Antenna Matching Advice Needed (Homebrew Mobile Tuner)

Antenna Matching Advice Needed (Homebrew Mobile Tuner)

Post by John Walla » Tue, 15 Jan 2002 23:46:41

In my mobile I am currently running a 102" whip antenna on 10m which works fine.
However, I would like to be able to use it on 12m as well. What I would like to
do is to homebrew a fixed L/C tuner (pre-tuned for the middle of the 12m band)
that I can just switch in when I want to work 12m, and out when I want to work
10m with no knobs to fiddle with. It also needs to handle around 400 watts. I
would like to wind my own inductor etc. for it so I would need the coil
dimensions, value of C, a schematic to see how this would all go together would
also be extremely helpful (this is my first project of this sort).  Any
assistance anyone can offer is greatly appreciated.

73.
JW

 
 
 

Antenna Matching Advice Needed (Homebrew Mobile Tuner)

Post by CAM » Wed, 16 Jan 2002 00:04:30



> In my mobile I am currently running a 102" whip antenna on 10m which works fine.
> However, I would like to be able to use it on 12m as well. What I would like to
> do is to homebrew a fixed L/C tuner (pre-tuned for the middle of the 12m band)
> that I can just switch in when I want to work 12m, and out when I want to work
> 10m with no knobs to fiddle with. It also needs to handle around 400 watts. I
> would like to wind my own inductor etc. for it so I would need the coil
> dimensions, value of C, a schematic to see how this would all go together would
> also be extremely helpful (this is my first project of this sort).  Any
> assistance anyone can offer is greatly appreciated.

This is pretty much a nobrainer assuming you have an antenna analyzer
like the MFJ259. All you need is one series coil (no capacitor) between
the center wire of the coax and the whip feedpoint. Wind the coil and
test with the analyzer. If the resonant frequency is too low, take turns
off the coil and if the resonant frequency is too high, put turns on the
coil. About 4-5 turns on a two inch diameter coil form should do it.
--
cheers, CAM   http://www.qsl.net/w5dxp
 
 
 

Antenna Matching Advice Needed (Homebrew Mobile Tuner)

Post by pete owe » Wed, 16 Jan 2002 02:38:36

Have a look at Arnie Coro's great page. You'll find it at:

http://www.radiohc.org/dxers/

He's got lots of ideas for home brew stuff.

Good Luck,

Pete

 
 
 

Antenna Matching Advice Needed (Homebrew Mobile Tuner)

Post by Reg Edward » Wed, 16 Jan 2002 03:00:51

John,

All you may need is a base loading coil for the 12 meter band which should
give you a good enough match to 50 ohm coax.

Download program BOTLOAD from website below in a few seconds.

Program will tell you coil inductance, number of turns of what wire
diameter, to wind on your choice of size and shape of coil former.

If you want an even better match, download program ENDFEED which will tell
you values of coil and capacitor for an L-match.  Or a T-match.

To design coils for a given inductance download program SOLNOID2.
---
***************************
Regards, Reg G4FGQ
Free Radio Modelling Programs
Http://www.g4fgq.com
***************************

--
***************************
Regards, Reg G4FGQ
Free Radio Modelling Programs
Http://www.g4fgq.com
***************************

Quote:> In my mobile I am currently running a 102" whip antenna on 10m which works
fine.
> However, I would like to be able to use it on 12m as well. What I would
like to
> do is to homebrew a fixed L/C tuner (pre-tuned for the middle of the 12m
band)
> that I can just switch in when I want to work 12m, and out when I want to
work
> 10m with no knobs to fiddle with. It also needs to handle around 400
watts. I
> would like to wind my own inductor etc. for it so I would need the coil
> dimensions, value of C, a schematic to see how this would all go together
would
> also be extremely helpful (this is my first project of this sort).  Any
> assistance anyone can offer is greatly appreciated.

> 73.
> JW

 
 
 

Antenna Matching Advice Needed (Homebrew Mobile Tuner)

Post by Irv Finklema » Wed, 16 Jan 2002 04:20:53


> In my mobile I am currently running a 102" whip antenna on 10m which works fine.
> However, I would like to be able to use it on 12m as well. What I would like to
> do is to homebrew a fixed L/C tuner (pre-tuned for the middle of the 12m band)
> that I can just switch in when I want to work 12m, and out when I want to work
> 10m with no knobs to fiddle with. It also needs to handle around 400 watts. I
> would like to wind my own inductor etc. for it so I would need the coil
> dimensions, value of C, a schematic to see how this would all go together would
> also be extremely helpful (this is my first project of this sort).  Any
> assistance anyone can offer is greatly appreciated.

> 73.
> JW

Jusy clip a 'stinger' -- a couple feet of stiff wire onto
the end of the
hustler whip and trim it down to resonance.
--
Diagnosed Type II Diabetes March 5 2001
Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
--------------------
Visit my website at http://members.home.net/finkirv/
--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada
 
 
 

Antenna Matching Advice Needed (Homebrew Mobile Tuner)

Post by Bob Coo » Wed, 16 Jan 2002 19:30:51

Reg, G4FGQ,

My compliments on your straight forward, multi-faceted, software based
suggestions here.
It helps us all.

Bob K9KKY

www.Ocean-Pro.com
Naples, Florida 34112
941-775-7435, 800-329-4884

 
 
 

Antenna Matching Advice Needed (Homebrew Mobile Tuner)

Post by Dick Carrol » Wed, 16 Jan 2002 23:23:38


> In my mobile I am currently running a 102" whip antenna on 10m which works fine.
> However, I would like to be able to use it on 12m as well. What I would like to
> do is to homebrew a fixed L/C tuner (pre-tuned for the middle of the 12m band)
> that I can just switch in when I want to work 12m, and out when I want to work
> 10m with no knobs to fiddle with. It also needs to handle around 400 watts. I
> would like to wind my own inductor etc. for it so I would need the coil
> dimensions, value of C, a schematic to see how this would all go together would
> also be extremely helpful (this is my first project of this sort).  Any
> assistance anyone can offer is greatly appreciated.

  You complicate the project considerably by your requirement to switch the netork
in and out without leaving the drivers seat (if I understand correctly). For base
station use a homemade trap would serve this purpose well, but would be unwieldy on
a mobile whip.
 You can use a ten meter Pro Am whip and change to a  longer "stinger" for 12
meters. Or use a 12 meter whip and change to a shorter stinger for 10. You can use
some older CB antennas and rewind them to use on the higher HF ham bands. I once did
this for 17 meters and worked all over the world with an Icom 735 running 50 watts
mobile.

Dick

 
 
 

Antenna Matching Advice Needed (Homebrew Mobile Tuner)

Post by Reg Edward » Wed, 16 Jan 2002 21:46:48

Irv, why didn't *I* think of that ?   Sometimes it's so easy to overlook the
glaringly obvious.
---
Reg.

============================

Quote:> Jusy clip a 'stinger' -- a couple feet of stiff wire onto
> the end of the
> hustler whip and trim it down to resonance.

 
 
 

Antenna Matching Advice Needed (Homebrew Mobile Tuner)

Post by carlto » Thu, 17 Jan 2002 10:01:10



> Irv, why didn't *I* think of that ?   Sometimes it's so easy to overlook the
> glaringly obvious.
> ---
> Reg.

> ============================
> > Jusy clip a 'stinger' -- a couple feet of stiff wire onto
> > the end of the
> > hustler whip and trim it down to resonance.

Someone out there is going to laugh at me, but at my age, I don't care.  If you
have a 10mtr whip already, is it not possible to get one of the old
telescoping whips for a CB portable, lash it to the top of the whip and
then extend it when you want to operate at 12mtrs?  I know this sounds
like real "amateur radio", but what the heck, that's the way the hobby
goes. :-)

BTW, for the purest, let's not worry about a return loss of 10 db versus 14 at
the desired freq.  Let's get on the air!  Keep that Poynting vector pointing in
the right direction.  E X H, rah, rah, rah!  :-)

Steve
WB4CZR
Plantation, FL

RF should be fun and not a pain.