Vertex VXR-7000 Motorola Repeater Stray RF

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anniegirl
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Vertex VXR-7000 Motorola Repeater Stray RF

Post by anniegirl »

These are now Motorola I guess. As soon as the radio is powered on my HT' s RD light comes on. I checked for TX output but none is noticeable. It's almost like a desense issue. We have 3 of these and only 1 of them have this issue. Everything else seems fine. Tried adding a good earth ground. It's a problem because the radios see it as the channel is busy. Any ideas before I have to resort to a expensive shop bill?
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d119
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Re: Vertex VXR-7000 Motorola Repeater Stray RF

Post by d119 »

If you walk away from the repeater, does the issue go away? It may be that you are just hearing low-level RF from the exciter of the station.
anniegirl
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Re: Vertex VXR-7000 Motorola Repeater Stray RF

Post by anniegirl »

Walked 2 blocks away and still present? My other 2 units do not cause the issue. Scratching my head?
ve3nsv
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Re: Vertex VXR-7000 Motorola Repeater Stray RF

Post by ve3nsv »

Remove busy channel lockout or channel free in TRBO gear and all your problems will be solved.

As mentioned before you are likely hearing the local TX oscillator.
anniegirl
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Re: Vertex VXR-7000 Motorola Repeater Stray RF

Post by anniegirl »

Ok, I will give it a try, but why don't I have this issue with the other 2 Vertex Repeaters that are the exact same models?
anniegirl
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Re: Vertex VXR-7000 Motorola Repeater Stray RF

Post by anniegirl »

I still don't understand why the other 2 exact same repeaters do not cause this issue.
anniegirl
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Re: Vertex VXR-7000 Motorola Repeater Stray RF

Post by anniegirl »

Maybe I didn't explain this correctly. Here goes: As soon as I power on the Repeater all radios on standby will enmity their receive leads like they are receiving an I'm coming transmission. I put my Moto R2660 in RX mode and there is no RF coming from the transmitter. I have 2 other VXR7000 units and they do no exhibit this condition. TX RX good
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fineshot1
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Re: Vertex VXR-7000 Motorola Repeater Stray RF

Post by fineshot1 »

anniegirl wrote:Maybe I didn't explain this correctly. Here goes: As soon as I power on the Repeater all radios on standby will enmity their receive leads like they are receiving an I'm coming transmission. I put my Moto R2660 in RX mode and there is no RF coming from the transmitter. I have 2 other VXR7000 units and they do no exhibit this condition. TX RX good
Some repeater transmitters will exhibit this condition. It comes from the TX PLL oscillator itself and you won't be able to
detect it at the repeater TX output connector via a service monitor. The amount of RF is too small via a service monitor
but your radios are sensitive enough to receive it at close range. The Quantar/Quantro series also exhibit this condition.
fineshot1
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Bill_G
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Re: Vertex VXR-7000 Motorola Repeater Stray RF

Post by Bill_G »

Agreed. It's a "birdie" of some kind occurring at the IF level. You won't see it at the carrier freq on a service monitor. It will be at a lower freq. Almost every piece of electronic equipment built emits a birdie, though not necessarily where you think it should be.

Case and Point - a local small city paid electrical engineers for a new SCADA system to monitor their sewer lift stations using licensed low speed UHF RF modems to transport the data back to their public works office. Shortly after implementation, they experienced multiple COMM FAILS from a number of sites. I was called in as a subcontractor to the engineering group to figure out why.

It was the LCD display mounted to the front door of the PLC panels. The solution was to put a toggle switch on the power line to the display.

These displays emitted a near direct hit on the rcvr IF making it impossible for the furthest stations to hear the master site polling. When the front door was closed, the display was inches away from the RF modem desensing the rcvr. When the panel was open, the display swung away reducing the interference, and the modem was able to transpond. There was a busy light on the modem, but with the door open, nothing was seen, and with the door closed, you couldn't see the modem indicators. I proved my point by pulling the display cable from the controller card, and ouila - fresh hot-n-cold running data. Plug it back in, and COMM FAIL galore.
anniegirl
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Re: Vertex VXR-7000 Motorola Repe4ater Stray RF

Post by anniegirl »

Thank you, that is what is going on. I dont know how far away this affects my Mobiles and HTs but 2 blocks away for sure. It is annoying to say the least. As soon as I pull the wiring harness from the TX board it stops so for sure it's coming from the TX board. NOT WHAT TO REPLACE TO FIX IT?
noloflashradio
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Re: Vertex VXR-7000 Motorola Repeater Stray RF

Post by noloflashradio »

Happy I found this string of posts.
I have noticed the same on my VXR-7000 but only due to a more serious problem I am having.

The repeater is sending out randomly timed bursts of TX noise that sounds like a squelch tail. The repeater is NOT receiving a signal when this occurs and the busy light does NOT come on. The TX light does com on during the burst.

Help is appreciated.

Thanks!
N
n3ssl
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Re: Vertex VXR-7000 Motorola Repeater Stray RF

Post by n3ssl »

A Few years from this post but for archives. It appears that different PA Boards and Different Exciter boards display this oscillation. also same on the UHF repeater.

http://www.repeater-builder.com/yvs/vxr ... 711-1a.pdf


Ryan n3ssl
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