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Miked
New member
Username: Miked
Post Number: 1
Registered: 4-2006
| | Posted on Thursday, April 27, 2006 - 7:55 pm: | 
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Is there supposed to be any continuity between the center hole and outer threaded section on the coax connectors on an SWR meter? I'm on my 2nd meter, and have been unable to get an acceptable SWR reading. Both meters have shown continuity from the inner to the outer sections of those connectors, and it seems like that shouldn't be the case...
Thanks. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1484
Registered: 9-2004
| | Posted on Friday, April 28, 2006 - 12:23 am: |
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miked,
not sure on that one, i will check mine when i get home.
for now, lets get into a bit more detail about what your actual problem is.
what is your setup?
(name each piece of equipment inline, including jumper lengths, and anything else you dont think will matter)
what is your antenna setup?
again, details!
what is your current SWR reading on ch. 1, 20, and 40?
matt |
Tech237
Moderator
Username: Tech237
Post Number: 310
Registered: 4-2004
| | Posted on Friday, April 28, 2006 - 10:06 am: |
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From memory - there should not be any continuity between the shell and the inner conductors on the sockets of a SWR meter.
Basically the two socket inners are connected by a track on the circuit board and the two shells should be grounded. The metering circuit picks up a small current from the center track by two loops - one either side of the center.
Now when you say continuity I have to ask - do you show a complete short or is there a specific amount of resistance shown?? |
Miked
New member
Username: Miked
Post Number: 2
Registered: 4-2006
| | Posted on Friday, April 28, 2006 - 12:24 pm: |
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Well, my setup is this:
3' Firestick II (KW3)
Stud Mount
18' Fire-Flex Coax (K-8)
Cobra WX ST II CB
RadioShack 21-534 SWR Meter (with 3' coax jumper)
When I say continuity, I'm saying a complete short. I haven't measured specific resistance yet. I've tested both coax lines, showing continuity along the center and the outside, but not between the two. The stud mount is attached to a custom bracket that's screwed into my fender under the cowl area. The nylon washers on the stud mount are seated properly, as I show zero continuity from the stud mount to the bracket.
The ground wire from the coax is screwed into my fender, and I show continuity from that point to several other points on my chassis...in the door jamb, on the hood, etc. So it seems that the ground is clean.
When everything is connected without the SWR meter and jumper, I show continuity from the top of the antenna (the adjustable screw up there) to the center pin of the coax that would screw into the back of the cb. I show no continuity from any of those points to the ground.
That changes when the SWR meter is attached. Then I show a short from any point on the antenna (top or base) to the ground. Without the SWR meter in place, that issue goes away, so that's why I tested the connectors on the meter for continuity.
My SWR meter shows the SWR off the chart on all channels. I can adjust the antenna to make the needle more consistent across the channels, but the reading is so far right that there's not a number associated with it. I realize several things can cause this (bad ground, bad antenna location, no ground plane, etc), but it seems to me that the meter itself is causing a grounding problem (but I am new to all this).
When I test the connector on the cb, there's no continuity from the inner section to the outer section. I don't know why the SWR meter would show that, but I've now had two that do, and I can't get my SWR readings even close to 3 with those meters. It may well be something other than the meter, but I want to eliminate that as a problem, hence my original question.
Thanks guys, I appreciate the help. |
Tech237
Moderator
Username: Tech237
Post Number: 313
Registered: 4-2004
| | Posted on Friday, April 28, 2006 - 3:36 pm: |
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How are you measuring the continuity?? With a Ohmmeter or just a simple make a noise type continuity tester?
If it is a meter what is the actual resistance between the inner and sheild on the SWR Meter? |
Rldrake
Intermediate Member
Username: Rldrake
Post Number: 119
Registered: 1-2006
| | Posted on Friday, April 28, 2006 - 3:54 pm: |
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What does the meter read when connected to a good 50 ohm dummy load? |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1488
Registered: 9-2004
| | Posted on Saturday, April 29, 2006 - 9:42 pm: |
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i forgot to check my meter last night. sorry.
i will do it though, and i think i have the same one you do.
for now, im going to assume that the meter is OK, since if you bought it new, it should be fine.
is there any sort of SWR indication on the radio itself?
like a built in meter, or an "AWI" (antenna warning indicator) light?
assuming that the meter itself works.
how much antenna do you have sticking up above the roof of the vehicle?
this is the only part of your antenna that is actyually "radiating" a signal. the rest is being absorbed by the vehicle itself.
we call this a "capacity hat".
marketing in this business is very misleading to say the least, with some manufacturers flat out lying about the performance of their gear.
what follows are only MY opinions.
i dont like firestick antennas. they make their money on the people that want a CB antenna but dont want a big honking thing sticking out the top of their vehicle.
this has always been the trade off in the CB world.
its all about performance versus uglyness.
the worse it looks, the better it performs.
with a 102" whip being the most obnoxious and the best performing, and the through-glass mount antennas looking the most discreet and totally negating the very idea of even HAVING a CB in the car in the first place.
i believe that the firestik antenna mounted on the fender is your problem. even mounted on the center of the roof, (the best spot) a three foot antenna is not going to work very well.
firestik relies on the fact that most people that buy their product dont even know what an SWR meter is, much less what its for, or how to use one.
also, with a firestick antenna, the coax is actually part of the radiating system. (wonder why they tell you NOT to cut the coax in the instructions?) so, much of your signal is never even leaving the car.
i would buy a mag mount wilson, or K40, stick it on the roof when needed, and in the trunk when not needed.
if we find out that the meter is the culprit, then great, you're off and running, but i really have to say that i have given this advice many times, and it always involves a firestick type antenna mounted low on the vehicle.
good luck,
matt |
Miked
New member
Username: Miked
Post Number: 3
Registered: 4-2006
| | Posted on Sunday, April 30, 2006 - 6:20 pm: |
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Update: I went to the cb shop at the local truck stop and picked up a different brand of SWR meter (says Astatic on the front). I asked the guy at the shop if there should be continuity from the inner to outer coax connector. He said he thought so, but didn't know. I tested the new meter (using the 'make a noise' continuity test on my multimeter, BTW), and guess what? No noise, no continuity. Long story short, I was able to adjust my antenna to SWR readings of 1.1 on channel 20, and 1.3 on channels 1 and 40.
Kid_vicious: I appreciate the comments on Firestik, although it was actually their website that stressed the importance of checking SWR. If I find this antenna isn't meeting my needs, then I may switch to a Wilson or K40, but for now, it seems I'm in business. My antenna does stick almost a foot above my roof line.
Tech237: Just to see, I measured the actual resitance on those connections on the two different meters. The new one, which seems to work fine, measures infinite resistance, while the RadioShack meter shows .2 ohms.
So I'm assuming there's not supposed to be any continuity there, and I'll be returning my RadioShack meter. Not sure if they got a bad batch, or what, but the 2nd unit I got had clearly been used before...so it may have been returned as well. Just bad luck, I guess. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1499
Registered: 9-2004
| | Posted on Sunday, April 30, 2006 - 11:28 pm: |
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right on miked!
as long as you were able to get a decent SWR; thats the main thing.
as for how far you can reach, only your own tests will tell.
good luck,
BTW, welcome to the forum!
matt |
Tech237
Moderator
Username: Tech237
Post Number: 316
Registered: 4-2004
| | Posted on Monday, May 01, 2006 - 1:37 pm: |
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Glad the new meter workded outnad you were able to set your antenna up properly.
As I said before their should not be any continuity between the center and shell of the socket on a meter. |
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