Its actually one of these... And it stays on continuously when in the vicinity of the antenna wire which is the wire in question...
http://bit.ly/9hI3As
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| Author: | Madhatter [ Fri Sep 10, 2010 5:38 pm ] |
| Post subject: | Antenna Question |
I have a wire antenna I am running right now that is working well, its been extended out to about 15' with a few other wires I dug up... I went to strip off some shielding with my teeth, only to get a mild shock... So I grabbed my tester and low and behold there is an AC charge on the line, it seems very mild I still get a light and tone on the tester... I have a Realistic 2004 that was given to me but works really well for running a feed. The question I have is: 1. is this normal? 2. Is having an unshielded wire antenna outside going to cause a major problem with the small AC charge on the line? Is there any potential for a short/fire/shock to someone/??? I would love to be able to run a proper antenna but right now that just ins't practical for me financially right now... and I live about 500' from a county repeater antenna anyway...so I can use pretty much anything I want for an antenna... Any ideas? |
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| Author: | Rich [ Fri Sep 10, 2010 8:28 pm ] |
| Post subject: | Re: Antenna Question |
Was the other end plugged into the radio when you got the shock ? This should not happen with a scanner as the antenna connector is typically connected to an LC filter then a frontend FET so there should be no AC or DC voltage present. However if its a 2-way radio there might be some DC leakage through the final transistor but this would usually be blocked by the T/R switching circuit. Last but not least it could be some sort of ground loop issue with the power adapter. Generally this sort of thing shouldn't be an issue with an antenna. I'm curious what the source of the voltage is. |
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| Author: | Jim [ Fri Sep 10, 2010 8:47 pm ] |
| Post subject: | Re: Antenna Question |
If I understand correctly this wire is connected to the PRO-2004 and you are getting the shock from it. If it is connected to the chassis of the PRO-2004 and you are outside standing on the ground it is very possible that the power supply is leaking a slight amount and it shows up on the meter and you feel a shock. What are you connecting the other lead of your meter to that has one lead hooked to the antenna bare wire? There are a couple of other possibilities. If you have a bunch of wires that are running parallel to each other in close proximity you may be seeing induced current on your wire similar to how a transformer works. When you hook a volt meter up to only one lead and don't have the other lead connected to anything you will probably see a slight voltage displayed caused by picking up electrical noise form close energized devices. I have an old PRO-2004 and it uses a power cord connected to the scanner itself unlike the present day scanners that use a wall wart power supply that changes the AC voltage to DC before it connects to the scanner. The wall wart act as line isolator and there is a lot less chance of shock than with the power supply with a cord that connects directly to the scanner. You might try turning the ac plug for the PRO-2004 180 degrees and plug it in and see if that corrects the problem. Sometimes the power supplies in the older units have the neutral lead hooked to ground. It may also have a leaky capacitor in the power supply that is causing the problem. I may be way off but those are a few possibilities. Let me know if I understood your problem correctly and if not we can go from there. |
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| Author: | chpalmer [ Fri Sep 10, 2010 10:12 pm ] |
| Post subject: | Re: Antenna Question |
That would be how I learned as a teenager not to strip wire with my teeth... Though mine was a tad bit higher voltage level. You could have some induction going on also. Hard to tell without seeing you situation. |
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| Author: | the Outlaw [ Sat Sep 11, 2010 3:02 pm ] |
| Post subject: | Re: Antenna Question |
Static electric built up?/; ground off would be the first thing I would try. Or the Ben Franklin approach. Let us know what you find out. |
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| Author: | Madhatter [ Sat Sep 11, 2010 7:14 pm ] |
| Post subject: | Re: Antenna Question |
Ok, let me see if I can hit everything here... Oh, and what I say shock...it was more like a 9V battery on the tongue, not a "HOLY CRAP THAT *&(^ HURT!!!" kinda shock... Rich - The Realistic 2004 is just a scanner, and it was plugged into the wall AC, as the scanner runs on AC and not a wall wart its that old... still an awesome scanner... My wire antenna was plugged into the BNC, and the scanner was on and running... I never thought that I would get a shock from an antenna, so thats what I didn't think anything about stripping wire with my teeth... Jim - What I have is a wire antenna that was a stock wire antenna came with a Bearcat scanner that is made for the interior of a car window that has a BNC... I took apart a DC adapter for a laptop that has one shielded wire inside, and a braid around that. I used the shielded to extend the wire antenna out, and used a drill to twist the braid into a wire which is bare... Hooked it all together, ran it out the window to a pole and taped it to the top so I have about 20' of wire antenna, about 5' of which is unshielded and end about 15' off the ground. I got a shock when a connection came apart so I attempted to strip the wire further down to get a stronger connection. So I then grabbed my voltage tester and there is AC on the line... I can't reverse the plug as it is polarized so thats a no go... I was thinking along the line that you are... That there is a bleed over from inside the scanner, which is causing the AC charge on the line... What I wish I had was a multi-meter to test the actual current, but all I have is the LED "Hey! This is LIVE" voltage tester. My reception went from decent, to WOW...but like I said I live about 500' from a county repeater site... But now I have an unshielded wire with AC running through it on a pole outdoors which I hesitate to ground, and possibly short out the scanner or worse damage the electrical wiring in my house... I don't think its static on the line either... |
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| Author: | N7QOR [ Sat Sep 11, 2010 7:20 pm ] |
| Post subject: | Re: Antenna Question |
I have (qty 2) PRO 2006, pretty similar. I suppose I could look into one of mine to answer the question I am about to ask. Is it a "switched mode" power supply inside? Those were late 80's, early 90's vintage radios. I have had experiences with switched mode power supplies that were not properly grounded, in those cases it was more of a half-shocked the shit outta me. About 60VAC on the chassis. I do know those are 2 prong AC plugs, so they are not grounded, and I tend to believe then they are NOT switched mode, but kinda curious all the same. When you say "some voltage" on the wire, can you be specific? Also, have you measured both AC and DC voltage? |
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| Author: | Madhatter [ Sat Sep 11, 2010 7:25 pm ] |
| Post subject: | Re: Antenna Question |
Unfortunately I don't have a multi-meter so I cant measure the actual voltage, but there is AC on the wire, as my voltage tester is AC only, and is sensitive from 50-1000V... |
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| Author: | N7QOR [ Sat Sep 11, 2010 7:51 pm ] |
| Post subject: | Re: Antenna Question |
Madhatter wrote: Unfortunately I don't have a multi-meter so I cant measure the actual voltage, but there is AC on the wire, as my voltage tester is AC only, and is sensitive from 50-1000V... Is it ticking continously while you hold it next to the wire? Or does it tick a few times when you place it next to, or pull away from, the wire in question? |
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| Author: | Madhatter [ Sat Sep 11, 2010 7:56 pm ] | ||
| Post subject: | Re: Antenna Question | ||
Its actually one of these... And it stays on continuously when in the vicinity of the antenna wire which is the wire in question... http://bit.ly/9hI3As
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| Author: | Jim [ Sat Sep 11, 2010 8:46 pm ] |
| Post subject: | Re: Antenna Question |
Try unplugging the PRO-2004 from the AC socket it is plugged into. That will eliminate the scanner from being the problem if you still light up your probe you are getting it from someplace else and not the scanner. |
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| Author: | Madhatter [ Sat Sep 11, 2010 8:51 pm ] |
| Post subject: | Re: Antenna Question |
Just tested this and it isn't coming from somewhere else... The antenna wire comes from a BNC to a vinyl window to a 6' mast... |
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| Author: | Jim [ Sat Sep 11, 2010 8:57 pm ] |
| Post subject: | Re: Antenna Question |
You are saying that the voltage goes away when you unplug the scanner from the AC source (outlet)? |
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| Author: | Madhatter [ Sat Sep 11, 2010 9:06 pm ] |
| Post subject: | Re: Antenna Question |
Yep... The voltage on the antenna wire goes away... Which leads me to believe its gotta be internal... |
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| Author: | Jim [ Sat Sep 11, 2010 9:19 pm ] |
| Post subject: | Re: Antenna Question |
Sounds like a ground loop problem. If you completely insulate the wire it won't matter if it has a little voltage on it. Make sure it is completely insulated from where it hooks to the BNC all the way to the tip that is outside. You could take the BNC off the scanner and stick a short wire in the BNC socket on the scanner (while it is unplugged) and see if touching the voltage probe will light it up. Does it have voltage when the scanner is plugged in and turned off? By any chance do you have the audio out of the scanner hooked to another device which is used to provide your feed? That may be the source of the ground loop if so. |
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