Repeater Troubleshooting

[WSAE734]

Hello, all. Warning, my next sentence is an obligatory one. 

I am new to GMRS setups (now that that is out of the way....)

I have, within the budget I have at the moment, tried to set up a small family repeater system primarily for emergency comms within my immediate area. I live an a pretty densely populated suburban area, so I already know I have things stacked against me. My set up is as follows:

Base:

-RT97S Repeater (7W output/SWR:1.00/.725 pair), 40' LMR400 up to a Sirio CX455 mounted 30' on a mast. 

Mobile:

-5W HT with a Nagoya UT-72G on top of an SUV

-5W HT with a Rugged Radio GMRS 1/2wave antenna mounted on the bed rack of a truck

I already know that one of my primary issues is the height of the antenna. However, that can't be changed at the moment and is as good at it will get for the time being. However, I am struggling to understand an issue I am having. There are certain places I have tested where the repeater can hear the HT, but not the other way around. I am curious as to whether or not this is a mobile antenna issue, a base station issue, or simply a LoS issue. I know, there is probably a lot more information needed or things I am not considering. I am not looking for miracles here at all, just trying to do the best with what I have in place at the moment. I will say, that it covers roughly 80% of the area I was hoping for in my challenging environment and for that I am glad, but the furthest point I can't reach. There are times when the HT will partially open the repeater at these further points, but I get no audio, and, as stated, they can't hear from the base antenna, even if i can hear them. With that in mind, perhaps I don't fully understand something, or maybe I am at the limits of my system and need to accept it until something can be changed more drastically.

Also, I had reasons for purchasing the RT97s beyond this use. We do a lot of road trips and felt that it would be a potentially useful piece of kit for that as well.

 

Thank you all for your time and consideration.

[Radioguy7268]

That Sirio CX455 antenna requires tuning. The center section slides in/out to adjust the tuning. What frequency did you tune it for? What did you use to adjust the tuning?

If I am reading your post correctly, you've got the repeater putting out 7 watts, with a measured VSWR of 1.0:1 on 462.725 ?  What's the VSWR on 467.725?

Those RT97 repeaters have a really small internal duplexer with poor isolation specs. If you go above 5 watts, you pretty much guarantee desense. I'd try turning down the power to see if the overall performance & balance of the system improves.

 

[SteveShannon]

6 hours ago, WSAE734 said:

I was able to actually run home and test it. On 467.725 I get an average SWR of 1.29:1.

That’s just fine.  And don’t worry about desense on your RT97.  Nobody has ever reported desensing the RT97 at factory power levels in this forum. Now if you started running an amplifier between the transmitter and the duplexer I could see it happening, but the RT97 actually consists of a completely separate transmitter and receiver.  For your purposes it should be fine.  

Take your repeater and handhelds someplace clear and flat and see how much range you get.

[BoxCar]

That's a tough one to diagnose with the limited info you've supplied. What would help is knowing the make and model of the HTs as that will tell us how sensitive the receiver is supposed to be and the conditions under which the failure occurs. How far away from the repeater are you and what is around you. It will also help if you can tell us if you have a watt/swr meter and have checked the power and SWR from your HTs to their antennas.

[WSAE734]

1 hour ago, BoxCar said:

That's a tough one to diagnose with the limited info you've supplied. What would help is knowing the make and model of the HTs as that will tell us how sensitive the receiver is supposed to be and the conditions under which the failure occurs. How far away from the repeater are you and what is around you. It will also help if you can tell us if you have a watt/swr meter and have checked the power and SWR from your HTs to their antennas.

They are UV-5G HTs. Meter shows 4.3W/1.01 SWR for one and 4.25W/1.00 SWR on the other.

The distance that is sketchy starts around 1 to 1.5 miles. I do have a good number of homes, trees, and other stores and structures around.

[BoxCar]

!.5 miles is pretty average for an HT in an urban area. The key point is antenna height. That goes for both your transmitting antenna on the HT (about 6 feet) and the height of the receiving antenna (your repeater). The buildings and trees interfere with the path, so that's why only the short distance. You would get about half the distance going HT to HT. The receiver in your HTs is not real good, it needs. 25 uv for a decent receive signal. I'd say the problem isn't the installation as much as it is the HT receivers and the only fix for that is a better radio. At $30 ea. for the pair, you got what you paid for them. Me, I'd throw them in a box for a SHTF event and get a couple decent mobile radios. Right now, Radioddity is selling their 25W mobile for $99 which is less than they are asking for their 20W model. 

Radioddity DB25-G GMRS Mobile Radio | 25W | Quad Watch | UHF VHF Scann

[WSAE734]

1 hour ago, Radioguy7268 said:

That Sirio CX455 antenna requires tuning. The center section slides in/out to adjust the tuning. What frequency did you tune it for? What did you use to adjust the tuning?

If I am reading your post correctly, you've got the repeater putting out 7 watts, with a measured VSWR of 1.0:1 on 462.725 ?  What's the VSWR on 467.725?

Those RT97 repeaters have a really small internal duplexer with poor isolation specs. If you go above 5 watts, you pretty much guarantee desense. I'd try turning down the power to see if the overall performance & balance of the system improves.

 

I was not aware of any tuning needed for the CX455. The insert with it specifically said no adjustments are needed and gave no directions to do so since it was already supposed to cover the gmrs freqs.

I'll check the SWR again on the Rx side of the offset when I can tomorrow. Is there a way to set a particular output wattage on the RT97S? I thought it was just "high" or "low" power and the internals did the rest. I was only expecting 5W and was surprised when I got 7W.

[WSAE734]

4 hours ago, BoxCar said:

!.5 miles is pretty average for an HT in an urban area. The key point is antenna height. That goes for both your transmitting antenna on the HT (about 6 feet) and the height of the receiving antenna (your repeater). The buildings and trees interfere with the path, so that's why only the short distance. You would get about half the distance going HT to HT. The receiver in your HTs is not real good, it needs. 25 uv for a decent receive signal. I'd say the problem isn't the installation as much as it is the HT receivers and the only fix for that is a better radio. At $30 ea. for the pair, you got what you paid for them. Me, I'd throw them in a box for a SHTF event and get a couple decent mobile radios. Right now, Radioddity is selling their 25W mobile for $99 which is less than they are asking for their 20W model. 

Radioddity DB25-G GMRS Mobile Radio | 25W | Quad Watch | UHF VHF Scann

That's about what I figured. I have considered getting better mobiles. My current budget didn't allow for it, and I wanted to get a system in place by at least this upcoming hurricane season to cover the homes of family. It does that in its current capacity, so what I'm pushing for is a little lagniappe at the moment. Maybe I'll be more set up to do the upgrade in a few months. 

I appreciate the suggestion and insight. Y'all on these forums have been very helpful as I learn.

Would lowering the squelch on the HT and the Repeater help with this issue at all, even if only in a small way?

[WSAE734]

18 minutes ago, WSAE734 said:

I was not aware of any tuning needed for the CX455. The insert with it specifically said no adjustments are needed and gave no directions to do so since it was already supposed to cover the gmrs freqs.

I'll check the SWR again on the Rx side of the offset when I can tomorrow. Is there a way to set a particular output wattage on the RT97S? I thought it was just "high" or "low" power and the internals did the rest. I was only expecting 5W and was surprised when I got 7W.

I was able to actually run home and test it. On 467.725 I get an average SWR of 1.29:1.

[BoxCar]

17 minutes ago, WSAE734 said:

That's about what I figured. I have considered getting better mobiles. My current budget didn't allow for it, and I wanted to get a system in place by at least this upcoming hurricane season to cover the homes of family. It does that in its current capacity, so what I'm pushing for is a little lagniappe at the moment. Maybe I'll be more set up to do the upgrade in a few months. 

I appreciate the suggestion and insight. Y'all on these forums have been very helpful as I learn.

Would lowering the squelch on the HT and the Repeater help with this issue at all, even if only in a small way?

Lowering the squelch will have an effect on the receive but if it helps is unknown. I usually run my squelch on either 1 or 2. But then my HTs run around $100 each. They are similar construction to yours, as in they are SOCs but their SINAD is .2 uv. 

[PugetSounder]

"Would lowering the squelch on the HT and the Repeater help with this issue at all, even if only in a small way?"

Absolutely. Lower the squelch until you get constant static. Then move the setting up a bit until it quiets. If you get occasional noise without readable traffic, move it up another notch. You're looking for the lowest squelch setting without annoying noise. Having squelch at lower settings helps to receive weaker signals that higher squelch settings will ignore.

Do one at a time though. I would start with my HTs on simplex.

[WSAE734]

4 hours ago, Sshannon said:

That’s just fine.  And don’t worry about desense on your RT97.  Nobody has ever reported desensing the RT97 at factory power levels in this forum. Now if you started running an amplifier between the transmitter and the duplexer I could see it happening, but the RT97 actually consists of a completely separate transmitter and receiver.  For your purposes it should be fine.  

Take your repeater and handhelds someplace clear and flat and see how much range you get.

Thank you. I'm hoping to be able to do just that sort of test soon.

[DSHIDS]

On 2/16/2024 at 7:57 PM, Radioguy7268 said:

That Sirio CX455 antenna requires tuning. The center section slides in/out to adjust the tuning. What frequency did you tune it for? What did you use to adjust the tuning?

If I am reading your post correctly, you've got the repeater putting out 7 watts, with a measured VSWR of 1.0:1 on 462.725 ?  What's the VSWR on 467.725?

Those RT97 repeaters have a really small internal duplexer with poor isolation specs. If you go above 5 watts, you pretty much guarantee desense. I'd try turning down the power to see if the overall performance & balance of the system improves.

 

How does the center section slide in and out for tuning of the CX455? Mine is resonant at 477 MHz using a Rigexpert 650 Zoom. The whip does not budge at all, and there is no documentation anywhere on the webs describing such a procedure. So my question would be what is the procedure to get the whip to slide in and out?

[DSHIDS]

So I pulled the black cap off of my CX455. Nope the CX455 or any other of the CX series are not tunable. Since mine resonates at exactly 477 MHz, quality control at Sirio must have put a CX470 whip on my CX455 or they put a wrong label on a CX470 as my CX455 needs about an inch longer whip.