| Author |
Message |
    
Philuk
New member
Username: Philuk
Post Number: 5
Registered: 4-2009
| | Posted on Friday, February 12, 2010 - 4:48 pm: | 
|
Trying to build a 0.64 wave shunt end fed wire to stick up my ultra lightweight telescopic FG pole for portable hill topping (11mts) using the imax 2000 design with no luck, looking at the breakdown by tech 833 I want to know if it would be possible to replace the inner shunt feed coil with a balun and the outer tuning coil/capacitive brass tube with a large plate capacitor or similar for the tuning to the half wave version
GOOGLE:
(The End Fed Half Wave Antenna)
Anybody know if this is possible (drawings would realy help if yes)
regards
Phil. |
Philuk
New member
Username: Philuk
Post Number: 6
Registered: 4-2009
| | Posted on Saturday, February 13, 2010 - 6:05 am: |
|
Sorry should have read "similar to the half wave version"
Phil. |
Tech833
Intermediate Member
Username: Tech833
Post Number: 140
Registered: 12-2001
| | Posted on Saturday, February 13, 2010 - 3:56 pm: |
|
Hi Phil.
Honestly, unless you are also planning on installing some type of ground radials, the end fed half wave will outperform your .64 wave wire on a fiberglass pole. Unless you get that .64 way, way up high.
To answer your specific question, you could certainly substitute a small tuning cap for the fixed cap in the Imax (and A99) matching networks. If you read the articles, you will find the schematics I drew for each antenna. The number of turns in each coil is accurately reflected in the schematics. That will get you pretty close.
It would be a lot easier to do a shunt fed half wave. You could also gamma feed it, if that is easier for you.
If all else fails, you can purchase w wire 1/2 wave already built and tuned. Do a google search for Par Electronics End Fedz antenna. Problem solved!
Your radio 'Mythbuster' since 1998
|
Tech237
Moderator
Username: Tech237
Post Number: 1298
Registered: 4-2004
| | Posted on Saturday, February 13, 2010 - 12:56 pm: |
|
Why not try an 11m J-Pole?? That I have information on - lol.
To my knowledge, and I'll admit I have not tried what you describe, I believe you need the coil for impedence matching. To use a balun I think you'd need one that is of an unusual ratio, but maybe Tech833 can elaborate on that.
Tech237
N7AUS
Chipmonks roasting on an open fire
Hot sauce dripping from their toes.
|
Philuk
New member
Username: Philuk
Post Number: 7
Registered: 4-2009
| | Posted on Sunday, February 14, 2010 - 7:16 am: |
|
Cheers Techs 833/237 the telescopic pole I have is very long, its a telecoms cable shaker and measuring pole to check the heights of cable dips over the UK main roads so I would be able to add some counterpoise/gp wires and use them as guides/supports, I have the plans and directions for the half wave version with a small wound 10:1 balun and tuning cap. and no counterpoise is required, but I was looking for max. gain as up on the hills I will be working qrp when there is no road access, I did think the .64 wave end shunt fed would be possible after looking at 1/2 wave drawings compared to the Imax 2000 drawing by Tech833 but as said by Tech237 I think the feed matching balun is going to be a strange ratio, I was hopeing (praying) somebody had already disected the Imax drawing and worked out the way to replicate it junkbox/ugly style with balun and variable cap wire coupler.
Oh well looks like its the half wave version with plans by Steve Yates(AA5TB)for the time being.
J-pole lol no thanks Ive got a commtel 444 sitting in bits, 1/2 wave over 1/4 wave monster which needs a crane to lift it.
Cheers lads if you do come up with anything you think may help on the subject please post it up as I will keep trying for that little bit more gain on an end fed wire. |
|
