RF choking

[loosecannon]

im sure beetle was taught the correct way, so i cant dispute what the "right" way is.

all i can say is ive tried it with a 100 watt gun, and with my hako, and i like the hako much better.

the 100 watt gun seemed to do what you say the small iron will do.
as in, heat up the whole connector to the point where it melts the dielectric.

the hako seems to keep the heat more localized. like, i can solder one hole with ease after its heated, but i cant leave the iron where it is and solder the next hole.
i have to put the iron on, or right next to the next hole to solder it.

maybe it was a mistake, but i purposely exaggerated the heating time because his connectors looked way under heated.

all i can say is that i have been doing it this way for over 5 years, and the way i do it works excellent.

and it doesnt take me 6 minutes either! LOL

that being said, i am self taught, as i am with everything i know about radio, and i have never had anyone show me anything in person.
everything i know, i learned from a book, an on-air conversation, the internet, and from good ole' trial and error.

so, when it comes to installing connectors, if you're not doing it the "right" way, is it necessarily wrong as long as it works and works well?

LC

 

[357]

"Well I was hoping to see a flat match."

then you still don't understand the purpose of the choke. it has nothing to do with VSWR and a high VSWR is no indication of feedline radiation.

"Only thing I see is a 1db drop in recieve.

that usually indicates that noise in the receiver due to common mode current on the outer shield of the feedline is being suppressed. that's one of the benefits of using a choke.

OK I thought that guys complaining, (me included) that coax length effects the SWR.
You shorten\lengthen the coax, the SWR changes.

Thats where I am. I nipped a few inches off and redid my PL259's and there went my velocity matched length.

With RG213 I cut 12 foot multiples.

Unfortunatly I can't cut off the remaining 11 feet or so to make it even.

So I read about the choke eliminating the coax radiating RF down the line and that coax lenth has no bearing on the antenna's SWR.

What else it can be is the IMAX 2000 is really a 10M antenna and 11M at 1.5SWR is fine for most people.

BUT when I get this tube amp, that 1.5 is gonna mean alot af watts reflected, where a 1.1.1 would really mean something.

 

[Marconi]

OK I thought that guys complaining, (me included) that coax length effects the SWR.
You shorten\lengthen the coax, the SWR changes.

Thats where I am. I nipped a few inches off and redid my PL259's and there went my velocity matched length.

With RG213 I cut 12 foot multiples.

Unfortunatly I can't cut off the remaining 11 feet or so to make it even.

So I read about the choke eliminating the coax radiating RF down the line and that coax lenth has no bearing on the antenna's SWR.

What else it can be is the IMAX 2000 is really a 10M antenna and 11M at 1.5SWR is fine for most people.

BUT when I get this tube amp, that 1.5 is gonna mean alot af watts reflected, where a 1.1.1 would really mean something.

357, have you tried to figure out the Imax by scanning up and down to maybe find where the match seems best. It helps if you can do this at the feed point without a feed line, because if your Imax is not set/tuned at its sweet spot your are likely experiencing a bit if transformation also and then almost every time you change the length of the line it will appear that the match has changed. You can find youself chasing your tail trying to fix that problem if you are using a feed line and it maybe even worse if you are testing thru your entire radio system.

Just my twenty dollars worth---two cents when you adjust for inflation which we are told has not happened since Jimmy Carter was.....

 

[delta]

Hi guys, I’m still a bit puzzled as to weather to use a rf choke or not with the new I-10K i'm buying and if I should isolate it from the tower mast or not. Does the I-10K require grounding and what happens if i don't ground it to the tower by isolating it? If i do isolate from the main mast do i still use a rf choke? The tower itself is very well grounded indeed. Is an antenna only grounded to the mast for lightning strike protection? What is a dc grounded antenna, is it just to control static discharges from the antenna? so if we isolate it from the mast would we get the static discharge problem? Yes I’m puzzled as to which way to go about mounting my new I-10k, or any other home base antenna for that matter...


Cheers guys..

 

[W5LZ]

From what you have said is sounds like you cut about a foot off your feed line? First thing that comes to mind is why not just add that foot back? Or, if you did the figuring with 12 feet, add 13 feet instead?

Feed line length reall doesn't make any difference under one condition, the load impedance has to be the same as the feed line's impedance. Which should be the same as the transmitter's impedance, naturally. In those conditions, the only difference the length of the feed line will make is in resistive losses, which you can't do anything about. The only way to reduce resistive losses is by shortening the feed line, and then it probably won't reach, right?
Now for the 'catches'. No transmitter's output impedance is always goign to be exactly 50 ohms. No feed line's characteristic impedance is going to be exactly what's printed on the jacket (why it's called a 'characteristic' impedance). And there are no commonly used resonant antennas which will ever have exactly 50 ohms input impedance. There will always be some small differences (unless you are luckier than is normal). So, actually seeing that 1:1 'ideal' SWR is very unlikely, and why seeing something like a 1.5:1 SWR is considered @#$ good. You with me so far?
So, what do you do? Well, the one thing you have the most control over, which typically will do the least damage if 'adjusted', is the input impedance of that antenna. So adjust the antenna for resonance, then do what's necessary to adjust it's input impedance to 50 ohms, or at least close to it. That's as close to 'ideal', or 'perfect', as you can do. It's not the most 'simple'/'common' way of doing things, but it is the best. There are quite a few ways of doing that, none of them impossible. None of them absolutely dirt cheap/easy/simple, but so what. "Just do it."...

RF chokes.
They typically don't do any harm, even when not necessary. They are frequency/band specific. What works on one band may not work on another. They are not fool proof. They are sort of simple though.

Grounding antennas usually isn't necessary except for 'safety'. The exceptions to that are antennas that use that grounding as the other half of the antenna (there is always the 'other half' of an antenna, sometimes just not what you expect it to be). If the antenna supporting device is grounded, why run a separate ground line? Which is 'best'? Beats me, try it and see.
- 'Doc

When in doubt, try what the manufacturer says...

 

[delta]

From what you have said is sounds like you cut about a foot off your feed line? First thing that comes to mind is why not just add that foot back? Or, if you did the figuring with 12 feet, add 13 feet instead?

Feed line length reall doesn't make any difference under one condition, the load impedance has to be the same as the feed line's impedance. Which should be the same as the transmitter's impedance, naturally. In those conditions, the only difference the length of the feed line will make is in resistive losses, which you can't do anything about. The only way to reduce resistive losses is by shortening the feed line, and then it probably won't reach, right?
Now for the 'catches'. No transmitter's output impedance is always goign to be exactly 50 ohms. No feed line's characteristic impedance is going to be exactly what's printed on the jacket (why it's called a 'characteristic' impedance). And there are no commonly used resonant antennas which will ever have exactly 50 ohms input impedance. There will always be some small differences (unless you are luckier than is normal). So, actually seeing that 1:1 'ideal' SWR is very unlikely, and why seeing something like a 1.5:1 SWR is considered @#$ good. You with me so far?
So, what do you do? Well, the one thing you have the most control over, which typically will do the least damage if 'adjusted', is the input impedance of that antenna. So adjust the antenna for resonance, then do what's necessary to adjust it's input impedance to 50 ohms, or at least close to it. That's as close to 'ideal', or 'perfect', as you can do. It's not the most 'simple'/'common' way of doing things, but it is the best. There are quite a few ways of doing that, none of them impossible. None of them absolutely dirt cheap/easy/simple, but so what. "Just do it."...

RF chokes.
They typically don't do any harm, even when not necessary. They are frequency/band specific. What works on one band may not work on another. They are not fool proof. They are sort of simple though.

Grounding antennas usually isn't necessary except for 'safety'. The exceptions to that are antennas that use that grounding as the other half of the antenna (there is always the 'other half' of an antenna, sometimes just not what you expect it to be). If the antenna supporting device is grounded, why run a separate ground line? Which is 'best'? Beats me, try it and see.
- 'Doc

When in doubt, try what the manufacturer says...

Hi there Doc.
The first part of your post was about cutting the feedline length and Vswr etc i think that was another guy asking about that subject not me, that is if you was answering that one to me Doc.

The choke info i mostly understand i think, i guessing the choke device provides a means of reducing or eliminating common-mode noise from an antenna feedline, resulting in an increase of the received signal quality. A choke should reduce unwanted feedline radiation or reception without the need for improved station grounding. Yes?

Grounding antennas...

Ok i understand why we should ground for safety reasons, what i don't get is why some say isolate the antenna from the mast. ( is this to stop the tower/mast becoming a part of the antenna and also radiating.) My tower is well grounded to earth but i was going to isolate just the antenna only where its mounted to the mast, and not connect any ground wire either from antenna back to mast, as some say what would the point in that be. So why do some say isolate the antenna from the mast ?

 

[W5LZ]

I thought the whole thing was your question(s). If not, don't worry about it. Still wonder about it though.

A choke has very little to do with a received signal and CMC, why would there be any CMC with a received signal?
A choke can help with CMC, or 'junk' on the outside of a coax feed line regardless of station grounding (or any other kind). You can have the best station grounding and still have CMC.

Why do some people say to insulate the antenna and mast/tower/pole? Because they feel it helps with receiving/transmitting. Does it? Haven't played with it so can't give a personal opinion. I can't see where it would make a huge difference either way. Some maybe, but enough to go to the trouble? Beats me, sort of doubt it, but then, I think it would depend on several other factors too. So your choice. Try insulating the antenna, then shorting it to the mast/tower/whatever and see it it makes a difference to you.
- 'Doc

 

[freecell]

coaxial rf chokes - Google Search

 

[W5LZ]

The basic idea of coax-choke is to introduce inductance/inductive reactance on only the outer shield of a coaxial feed line which will reduce/stop those CMCs. That's a 'given', why the thing will work at all.
From one of the opening statements in the above link, (the first one), the important part is the length of the coax cable, not the number of turns of the coil, or the diameter of that coil. That is just not true. Other wise, just using the straight run of cable would supply the required inductance. Seems to me to be just another version of that feed line length 'myth'. Maybe it's because using SWR as a measuring device is faulty. Not the meter, but the entire concept of SWR telling you much of anything useful.
An inductor's size/shape/dimensions determine how much inductance is produced. Has very little to do with the actual physical length of the conductor used for that inductor.
The amount of inductance required to reduce/stop that CMC on the outer shield of coax varies with frequency. The lower the frequency the greater the amount of inductance required. That frequency range is by band, by the way.
So the author of that first 'hit' in that site list is incorrect in a few of his assumptions. I'm not going to look at all of those listed sites so can't say anything about the rest of them. Just cuz it's published on the internet does not make it right/true.
- 'Doc

 

[Beetle]

Only thing I see is a 1db drop in recieve.

How exactly are you measuring this one dB drop? Please don't tell me you're using your S-meter.

 

[W5LZ]

"Thinking about it, cutting your coax to resonant lengths would seem rather pointless if you used an effective choke balun." ... That's true, but then there is no such thing as a "choke balun", so the point it mute.

It's been my experience that anything with "without a doubt" in it is doubtful.

Got a feeling there's just a touch too much thought going into this. "If ; thens" works great in basic or when dealing with facts. With conjectures, it isn't very good for much, too many possibilities.
- 'Doc

 

[W5LZ]

And the absolute mostest best solution to CMC or any form of RF on the outside of a feed line is my super duper ~Stray RF Remover~! It comes in a handy spray bottle, or the more economical squeeze bottle! Only one application will keep you transmission lines clean for ages! It has a money back gaurantee if I can't tell you what you are dong wrong! Comes in two, that's right, two colors! A 'clear', and for the more discriminating tastes, PINK! Get yours today! Supplies are limited so hurry not to miss this fabulous opportunity!
- 'Doc

 

[delta]

Ha ha that's quite a funny one that Doc:laugh:, i've heard that theres a special cb rx and tx snake oil for those that need it that's just fantastic for increasing your tx signal and gives a much quieter noise floor on rx the thing is it only comes in half pint bottles and you have to return the bottle after you have used it..

I'D buy that for a Dollar!

 

[357]

I give up!

 

[delta]

choke pictures

Some of those chokes look like there quite well made, some look rubbish too. Well I'm going to mount the I-10K and see what happens and then i'll do what needs to be done if anything does.. All this talk about instaling chokes and isolating from the mast seems to have difference of opinions etc, i guess i'll just try one step at a time and adjust things if i need too..

Thanks guys for your time and replies

CBR is a lotta fun when you get it right.