Disappointed in XPR 8300

[jackel0228]

I have a xpr 8300 uhf that I've been trying to get working for several months now. It's been bench tested, tuned, programed and I still can't get more than about 1.5 miles out of it. I'm curious how these ham guys claim to be working repeaters from 30 miles away and I can't even seem to get around the block? I suppose it's just a bummed project for me...

Other than the helpful people online, there are very little local resources, at least in my area.

 

[62Truck]

How many watts are you getting out of the duplexer? What kind of Duplexer are you using? Are you running a preamp? Are you running an external amplifier? What kind of feedline are you using? How long is the run of feedline? What kind of antenna are you using? How high is the antenna?

 

[rescue161]

Antenna and duplexer are key. What band are you using? What type of duplexer are you using? What type of feedline? What type of antenna? The repeater is the cheapest part of a complete system. I get 30+ miles out of the repeaters that I'm using, but I'm using 2 runs of 7/8" Heliax on a split antenna system with a pre-amp/multi-coupler on the receive and a 5 channel combiner on the transmit side.

Sorry, I was typing when you posted...lol

Yes, height is very key!

 

[jackel0228]

How many watts are you getting out of the duplexer? What kind of Duplexer are you using? Are you running a preamp? Are you running an external amplifier? What kind of feedline are you using? How long is the run of feedline? What kind of antenna are you using? How high is the antenna?

I'm showing 30 watt at the antenna. 1/2" coax, brand unknown as I'm not right there at the moment. Run 35 ft. Antenna height about 32-35 ft agl. No external equipment of any kind. Antenna is a commscope db-201.

 

[rescue161]

What kind of duplexer?

 

[jackel0228]

What kind of duplexer?

Sinclair mobile style duplexer

 

[rescue161]

That is a large part of your problem. The mobile notch type duplexers are not the best option. A band-reject/band-pass filter will do much better. Also, the 201 antenna is a no-gain ground-plane antenna. If you were to use a folded dipole array, that would certainly improve things.

The coax sounds okay if it is Heliax type 1/2" corrogated feedline.

 

[rescue161]

You also have to make sure the coax jumpers are sized correctly and that they are double-shielded. I am assuming that this is UHF. If that's the case, then all of the above equipment that I mentioned can be had for reasonable prices. VHF is going to increase the price of the antenna and the duplexer.

 

[N4KVE]

Finding a roof on top of a 40 story building would help too.

 

[ab5r]

Where are you in TEXAS?

 

[RadioGuy7268]

Unknown problem

That is a large part of your problem. The mobile notch type duplexers are not the best option. A band-reject/band-pass filter will do much better. Also, the 201 antenna is a no-gain ground-plane antenna. If you were to use a folded dipole array, that would certainly improve things.

The coax sounds okay if it is Heliax type 1/2" corrogated feedline.

With all due respect, there's no way you (or anyone else here) can know that a notch type duplexer "is a large part of your problem".

If you're getting the isolation you need out of a duplexer, it really doesn't matter how you got it. Yes, a BP/BR 6 can cavity duplexer is a much better duplexer when it comes to spec's, but I've seen plenty of notch type compact duplexers that operated fine, and gave 15-20 miles of coverage.

Measure de-sense, measure sensitivity, measure VSWR and start eliminating the problems in a step by step manner. That's when we will know what part of his problem a duplexer might be.

 

[rescue161]

Fair enough. I have seen notch duplexers perform okay sometimes, but they have also been the main problem area for systems that were having problems. We don't use them in my line of work for a reason.

 

[jackel0228]

Where are you in TEXAS?

Beaumont area

 

[jackel0228]

With all due respect, there's no way you (or anyone else here) can know that a notch type duplexer "is a large part of your problem".

If you're getting the isolation you need out of a duplexer, it really doesn't matter how you got it. Yes, a BP/BR 6 can cavity duplexer is a much better duplexer when it comes to spec's, but I've seen plenty of notch type compact duplexers that operated fine, and gave 15-20 miles of coverage.

Measure de-sense, measure sensitivity, measure VSWR and start eliminating the problems in a step by step manner. That's when we will know what part of his problem a duplexer might be.

It's just tough to diagnose the problem when I don't have all the tools to measure these things with. Even more so when I'm dependent on the local establishment for things like tuning a duplexer.... Which they did at least once... Its just a headache.

 

[N4KVE]

Many of the repeaters here use separate rx, & tx antennas to avoid this exact problem. The RX antenna is always the higher one.

 

[RadioGuy7268]

If you've dealt with a local shop to get the repeater & duplexer tuned up, and they are verifying proper operation on the bench - let's assume that they know what they're doing and that part is all good.

Now, tell us a little more about your site location and environment. I'm assuming you've got this repeater set up at your house and you don't have high tension power lines running through your neighborhood, or live right next to some other kind of EMI nightmare.

How old is your feedline? Do you have a VSWR meter?

Those DB201 antennas we used to call a trombone antenna - and they need to be tuned to frequency. Has it been tuned? By who? using what?

What are your operating frequencies?

 

[jackel0228]

If you've dealt with a local shop to get the repeater & duplexer tuned up, and they are verifying proper operation on the bench - let's assume that they know what they're doing and that part is all good.

Now, tell us a little more about your site location and environment. I'm assuming you've got this repeater set up at your house and you don't have high tension power lines running through your neighborhood, or live right next to some other kind of EMI nightmare.

How old is your feedline? Do you have a VSWR meter?

Those DB201 antennas we used to call a trombone antenna - and they need to be tuned to frequency. Has it been tuned? By who? using what?

What are your operating frequencies?

Okay so here's my answers to all of the questions above....
The site is at the house as you suspected. I have the repeater in the attic and the antenna on a pole mount about 7 feet above the apex of the roof. Metal roof a problem? The feed line is between unknown age and a month or two old. I got an additional brand new length from the local shop so I could more adequately troubleshoot my issues. No, the antenna hasn't been tuned or retuned however I have tried my Laird mobile antenna in its place with very similar results. I purchased a swr meter from Amazon but after much headache I concluded that It was less reliable than any other part of the system and its results untrustworthy.
Frequencies are 451.875 & 456.875.

 

[Project25_MASTR]

First thing's first...eliminate what it's not.

How much power are you getting out of the repeater through the duplexer? How much reflected? How much power are you getting reflected on the antenna? You can actually calculate the insertion loss buy using the the formula L = 10*log(D/R) where D is the power our of the duplexer and R is the power out of the repeater.

You say you don't have the ability to test the receive sensitivity of the repeater...ask the shop what it was (seriously, they should have it written down somewhere and if not, find another shop). Ask them what the desense of the repeater was (they should've done this test as well).

It does sound like however, that you don't have much height. Typically when we talk about these systems, we are talking several hundred feet of elevation for that kind of range.

 

[jackel0228]

First thing's first...eliminate what it's not.

How much power are you getting out of the repeater through the duplexer? How much reflected? How much power are you getting reflected on the antenna? You can actually calculate the insertion loss buy using the the formula L = 10*log(D/R) where D is the power our of the duplexer and R is the power out of the repeater.

You say you don't have the ability to test the receive sensitivity of the repeater...ask the shop what it was (seriously, they should have it written down somewhere and if not, find another shop). Ask them what the desense of the repeater was (they should've done this test as well).

It does sound like however, that you don't have much height. Typically when we talk about these systems, we are talking several hundred feet of elevation for that kind of range.

I understand that completely. Elevation is everything. But if I can't get 5 or 6 miles from 30-35+ feet why would I invest in what it takes to get to several hundred feet? If I can't get what I've got working I can't justify digging in deeper... Can I?

 

[RadioGuy7268]

If you don't have tools to test things, then troubleshooting gets tough.

Do you have two portables you can set to work on Talkaround simplex at 451.875? Do you have the ability to adapt a portable onto your outside antenna?

I'd start out running someone out to the edge of the repeater coverage you were getting, and try talking to them using just portable to portable (with one portable up in the attic.) What's the result?

Then, switch the portable over to the outside antenna and test. You should have much better range with the outdoor antenna compared to the portable antenna inside the attic. If your distance drops after you hook to the outside antenna, then you've got a real good idea that the antenna and/or the feedline is your problem.

If the 4 watt portables on simplex with the outside antenna are out-talking your repeater, then you've got to go have a talk with the shop that was supposed to have tuned the repeater.