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Old 12-23-2013, 4:21 AM
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Default Repeater Coverage / Ideas

Hello everyone,

I am getting ready to purchase and install a new UHF repeater in Erie, PA. This area is the home of practically everything 2M, and in being in an urban area like the City of Erie, I feel it would be beneficial to install a UHF repeater for the amateur radio community.

I had my own UHF repeater setup on GMRS and it was kind of rocky at best coverage-wise. So, I am trying to see what other operators have in mind for my setup.

Right now, I will be using two Motorola mobile radios, the transmit radio rated at 45 watts. I want to get a Comet CA-712EF UHF antenna to use on the system. The radios would have a mobile duplexer tuned to the frequencies I plan to use.

Now, I can have the antenna anywhere from 35 to maybe 60 feet safely in the air. My question is, what kind of coverage can be anticipated from a small repeater with an antenna at this height? I'm more concerned about portable coverage than anything else.

The antenna has a rated gain of 9dbi. The place where the repeater antenna is being installed is at my residence, a flat urban area - but with other small obstructions in the residential neighborhood, like houses (no higher than two stories). I am about 20 blocks from the downtown area with large buildings and towers.

So, is this something I should invest money into? Or is it something that won't get a lot of good coverage in ones opinion? I hate to see spending the money, and it becoming a "wannabe-repeater".

Any comments or advice are appreciated, along with any questions! It would be nice to get input from others who may have done a simlar task and their results!

Plese remember, this is a low-profile repeater with the hopes of having some decent coverage -- even if it is limited to mobiles in distant ranges.
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Last edited by Driv3r912; 12-23-2013 at 4:25 AM..
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Old 12-23-2013, 7:48 AM
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The first thing you will need to do is apply for a frequency pair through your repeater council. In this process you will also need to work through your HAAT (height above average terrain) along with power out and effective power out. If you need the equations let me know.
http://www.wprcinfo.org/

The HAAT is going to give you a good idea of your coverage area.

I don't know what you mean by a "mobile duplexer" but in order to use a single antenna for both transmit and receive you will need a certain amount of isolation with respect to your output power. For example, 50 watts of transmitter output power would require 58db of isolation based on 5 mHz of frequency pair separation. You will want to be sure your duplexer is capable of that or more isolation or it will greatly reduce your receivers ability to hear.
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Last edited by n8zcc; 12-23-2013 at 7:51 AM..
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Old 12-23-2013, 8:11 AM
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Quote:
Originally Posted by Driv3r912 View Post
...I feel it would be beneficial to install a UHF repeater for the amateur radio community.
The first question is, on what do you base this feeling?

Granted, repeater databases are notorious for being inaccurate and out of date, but the Atrscipub database shows 4 UHF repeaters in Erie:
1) 443.375 N3APP (Private owner)
2) 444.500 N3BXL (Private owner)
3) 444.875 W3ERC (Erie Red Cross Amateur Radio Association)
4) 445.375 K3WWA (Wattsburg Wireless Association)

Repeaterbook.com shows 3 UHF repeaters:
1) 442.150 KB5ELV (Private owner)
2) 444.500 KA3MJN (Private owner)
3) 444.875 W3GV (Radio Association of Erie Inc)

Two repeaters show up on both lists but with different trustees/owners, but there appears to be or have been at least 5 repeaters in your area.

So really the first question should really be, how many of these are still actively being used? If one or more of them are dormant or have been decomissioned, why has that happened? You should try and talk to these people and find out why their repeater is no longer active. Since you apparently are not planning on having the resources (money, expertise, time and money - yes I said that twice!) of a club to install, operate and maintain your repeater, I would really make sure to talk to the private owners and find out what their experiences are with owning a repeater. It is a much bigger undertaking than I think you realize, especially if you plan on "flying solo".

So really, the ultimate question is if there are already a couple of UHF repeaters in your area, what will your "small repeater" offer the amateurs in the area that those existing repeaters do not already offer?
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Old 12-23-2013, 8:13 AM
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Wirelessly posted (Mozilla/5.0 (iPhone; CPU iPhone OS 7_0_4 like Mac OS X) AppleWebKit/537.51.1 (KHTML, like Gecko) Version/7.0 Mobile/11B554a Safari/9537.53)

I'm assuming the mobile duplexer you're referring to is the compact trunk-mounted multi cavity type intended for mobile use... And that you probably had one on your GMRS repeater. They are readily available on eBay. I have one on my GMRS repeater and they work fine when properly tuned and operated within their specified power ratings.
If your GMRS repeater was in the same place where you're planning to install the ham UHF antenna, your coverage is going to be very similar to what you had on GMRS. If the antenna is higher then your ham UHF repeater is going to have better coverage.
If you want to try predicting coverage for a given location, height, gain, power, and antenna type use Radio Mobile software from Roger Coude VE2DBE (free) or any commercial RF prediction application (usually very NOT free).

Last edited by popnokick; 12-23-2013 at 8:16 AM..
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Old 12-23-2013, 8:19 AM
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If you haven't already, check out Repeater Builder. It's stuffed full of info, ideas, links, pictures, how-to's, and just about everything else you can think of pertaining to repeaters.
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Old 12-23-2013, 8:30 AM
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Of course....
if it doesn't have decent coverage, it's what many people refer to as a "backyard repeater" all it does is take up a pair.

Before you waste another minute you can can run a splat coverage plot and analyze your path.
W5GFE Splat Page

To run at that power level you will need to invest in a duplexer and and adequate cooling. Most commercial radios don't have anywhere near the duty cycle that would be needed for a ham repeater assuming it's one that people can actually hit and use. Also what N0IU said is worth repeating. If you want to build a repeater just to build one, there's nothing wrong with that but I live in a metro area with 6 million people and 440 is so quiet you can hear a pin drop.

Last edited by rapidcharger; 12-23-2013 at 8:32 AM..
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Old 12-23-2013, 9:30 AM
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Quote:
Originally Posted by N0IU View Post
The first question is, on what do you base this feeling?

So really, the ultimate question is if there are already a couple of UHF repeaters in your area, what will your "small repeater" offer the amateurs in the area that those existing repeaters do not already offer?
Wow, guessing you forgot one of the purposes of amateur radio;

Part 97.1(cd)
Encouragement and improvement of the amateur service through rules which provide for advancing skills in both the communication and technical phases of the art.

Expansion of the existing reservoir within the amateur radio service of trained operators, technicians, and electronics experts.

We should be helping and not shooting him down.
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Old 12-23-2013, 1:32 PM
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Quote:
Originally Posted by n8zcc View Post
We should be helping and not shooting him down.
I see your point, and agree with it. However, the OP asked if it was worth taking on the expense to put up his own repeater.

Building and maintaining a repeater is a huge undertaking. It's fun and aggravating, enjoyable and a burden, and a great way to expand a ham's knowledge. Getting the repeater is only half of the battle. The other half is having people to put the repeater to use.

In my area there are about 30 70cm repeaters. Some of these are paper repeaters that don't exist, except only to make someone feel good that they have their callsign in the repeater directory. Some of them are linked to other repeaters on 2 meters, and while they are active repeaters - no one uses the 70cm input of the repeater. As for the other 70cm repeaters in my area, the only time you hear any activity on them is when they ID every hour.

So if a ham in my area decided they wanted to put up a repeater on 70cm, the obvious question would be "why?" If there's 30 other repeaters not being used, is it worth the time, trouble, and money to put up the repeater only to have it sit idle?

I believe N0IU brings up a good point, would anyone use the repeater if it was put on the air? The answer to that question can help the OP decide if (as he asked) it is worth spending the money to build a repeater.
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Old 12-23-2013, 2:28 PM
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Thank you Brandon! At least someone gets the point I was trying to make. There is a huge difference between "shooting down" someone's idea and giving them a reality check.
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Old 12-23-2013, 4:50 PM
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The biggest hurtle will be satisfying the FCC requirements for a means of controlling the repeater and providing "control operators" to monitor the repeater operation and be able to take appropriate actions to fulfill the FCC requirements.

If you build it and they come, be prepared to provide the needed maintenance to keep it on the air and the resources to fix it when it breaks.
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Old 12-23-2013, 9:42 PM
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To answer and clarify a few questions: first, we do have a lot of public service in area and use repeaters for several different events such as triathalons, runs, red cross drills, and SKYWARN. So, it would be my hopes that I could get a reliable UHF repeater on the air for use in more of the urban areas of the city. We have nightly local nets to pass traffic, and perform other things such as NBEMS, and a ragchew net. So, maybe with coordination and permission from other repeater operators, I could link in to those repeaters and have a re-transmission on UHF.

The UHF repeaters that were listed are mostly all gone - except for the Red Cross which isn't always on the air (and that in itself is a as someone called it "backyard repeater"). The other repeater operated by N3APP is currently out of service as the transmitter is not functioning. I do not believe that the KB5ELV repeater is on the air. I was speaking to a couple different hams who stated that we didn't have any good UHF repeaters on the air. So, maybe I could try and better that.

The mobile duplexers I mentioned are the small, compact vehicle-style duplexers. Now, my GMRS repeater had a different antenna than the one I am looking at purchasing. The antenna on that was a dual band Diamond X-300A, and it was much lower than where I want to place my new antenna -- which is a UHF only antenna.

I understand the mobile radios aren't rated for "continuous-duty" transmission; but if there isn't a lot of traffic on the repeater, I wouldn't have to worry about that too much. Also, if I brought down the power output of the transmitter, that should keep it a tad bit cooler.

My GMRS repeater was a Motorola GR300 (two GM300 Mobile Radios), with a controller, duplexer, power supply, and cooling equipment (a fan running all the time).

So, it is still something I am thinking about. And, maybe I won't go about it. But, just something to think about. There were a couple of radio operators that were interested in having a UHF repeater located in the city. And, maybe down the road for some exposure, I can set it up to EchoLink, etc...

It's all a work in progress (in my head) though folks! Thank you everyone for the input thus far.
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Old 12-23-2013, 11:16 PM
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Here's an alternative thought...If the other UHF repeaters that aren't currently on the air or aren't reliable have good sites, you could put your time and resources towards helping to make those repeaters better rather than building your own repeater. When it comes to amateur radio repeaters, getting access to a good site with an antenna at a high elevation is huge. If I had to choose between putting my eggs into a "backyard" site at low elevation vs. sharing my eggs at a site with higher elevation, I think I'd choose the latter.
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Old 12-23-2013, 11:40 PM
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Yeah, I'll have to agree with that. I might just save up my money and build a nice base radio station setup. Just came across a Powerwerx DB-750X radio, and it looks like a nice radio for my base station.

Thanks guys for the advice, but it does seem a bit tedious to place another repeater on the air which may or may not be used. That, and I'll be able to keep my electricity bill down !
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Old 12-23-2013, 11:48 PM
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Quote:
Originally Posted by W9BU View Post
...If I had to choose between putting my eggs into a "backyard" site at low elevation vs. sharing my eggs at a site with higher elevation, I think I'd choose the latter.
I agree with this. But it really depends on what the purpose of the repeater is. If the purpose is to create a place for area hams to congregate, a low level backyard repeater isn't going to be it. The coverage usually isn't enough to be a draw for people.

Trying to share your "eggs" with an existing system usually doesn't work. Repeater owners are not fond of some new guy coming along and offering to "help". If you're a member of a club that has a 2m repeater already, offering to furnish, build, and install a UHF repeater for the same site might go down easier.

If the purpose of the repeater is to experiment with a few nearby friends, learn how to make them work and sound good, then maybe it's a worthwhile project, even if it is a money hole.

With the OP's original comments taken into account, with the idea of a UHF repeater to serve "the amateur radio community", it's really not practical. You're working backwards and sideways, and that will end up being a waste of time and money.

First, define what you want to actually accomplish. Then, define the "community" that you want this thing to serve. Determining the coverage area can be as simple or as complicated as you want. Get a copy of Radio Mobile. Take a few months to learn how to use it, and you can make some pretty accurate plots. But it's not user friendly or easy. Never used Splat, but I hear tell it's pretty simple. In coverage predictions, though, be warned... simple usually means less accurate.

Determine if the area you want to serve is even doable from your location. If not, you either need to drop the project, or redefine the goals. If just building a repeater is the goal, then just build the damned thing, get it coordinated, and put it on the air. And expect few to zero users.

Start by defining your requirements and your resources, and THEN make an intelligent decision on whether or not to build it.
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Last edited by zz0468; 12-23-2013 at 11:50 PM..
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Old 12-24-2013, 12:21 AM
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Quote:
Originally Posted by Driv3r912 View Post
There were a couple of radio operators that were interested in having a UHF repeater located in the city.
To me, this is a HUGE red flag!

Just how interested are they? Now go back and ask these guys how much they are willing to pony up towards getting a new repeater on the air. I am sure they would love to have a UHF repeater in the city... as long as they don't have to pay for it. Why should you have to bear the burden entirely by yourself?
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Old 12-24-2013, 3:28 AM
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Yeah, you are correct. But, if anything - I'd make it a learning experience just setting it up and all that stuff...

But, I already decided on "no", just for the sake of it. It was just something I was thinking about doing for a project.

However, my new project is going to be setting up my base radio station instead of a repeater .
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Old 12-24-2013, 8:19 AM
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It's been 24 hours since my last reply. Have you run a coverage plot yet?
I can help you do it if you run into difficulties.
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Old 12-24-2013, 11:54 AM
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The coverage plot are actually extremely useful tools. I'm not a fan of Radio Mobile for two big reasons, runs on Windows and will only allow you to input amateur frequencies on it. My preference is SPLAT! which is a little more difficult to use (no GUI, Linux utility) which is great if you're like me an already have a linux server running at your house but it has some features that Radio Mobile doesn't have. Both are free, SPLAT! is open source, not sure about Radio Mobile.

Both also have online utilities.
Radio Mobile Online
SPLAT! Online

One thing I like about GMRS, experimenting with low power UHF systems is a little easier than on the 70 cm band. A lot of people will bash mobile (notch) duplexers but when you factor in the fact you can mount a mobile radio/duplexer in a tower box running 25W and a DB420, run power to it and put it on the tower 800 ft up with 10 ft of feed line it sure beats running 800 ft of feed line (and suffering line losses) using a more powerful (more expensive) system.

What the guys are saying about other repeaters already in service, that is the exact reason I'll only put GMRS repeaters up in Lubbock. 30 2m/70cm repeaters, only 5 get used on a regular basis. Actually the reason why I told the club I would not put up the D*Star repeater.
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Old 12-24-2013, 12:11 PM
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Quote:
Originally Posted by W5PKY View Post
I'm not a fan of Radio Mobile for two big reasons, runs on Windows and will only allow you to input amateur frequencies on it.
Where did you get the idea that you can only input amateur frequencies? It works from 20 MHz to 20 GHz.
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Old 12-24-2013, 1:19 PM
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Quote:
Originally Posted by nd5y View Post
Where did you get the idea that you can only input amateur frequencies? It works from 20 MHz to 20 GHz.
Online versions won't. I think it is more work to actually install Radio Mobile than it is to install Splat…especially when I have to find a computer that still has Windows on it.
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