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Unread 12-09-2007, 06:19 PM   #1
expat
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Default Continuity 101 please

I have no clue for electronics and I need some help. Have looked online but nothing basic enough for me

I want to check the continuity on my cb antenna mounting.

I want to test the continuity of the labels marked G and H. (setup on the right)



Thing is I don't know how to use a multimeter and the instructions are gobbledy gook...

I have this multimeter http://www.radioshack.com/sm-15-rang...i-2103174.html

I have no clue what setting I should be setting it to to check continuity. The options on the meter include

DCV - 500, 200, 20, 2 V,
OHM - 2M, 200K, 20K, 2K, 200
DCA - 2, 20, 200 mA
ACV - 200, 500 V

Also, can anyone tell me about the Fire-ring...it has a plastic insert that must face into the mounting surface (metal). The plastic insert has a metal ring on the outside. I assume the metal ring is meant to touch the mounting surface correct? Given that the metal ring also touches the bolt head (nothing appears to insulate it) that would mean the bolt is earthed to the mounting surface correct? So then the bolt, metal ring and the the antenna mounting coupling nut (top section) are all earthed correct? That being the case what is the plastic insert doing - is it meant to insulate anything or is it just some spacer? If it was a spacer why wouldn't they make it from metal?



This is counter-intuitive (look at me with big words now!!!) as the diagram shows there should be no continuity between the bolt head (H) and the the metal ring (G) and yet the bolt head touches the lower metal surface of the Fire-ring (H) which is part of the top part of the f-ring (yes I said f-ring!) (G).



If someone can walk me thru a step by step procedure (and remember to expect no knowledge from me on this subject) I would be in mucho appreciation.
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Last edited by expat; 12-09-2007 at 06:38 PM.
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Unread 12-09-2007, 07:21 PM   #2
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I might help a little. I run this same setup. The two metal sides on the fire-ring are insulated from eachother (to my knowledge). I have/had mine attached thru the front bumper (steel bumper). The bumper didn't seem to provide enough of a ground plane, so I placed a ring terminal between the negative face of the fire-ring and the bottom face of the bumper and ran that wire to ground on the firewall. I have a 4ft firestick and with this setup I have it tuned down to just under 2 SWR on the low side and just over 2 on the upper channels. If the two sides of the Fire-ring terminal weren't insulated from eachother, I'm positive I would never be able to get the SWR tuned that low.

I guess what I am saying is that what you have a picture of will work as long as the bottom face of the mounting surface provides a good ground.
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Unread 12-09-2007, 08:46 PM   #3
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Ok, that's part of my answer then. The fire-ring metal piece is in two parts, that makes sense. Thanks Bill!

So now I just need to know how to check the continuity with the multimeter.
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Unread 12-09-2007, 10:58 PM   #4
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Looks like your multimeter has a diode check function. This function normally produces a beep when there continuity. So set it on the Diode function. Then touch the 2 probes of the multimeter on each other and you shoudl hear the beep. That means you have continuity between the 2 probes. Teh diode test function is just the symbol of a diode ---|<|----- something like that (looks like an arrow).

SO now when the circuit between the probes are closed you will hear the beep = continuity. If it doesn't beep it means it is open circuit = no continuity. This makes it easy to test as you will have audio confirmation when you put the probes on the parts you want to test. Make sure to unplug the cable from the radio and leave that end open.

If your multimeter doesn't beep on the diode test function, you cna simply use the ohm meter. set it to 200 (in your case). WHen you touch the surfaces with your probes it will normally show 0 or a very low value like 0.001 if there is continuity between the surfaces you touch. If their is no continuity it will normally show nothing or a funky symbol or a 0 with spaces before the .

I prefer to use the diode function as I can then hear what is going on while looking at the point so rsurfaces I'm testing.

Hope this helps with your question.

Seems like they just want to make sure that the fire ring doesn't short to the groudn and has good contact wiht the antenna screw nut on the top. Guess this is for your bullbar mount.

BTW make sure you knwo which side of the fire ring is ground and which is the signal, you don't want to short your signal wire to ground. Your radio will not like that
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Last edited by bulldog; 12-09-2007 at 11:01 PM.
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