Today's Message Index:
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1. 05:58 AM - Re: Antenna Ground Plane ()
2. 09:00 AM - Re: Antenna Ground Plane (Robert L. Nuckolls, III)
3. 09:01 AM - Re: Antenna Ground Plane (Robert L. Nuckolls, III)
4. 10:04 AM - Re: Antenna Ground Plane (Robert L. Nuckolls, III)
5. 01:31 PM - Re: AeroElectric-List Digest: 1 Msgs - 05/28/19 (Scott A Klemptner)
Message 1
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| Subject: | Antenna Ground Plane |
Think I just figured it out, it is the one with 2 V shapes. One leg 7.3
inches and one 22.5 as per
www.matronics.com/forums/viewtopic.php?t-222&highlight=&sid=23bc0da12eeb24
ba261ca5ac45ec04b3
Thanks again for the help
Mike
The antenna is two dipoles . . . one centered on
121.5 MHz, the other on 402 MHz.
You have lost me here, I do not understand two dipoles concept. Please
explain in more detail if you don't mind
Thanks
Mike
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Message 2
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| Subject: | Antenna Ground Plane |
At 12:57 AM 6/4/2019, you wrote:
>I am working on an antenna for a homebuilt and I read from the
>AEROLECTRIC column in KITPLANES about using ferrite toroid's for a
>balun arrangement. However, I seem to remember that the material
>used in the toroids must be of a certain mixture to get the desired
>effect for RF signals. Can anyone tell me which toroids to use and
>which ones not to use. Apparently some work for RF and some work
>better for audio frequencies.
I included Jim Weir's string-of-beads concept in the 'Connection
many moons ago . . . the idea was intuitively logical but physically flawed.
That fact was not discovered until a years later when I was
working some EMC issues at RAC/Beech and gained access to the
EMC lab.
I did some testing of Jim's string-of-beads design and
found that the differences to be barely perceptible
for beads-on versus beads-off. As mentioned in an
earlier post, a single toroid with multiple passes
through the core is many times more effective . . .
however . . .
It is true that the material from which the toroid is molded
should be optimized for the frequency of interest . . . in
the case of the glideslope antenna illustrated in the
'Connection, the toroids should demonstrate good performance
at 300+ Mhz. Looking through the various manufacturer's
catalogs for toroids, we find very few recommended for
service above 100Mhz with most at 30Mhz and below.
The antenna chapter needs some work and the string-of-
beads idea is going to be removed.
What kind of antenna are you contemplating a
need for a balun?
Bob . . .
Message 3
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| Subject: | Antenna Ground Plane |
At 07:56 AM 6/4/2019, you wrote:
>
>
>Think I just figured it out, it is the one
>with 2 V shapes. One leg 7.3 inches and one 22.5 as per . . .
You got it . . .
Bob . . .
Message 4
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| Subject: | Antenna Ground Plane |
I did some testing of Jim's string-of-beads design and
found that the differences to be barely perceptible
for beads-on versus beads-off. As mentioned in an
earlier post, a single toroid with multiple passes
through the core is many times more effective . . .
however . . .
Did some digging in the archives and I think
these (or very similar) cores were used in Jim's
kit:
https://tinyurl.com/y2laaf78
This is Type 52 material which offers pretty
good performance up to 300Mhz . . . but
it still takes a LOT of cores for an effective
implementation of string-of-beads.
A multi-pass common mode choke could be
implemented with a small diameter
feedline (like RG174) through the
center of this one
https://tinyurl.com/y58fqdlh
This might be suited for de-coupling
the feedline on the dual-dipole ELT
antenna.
Bob . . .
Message 5
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| Subject: | Re: AeroElectric-List Digest: 1 Msgs - 05/28/19 |
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