VXR 7000 Transmit issue

[WRPR843]

Wanted to know if any of you have some suggestions on a home repeater I set up for GMRS. 

I got a VXR 7000 and I got the duplexer pre-tuned to the freq pair I need and even checked it with VNA and it appears good.  The issue is that I cannot get any significant transmit out.  I am measuring about 20w after the duplexer and SWR is 1.1 with the equiv of LMR400 coax.  I can receive about 8 miles or more in a suburban neighborhood - but only seems to transmit about 1/2 mile...

Any ideas what could be the issue? I am at a loss...

[OffRoaderX]

What happens when you connect another radio up to the same coax and antenna and transmit?

[Radioguy7268]

Double check your programming on both sides (repeater and mobile/portables). I'd think that it's more likely a fat-fingered typo than a problem with the antenna & line.  It's either that, or you're describing a de-sense issue in a unique way...

The suggestion of testing in simplex with another radio hooked up in place of the repeater is a real good test for basic troubleshooting. If a portable works just fine in simplex mode, then there's likely a problem with the repeater or duplexer. If you experience the same problem when testing with a portable - then you know you're looking at a coax/antenna issue.

 

[Sshannon]

8 hours ago, OffRoaderX said:

What happens when you connect another radio up to the same coax and antenna and transmit?

This is what I wonder too.  If he’s getting 20 watts out after the duplexer (assuming the right frequency), the problem sounds like something to do with the cable and antenna.

[Flameout]

Not sure, but I dont think LMR400 is especially good for repeater use. Maybe looking into so something like Andrew Heliax LDF4-50a

[OffRoaderX]

22 minutes ago, Flameout said:

I dont think LMR400 is especially good for repeater use. Maybe looking into so something like Andrew Heliax LDF4-50a

75Feet of LMR400 from my VXR7000 gets me ~50 miles of farz, so I'd say LMR400 works just fine - Not "The best", but good enough for most normal people with low-power, non commercial installations.

[Flameout]

4 minutes ago, OffRoaderX said:

75Feet of LMR400 from my VXR7000 gets me ~50 miles of farz, so I'd say LMR400 works just fine - Not "The best", but good enough for most normal people with low-power, non commercial installations.

OK, good to know. I was just going by what others have posted. The LMR400 is certainly a lot cheaper than hardline

[OffRoaderX]

Just now, Flameout said:

 I was just going by what others have posted.

Yah, there's your problem, right there..  Many of the "experts" I have seen posting stuff here really struggle understanding the difference between "will not work/does not work/is bad" and "may not work 100% the best".

[Sshannon]

First, there are many different types of coax cables that people call LMR400. Some have a shield that consists of aluminum foil over copper braid. Some, like the M&P 10mm stuff have copper for both layers. LMR400 is the Kleenex of coax. 
Does it make a difference during full duplex transmissions?

Darned if I know, but I’m certain that this range problem isn’t because of LMR400.

I just read an older thread on another forum where a guy said “my company has several repeaters that work just fine with LMR400, but I’m looking at making a portable repeater and I want something more flexible.”

Immediately someone went into great lengths telling him not to use LMR400 for repeaters. 

[OffRoaderX]

16 minutes ago, Sshannon said:

there are many different types of coax cables that people call LMR400.

Good point.. I only use that Times New Roman "real" LMR400, or whatever its called.

[nokones]

On 9/19/2023 at 10:54 AM, OffRoaderX said:

Good point.. I only use that Times New Roman "real" LMR400, or whatever its called.

Isn't "Times New Roman" a font style? You probably trying to say "Times Microwave" for the real LMR400.

Not an expert, just lowly ol' internet user.

[OffRoaderX]

1 minute ago, nokones said:

You probably trying to say "Times Microwave" for the real LMR400.

No, they don't make Microwaves, just coax. Pretty sure its Times New Roman.

[nokones]

5 minutes ago, OffRoaderX said:

No, they don't make Microwaves, just coax. Pretty sure its Times New Roman.

That could be "BOLD"

[Radioguy7268]

Microwaves were invented during Roman times - Emperor Nero cut off some dude's fingers & left him with only his thumbs. 

That same guy (Digitalis Minimus)  went on to invent the UHF PL-259 connector, for hams who were 'all thumbs'.  True story.

[WRXB215]

Man! All this "Times New Microwave" stuff is making my head spin. That's not going to be on the test is it? 

[Sshannon]

50 minutes ago, Radioguy7268 said:

Microwaves were invented during Roman times - Emperor Nero cut off some dude's fingers & left him with only his thumbs. 

That same guy (Digitalis Minimus)  went on to invent the UHF PL-259 connector, for hams who were 'all thumbs'.  True story.

It’s also the origin of another word. Nero shortened the guy’s fingers because he had been impolite. The Latin word for short is “corto”.  From that comes our word “courteous”, which that stubby fingered fella was afterwards. 

[nokones]

8 hours ago, WRXB215 said:

Man! All this "Times New Microwave" stuff is making my head spin. That's not going to be on the test is it? 

You can relax and take a pill because there is no test. The tests are only for those "HAM People".

[jsneezy]

On 9/21/2023 at 8:08 PM, nokones said:

You can relax and take a pill because there is no test. The tests are only for those "HAM People".

I was told figuring out the FCCs mess of a website and all the hoops to jump through in order to get the license was considered to be "the test" for GMRS.

[WRPR843]

On 9/18/2023 at 11:45 PM, OffRoaderX said:

What happens when you connect another radio up to the same coax and antenna and transmit?

Sorry for taking so long to respond - but also similar issue...I think I am assuming the receive and transmit should be approximately the same (at the same power) - when they are not. I am going to raise the antenna another 15ft and see if that is the issue.  It must be much easier to receive through obstructions than the transmit and raising it will hopefully clear all the houses in the area. Thanks.

[WRUE951]

On 9/20/2023 at 1:09 PM, OffRoaderX said:

No, they don't make Microwaves, just coax. Pretty sure its Times New Roman.

Pretty sure it’s Times Microwave.,,,   https://timesmicrowave.com

[WRYU400]

Should not use LMRxxx on a duplex system. It’s fine for a simplex system. 1/2” heliax is a start, 7/8 would be more appropriate.

[Radioguy7268]

5 hours ago, WRPR843 said:

Sorry for taking so long to respond - but apparently I didn't bother to do any of the simple testing suggested, and now I've got more questions about why things don't work the way I wish they would. (OK, so I edited a little, but it sure reads like that to me).

Radio waves don't know the direction in which they are heading - ie: being transmitted or received. The signal is the signal. The trouble you originally described would not be due to antenna height.

Why go through the trouble of raising up the antenna, but avoid doing a simple 5 minute troubleshooting test and report on the results?