Seeking guidance for my first repeater

[Stripes]

Hello Internet!

 

It has been awhile since I've been playing around in GMRS and I have learned a lot of things over the past few months. I believe I am finally ready to try and create a repeater of my own. My location is favorable as im on top of a hill that oversees the township so I want to give it a go. The ideal use of the repeater is to provide a method of local communication within the township. Im located near and in range of the CSRA Columbia network, but I want something small and local, plus its just a fun project to try and accomplish. I have developed a rough plan and got some equipment I have looked at and will start collecting soon based on how this thread goes.

So far I have got 2 Motorola GM300 UHF radios as they were fairly cheap and work well with the repeater interface I got for it. I plan to run theses radios at 25 Watt output. For the repeater interface I chose a Motorola HLN3333B R.I.C.K. as its just plug and play with the GM300's plus it adds the option of remotely shutting down the repeater via DTMF if I desire. I already have covered a power supply so that's good there. I want to get a duplexer and this one offered on MyGMRS looks good but I want some opinions about it from folk who know a bit more first before committing on buying it. If there are other duplexers out there that I should consider, let me know. The antenna I have planned to get is a Tram 1486, also offered by MyGMRS as a option and i'll have this mounted straight above the set up which is inside of the shop. From floor to antenna base, about how tall should I mount the antenna? And for coax, I am leaning towards using 100ft of LMR400 coax cabling. I herd it would get the job done well and its not too expensive. So far that is everything I have on the list. I'll worry about building antenna mounts and a cabinet for the radios later.

I know i'm not making something that is perfect and i'm not trying to cover an entire county, but I want something that works well for a starter and to go from there. Im hoping to achieve about 20~ miles and I hope im making the right decisions with some of the equipment I have and plan to get. Let me know what you experts think and help guide me in the right direction.

Looking forward to learning more!

[OffRoaderX]

Be wary of those that confuse a simple home setup with a commercial/heavy-duty application and try to drastically over-complicate things or spend all of your money for you..

Shorter is better for coax, but on my home/garage repeater I have ~75 feet of LMR400 going through a couple of N-type to PL259 adaptors, up to my Tram 1486 about 50 feet above the ground.

With this setup HTs 15-20 miles away can hit/use the repeater and mobile radios can use the repeater 55 miles away.. It would probably be further, but there are mountains at 55 miles.

Is it a perfect setup? NO.. is it "the best"? NO .. Is it "good enough" - YUP

 

 

[gortex2]

So first thing I would try to do is get your antenna cable alot shorter than 100' between antenna and repeater. Unless its going up a tower the closest is the best. Even LMR will have almost 3dblossi n 100'. That just took your 25 watt repeater to 12.5 and that no duplexer. You will have loss there also. 

The duplexer is a good unit. Get it tuned professionally and a home repeater should not have issues. Im not a fan of the antenna you picked but I prefer quality. the DB404 would be ideal but know folks dont like the look of it or the price. If you want a small fiberglass stick look at the Laird FG series in the other links on the page. You will find them a much better build than a put together antenna. 

Manage expectations. I know you want 20 miles. If you can talk that simplex then your repeater may play nice. The GM300 is a good little radio. Built many repeaters in my shop days out of the same parts you mentioned and many are still in service today. The GM is not a continuous duty radio so make sure you have a fan on it also. 

 

[JohnE]

I will echo what Gotex and Gman have said. At 100' 1/2" heliax at the minimum and would have a 1.5 dB loss.

seeing as you have the radios already I would do a propagation map to see what your coverage might look like.

link

https://www.ve2dbe.com/rmonline_s.asp

when you do the map here are a few thing you need to know in order to make it accurate

antenna gain 4.5

TX power 25W

TX line loss 4.5 db

required reliability  85%

I think you can figure out the rest

just my thoughts

 

[Radioguy7268]

Good, Fast, Cheap.  Pick any two

The same could apply to radios with: Good Coverage, Low Price, Easy to Acquire. Except you can only pick 1...

20 miles reliable coverage to hand held portables is usually not going to happen with a "garage" repeater at your home location.

In years past, I've seen those GR300 desktop repeaters at tower sites with good elevation - and as Gman says, they usually have a bunch of bandpass cavities, preselectors, and pre-amps wired in, which kid of defeats the whole "done on the cheap" - spending $350 for a GR300 vs. $1000 - $1500 for a used Quantar/MTR2000.

[gman1971]

One thing to be aware with higher gain, is that your reduce the vertical beam cone, imagine a flashlight with adjustable focus: flood and throw.... so you get more throw, but then the cone of light gets narrower. So if there are a lot of elevation changes, it might be more detrimental than just running a lower gain antenna with a wider "cone of light"

G

[JohnE]

Height and noise floor will be everything IMO

If this is going in a private location and is not near any big RF "sites" it shouldn't be a problem for GM's/CDM's

[gman1971]

Just now, JohnE said:

Height and noise floor will be everything IMO

If this is going in a private location and is not near any big RF "sites" it shouldn't be a problem for GM's/CDM's

Height is king.

Noise floor seems to be less of a problem in UHF, even at <1 mile from a big 1400' angry RF firebreathing tower, the measured RSSI noise floor in the GMRS channels is always in the high -120dBm range.. that's pretty good.

The issue with UHF is the 10dB attenuation loss over VHF in long range distances, and the fact that anything it touches attenuates the signal like its going out of style... rain? boom, range goes to crap, snow? boom, range goes to crap, vegetation nearby? boom, there goes some more range... The only thing, like you've stated, that will will fix this is more height. And a good antenna setup.

G.

[Stripes]

Wow I have gained a lot to think about. I'm going to see if I can get away with shortening my coax and spend a little more and get heliax 1/2". I'm now looking at the Laird FG-4603 antenna as gman1971 recommended since I mainly chosen the Tram 1486 from length and style.

Im not expecting fantastic results but a good start that can eventually lead me to where I was aiming for. I appreciate the kind words from everyone here, it's really got me excited to try and figure this out! I guess that's what it's all about

[gman1971]

Depending on the radio you end up using, you might want to look into a UHF cavity to help the front end. Something like this guy

https://www.ebay.com/itm/194836529443?hash=item2d5d298123:g:JYgAAOSw5oFh6Yqw

I know it uses the PL/SO-239 UHF connectors which are not ideal for 462 mhz stuff, but its quite affordable a pair of UHF to N adapters should work on a pinch.

G.

 

[WRKC935]

On 3/3/2022 at 11:28 AM, gman1971 said:

Depending on the radio you end up using, you might want to look into a UHF cavity to help the front end. Something like this guy

https://www.ebay.com/itm/194836529443?hash=item2d5d298123:g:JYgAAOSw5oFh6Yqw

I know it uses the PL/SO-239 UHF connectors which are not ideal for 462 mhz stuff, but its quite affordable a pair of UHF to N adapters should work on a pinch.

G.

 

I'm sorry but NO... do NOT use adapters.  Get the connectors that are correct for the application and don't adapt anything.  Adapters are for testing things and NOT for permanent installations. 

I too would advise NOT using the LMR400.  for 100 feet of run it's better to use 7/8 but the cost of that can be a bit much.  1/2 heliax would be better as well but another option is LMR 600 cable which has loss numbers similar to the 1/2 heliax, but at less cost. 

You will want to have your jumpers made up for your duplexer to the radios with good cable. The connectors on the GM300 radios are a mini-uhf.

I would advise finding jumpers made from RG142 cable (double shielded) with the other connector matching whatever is on the duplexer.  The runs between the duplexer and radios are important especially the receive cable.  You want that to be as shielded as possible. 

 

 

[gman1971]

@WRKC935

I understand that adapters are not ideal, right?, but when you are trying to get something together then that qualifies as "testing" in my book. Also, the OP wasn't being forced to buy that particular cavity I posted a link to. But then again, having anything PL-259 terminated cable is a total waste in my book, even if it is the right connector to that cavity as you state. I wouldn't buy a PL-259 cable, I'll just change the SO-239 of the radio, as I've already done for many radios, to an N female, again, just to not have to buy anything with a POS SO-239 cable. Personally I would've swapped these two SO-239 on that cavity to N connectors, and not have to use adapters, but the OP might not feel like doing that, hence the adapter.

The reason for the adapters was so the OP could start by buying N-to-N cables from the get go... and then just ditch the SO-239 adapters when moving to a better N terminated cavity, or replacing the SO-239 in the cavity, etc, but I guess you didn't read into that.

Also, since you are into what not to do, here is what I would advise the OP NOT to do: don't use RG142 as a jumper cable. Wny? b/c its a solid steel copper inner and it WILL develop micro cracks after bending it a few times, or bending it too much and the unbending it, and cause a crap ton of PIM when using duplex (two radios), while you might've not experienced it, well, I have and it sucks. Solution: if you can splurge it, get RG400 patch cables instead, with either silver N connectors or trimetal, and since RG400 has a stranded inner core, it can take the bending all day long. Oh, yeah, be aware, the RG400 has a hair more loss, but don't buy into the BS that a 0.03 dB extra loss will affect your range much. It wont affect your range the slightest bit, actually. I currently have ~2.3dB Insertion Loss in my feedline setup and my range to portable is over 20 miles... 

Heck, one can get fancy and recommend using 1 5/8" Heliax, Quantars and Telewave folded dipole arrays on 1400 foot towers here too, but the OP just wants to get something going, and there is a middle ground between the Quantar/Telewave and the KMR POS cables that fall apart just from sitting outside two days under the Sun... A simple cavity, any cavity really, will always help any radio front end and intermodulation from getting into the TX as well. If you don't have the cables, then an adapter is fine to get you going.

LMR400 with chrome plated connectors will works on a pinch, to get you going, and so long people are aware that they'll most likely be buying twice, its fine. In addition, from my experience using LMR400, the dreaded PIM on genuine LMR400 cable usually takes a while to develop, so it should be fine just to get started. Also, so you know, I'be been running LMR600 with silver plated N connectors on two of the longest runs on the premises here for a few years now without a problem. No PIM detected. The takeaway here is that LMR cable works just fine for simplex stuff.

Now, my only strong recommendation would be to at least start with all N connectors on all cables, if possible.

@OffRoaderX

You must be living either in really flat terrain, and/or on top of a hill/mountain, b/c to get those kind of numbers, reliably, here in WI for a UHF repeater (keyword UHF, not VHF), you'll need at least double that height in the tower due to the roughness of the terrain. 

G.

[WRMN374]

On 3/3/2022 at 7:58 AM, gortex2 said:

So first thing I would try to do is get your antenna cable alot shorter than 100' between antenna and repeater. Unless its going up a tower the closest is the best. Even LMR will have almost 3dblossi n 100'. That just took your 25 watt repeater to 12.5 and that no duplexer. You will have loss there also. 

The duplexer is a good unit. Get it tuned professionally and a home repeater should not have issues. Im not a fan of the antenna you picked but I prefer quality. the DB404 would be ideal but know folks dont like the look of it or the price. If you want a small fiberglass stick look at the Laird FG series in the other links on the page. You will find them a much better build than a put together antenna. 

Manage expectations. I know you want 20 miles. If you can talk that simplex then your repeater may play nice. The GM300 is a good little radio. Built many repeaters in my shop days out of the same parts you mentioned and many are still in service today. The GM is not a continuous duty radio so make sure you have a fan on it also. 

 

As a matter of fact, I'm doing my first repeater build also. I live on a hill, so I'm trying to get 20+ miles also. I was looking at the Laird FG4605 or FG4607. Would they make great repeater antennas? I would love to have the DB404, and I haven't purchased an antenna or cable. I was still debating cuz my current plan uses SO239 connectors and not N connectors. And I'm concerned about DB loss. It's gonna be a 50' run.

[WRMN374]

On 3/3/2022 at 8:30 AM, gman1971 said:

"Not expensive" and "long range" in radio usually don't belong on the same sentence. If you want long range out of UHF, be prepared to sped time and money.

As for antenna, the Laird FG-4603 would be my next choice if you don't want a folded dipole array, which I would strongly recommend. There is a Harvest 2-bay dipole available on eBay that might be a good compromise.

Manage expectations: 20 miles from base to a portable, reliably, and out of UHF GMRS will require a decent location, a tall tower/mast and very good antenna (which doesn't develop high SWR after 3 months of being installed), a good feedline (probably look into heliax 1/2" at the very least if you really need a 100' run). And a very good radio/repeater with a receiver that will not get overwhelmed when mated to a good antenna placed that high. Most likely you'll need additional filtering if you use low end stuff.

G.

I am considering my own repeater antenna also. Initially, I decided on the DB404. But the price spooked me. So I have it narrowed down to Laird FG4605 or 4607. But the price difference is only $100. I'm on a hill and I only need a 50' run. And what about the SWR not developing for 3 months after installation?

[JohnE]

Quote

As a matter of fact, I'm doing my first repeater build also. I live on a hill, so I'm trying to get 20+ miles also. I was looking at the Laird FG4605 or FG4607. Would they make great repeater antennas? I would love to have the DB404, and I haven't purchased an antenna or cable. I was still debating cuz my current plan uses SO239 connectors and not N connectors. And I'm concerned about DB loss. It's gonna be a 50' run.

50' LMR and a "mobile" duplexer will have a rough net loss of ~2.5-3 dB.
A quick prop map shows that you'll be pretty good north but hindered to the south based on 3db losses and 5 dBd antenna w/50W and 40' of height assuming you clear the trees that should be pretty close. If you don't clear the trees your range will be significantly less.

Again just an observation.

[gortex2]

Going with the DB404 and a 50' piece of 1/2" LDF will give you much better results. LMR will give you about 1.5db of loss. LDF is about .75db of loss. If your using adapters there is some loss, not enough to really argue one way or another but LMR and adapter will be a bit more than predictd loss. 

My thought is spend the funds the first time to do it right vs something that will not meet expectations, then spending more money after. Sometimes waiting a bit longer to accomplish the goal makes the experience better in the long run. 

[WRMN374]

On 4/15/2022 at 10:40 PM, JohnE said:

50' LMR and a "mobile" duplexer will have a rough net loss of ~2.5-3 dB.
A quick prop map shows that you'll be pretty good north but hindered to the south based on 3db losses and 5 dBd antenna w/50W and 40' of height assuming you clear the trees that should be pretty close. If you don't clear the trees your range will be significantly less.

Again just an observation.

I see that also, and you're right. I'm trying to run SO-239 connectors thru radio, and duplexer to keep from losing more dB. That's what is on radio and duplexer now. The problem is the N connector on the Laird 4605 and 4607. As well as the N connector on the DB-404. Which I think my choices have narrowed to Laird 4607 and the DB404. Plus, I'm not too sure of the height. What are some good towers, so I don't have to get up there and adjust in case I ever need to?

[WRMN374]

On 4/16/2022 at 8:23 AM, gortex2 said:

Going with the DB404 and a 50' piece of 1/2" LDF will give you much better results. LMR will give you about 1.5db of loss. LDF is about .75db of loss. If your using adapters there is some loss, not enough to really argue one way or another but LMR and adapter will be a bit more than predictd loss. 

My thought is spend the funds the first time to do it right vs something that will not meet expectations, then spending more money after. Sometimes waiting a bit longer to accomplish the goal makes the experience better in the long run. 

Yes, I agree on doing it right the first time. So you're speaking of LDF4-50A CommScope® / Andrew HELIAX® 1/2" Low Density Foam Coaxial Cable? After doing research awhile back that became my second go to choice in cable to antenna. Is it hard to cut thru the copper conduit? I've been watching some youtube on this. And JohnE mentioned a 40' tower.

[JohnE]

Quote

And JohnE mentioned a 40' tower

I was assuming a 2 story house , pitched roof and 10' pipe and the antenna over that not a tower.

Quote

Is it hard to cut thru the copper conduit? I've been watching some youtube on this.

The cable is not hard to cut and the  connector can be done w/razor knife and a couple of wrenches. Its not hard you just need to be meticulous.

Quote

Which I think my choices have narrowed to Laird 4607 and the DB404.

    The 404 is a professional site antenna the others I would consider base or control station antennas. I cheaped out when I did one of my sites and used a Comtelco. What I should have done was a DB 408(6dBd) , 411(9dBd) or a Commander 201 or 1150(both 5dBd), all not cheap antennas.

It all depends on your budget and what you are willing to spend for the coverage you want.

again just my thoughts

[gman1971]

"Not expensive" and "long range" in radio usually don't belong on the same sentence. If you want long range out of UHF, be prepared to sped time and money.

As for antenna, the Laird FG-4603 would be my next choice if you don't want a folded dipole array, which I would strongly recommend. There is a Harvest 2-bay dipole available on eBay that might be a good compromise.

Manage expectations: 20 miles from base to a portable, reliably, and out of UHF GMRS will require a decent location, a tall tower/mast and very good antenna (which doesn't develop high SWR after 3 months of being installed), a good feedline (probably look into heliax 1/2" at the very least if you really need a 100' run). And a very good radio/repeater with a receiver that will not get overwhelmed when mated to a good antenna placed that high. Most likely you'll need additional filtering if you use low end stuff.

G.

Edited March 3, 2022 by gman1971
antenna model was wrong it 4603 (not 4503)