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VXR 7000 Transmit issue

WRPR843

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WRPR843 Newbie

WRPR843

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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...

21 answers to this question

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Radioguy7268 Rising Star

Radioguy7268

Posted
Posted

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.

 

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OffRoaderX Grand Master

OffRoaderX

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  On 9/19/2023 at 4:45 PM, Flameout said:

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

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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.

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Flameout Collaborator

Flameout

Posted
Posted
  On 9/19/2023 at 5:06 PM, 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.

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

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OffRoaderX Grand Master

OffRoaderX

Posted
Posted
  On 9/19/2023 at 5:12 PM, Flameout said:

 I was just going by what others have posted.

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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".

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SteveShannon Grand Master

SteveShannon

Posted
Posted

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. 

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SteveShannon Grand Master

SteveShannon

Posted
Posted
  On 9/21/2023 at 5:36 PM, 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.

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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. 

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WRPR843 Newbie

WRPR843

Posted
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Posted
  On 9/19/2023 at 4:45 AM, OffRoaderX said:

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

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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.

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Radioguy7268 Rising Star

Radioguy7268

Posted
Posted
  On 10/3/2023 at 3:27 AM, 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).

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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?

 

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