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Odd issue with Range.

Range Problems repeater

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#1 WRAK968

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Posted 15 February 2018 - 09:45 PM

Ok, so I am having an issue and before I go any further with pulling my hair out I figured I would ask everyone here.

 

I finally set up my GR1225 repeater and was all excited to test it out. However, when I tested it, I found my range was only 1-2 blocks distance [about .23 of a mile. Going portable to portable at ground level I get at least half a mile range.

 

The repeater is running 45 watts with a 15A power supply. I have a diamond u200 mounted about 15 feet up with an SWR of 1.3 on 467 and 1.7 on 462, flat pack duplexer which I purchased new and was "tuned" when they sent it to me, and 30 feet of LMR400.

I have done some limited testing with equipment I have here.

 

I know the GR1225 is not to blame as I swapped it out with a pair of m1225's set up as a repeater. They can run 15 watts and 35 watts, but no-matter the power setting, the range was exactly the same. So I know its further down the line.
 

Feedline is not the issue. First tests were with RG-8X and later upgraded to LMR400 with no change to range, however my SWR went from 1.3 on both rx/tx freqs to 1.7 on TX, 1.3 on RX. I was told by family listening to the repeaters speaker that I was clear coming in, which makes me suspect the antenna, however SWR of 1.7 shouldn't result in that drastic loss of range but I could be wrong.

 

That leaves the duplexer, which as I said was new and tuned before being shipped to me. I have no way of testing it myself so it would need to be sent to a shop.

 

Im not sure which way to go first. If I replace the antenna Ill be getting a comet 712 so Im looking at $150 there, and I dont even know which shops can check and tune a duplexer, let alone how much they charge. I would rather fix the issue than keep guessing like I have been. Anyone have any ideas?



#2 Corey

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Posted 16 February 2018 - 08:11 AM

Several thing I would not have done.

 

1. diamond u200 (worthless in duplex service, its a dual band HAM antenna)

2. LMR400 is a total no no in duplex service, you can and will have noise and desence issues.

3. Mobile Duplexer

4. Talk of purchasing a comet 712 (this is about as efective as a dummy load)

 

If you are at all serious about this purchase a quality commercial antenna in the 460-470 range, I prefer folded dipoles like the DB-404, DB408 but any quality commercial antenna in the 460-470. As far as the coax, that has to go, for what you spent on that you could have bought some 213 or even 1/2 hard line for less then 2 bucks a foot. Now the duplexer, it you purchased one of the many Chinese mobile duplexers on eBay it will need to be re-tuned, its been proven over and over again they dont tune them properly. A better option would have been a used cavity type pass / reject duplexer.

 

Rule of thumb, spend your money on the antenna, feed-line and duplexer because with out QUALITY components a 10k dollar repeater won't work with a poor antenna system. In the beginning I tried the cheep rout only to spend more money doing it right the second time. My first real repeater site was a 150' tower, I installed 7/8 hard line and a DB-420 antenna, since I had already spent all the money on the cable, antenna and climber I was left with an old 20 Watt Motorola R100 repeater that ended up having 35 miles of coverage around the antenna. It served us well for years, the next machine and still current is a Motorola MTR200 linked to 6 other sites. https://mwgmrs.com


  • eubank282 likes this

Just My $.02

 

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#3 WRAK968

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Posted 16 February 2018 - 09:48 AM

Thanks for the input Corey. The Diamond antenna I have is a BC200U [sorry for not posting the proper model number] It is a commercial antenna tuned for 460-470.

 

Hard line is out of the question. This is a simple family repeater going no more than 20-25 feet up. I do not own a tower [and my local zoning office likely wouldn't approve of one being built where I am.]  I will look into getting the 213 cable when I can, but still 30' of LMR400 shouldn't affect the signal that much.

 

I think you hit a nail with the duplexer. Its an SGQ-889. Running out of the living room, I wanted to get everything into the GR1225's case to make it look nice. I know a lot of people said in a high RF area flat packs are no good but running out of a garage [or in my case the living room] it shouldn't be too much of an issue. I know I wont get a 30 or even 20 mile range, but I am ok with that for now. You mentioned these duplexers need to be re-tuned as they are never tuned properly. This answers one of my questions that it is likely the duplexer that is the issue. So I guess that is there I'll start and move forward from there.

 

Thanks again Corey :)



#4 Logan5

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Posted 16 February 2018 - 11:47 AM

If you are a licensed HAM operator a tower can be erected almost any where. Code should only evaluate the project for safety issues, not aesthetics. We live in a close quarters neighborhood, 15 to 20 feet between houses. I thought for sure we would be denied the permit and we were, but not for what we thought. Code required an FAA sign off and wet stamped engineering documents from the Tower manufacture. ARRL helped with legal documents, and although we did obtain a lawyer, I suspect we could have accomplished this with out one.



#5 n4gix

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Posted 16 February 2018 - 12:23 PM

Just for information, a base antenna height of 15' provides a line-of-sight (LOS) approximately 5 miles. Assuming a portable's antenna height of 5' provides a LOS of approximately 3 miles.

Adding the two LOS distances yields approximately 8 miles in total.

Of course, those numbers are subject to reduction based on the buildings in between the repeater and the portable, as well as the topography of your neighborhood.

#6 Durake

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Posted 16 February 2018 - 01:58 PM

Kinda funny... I posted on RR the other day asking about my amateur one that I just got recently as well. I discovered the issue by narrowing it down. 

 

I at first thought the PA blew, so I swapped radios and it showed the same results, then I tried a different antenna, still same results... It was that the duplexer wasn't tuned as I thought it was, so I'm going to get it tuned this next Monday. 

 

Oh, and I agree with Corey, the duplexers are literally never tuned right.. Find someone you know that can tune it and let them do it!

 

2. LMR400 is a total no no in duplex service, you can and will have noise and desence issues.

 

Weeeeelll. My cousin works for a communications company and he has a statewide TRBO system and they use LMR400 for all their stuff. I was telling him about my repeater and he got me a 75 foot roll of it. I'm not here to argue but am curious as to your statement, he has an unlimited budget for the system so, why would they pick LMR400 when they (presumably) know that it will have noise and desence issues? Much less why would anyone use it if its going to have both of those issues. I could see that if budget was the problem. Just curious :P


Drake Robinson | "Motoballa"

EMS Dispatcher @ Mount Hope, WV

Dallas County REACT183

 

 

 

#7 WRAK968

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Posted 16 February 2018 - 03:15 PM

Logan5 Safety would be the issue unfortunately. I could put up a 20-25 foot tower but anything higher and it risks hitting hitting a house no matter the direction it falls. I also unfortunately have one of /those/ neighbors who likes to complain and call a lawyer for anything he doesn't like. I had someone show up at my door to "investigate" how dangerous the Jpole I put up was. I could only imagine what I would go through with a tower lol. We can all dream though right?

 

N4GIX, I know the range calculations and what they could be line of sight, however when your portables at 5 watts on level ground outdo the repeater running 45 watts 15' up then somethings been done wrong. This is mostly a family/local repeater so I am not expecting very long range on the unit, yet :)

 

Durake, THANK YOU THANK YOU THANK YOU! lol, you actually gave me a straight answer lol. Now I need to find someone who can tune the duplexer. I checked with a buddy of mine who programmed the GR1225 however he does not have the equipment. He's really the only one I know that would have the equipment. Keep me posted on how your duplexer turns out, if things work out perhaps Ill send it to the same place [If they are looking for a little extra business.]

 

Also thanks for the info about the LMR400/213 issue. I thought several users mentioned using LMR400 over all else due to the price over quality of signal, then I couldn't find the posts lol [that what I get for working all night!]

 


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#8 Hans

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Posted 16 February 2018 - 04:30 PM

There are quite a few articles on the potential issues with LMR400 and repeater use. I can't, at the moment, find some of the more technical/credible ones but I have read enough of them in the past to convince me.
 

http://kd2sl.wordpre...9/wire-matters/

The answer lies in that aluminum foil shield, covered by a tinned copper braid. Dissimilar metals in contact with each other are bad news. In the presence of high RF power levels (such as you get when the repeater is transmitting while simultaneously receiving), all those millions of contact points between the braid and foil become millions of little tiny diodes, signal is rectified, and noise is heard on receive. It might not happen when the cable is new, but eventually it WILL happen – especially if you have it outside, blowing in the breeze. (An excellent article on repeater duplex noise is available here. I highly recommend you take time to read it.)



#9 Radioguy7268

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Posted 16 February 2018 - 08:20 PM

Make sure you've got the duplexer connected properly (LOW to transmit, HIGH to receive) and you don't have a cable or connector issue on the jumpers. To me, that's your likely problem from what you're describing.


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#10 WRAK968

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Posted 16 February 2018 - 09:44 PM

Checked and confirmed, the RX wire went to the high side [467] and TX wire went to the low side [462]



#11 PB92

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Posted 17 February 2018 - 06:25 PM

Oddly enough, the LMR400 was the first thing that came to mind.



#12 Durake

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Posted 20 February 2018 - 02:24 PM

Durake, THANK YOU THANK YOU THANK YOU! lol, you actually gave me a straight answer lol. Now I need to find someone who can tune the duplexer. I checked with a buddy of mine who programmed the GR1225 however he does not have the equipment. He's really the only one I know that would have the equipment. Keep me posted on how your duplexer turns out, if things work out perhaps Ill send it to the same place [If they are looking for a little extra business.]

 

My friend in REACT works at a radio station so he has all the right stuff, I'm hoping he is at the meeting tonight so I can give him it. I'd get on the radio and ask around if you haven't already, I'm usually on this 440 repeater and it's only me and the same guys everyday talking on it, one night at about 8pm I threw my call out and asked if anyone could answer a question I had about antennas and dude, literally like 10 people I've never heard before got on haha, it was like crazy! So ask and see what returns, maybe someone would be willing to do it. :P


Drake Robinson | "Motoballa"

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Dallas County REACT183

 

 

 

#13 WRAK968

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Posted 23 February 2018 - 09:35 PM

Well, I sent the duplexer out the other day to be tuned and low and behold, the duplexer wasn't even close to being properly tuned. As of now the duplexer is tunes 92dB from the TX and 82 dB from the RX. When it arrives on Monday I will do another test and see if there is much difference.

I do want to thank everyone who commented. As I said before I am rather new with repeaters and I am learning quite a bit. I was told from a few pros that the LMR400 should be ok for the time being. The antenna I have set up should also be ok [though they said I should look into replacement eventually as it is not exactly set up for repeater service.] For now though, just getting everything online and working is the goal, Fine tuning and tweaking can come later :)


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#14 WRAK968

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Posted 27 March 2018 - 04:36 PM

Ok, with the duplexer now tuned, still had the same issue, so time to test the PA's on BOTH systems to see what is happening. So, I purchased a better watt meter that will give me SWR, frequency, power out, reflected power and such. I also replaced the antenna with a loaner which gives me much better SWR readings on the MFJ meter.

Here are the results;

The GR1225 has no power out, or at least, not enough power for the meter to read when placed between the transmitter side and the antenna. Note I did not use the duplexer in this test so I know there are no losses from there. My thinking is that either A) the dreaded but common de-soldering issue has shown its face, Ill be looking into that later, or B )the PA went completely. From my understanding, any power output less than .5 watt will show a blank reading on the meter, and I think this would explain why I have shorter range using the repeater than I do using a 5 watt portable.

So, I switched to the other repeater which only has a max output of 20 watts as it is only two mobile radios [m1225 series] This was planned to only be used for camping or as a back up when needed. I set everything up and ran the TX unit to the meter and out to the antenna, SWR is 1.2, frequency is spot on, power showed 13.9 watts out on low power. Wonderful I'm thinking, so I test high power and I have 22.5 watts out, still on the 625 frequency, swr went to 1.3 which, I didn't really think power out would increase the swr but, it is within spec so I wont complain.

Now, for giggles, I figured I would add in the duplexer, and put the swr meter between the tx radio and the tx side of the duplexer, and the swr shot way up to 19.4. Now I know I have said a million and one times that I am still very new to this, but that number seems way too high for use and could have damaged the gr1225, and potentially damage the m1225 back up system. I tried to look it up but everywhere I have gone says I need to use a VNA to test swr of a duplexer, and nothing about using a normal meter.

I rather not risk burning a second repeater up, so before I do more harm I need to know if this reading is simply because of the reject of the upper frequency or if there are other horrors at play.



#15 Corey

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Posted 28 March 2018 - 07:25 AM

Is the duplexer possibly tuned backwards?


  • berkinet likes this

Just My $.02

 

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#16 WRAK968

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Posted 28 March 2018 - 01:28 PM

Hey Corey, I was thinking that myself, so I switched the jumpers around again and had the same 19.5 reading. So I had an idea, sweep the range until I find the sweet spot... I found it at 450.625 which gives an swr reading of 1.13 on the low side which is backed up by the MFJ tester, I cant even get a low reading on the high side with either meter, which tells me I am not doing something right for the test, but I am gonna go on a limb and say the dang duplexer is still not tuned properly.

Sorry if I seem a bit short or anything, This repeater was meant to be a simple home repeater and an introduction to a new side of radio I hadn't had much practice with yet. Just seems frustrating to keep throwing money in but not be 100% sure if it will help. I'll send you a private message about some assistance you offered before, if your still willing to help out. :) And thank you for sticking around, I really am trying to get this thing off the ground before getting the much more expensive parts for it.


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#17 WRAK968

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Posted 13 April 2018 - 01:54 PM

Final update to this post.

Finally the repeater is working. After a coworker Kevin (WQWU443) recommended I take the duplexer to A.R. Communications in Monmouth County NJ. I have to say the owner of the company was really cool and showed me around the shop while they looked into what was wrong. After re-tuning the duplexer, they hooked the repeater up to the duplexer and found a ton of de-sence and the SWR sky high [same issue I was having at home.] They kept the system for the weekend and on Tuesday it was ready.

Here are the problems they found:

1) A minor issue inside one of the "cans" of the duplexer. I am not sure how the insides of the flat packs look, but I was told there was a small dent or something causing some of the issue. They "swapped" sides putting the low frequency on the high side and high frequency on the low and were able to by-pass whatever the dent was doing.

2) The stock jumper's between the radio and the duplexer were causing some issues with loss. They replaced the jumpers free of charge.
3) They recommended I check my power supply as on their equipment was letting the TX side run 25-40 watts on low/hi power. At home, I checked and was only getting 17 watts only. Turns out that even though I have a 15A continuous power supply at 12.5V, the system requires 13.5 at 20A to work properly. For safety I ordered a 30A 13V power supply recommended by a few hams as a replacement. This should let me get full power output when it arrives.
 

I also found a problem, and that is that the GR1225 seems to drop its TX power from 40 watts to less than one watt. It does transmit and I can hear it on a portable if I am within a few hundred yards, but the meter doesn't even kick on when I transmit. For the time being a back up repeater is in use and is showing results.

 

The SWR is very low, 1.04 and a .0071 reflection which is MUCH better than the 19 I was getting. With the test unity antenna about 15 feet up at 17 watts and a very rf unfriendly area [a lot of trees and buildings] I was able to talk clear across town (about 4 miles.) Now before anyone says 'thats not that far' keep in mind that this is low power, no gain, low height and a congested area [buildings and trees] so I would think its reasonable. :)

I want to thank everyone again, Especially Corey and Kevin and the guys at A.R. Communications. I've learned quite a bit from this whole experience and hope to learn a bit more while improving the system overall!


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#18 gatekeep

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Posted 13 April 2018 - 02:25 PM

Just a useful note, if your not already aware, that the GR1225 isn't meant for 100% duty cycle at 40W, the PA in the unit will cook itself over time at this power level with moderate usage.

 

Did you happen to note if when the power drops off if the heatsink on the repeater is warm/hot?


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#19 WRAK968

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Posted 13 April 2018 - 04:35 PM

Just a useful note, if your not already aware, that the GR1225 isn't meant for 100% duty cycle at 40W, the PA in the unit will cook itself over time at this power level with moderate usage.

 

Did you happen to note if when the power drops off if the heatsink on the repeater is warm/hot?

Its within the first minute of being turned on. does it regardless of being on high(40W) or low(25W) Regardless of which is chosen, it shows 15W output that drops down to less than 1 watt, which is not enough power to trigger the meter for a reading. I believe the PA may have been fried, either before I purchased it, or due to the issue with the duplexer and such, and constant testing under those conditions. I did check the solder contacts which all looked fine, but I reheated the solder to make sure it had good contact.



#20 kb2ztx

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Posted 13 April 2018 - 04:51 PM

look at the power directly from the transmitter with duplexer removed and a 50 ohm load. There is a chance the PA is shutting down for some reason. 







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