an MSF5000) can it be 50 watts at the circulator output port? What if there is a duplexer inside the cabinet with the isolator panel? Can it still be 50 watts? This is a common configuration and to meet 50 watts, might require 75 or 80 watts final output.

The effect is same, 50 watts station output. But with more built in protection.
 
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