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You just got your GMRS license, now you want your own repeater?


coryb27
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11 minutes ago, Sshannon said:

I probably could get away with driving a post, but we share it with a rancher who grazes his cattle there.  If something happened and he complained to the BLM we might lose access.  I’d rather not chance it.  Instead I thought I’d use the weight of the batteries to stabilize the antenna base.  As I learn more about antennas I might be forced to admit you’re right. If so I’ll contact the rancher and the BLM before driving a post.  We use aluminum 1010 rail for our launch rails and we have some tripod or quad pod bases for launch pads that I thought I might be able to repurpose as an antenna base, weighted down with the SLA batteries.

As an alternative to a post sticking up, what about driving a larger piece of pipe into the ground, so your "mast" can slide down into it rather than over it, while not leaving something sticking up that could be a hazard when it isn't being used. That might be a little easier sell than something sticking up, though then it's how to mark it in a non-hazardous way...flexible flag of some kind?

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43 minutes ago, Lscott said:

I’ve given up on SLA batteries. Switched over to using LFP, lithium iron phosphate, types. A good source is at the link below. 
 

https://www.bioennopower.com

For solar charging in the field you need LFP specific charge controllers. I have several of the GV-5’s from this company.

https://sunforgellc.com/genasun/

 

Thanks for the info. I’ll look at those, but based on my anticipated usage, I doubt we’ll deplete the battery charge during a typical launch as it is.  

We’ve used SLA 12v x 7000 mAh batteries for 19 years for the launch system and I can count on one hand the number of times we’ve had a battery fail.  I recycled ten or so last year that were 18 years old, but continued working.  If I ever get through the big pile of batteries that’s in my shop I’ll be very eager to try whatever new technology is available. 

Edited by Sshannon
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27 minutes ago, wayoverthere said:

As an alternative to a post sticking up, what about driving a larger piece of pipe into the ground, so your "mast" can slide down into it rather than over it, while not leaving something sticking up that could be a hazard when it isn't being used. That might be a little easier sell than something sticking up, though then it's how to mark it in a non-hazardous way...flexible flag of some kind?

That’s an idea.  An in-ground socket.  Maybe a flange at the top to make it easy to find.  I’d probably plug it so it doesn’t fill with dirt between launches. Thanks for the idea.

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On 12/13/2021 at 7:49 PM, Sshannon said:

Very new guy here, but what I first noticed is the notion that a cheap repeater won’t do what a person wants, but that’s entirely based on an assumption of what that person wants, without ever asking.

So, here’s my use case:

I’m in an amateur rocketry club, launching from hilly land.  The hills make simplex communications impossible when we’re retrieving rockets, even though the range is always under five miles and usually within one mile.  However, there’s a tall hill to the east which is visible from most places.  I suspect that hill would make a good spot for a temporary repeater in a man portable can. Because it’s BLM property, nothing permanent can be erected.

The repeater is only needed one day per month for about 8 hours and total air time is probably under a half hour. There are no GMRS repeaters within maybe 100 miles.

This seems like something that the Retevis RT-97 might do well.  Because I would have to carry it to the top of the hill, it has to be something lightweight.  We may not drive off-road and no roads go to the top of that hill.

This would probably be paid for out of my own pocket.

Why wouldn’t something like the Retevis, a whip antenna, and a couple SLA batteries in a five gallon bucket be appropriate for my purposes?

Thanks for your help,

Noob Steve

WROM258

Sounds like a solar recharged RT97 w/ a simple N9TAX rollup antenna might work for you. Simple, small, portable, and little to no environment impact.

If you want a complete setup that can be carried in a large backpack:

A 30 watt solar panel can fit in a large backpack. A 30 watt panel and a 14 amp hour SLA battery seems to work well here in Alaska during the Spring/Summer/Fall Season but can't keep up during the cold winters with little sun. If you are not in an area that suffered from greatly reduced solar in the winter it would be a solid place to start.

Use some alum angle riveted to the back to mount the RT97 and a small solar controller directly to the back of the panel. You can attach the panel directly to a tree, place the SLA battery at the base, and hang the N9TAX in the tree itself.   I have posts in this forum about my setup and it might stir some ideas for you.

Is this some 100% Duty Cycle Commercial Grade Setup? Nope. But I get 20-30 miles out of mine to 5 watt handhelds and it works for us.
 


 

20210913_111143.jpg

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@WRFP399 That’s pretty slick.  Because I only need it once a month and during that time to listen for 7-8 hours at a time and possibly transmit for a total of (much) less than an hour, I probably wouldn’t even add the solar charger, at least initially.  I’ll look into the antenna (N9TAX) and I’ll gladly pore over your posts on battery life. Nothing beats empirical data!

Thanks!

Edited by Sshannon
Misspelled word “beast” instead of “least”
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Recently I have mentioned to a few people that have gone down the GMRS license path, and recommended UHF GR1225 and GR300 Motorola desktop repeaters. Add in a decent antenna and an old GR series repeater can do very well, especially if you swap the old radio (M120 mobiles in my GR300) for something newer, like an XPR4550 Trbo radio stack. However, one person I made this recommendation to, ended up attaching a Cobra magnet mount antenna (as in 27 Mhz CB), can you say, convoy......

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  • 3 months later...

Just a note I thought of as I a looked at repeater updates this week... 

Whether you are an experienced radio guru, know enough to be dangerous. or a beginner, keep this in mind about repeaters: 

If you put up the highest gain antenna you can find, the biggest low loss transmission line and set your power out to get right on 50 out of the tx cans of the duplexer, and score a site 1500 feet AAT....the question is, how much do I need? 

If your best radio, or a user on your repeater, his best radio can get in from a maximum of, say 10 miles out, but your repeater can be heard for 50 miles...you might be overdoing it. Not only that, you might be keeping another GMRS-er from being able to use the frequency elsewhere if there is crowding, even if your tone is different. Remember, it's a user coordinated service, it's up to us to share. 

I once had a customer who had a 125 Watt VHF repeater, and on a good day his reliable coverage was 30 miles with mobiles, 40 miles if you were knowledgeable. You could hear it for 150 miles depending on where you were that far out. We turned it down to 75 watts and they never knew a difference. 

So, just my opinion, but I do believe in the ham theory that you only need as much power as it takes, no more. 

-

 

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12 minutes ago, quarterwave said:

If your best radio, or a user on your repeater, his best radio can get in from a maximum of, say 10 miles out, but your repeater can be heard for 50 miles...

That's known as a "gator mouth" repeater. Absolutely adjust ERP to match the receiver's ability.

On the other hand, given your hypothetical parameters, if the repeater can receive no more than 10 miles, something else is likely wrong!

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We used to balance all our repeaters in the LMR B&I world when i was with a shop. Exactly as you said. If all your portables are 4 watts and your antenna is on the building you operate in there is no reason to have a 100 MTR on the roof. In commercial many times we shared channels in the same city so balancing TX/RX was a way to eliminate the complaints of interfearance and hey my radios doesn't work ! 

 

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Talk In versus Talk Out range, something that does need to be emphasized at times. Kudos to those that did in this forum. 

I use a 25 Watt Spectra briefcase repeater when I head into parts unknown. With an antenna on a tripod about 30 feet above ground level usually gets me a few miles increased range, if on a hill, often ten or more. This works for my use case, as all other users are carrying four to five watt handhelds. Great portable repeaters, but getting harder to find. I use two deep cycle marine Optima batteries and often get an entire weeks of use before a charge.

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1 hour ago, quarterwave said:

So, just my opinion, but I do believe in the ham theory that you only need as much power as it takes, no more.

 

I like the post... just a minor point of interest here.  It's not a Ham theory... the FCC rules say that amateur stations are limited to the least amount a power required for reliable communications, with maximum power limits.

 

47 CFR § 97.313 - Transmitter power standards.

(a) An amateur station must use the minimum transmitter power necessary to carry out the desired communications.

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On 3/28/2022 at 8:54 PM, marcspaz said:

 

I like the post... just a minor point of interest here.  It's not a Ham theory... the FCC rules say that amateur stations are limited to the least amount a power required for reliable communications, with maximum power limits.

 

47 CFR § 97.313 - Transmitter power standards.

(a) An amateur station must use the minimum transmitter power necessary to carry out the desired communications.

Yep...point being just because it says 50 on the license doesn't mean you need it. You know. 

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