Antenna, Coax and OCD

[Cajun Invader]

Hey Guys, I need help. More so than the obvious. lol

I have a problem called OCD. Everything I do has to be perfect that's why I have yet to get my base up and running.

While on my quest for perfection with my base antenna I did a continuity test on the coax and antenna. I do not like what I have found and I am getting mixed reports as to whether this is normal or not.

When I use my multi meter with the audible continuity function I am getting the 'beep' when I touch the center pin with one probe and the shield with another. I removed the PL259's and the outcome is the same. Not good is what my thinking is. The coax is 9913.

I also get the 'beep' when I check the antenna. One probe inserted where the center pin goes and the other on the threaded part of the S0239. The antenna is an Imax 2000 that is being replaced with an I 10K.

My thinking is that the coax and antenna are done. Can I get some confirmation here one way or the other. This obsession I have for perfection is going to kill me yet.

Side Note.....Radio and amp was up and running fine on a test run with an SWR of 1.4 when running 300 watts. I just have to know about this continuity issue.

 

[Marconi]

The I10K will show you the same result when assembled and is normal for the matching device used in both antennas. A center fed dipole, a Starduster, any element fed using a gamma device, should show you the kind of results you are expecting.

Coax should always show results like you are expecting when testing center to shield with the opposite end of the feedline open. It appears to me that only your coax is bad. Check each end carefully and look for a tiny shield wire touching the center conductor somewhere. If no problem is found at the cut ends, then something bad is going on inside the piece of coax that is causing a direct short.

 

[Cajun Invader]

The I10K will show you the same result when assembled and is normal for the matching device used in both antennas. A center fed dipole, a Starduster, any element fed using a gamma device, should show you the kind of results you are expecting.

Coax should always show results like you are expecting when testing center to shield with the opposite end of the feedline open. It appears to me that only your coax is bad. Check each end carefully and look for a tiny shield wire touching the center conductor somewhere. If no problem is found at the cut ends, then something bad is going on inside the piece of coax that is causing a direct short.

I cut a few feet off each end of the coax and re-checked. It must have been a bad section of coax. Now there is not any continuity between sheild and center. The Imax 2000 however is showing continuity and if I am understanding you correctly that's how it should be.

Now here comes the OCD. I went and checked the coax in my vehicle which is run to a Wilson roof mounted antenna. My coax is NOT showing any continuity. Should it show continuity seeing that the Wilson is a base load antenna?

I really hate to ask so many questions but I am bound and determined to learn about antenna theory.

 

[W5LZ]

Big difference between a loaded antenna and one that uses a coil for impedance matching, they will show the opposite when testing continuity. That matching coil bridges between the center pin and shield connections so will show a short. A loading coil doesn't 'bridge' anything so will show an open circuit. That's all at DC, not at RF/AC, your continuity tester is a DC instrument.
I can't specifically answer your question about that mobile antenna, never had my hands on one or seen them 'opened up'. Sorry.
- 'Doc

 

[ron103067]

on your mobile you should NOT get continuity center to outer. If you do you have a problem. you should get continuity by touching the center lead and the antenna shaft. And you could get continuity when you touch the outer shied and a ground on you car. I know if your antenna is herd mounted you will just not sure how well it will work with a magnet mount. I hope that explains it

 

[Cajun Invader]

Ok, I do believe I've got it now when it comes to the continuity. Now haw about the SWR? A reading of 1.4 with 300 watts seems high when you factor in that they are increasing as power is added. I'm using a Palstar that has the cross needle application. I considered the fact that I may be seeing harmonics. There is no way to calibrate this meter for SWR so I am also wondering if it's accurate.

 

[linearone]

get them harmonicas out of there, theyrs not needed.

 

[bob85]

cajun,
what i told you last night is correct, your 5000 base load is a shunt fed antenna and SHOULD show a dc short with your multimeter,
i just tested my 5000 base load to remove any doubt, your imax should also show a dc short,
the wilson truckers are not shunt fed antennas, as eddy said they are a different animal and should not show a dc short with the meter.
test your 5000 antenna and then check your coax and mount in the mobile, if you get stuck give me a call,

good luck

 

[Jay in the Mojave]

Hello Cajun Invader:

Give Steve a call (661 256 6976) he has answered many questions on antennas and there installation. Ask him to give you my phone number and I'll talk to you also.

Any one whos says their an expert on antennas is lying to you!

We go ahead with antennas after a long and involved testing period, and put our money where our mouth is in buying the materials and selling the products. We also believe that helping out a customer is part of the job.

(The Waves of the Further)))))))))))

Jay in the Mojave


Added 6 Feb 09: Hello CI I must not have read all your posting or didn't get all downloaded some how?!??! Yeah I'd say your installation is working. Yes the I-max 2000 and the I-10K will show a short or continuity between the center pin of the coax and the shield wire. This short as some call it is the connection of the T2 Trombone Tuning Hoop connectiong to ground. Which is how the I-10K Antenna is designed. Its OK!

We get a lot of questions on how high the a antenna needs to be, we answer the higher the better for antenna performance. But at the same time you don't want the antenna to be to high to be unsafe and fall into power lines of the neighbors new car.

Again feel free to call.

Jay in the Mojave

 

[Marconi]

I cut a few feet off each end of the coax and re-checked. It must have been a bad section of coax. Now there is not any continuity between sheild and center. The Imax 2000 however is showing continuity and if I am understanding you correctly that's how it should be.

Now here comes the OCD. I went and checked the coax in my vehicle which is run to a Wilson roof mounted antenna. My coax is NOT showing any continuity. Should it show continuity seeing that the Wilson is a base load antenna?

I really hate to ask so many questions but I am bound and determined to learn about antenna theory.

CI, "Yes" you are correct: the Imax should make your buzzer go off. I think "Doc gave you some limited information explaining something about those possible issues. Just reading it here on the forum however, may not give you a through understanding.

You will probably find that some Wilson mobile antennas will correctly show an open circuit with your OHM tester while others will show a shorted circuit. Sounds like you are talking about a Wilson 1000, 5000. When reading my 1000 physically at the base of the coil, my 1000 shows continuity between the shield and center conductor. It would make you buzzer go off.

My position now is, I like Linearone's answer best so far. I think he was making a special point, without really saying. This came about after re-reading your post. It is because of the way the way you posed your supposed dilemma. I can just bet that you have been listening intently to some in the big swing, big power, big antenna, key-down bunch. No doubt some of those guys may really know what they are talking about, but I wouldn't hold my breath waiting for the real truth about a lot of ideas they hold. Listening and talking their talk is not a problem, as long as you keep a mind towards real understanding and not just assimilating some pumped up hype about this or that.

You should slow down and get control of your OCD. That may be the only problem you have right now. You can't go Will-Nilly, and start cutting off pieces of coax and expect to define a problem or develop understanding with your testing, comparisons, or experimenting. After telling us your coax was bad, then telling us that you found out a part of the segment of coax was good---does not explain what the problem was. In fact, you did not have a problem---except maybe in understanding. I miss-read your original post, as being a question about a problem. I have read Tom Sawyer already.

 

[Cajun Invader]

I can just bet that you have been listening intently to some in the big swing, big power, big antenna, key-down bunch. You should slow down and get control of your OCD. That may be the only problem you have right now.

You are exactly right, I was being feed wrong information and as always that is why I came to the WWDX seeking the truth. Bob-85 took the time to explain antenna theory to me in detail and gave me some excellent reading material.

I used to think that it was all about the watts. No I see it's more about how you deliver them. You might be able to fool a meter but you can't fool mother nature.

Thanks for all that helped me with this. As Marconi said, it was all the OCD. I was actually 10-8 the whole time.

 

[Marconi]

You are exactly right, I was being feed wrong information and as always that is why I came to the WWDX seeking the truth. Bob-85 took the time to explain antenna theory to me in detail and gave me some excellent reading material.

I used to think that it was all about the watts. No I see it's more about how you deliver them. You might be able to fool a meter but you can't fool mother nature.

Thanks for all that helped me with this. As Marconi said, it was all the OCD. I was actually 10-8 the whole time.

Well CI, I was concerned that you might take my words wrong and develop a bad attitude along with the OCD. It is refreshing to still find young fellows that don't take offense at being fussed at a little bit.

You can't go wrong listening to Bob.

If my words ever really hurt anybody, then I would figure out some way to make a living at it.

Thanks for hanging in there,

Marconi

 

[BOOTY MONSTER]

LOL . dont worry about the OCD cajun . i had that bad when i was learning about amps and asked a ton of questions befor i figgured out what i wanted . many folks were helpful . one guy still complains about me asking so many questions , LOL . good thing i came to learn and not make everybody happy . hahahaha