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Freebander

Registered: 04-2009
Posts: 197
Karma: -2 (+0/-2)
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Custom mobile antenna for 21m 13.930mhz


Hi lads, after talking to Dave 26FB225 today on a vertical antenna he had in in loft which he was tuning up for 21m. I decided to see if i could make something small for the mobile that would be resonant on 13.930mhz.
I found an old mobile 11m antenna I had kicking around. Its about 3ft long and looks similar to a small firestick type aerial.
I pulled off the end cap and cut the sleeving to expose the wire. Pulled out a 3inch section of wire and removed the coating with some sand paper, so now its bare copper.
I found an old whip section off another old antenna and taped it to the fibreglass piece of the antenna about 3inchs from the end.
Then the wire from the original firestick I twisted round the whip.
Then taped it all up nice and tight and fitted the end cap(not shown in pic)
After a few attempts with the swr and cutting the whip to the right length, hey presto, a resonant antenna for 21m.
Yes I know its very heath robinson, but it was just for something to do, but very interesting as this band is becoming very good for distance work.
Dave 225 was 5 and 9 plus 20db today with an out of band 8ft antenna in his loft and I'm in Spain.
Food for thought...This one is only 62 inch's long
Here are some pics.
VC7 Jon
Image

Image

Last edited by VC7, 7/Mar/2010, 12:14 pm
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Freebander

Registered: 04-2009
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Re: Custom mobile antenna for 21m 13.930mhz


Before anyone says, yes poor photos and yes I could bore out the fibrglass and insert the whip.....Glue it all up and fit the end cap. maybe later...lol
VC7 Jon
4/Mar/2010, 4:26 pm Link to this post Send Email to VC7   Send PM to VC7
 
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Freebander

Registered: 02-2010
Posts: 66
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Re: Custom mobile antenna for 21m 13.930mhz


A loaded whip resonant on 21 should work even better than my 11 meter whip through the tuner. If I get a chance this weekend I'll knock one up here. It will be interesting to do some comparison tests Jon. I,ll even string up a dipole cut exactly for 21 to see how vertical works against horizontal etc. Should be fun {radio is always fun anyway ). Good post Jon.
4/Mar/2010, 6:56 pm Link to this post Send Email to 163fb225   Send PM to 163fb225
 
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Freebander

Registered: 04-2009
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Re: Custom mobile antenna for 21m 13.930mhz


Well lads it looks like the mobile antenna works.
I was speaking to 29FB018 from my qth in Spain,,,,,5 and 5 5 and 6.
Might take it down and drill out and glue the whip in and pretty it up a bit.

VC7 Jon
5/Mar/2010, 9:57 am Link to this post Send Email to VC7   Send PM to VC7
 
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Freebander

Registered: 04-2009
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Re: Custom mobile antenna for 21m 13.930mhz


Right......I felt that I had let myself down a bit by showing you the heath Robinson way I had made the antenna.
So I decided to tidy it up and make a better job of it..

1. I drilled out the end section of the fibre glass as shown.
2. Cut a grove for the wire to lie in and tucked the wire in the drilled section.
3.Glued in place the double female with the stub section inside the fibre glass.
4. Fitted the whip and taped it all up.

Not the greatest job but never the less an swr of 1.2 on 13.930 and only 62 inches long.

Image
Image
Image
Image

VC7 Jon
5/Mar/2010, 1:53 pm Link to this post Send Email to VC7   Send PM to VC7
 
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Freebander

Registered: 02-2010
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Re: Custom mobile antenna for 21m 13.930mhz


Not quite so Heath Robinson now Jon. Have you tested it out yet ?
5/Mar/2010, 2:14 pm Link to this post Send Email to 163fb225   Send PM to 163fb225
 
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Freebander

Registered: 04-2009
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Re: Custom mobile antenna for 21m 13.930mhz


yes Dave, had contacts with Ireland and England.
Seems to work fine and has a good bandwidth.
Had about half an hour listening on 20m and it receives great.
VC7 Jon
5/Mar/2010, 3:01 pm Link to this post Send Email to VC7   Send PM to VC7
 
madmark1 Profile
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Accomplished DX-er

Registered: 10-2009
Location: Abertillery
Posts: 454
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Re: Custom mobile antenna for 21m 13.930mhz


here is my similair antenna made it a while back, it started life as a 5ft firestick, rewound the coil and added a brass top peice from a cherokee cb antenna and used a whip from a sirio hi-power.

overall its 10-1/2 feet long, so its not possible to drive with it, but it shure works well on 20 mtrs and if the whip is changed it will work on 17 mtrs and 15 mtrs using shorter lenghts of whip.

http://i925.photobucket.com/albums/ad100/madmark42/5ftfiresticka.jpg

http://i925.photobucket.com/albums/ad100/madmark42/5ftfirestick.jpg

http://i925.photobucket.com/albums/ad100/madmark42/5ftfirestickb.jpg


should work now.

mark 163fb20

Last edited by madmark1, 9/Mar/2010, 10:50 pm


---
http://www.youtube.com/MrMadjones

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5/Mar/2010, 6:37 pm Link to this post Send Email to madmark1   Send PM to madmark1 Blog
 
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Freebander

Registered: 02-2010
Posts: 66
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Re: Custom mobile antenna for 21m 13.930mhz


Can't get those links to work Mark, even copy & paste wont work.
5/Mar/2010, 7:15 pm Link to this post Send Email to 163fb225   Send PM to 163fb225
 
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Freebander

Registered: 02-2010
Posts: 66
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Re: Custom mobile antenna for 21m 13.930mhz


Jon. I did a quick lash-up today on a simple attic ground plane cut for 13970. It's 17 feet of thin telephone wire ( the stuff inside phone extension cables } helically wound on a 40mm upvc waste pipe six feet long. I'm running just one 17 foot ground plane wire off it at the moment. I have not trimmed it yet for 13970 but the analyser shows resonance around 14.8 mhz so for now I'll leave it at that as the tuner trims it nicely to the 21 meter band. 20 meter ham band stateside signals are coming in at 20 over on it tonight so it's got to work ok on 21. If you,re around tomorrow (saturday ) we can give both antennas a whirl, if conditions permit. If all goes well I'll run extra ground planes off the lower end which should improve things further

Last edited by 163fb225, 5/Mar/2010, 8:44 pm
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