A99 VS. I MAX CHOICE AT IMPROPER HIGHT

[wavrider]

Good on ya Stella, do not give up, look at it as an opportunity to learn.

I am fond of telling other op's I assist that NO I do not know all about anything, but I sure have made about all the mistakes there are to make.

Going to the choke. I believe it is 5 1/4 or 5 1/2 turns on a 4 inch diameter. for 27 mhz,
Anything close will do per say ( let the bashing begin).

SO let's play with the choke while you have your antenna down.

Say mount the I2K on a 10 foot pole make it easy for you to raise and lower. Need at least a 9 foot pole for counter poise, I2K uses your coax as the other half of the antenna. By adding the choke at the feed point you take your coax out of the antenna counterpoise thus your antenna mast/pole becomes the other half per say.

All the above changes if you have ground radials on the I2K, so will the bandwidth.

Take your readings on ch1,ch20 ch40 write them down.

THEN insert your choke close to the feed point, DO NOT CHANGE tuning rings.

Once again take your readings on CH1 CH20 and CH40.

Compare the readings and see if there is any VSWR difference.

 

[Heavy Metal]

My setup for now rg8x, 5 turn's 4.25", approx 21" below SO-239/PL-259 connection.

 

[Heavy Metal]

My Hexbeam covers 14, 18, 21, 24, 28 and 50MHz. What length do I choose? When I ran my 75ft long inverted L I ran that with a SGC230 antenna coupler on 1.6, 3.5, 5, 7, 10, 14, 18, 21, 24 and 28MHz. What length do I choose for that?

Shortest length between transmitter and antenna and between all accessories (rig to SWR meter etc) is the only correct answer for both and its the same for CB. If the length of coax is critical to getting a good SWR then that has to be because the coax is forming part of the antenna which we do not want. And unless the antenna is a design that is meant to do that then the only reason it is is because the antenna system hasn't been installed properly, usually down to a piss poor RF ground and lack of choking.

Cool, so basically can run 1 foot 2 foot 3 4 5 6 9 12 foot jumpers length between equupmemt doesnt matter? For ANY and all be it imax 2000 a99 or a multi band wire. And be it 50 feet to 200 feet from antenna to inside what ever meets ones needs correct.

 

[wavrider]

HM any length jumpers within reason

 

[Heavy Metal]

I use 9 foot

 

[Heavy Metal]

Does velocity play a factor in it and can you mix and match? Say 9913f7 and lmr400 if?

 

[222DBFL]

Yes you can mix and match 50 ohm coax. Dont over concern yourself with the length. As long as the run isn't too long, like 200ft, LMR400 should be fine to 100-150ft, anymore than that and I would step it up to LDF4-50A or larger depending on the length of the run. For short runs again, use whatever reaches from point A to point B should work fine unless you have other issues.

 

[Stellasstillarat]

Wavrider. I really want to thank you. I'm a pessimist.
You'd be surprised how an optimist or an optimistic comment can inspire.
When I said I was gonna pack everything away I wasn't kidding. And it would've been ashame because I really enjoy the hobby and use my radio way more then I imagined I would've when I first installed it.
The fact that there are total stranger's who are connected only by a common interest (ours being radio communications) that will say what In my case was what I need to hear to give me the push that was needed..

With patients and some reading/research eventually l will find and correct the problem. After much thought I'm accually glad this happened because I truly belive after the problem is found and rectified my antenna/station will perform better than it did from day one.
I now have a better understanding of antennas, coax and how this is by far the single most important part and investment of any station.
I'm convinced this is going to be the best lesson one with no knowlage (myself) will come through not only with a better understanding but an understanding period.

Thank to everyone who's helped. And might I say your use of that tree as an antenna support was an excelent idea. It also looks like a very clean install that without having to ask i know does a great job for you. [Q☝UOTE="wavrider, post: 526208, member: 9893"]Good on ya Stella, do not give up, look at it as an opportunity to learn.

I am fond of telling other op's I assist that NO I do not know all about anything, but I sure have made about all the mistakes there are to make.

Going to the choke. I believe it is 5 1/4 or 5 1/2 turns on a 4 inch diameter. for 27 mhz,
Anything close will do per say ( let the bashing begin).

SO let's play with the choke while you have your antenna down.

Say mount the I2K on a 10 foot pole make it easy for you to raise and lower. Need at least a 9 foot pole for counter poise, I2K uses your coax as the other half of the antenna. By adding the choke at the feed point you take your coax out of the antenna counterpoise thus your antenna mast/pole becomes the other half per say.

All the above changes if you have ground radials on the I2K, so will the bandwidth.

Take your readings on ch1,ch20 ch40 write them down.

THEN insert your choke close to the feed point, DO NOT CHANGE tuning rings.

Once again take your readings on CH1 CH20 and CH40.

Compare the readings and see if there is any VSWR difference.[/QUOTE]

 

[M0GVZ]

Cool, so basically can run 1 foot 2 foot 3 4 5 6 9 12 foot jumpers length between equupmemt doesnt matter? For ANY and all be it imax 2000 a99 or a multi band wire. And be it 50 feet to 200 feet from antenna to inside what ever meets ones needs correct.

Correct. How I measure my jumper cables is I have the gear where it is going to sit, get my coax, drag out enough to go from one to the other, add a bit to give a bit of slack and to account for cocking up putting a plug on and make them up. The one for my Hexbeam to the shack was done by soldering a plug on one end of a drum of Ultraflex 10, attaching it to the RF choke below the rotator, sending the mast up to its max height, rolling the cable out until it got to the point where it was going to go through the wall into the shack and cutting another half dozen or so feet off the drum to feed through the wall. Didn't use a tape measure at all, couldn't tell you how long it is other than a rough estimation.

 

[M0GVZ]

[QUOTE="Stellasstillarat, post: 526277, member: 42401"
Going to the choke. I believe it is 5 1/4 or 5 1/2 turns on a 4 inch diameter. for 27 mhz,
Anything close will do per say ( let the bashing begin).
[/QUOTE]

Because of how narrow the bandwidth is on an air wound choke it needs to be spot on. Going from 5 turns of RG213 on a 4.25 inch core to 7 turns will move where it works from 26-28MHz down to 17-18MHz. Two turns and you have an almost 10MHz drop in the frequency it works on so half a turn can see you move the peak choking to above or below the 11m band quite easily.

Using ferrite rings and coax to make the choke, the peak choking bandwidth is 15-20MHz wide so getting it wrong by half a turn or so is not as critical as with an air wound.

 

[Heavy Metal]

I had rg8x so I followed the rg58 5T Rg58 on 4.25 air coil, do far not single bit if interference on anything. Did not adjust tuning rings where they came at is were their at.at.a only up 2 top fence rails high. Could say palm tree high lol

 

[Heavy Metal]

[QUOTE="Stellasstillarat, post: 526277, member: 42401"
Going to the choke. I believe it is 5 1/4 or 5 1/2 turns on a 4 inch diameter. for 27 mhz,
Anything close will do per say ( let the bashing begin).

Because of how narrow the bandwidth is on an air wound choke it needs to be spot on. Going from 5 turns of RG213 on a 4.25 inch core to 7 turns will move where it works from 26-28MHz down to 17-18MHz. Two turns and you have an almost 10MHz drop in the frequency it works on so half a turn can see you move the peak choking to above or below the 11m band quite easily.

Using ferrite rings and coax to make the choke, the peak choking bandwidth is 15-20MHz wide so getting it wrong by half a turn or so is not as critical as with an air wound.[/QUOTE]


OK let's go futher and do as I did 5T 4.25" and add 5 10 15 or 20 beads of 31mix from palmar or 18 to 24 inches of beads into the 5T's. Now what? Do I get BOTH narrow window 25Mhz to 30Mhz via 5T''s and adding beads oq what happen's? Just curious?

 

[Stellasstillarat]

I've yet to begin putting up my antenna which i decided to take dow as I'm convinced in order to discover the problems I was having with my swr,dropped output on higher frequencys and other issues that I won't get into until I start over and ask and hope to receive suggestions on how to rectify them.

One problem handled at a time. The only problem I didn't. have was bothering nabour's with rfi. This is why I not only decided to save the I max 2000 i purvhrsed to replace the a99 buy will save it for a backup

I took down my a99 and purchesed a new one ss I began tuning the rings and everything got so out of control that i became overwhelming trying to correct it.

But this is about the choke. And if one uses the search of this site to check out the information on chokes (ugly Balun). Most responses are it's not rocket science but with many writing that it must be constructed to such exacting mesurments that until I myself can understand how to construct and install it will not be a concideration for my antenna unless it's absolutely needed.

And if I'm correct in most cases its not a necessity but an item that will improve aspects of one antenna and how it stops or lessons rf from returning to it source (transmitter) snf in some cases it doesn't wotk and others it will.

My op about the choke has yielded as many different ways to make one then as the ssme amount of people who answered the op. Who's correct? Who's somewhat accurate and who's totally wrong?

I don't know as there's no one definitive directions. Almost everyone has different amount of turns. Different diamiters for different types of 11 (50 onm) meter coax.

Until my research convinces me that by putting all the information together and can trust myself that I'm doing it the correctly , I will leave this out of the equation and take care of the important aspects of my antenna install and doing what I need to do in order to get my swr/ref power at an acceptable or brtter than exceptable level, the chokes on the back burner.

I hope my new (starting all over fron A-Z) will go well enough that an rf choke won't be needed.

I'm not even going to ask how to construct a choke as you can read all the different answers to a single question for yourself. What some exsplan as not rocket science others certainly seem to br turning it into a job for a physicist or atleast a mathamatic's professor. Check out K3DAV's page i linked it below. His exspanation how to make one differs from as many as the one differ in the ones listed in this thread. And I've read op's that used Dave's instructions with excellent results. Thanks to everyone.

Because of how narrow the bandwidth is on an air wound choke it needs to be spot on. Going from 5 turns of RG213 on a 4.25 inch core to 7 turns will move where it works from 26-28MHz down to 17-18MHz. Two turns and you have an almost 10MHz drop in the frequency it works on so half a turn can see you move the peak choking to above or below the 11m band quite easily.

Using ferrite rings and coax to make the choke, the peak choking bandwidth is 15-20MHz wide so getting it wrong by half a turn or so is not as critical as with an air wound.

OK let's go futher and do as I did 5T 4.25" and add 5 10 15 or 20 beads of 31mix from palmar or 18 to 24 inches of beads into the 5T's. Now what? Do I get BOTH narrow window 25Mhz to 30Mhz via 5T''s and adding beads oq what happen's? Just curious?

 

[M0GVZ]

But this is about the choke. And if one uses the search of this site to check out the information on chokes (ugly Balun). Most responses are it's not rocket science but with many writing that it must be constructed to such exacting mesurments that until I myself can understand how to construct and install it will not be a concideration for my antenna unless it's absolutely needed.

Read the full page.

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

Steve G3TXQ has done a lot of experimentation into baluns, ununs and common mode RF. The chart I posted is one he did using proper measurement techniques and equipment. As far as I know he's the only one who has published such data.

And if I'm correct in most cases its not a necessity but an item that will improve aspects of one antenna and how it stops or lessons rf from returning to it source (transmitter) snf in some cases it doesn't wotk and others it will.

It is a necessity. Whenever you're using an unbalanced feeder, aka coax, you need one to prevent the coax becoming part of the antenna even when you're using a perfectly balanced dipole antenna.
The problem with it is that in many cases there will be no noticeable difference to the end user so they think that its doing nothing because noise on RX and RFI is the only measurement they use and that was the same after they installed a RF choke as before they did. They don't ever measure common mode on the coax and, in the case of balanced antennas like yagis and dipoles, the radiation pattern as it is altered by not having a RF choke and the coax becoming part of the antenna.

Without a RF choke throw 100W into your antenna, get a small flourescent tube and place it near the coax at various points and you'll see it light to various degrees with no other source of power. That is proof of the existence of common mode. Fit your RF choke at the feedpoint and repeat the experiment. Depending on the effectiveness of the choking and assuming its been built properly you'll see either the tube not lighting at all or lighting far dimmer thus proving the choking is working.

If it helps, think of using a RF choke as "best practice". Do it for the same reasons you don't just take your coax, strip back the insulation and just shove the wire into the antenna socket, holding it in place with matches and insulation tape and instead solder a PL259 on the end even though the other way works.

 

[M0GVZ]

OK let's go futher and do as I did 5T 4.25" and add 5 10 15 or 20 beads of 31mix from palmar or 18 to 24 inches of beads into the 5T's. Now what? Do I get BOTH narrow window 25Mhz to 30Mhz via 5T''s and adding beads oq what happen's? Just curious?

You do not want to add the beads into the 5 turns, it'll skew how it works, basically what frequency its tuned for, because it is an LC circuit. By adding beads you're altering the overall inductance and it'll affect the capacitance because you're also altering the spacing between the turns so therefore the capacitance between turns.

Think of a RF choke being similar to a tuned trap LC circuit for a multiband single element antenna. Alter either the capacitance or the inductance and you shift the frequency it works at because the frequency it works at is dictated by the formula

1/ 2pi√LC


What would be better is adding them to the feedline prior or after the air wound choke because they have no effect on the LC circuit. So assuming its correct as per the chart when you measure it, the choking of the two is combined so if you've 2k from the air wound choke at a certain frequency and a total of 1k from the beads ( the spec sheet should have a chart for impedance at specific frequencies for numbers of turns), you've a total of 3k at that frequency.