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nuckolls.bob(at)aeroelect
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 Posted: Wed Dec 02, 2009 10:10 am Post subject: DIY VHF Comm antenna |
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See:
http://aeroelectric.com/Pictures/Antenna/DIY_Comm_Antenna.jpg
Here's a starting point for any readers who would
like to experiment with their own DIY comm antennas:
This design starts with a CB radio antenna mounting
stud:
http://tinyurl.com/yzygjbq
The design goal is to add a steel (preferably
stainless) antenna rod to the antenna side of
the mounting stud, prevent rotation of assembly in
the mounting hole, and (optionally) add an adapter
that is friendly to the commonly used BNC feedline
connectors.
In the example illustrated, I silver soldered a
piece of 3/16 stainless rod in a hole drilled into
a steel hex head 3/8-24 x 1/2" bolt. 10% of thread
area on the bolt are "buggered" up to provide an "upset-
metal" connection between the bolt and female threads
in the mounting stud. Avoid damage to first three threads
so that the bolt will start easily.
Put upper coupler of antenna stud in vise. Coat threads of
antenna rod with a thread-locker . . . or just E-6000
adhesive. This is more for moisture sealing than anything
else. Thread the antenna into the coupler. It will go in with some
resistance due to "damaged" threads . . . but the goal
is to achieve some level of gas-tightness between the
bolt and the coupler.
Fabricate a piece of .060 or so brass tab and soft-solder
with 63/37 alloy. You'll have to clean the plating off
the interface surface of the lower half of the coupler
to get a good sweat. Avoid excessive heat that will damage
the stud's plastic insulator.
Add UHF to BNC adapter as shown or plan on using a
UHF male connector at the end of your feedline.
Cut the overall length of the antenna to 22" (tip
to mounting surface). Round tip on grinder to avoid
sharp edges at the end. If you like, put a 45 degree
or so "rakish" bend in the antenna rod beginning about
6" off the mounting surface.
Mount to airplane in a robust skin doubler riveted
to the skin and picking up some structure if possible.
Brighten the surfaces that come together. Use #8 hardware
to ground the anti-rotation tab. Truss head screws are
suggested.
This is about #3 in a series of designs I've considered
writing up in the 'Connection. It has evolved to the
stage that it would be good for some of you folks to take
a whack at building it. Let me know what problems you
encounter with fabrication, installation or service.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
[quote][b]
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echristley(at)nc.rr.com
Guest
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| Posted: Wed Dec 02, 2009 11:30 am Post subject: DIY VHF Comm antenna |
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Robert L. Nuckolls, III wrote:
| Quote: | See:
http://aeroelectric.com/Pictures/Antenna/DIY_Comm_Antenna.jpg
Here's a starting point for any readers who would
like to experiment with their own DIY comm antennas:
This design starts with a CB radio antenna mounting
stud:
* http://tinyurl.com/yzygjbq*
The design goal is to add a steel (preferably
stainless) antenna rod to the antenna side of
the mounting stud, prevent rotation of assembly in
the mounting hole, and (optionally) add an adapter
that is friendly to the commonly used BNC feedline
connectors.
In the example illustrated, I silver soldered a
piece of 3/16 stainless rod in a hole drilled into
a steel hex head 3/8-24 x 1/2" bolt.
That's a might steep stress riser, going from a whippy piece of
|
stainless into a bolt. How about slipping a few inches of shrink wrap
over the base, so that it comes up the whip a bit, and pack it full of
E6000? Just a few seconds with a butane flame to give the heat shrink
filled tube a taper toward the tip, allowing excess E6000 to be squeezed
out. Now you have a strain relief, and another layer of sealing.
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sportav8r(at)gmail.com
Guest
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| Posted: Wed Dec 02, 2009 12:46 pm Post subject: DIY VHF Comm antenna |
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Or have this guy make you what you need - it will probably outlast your airframe.
http://bellsouthpwp.net/b/r/breedlove1/
Bill N4DLN
Not a customer of his (yet) but he has good reviews on the HF mobile groups
On Wed, Dec 2, 2009 at 1:05 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote] See:
http://aeroelectric.com/Pictures/Antenna/DIY_Comm_Antenna.jpg
Here's a starting point for any readers who would
like to experiment with their own DIY comm antennas:
This design starts with a CB radio antenna mounting
stud:
http://tinyurl.com/yzygjbq
The design goal is to add a steel (preferably
stainless) antenna rod to the antenna side of
the mounting stud, prevent rotation of assembly in
the mounting hole, and (optionally) add an adapter
that is friendly to the commonly used BNC feedline
connectors.
In the example illustrated, I silver soldered a
piece of 3/16 stainless rod in a hole drilled into
a steel hex head 3/8-24 x 1/2" bolt. 10% of thread
area on the bolt are "buggered" up to provide an "upset-
metal" connection between the bolt and female threads
in the mounting stud. Avoid damage to first three threads
so that the bolt will start easily.
Put upper coupler of antenna stud in vise. Coat threads of
antenna rod with a thread-locker . . . or just E-6000
adhesive. This is more for moisture sealing than anything
else. Thread the antenna into the coupler. It will go in with some
resistance due to "damaged" threads . . . but the goal
is to achieve some level of gas-tightness between the
bolt and the coupler.
Fabricate a piece of .060 or so brass tab and soft-solder
with 63/37 alloy. You'll have to clean the plating off
the interface surface of the lower half of the coupler
to get a good sweat. Avoid excessive heat that will damage
the stud's plastic insulator.
Add UHF to BNC adapter as shown or plan on using a
UHF male connector at the end of your feedline.
Cut the overall length of the antenna to 22" (tip
to mounting surface). Round tip on grinder to avoid
sharp edges at the end. If you like, put a 45 degree
or so "rakish" bend in the antenna rod beginning about
6" off the mounting surface.
Mount to airplane in a robust skin doubler riveted
to the skin and picking up some structure if possible.
Brighten the surfaces that come together. Use #8 hardware
to ground the anti-rotation tab. Truss head screws are
suggested.
This is about #3 in a series of designs I've considered
writing up in the 'Connection. It has evolved to the
stage that it would be good for some of you folks to take
a whack at building it. Let me know what problems you
encounter with fabrication, installation or service.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
| Quote: |
_blank">www.aeroelectric.com
.com" target="_blank">www.buildersbooks.com
="_blank">www.homebuilthelp.com
_blank">http://www.matronics.com/contribution
ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
tp://forums.matronics.com
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[b]
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mprather(at)spro.net
Guest
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| Posted: Wed Dec 02, 2009 1:10 pm Post subject: DIY VHF Comm antenna |
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| Quote: |
<echristley(at)nc.rr.com>
Robert L. Nuckolls, III wrote:
> See:
>
> http://aeroelectric.com/Pictures/Antenna/DIY_Comm_Antenna.jpg
>
> Here's a starting point for any readers who would
> like to experiment with their own DIY comm antennas:
>
> This design starts with a CB radio antenna mounting
> stud:
>
> * http://tinyurl.com/yzygjbq*
>
> The design goal is to add a steel (preferably
> stainless) antenna rod to the antenna side of
> the mounting stud, prevent rotation of assembly in
> the mounting hole, and (optionally) add an adapter
> that is friendly to the commonly used BNC feedline
> connectors.
>
> In the example illustrated, I silver soldered a
> piece of 3/16 stainless rod in a hole drilled into
> a steel hex head 3/8-24 x 1/2" bolt.
That's a might steep stress riser, going from a whippy piece of
stainless into a bolt. How about slipping a few inches of shrink wrap
over the base, so that it comes up the whip a bit, and pack it full of
E6000? Just a few seconds with a butane flame to give the heat shrink
filled tube a taper toward the tip, allowing excess E6000 to be squeezed
out. Now you have a strain relief, and another layer of sealing.
|
This is probably a good idea. However, several years ago I built a 5/8
wave whip for a 2m mobile rig - for my car. I started with a CB whip and
used a hardware store bolt (5/16" dia, maybe 10" long) to extend the
length enough to tune it (on top of a coil wrapped around a teflon core).
The total length was something like 48". I whacked a lot of tree branches
and several parking garages with it and it never failed. One of the
parking garages hooked it while I was pulling into a parking spot.. I
didn't think much of it until backing out of the spot it made an
abnormally loud "sproing!" sound. Somehow it had put about a 20deg bend
about 8" from the end of the whip - it still functioned fine, routinely
allowing me to talk with stations 60mi away. I still have the antenna -
very low SWR..
Anecdotal, obviously.. But I think the loads are well within the strength
of the stainless wire commonly used for antenna whips.
Matt-
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pmather
Joined: 17 Sep 2009
Posts: 33
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| Posted: Thu Dec 03, 2009 1:07 am Post subject: DIY VHF Comm antenna |
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Bob
Why not use a whip adapter like http://tinyurl.com/ydstkmb to mount the antenna to the mounting stud?
Best regards
Peter
---
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Thu Dec 03, 2009 6:19 am Post subject: DIY VHF Comm antenna |
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At 03:04 AM 12/3/2009, you wrote:
That could work. Keep in mind that one design goal for
antennas is to drive the metallic joins to as close
to zero-ohms as possible . . . particularly at the
high current segments of the antenna (at the bottom).
Further, one is interested in mechanical robustness.
A set-screw doesn't offer much security for retaining
the antenna rod in the adapter. Of course, you could
silver-solder the rod into the adapter basically turning
it into a fancy bolt. It's a option to consider while
seeking the elegant solution. Thanks for the heads-up!
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
[quote][b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Thu Dec 03, 2009 6:20 am Post subject: DIY VHF Comm antenna |
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At 02:41 PM 12/2/2009, you wrote:
| Quote: | Or have this guy make you what you need - it will probably outlast your airframe.
http://bellsouthpwp.net/b/r/breedlove1/
Bill N4DLN
Not a customer of his (yet) but he has good reviews on the HF mobile groups
|
Hmmm . . . nice find. I might write to him with some
design goals and see what he suggests. Looks like
a talented and capable fellow . . .
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
[quote][b]
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