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Few quetions about a choke....

??????;s.....


Will adding this choke have any affect on my swr ?....

You guys who run these things, how far did you mount it away from the mast pipe ??............

This will be used on the 11 meter band and later on the 10 meter band too..
 
Marconi said:
I have never had a radio that could detect CM currents at my station, but I do keep a free standing field strength meter, and when I see it working noticeably I can detect a problem and check it out. Most of the time I have found something loose (a construction issue) on the antenna.
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Some radios react differently to RF feedback caused by CMC's. Some will shut completely down while others hardly blink.

Question for you. I have run with a fieldstrength meter in the shack before as well and I am curious as to how you or your meter are able to tell radiation caused by CMC's from normal radiation from the antenna. I can get a field strength indication when no CMC's are present. That is the nature of a field strength meter. Did you take readings to use as a baseline reference and then compare things too later? One prettty sure fire way to detect CMC's is to move the coax cable or roll it into a loop while watching the SWR. If it changes you have CMC's.
 
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Good question CK.

...I set the meter on or near my radio and set the sensitivity to about 1/2 way or less, with a good acting setup I usually have around. Not every setup I have shows to be bad at that setting, so I can get a sense if one is going to be an issue maybe.

I can always take a mobile sniffer out to check the feed line up close as it comes down the mast.
 
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Oatmeal said:
Ok, Ive been reading on a few other forums about the length of coax that's used for making a choke.....some guys say to use 18-21ft for it, some says use less, who is right on what length of coax needs to be used ?...

I was told, if your going to make a choke, and if you didn't make it with 18-21ft of coax, there wasn't any use making one, any truth to this ?...

Seems like for the 11 meter band the graph said to use 5ft of coax for the choke, to be used on 11 meters....

2nd question, how far from the mast pipe does the choke need to be, or does this make any differences ?...

Last one, how far below the antenna does the choke need to be mounted on the mast pipe ?....

Sorry guys, but Im a little confused here...
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First of all, a choke isn't a necessity to have. Depends on the antenna you have; some need it more than others. Some don't require it at all. All it does is keep stray RF from using the outer shield of the coax as a return path.

So; what antenna are you planning to use?

A choke is a tuned RF coil that acts on the band that it is tuned for. For 11m/CB, the standard tuning for a choke is 5 turns on a 4 1/4" ID non-conductive coil form. If you were going to make it specific for another band like 20m; then its dimensions would have the same ID but more winds. So; it needs to be wound specifically for the band you use. Five turns for a CBer - is the ticket . . .

It doesn't hurt anything to put one on just about any antenna; but it isn't always necessary either.

CK covered why you might need one already; what makes you think you need it?
 
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My philosophy is and has always been, why fix it it it isn't broke. In all my years and all my antennas, oh God there were many, I have only used a choke on my tribander and will again on my 12/17m dual bander yagi and my Ex-14 quad bander (10-40m) and only because I want to preserve as much symmetry as I can as the antennas are rotatable. It should help with side-lobes as well a little bit. I did install a toroid impedance transformer (not a choke) on an inverted L to raise the feedpoint impedance up from a measly 4 ohms on 160m. Unless you need a feedline choke why install one?
 
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Why do I think I may need a choke ?....

For one, Im running a Imax 2k...in which will be around 25-27ft off the ground..
Wont be able to get very high with it....

2nd, have neighbors close to me and I live in a trl park and also one across the road..

And later on I do plan on getting me a amp...

" How far does the choke need to be mounted off the mast pipe ? ".....
Or, how far does the coax need to be out away from the mast pipe ?..
Or does this not matter..
 
For one, Im running a Imax 2k...in which will be around 25-27ft off the ground..
Wont be able to get very high with it....

2nd, have neighbors close to me and I live in a trl park and also one across the road..

And later on I do plan on getting me a amp...
Click to expand...

Don't think a choke is going to help much in this situation, if at all. You will have issues with neighbors simply because of your proximity with them. Only made worse with an amp. No way to beat the proximity effect.

You might spend more effort twards getting the antenna higher, getting some ground planes for the Imax, isolating/insulating it from the mast, and then use a coax choke. Even with all of that, there is no guarantee that you won't create problems with your neighbors. Your radio too - if it has been improperly modified - will also add to the problem.
 
Oatmeal said:
Why do I think I may need a choke ?....

For one, Im running a Imax 2k...in which will be around 25-27ft off the ground..
Wont be able to get very high with it....
Click to expand...

It may help with an Imax 2K because of the antenna design itself. No guarantee it will help however. Also no guarantee you will need it.

2nd, have neighbors close to me and I live in a trl park and also one across the road..
Click to expand...

Completely irrelevant as to the need for a choke at the feedpoint. Close neighbors can be affected by a perfect installation.

And later on I do plan on getting me a amp...
Click to expand...

Again irrelevant. Front end overload is the more likely culprit when running an amp in close proximity to neighbors.

" How far does the choke need to be mounted off the mast pipe ? ".....
Or, how far does the coax need to be out away from the mast pipe ?..
Or does this not matter..
Click to expand...



Choke%20Coil%201.jpg
 
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