Today's Message Index:
----------------------
1. 09:26 AM - Antenna bracket material (Jared Yates)
2. 05:08 PM - Re: Antenna bracket material (Robert L. Nuckolls, III)
3. 05:10 PM - Re: Antenna bracket material P.S. (Robert L. Nuckolls, III)
Message 1
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| Subject: | Antenna bracket material |
I have made a glide slope antenna by stripping back the shield on a piece of coax
and doubling it back, as described by Bob and others. The end result is very
clean, but now I'm not sure what to do with it. One good place to mount it is
on the top of the wind screen, where there is some steel structure that will
run parallel to the antenna. How far should I try to get the antenna from that
structure? I have thought about making a bracket to hold it out there, but
I don't have any non-conductive material handy. Would something like a carbon
fiber mat have any meaningful RF implications?
Message 2
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| Subject: | Re: Antenna bracket material |
At 11:19 AM 5/30/2013, you wrote:
>
>I have made a glide slope antenna by stripping back the shield on a
>piece of coax and doubling it back, as described by Bob and others.
>The end result is very clean, but now I'm not sure what to do with
>it. One good place to mount it is on the top of the wind screen,
>where there is some steel structure that will run parallel to the
>antenna. How far should I try to get the antenna from that
>structure? I have thought about making a bracket to hold it out
>there, but I don't have any non-conductive material handy. Would
>something like a carbon fiber mat have any meaningful RF implications?
What kind of airplane are we talking about?
Cessna single-engine plant used to mount their
GS antenna about 2" down from the top of the
windscreen frame on centerline. Obviously,
WAAYyyyy too close to avoid significant
de-optimization of pattern and swr performance.
Signal strength for an ILS system is big.
I've seen the flags raise on the ILS system
10-15 miles out. Given that most final approach
fixes are 5nm out, it seems likely that one can
suffer severe antenna shortcomings without affecting
usefulness of the system.
Have you considered a 9' whisker on the belly?
Yeah, it's polarized wrong but I think it would
work fine.
It's a simple experiment. Install the antenna
and go do some vmc approaches. See how far out
that you can raise the GS flag and get a steady
needle. It's a whole lot easier to install and
doesn't clutter up the windshield.
Bob . . .
Message 3
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| Subject: | Re: Antenna bracket material P.S. |
At 11:19 AM 5/30/2013, you wrote:
>
>I have made a glide slope antenna by stripping back the shield on a
>piece of coax and doubling it back, as described by Bob and others.
>The end result is very clean, but now I'm not sure what to do with
>it. One good place to mount it is on the top of the wind screen,
>where there is some steel structure that will run parallel to the
>antenna. How far should I try to get the antenna from that
>structure? I have thought about making a bracket to hold it out
>there, but I don't have any non-conductive material handy. Would
>something like a carbon fiber mat have any meaningful RF implications?
What kind of airplane are we talking about?
Cessna single-engine plant used to mount their
GS antenna about 2" down from the top of the
windscreen frame on centerline. Obviously,
WAAYyyyy too close to avoid significant
de-optimization of pattern and swr performance.
Signal strength for an ILS system is big.
I've seen the flags raise on the ILS system
10-15 miles out. Given that most final approach
fixes are 5nm out, it seems likely that one can
suffer severe antenna shortcomings without affecting
usefulness of the system.
Have you considered a 9' whisker on the belly?
Yeah, it's polarized wrong but I think it would
work fine.
It's a simple experiment. Install the antenna
and go do some vmc approaches. See how far out
that you can raise the GS flag and get a steady
needle. It's a whole lot easier to install and
doesn't clutter up the windshield.
P.S. if you really want to put the dipole at
the top of your windscreen, you can cut a 'former'
out of polyethylene cutting board material. If
you can find some 3/8" pvc pipe, you might snake
the coax dipole into the pipe through a center
hole.
Bob . . .
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