Need some help

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eclipse3256

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ocean county nj
hopefully someone can help me. Here it goes. i have a discone base antenna and also a nmo moile to base antenna mounted mounted on the roof. I own a taxi company in nj along the shore so reception shouldn't be a problem right?? wrong!! the discone when hooked up to my bc780 receives fine. the problem i'm having is the "commercial" nmo mobile to base antenna hooked up to my cdm1550 at my dispatch desk. the "commercial" antenna is about 35 feet high and picks up very faintly. and the repeater i use is 8 miles away. mind you that the antenna mast is grounded.. I also get a little shock on the connectors of the coax. There is a computer and cable modem in the area of both radios. does anyone have a clue whats going on?? i tried to elaborate as best as i can. any help would be appreciated!!
 

Cochran_rick

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You certainly have RF coming back down your coax into your shack. I would put a choke on the coax to stop that. It should stop you from getting a shock. And I would check for a loose connection in your feed line. Monitor your SWR's, preferably if the wind is blowing, and see if they are bouncing up and down. If they jump around I would say you have a feed line problem. Could be as simple as a loose connection, or a break in the line. All this may be nothing, but wouldn't take much to rule out the simple stuff first. Good luck!
 

prcguy

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The shock is not from RF and a choke in the coax will not help, its because the mast is grounded to a point that is not in common with the building electrical ground. This is will not cause any reception problems, its just dangerous.

I would try swapping the cable from the antenna with good reception to the bad one and see if it improves. If not the antenna is probably the culprit.
prcguy

You certainly have RF coming back down your coax into your shack. I would put a choke on the coax to stop that. It should stop you from getting a shock. And I would check for a loose connection in your feed line. Monitor your SWR's, preferably if the wind is blowing, and see if they are bouncing up and down. If they jump around I would say you have a feed line problem. Could be as simple as a loose connection, or a break in the line. All this may be nothing, but wouldn't take much to rule out the simple stuff first. Good luck!
 

kb2vxa

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A commercial radio installation is not for amateurs to monkey with, especially when it comes to one asking questions on a scanner forum. Here we have a case of the blind leading the blind which can only end in disaster, mess it up and there goes your business down the tubes. It's a business, treat it as a business tool and hire a professional, let your tax accountant work the advantages of "business expenses". There is no tax advantage in medical expenses when you fall from the tower.
 

prcguy

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I agree a scanner forum is an unusual place for commercial radio advise, but was the blind leading the blind comment directed towards me?
prcguy


A commercial radio installation is not for amateurs to monkey with, especially when it comes to one asking questions on a scanner forum. Here we have a case of the blind leading the blind which can only end in disaster, mess it up and there goes your business down the tubes. It's a business, treat it as a business tool and hire a professional, let your tax accountant work the advantages of "business expenses". There is no tax advantage in medical expenses when you fall from the tower.
 

Kennrth

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Bay Shore Long Island NY
I'm totally confused. You have an NMO Mobile antenna mounted on the roof. Is this a magnetic mount? What is it using as a ground plane. Your discone is on the 35 foot tower? Are they both mounted on a tower up on the roof? Discone has a ground plane built in. Mobile antennas do not.
The mobile antenna should be mounted on a car. It needs the car as a ground plane and will have a very high swr without it. So high you would not be able to tranmit out of it. Mobile antennas will not work on a roof unless you have a gound plane. The metal of the car is the ground plane.
Are you getting shocked only during transmission then it is most likely and rf problem. Antenna not matched with receiver bad coax or twin leads. Check SWR to Antenna. Transmission lines if twin lead need to be at a 90 degree angle to the antenna radiator elements. At High Power driven elements can cause a near field effect on passive elements causing rf to come back down the line. You should have a Balun in line to prevent this. High SWR can cause power to reflect down the transmision line depending on the kind of fault that is causing high SWR. Shorted Coax or twin lead transmission line is more than likely.
If your getting shocked all the time then you have a electrical power problem. More than one ground, a ground loop . No ground at all. Phasing problem. Nuetral and Hot swapped on a piece of equipment - can cause 60Vac on ground.

You have more than one problem my friend.
Receiving and transmitting are different issues.
Electrical shock is another.
 
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k9rzz

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Dec 12, 2005
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Milwaukee, WI
hopefully someone can help me. Here it goes. i have a discone base antenna and also a nmo moile to base antenna mounted mounted on the roof. I own a taxi company in nj along the shore so reception shouldn't be a problem right?? wrong!! the discone when hooked up to my bc780 receives fine. the problem i'm having is the "commercial" nmo mobile to base antenna hooked up to my cdm1550 at my dispatch desk. the "commercial" antenna is about 35 feet high and picks up very faintly. and the repeater i use is 8 miles away. mind you that the antenna mast is grounded.. I also get a little shock on the connectors of the coax. There is a computer and cable modem in the area of both radios. does anyone have a clue whats going on?? i tried to elaborate as best as i can. any help would be appreciated!![
What's the major problem? Not getting the commercial repeater? or the shock? Any idea what frequency (roughly) the repeater is? (150mhz or 450mhz?)
 
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