IM SURE THE RF CHOKES GETTING ANNOYING

[Stellasstillarat]

If weather holds up today I'm gonna add rf choke.

Problem is. I've read twenty other posts with fifteen different answers about the correct choke amount winding and diamiter.

Please .I need to get it right the first time.

LMR 400. Five turns at 8" diameter, correct?

Thanks p.s. if it matters antennas an a99. Thanks again and again. I'm not trusting all these other postings on the web..

At the same time I'm getting confused by all the golden screwdriver misinformation.

 

[M0GVZ]

At the same time I'm getting confused by all the golden screwdriver misinformation.

Making it from coax, all bets are off without proper equipment to measure. The guide that Steve G3TXQ does and the chart he has on the following link are all done using proper test equipment unlike many suggestions from the internet.

http://www.karinya.net/g3txq/chokes/

On the chart below, where there is a black line under the coloured bar that is where the choking is resistive. Resistive is far better than reactive even if the overall value of choking is lower.

Depending on the power you're using 8 turns of RG58 on a FT240-61 mix core is the best overall for 11m and with a low SWR that would be good for 300-400W.

Without the ferrite core for an air wound 5 turns on a 8.5" diameter is the best.

 

[jdobbs2001]

you can just buy a isolation balun. they are rated to 1.5kw pep.

 

[Heavy Metal]

Ok has rg58 rg213 so rg8x wold follow the rg58 specs and for lmr 400 and 9913 follow the rg213 specs

 

[Heavy Metal]

Making it from coax, all bets are off without proper equipment to measure. The guide that Steve G3TXQ does and the chart he has on the following link are all done using proper test equipment unlike many suggestions from the internet.

http://www.karinya.net/g3txq/chokes/

On the chart below, where there is a black line under the coloured bar that is where the choking is resistive. Resistive is far better than reactive even if the overall value of choking is lower.

Depending on the power you're using 8 turns of RG58 on a FT240-61 mix core is the best overall for 11m and with a low SWR that would be good for 300-400W.

Without the ferrite core for an air wound 5 turns on a 8.5" diameter is the best.

I take it rg8x would be same as rg58 or rg213?
I did this based on 4.25" air coil. And about 18"-21" from SO-239 to coil and did 5 Turns. Does this look right? It's rg8x coax till I get a 36' pole and do up the rg9913f7 coax.

 

[Heavy Metal]

Someone explain this chart a little better, now the more towards the green the better correct, and more toads the red is min or not so good, now each ones shows the spectrum/band width of it so outside the colors theirs nothing hhappening/or helping correct and the ones above with the darker lines for the Rs>Xs I'd for and all, explain this and why. Trying to get a perspective on all this. I would be very thankful on any and all info on this.

 

[Stellasstillarat]

My cable is LMR 400. Truth be told the answer about the amount of turns differed . Im fairly convinced it's five turns at 8" diamater .I'm adding a 5 ' masts to my a99 tomorrow and as of this moment I've decided not to add thechoke. . If I change my mind and go with it I will use five turns at an 8" diamater. Your choke looks a bit far from the feed point. Everyone who answerd my op were all together on one issue. That was the choke should be as close to the feed point as possible. If I change my mind once again and decide to go with the choke I install will be no lower from the feed point than 10". The picture you posted from the information I've gathered for an 11 meter omnidirectional vertical that choke looks way to low.

Making it from coax, all bets are off without proper equipment to measure. The guide that Steve G3TXQ does and the chart he has on the following link are all done using proper test equipment unlike many suggestions from the internet.

http://www.karinya.net/g3txq/chokes/

On the chart below, where there is a black line under the coloured bar that is where the choking is resistive. Resistive is far better than reactive even if the overall value of choking is lower.

Depending on the power you're using 8 turns of RG58 on a FT240-61 mix core is the best overall for 11m and with a low SWR that would be good for 300-400W.

Without the ferrite core for an air wound 5 turns on a 8.5" diameter is the best.

 

[Heavy Metal]

It's @21" away as it starts into the first winding.

 

[Stellasstillarat]

I respect your 21" distance.

I'm not sure if you came up with this exacting distance using a mathematical formula or from information floating around on the web.

Maybe you have the knowledge that led you to this measurement, but I've never read this or any exacting number for the an 11 meter distance between the choke and feed point.

As a matter of fact the concensus seems to be get it ss close as possible.

This is why I've decided not to install one.
Atlest untill I get the information ftom someone I belive, period. Building/installing measurements are all over the plsce, most likly ill do much more research then like most things supposedly set in stone as far as antenna theory and everything else radio communications related it's comes down to who you believe to be the most exspearianced.

It's @21" away as it starts into the first winding.

 

[The DB]

A few things...

Five wraps on an eight inch form for LMR-400 is to many wraps. LMR-400 is very close to the diameter of RG-213, and the RG-213 data from the chart posted above will get you very close. Five turns on an eight inch diameter form will push the use able frequency below the CB band. Look at the 5 turns of RG-213 on a 7 inch form as a starting point, and the larger 8 inch form will lower the effective choking frequencies even further.

When it comes to choke placement, there is one correct location, and that is as close to the feedpoint as you can get it. The further away from the feedpoint the choke is the more common mode currents will flow on the stretch of coax between the feedpoint and the choke. While a foot or two isn't enough to drastically alter anything, if you put the choke far enough away, and common mode currents are present, they can actually affect the tuning of the antenna. That being said, just because you have an antenna up doesn't automagically mean you have to deal with common mode currents. Some antenna designs are naturally better at dealing with them than others.

most likly ill do much more research

Research is always a good thing. I always encourage this line of thinking. Just make sure your sources are reputable. There are several good books on the topic available, I highly suggest starting with those, even if they are more expensive than looking things up on the internet...

then like most things supposedly set in stone as far as antenna theory and everything else radio communications related it's comes down to who you believe to be the most exspearianced.

Be careful about things that are supposedly set in stone when it comes to antenna theory, some things are, but many things that people believe are set in stone really are not. Someone who truly understands antenna theory will easily be able to point these out.

Also, be careful about who you believe. There are those that appear knowledgeable at first glance, but really know far less than they think.

And finally experience, in and of itself, will only get you so far. It is often touted as the end all and be all of antenna knowledge, but without an understanding of theory to frame that experience, it will only get you so far. Look for someone who has both. Such people are much harder to find, but they do exist.


The DB

 

[Stellasstillarat]

I think Marconi (if he were alive today) would've responded to my concerns exactly as you have. Leson learnd and advice well taken .

A few things...

Five wraps on an eight inch form for LMR-400 is to many wraps. LMR-400 is very close to the diameter of RG-213, and the RG-213 data from the chart posted above will get you very close. Five turns on an eight inch diameter form will push the use able frequency below the CB band. Look at the 5 turns of RG-213 on a 7 inch form as a starting point, and the larger 8 inch form will lower the effective choking frequencies even further.

When it comes to choke placement, there is one correct location, and that is as close to the feedpoint as you can get it. The further away from the feedpoint the choke is the more common mode currents will flow on the stretch of coax between the feedpoint and the choke. While a foot or two isn't enough to drastically alter anything, if you put the choke far enough away, and common mode currents are present, they can actually affect the tuning of the antenna. That being said, just because you have an antenna up doesn't automagically mean you have to deal with common mode currents. Some antenna designs are naturally better at dealing with them than others.



Research is always a good thing. I always encourage this line of thinking. Just make sure your sources are reputable. There are several good books on the topic available, I highly suggest starting with those, even if they are more expensive than looking things up on the internet...



Be careful about things that are supposedly set in stone when it comes to antenna theory, some things are, but many things that people believe are set in stone really are not. Someone who truly understands antenna theory will easily be able to point these out.

Also, be careful about who you believe. There are those that appear knowledgeable at first glance, but really know far less than they think.

And finally experience, in and of itself, will only get you so far. It is often touted as the end all and be all of antenna knowledge, but without an understanding of theory to frame that experience, it will only get you so far. Look for someone who has both. Such people are much harder to find, but they do exist.


The DB

 

[Heavy Metal]

My SWRs are pretty cool according to the MFJ-259C 21-30 is 1.7:1 or less and 17m 2.1:1-2.5:1 tunable I take it. E even 20m 2.5:1-3:1. As seen in pic the tuning rings are low not centered and antenna is 270" from above black tuning area.

 

[wavrider]

If you have an I2K install HM that is about identical to my VSWR readings on the mfj 259B I use the I2K 10 through 15 meters, never tried 17 or 20 on it.

Works good for what it is.

My Choke is about 20" below the feed point, no issues with TVI RFI on the computer speakers or any thing else that I know of, No complaints from the neighbors and I have used Full legal limit through that I2K, no issues

 

[Heavy Metal]

Maybe a silly questions on this, but is higher choke better and at what frequencys? And using beads better 31 mix type and using alone or in conjunction with air wound as well?and if both were should beads go under so-239 then air wound? And either or how far down should one place core's under so-239 as well as air coil to start?

 

[M0GVZ]

Someone explain this chart a little better, now the more towards the green the better correct, and more toads the red is min or not so good, now each ones shows the spectrum/band width of it so outside the colors theirs nothing hhappening/or helping correct and the ones above with the darker lines for the Rs>Xs I'd for and all, explain this and why. Trying to get a perspective on all this. I would be very thankful on any and all info on this.

Correct, green is better, dark green is best, yellow is really the minimum you want to be looking at and outside of the red there's nothing happening. Now you'll notice some of them have black lines under parts of the scale. That is where the choking is resistive which is far better than reactive which all of the air wound ones are. If you get reactive chokes wrong it can make matters worse and increase common mode RFI.