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nuckolls.bob(at)aeroelect
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 Posted: Mon May 23, 2016 6:40 am Post subject: Transponder and ADS Antenna Mounting Location Questions F |
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There are two prime issues here . . . antenna performance with
respect to ground plane which is easily addressed by
reciting the physics behind the idea of ground plane.
(1) If your antenna is hanging out in the breeze or perhaps
located on top of a mast, there is no practical way to
provide the ultimate in ground planes . . . conductive
material radiating out from the base all the way to
the horizon.
Experience and measurement has demonstrated that a
artificial plane fabricated of 'radials' can be a useful
alternative to the acme of grounds . . . 4 or more RESONANT
radials at the base of the antenna. More that 4 can be
expanded upon to be an 'infinite' number of radials whereupon
you have generated a solid disk with a radius equal to
the height of the antenna.
Yes, there ARE proximity effects for location of the
antenna on unsymmetrical grounds . . . but you have
to go into an RF lab with REALLY good equipment to
identify/measure the effects.
On a composite airplane, mount it on the disk. On
a metal airplane, mount it to the skin . . . anywhere
pending other issues wrapped up on proximity to
a strong radiated signal . . . the transponder.
(2) ADSB receivers are listening to 100+ watt
digital signals from transmitters in line of sight
and 10 miles or less distant. That is a HUGE signal
compared to looking for a 25w marker beacon 50 miles
away and perhaps over the horizon.
A wet string hung under the fuselage would probably
do must fine in terms of performance for receiving
ADSB squitter. KISS . . . disk of aluminum with a
legacy monopole is cheap, easy, works good, lasts a
long time.
Bob . . .
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billhuntersemail(at)gmail
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| Posted: Mon May 23, 2016 6:58 am Post subject: Transponder and ADS Antenna Mounting Location Questions F |
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Wow…this inherent anal retentive desire I have to “do it right the first time” is a real pain in the butt!!!
| Quote: | A wet string hung under the fuselage would probably do must fine in terms of performance for receiving ADSB squitter. KISS . . . disk of aluminum with a legacy monopole is cheap, easy, works good, lasts a long time.>
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The Dynon manual sure made a big deal about the EXACT size and shape of the antenna in a composite…I was thinking that an aluminum airplane would certainly not be the exact size and shape…
Anyhoo…Bob to confirm your communication before I start cutting and gluing…
With respect to the ADS-B antenna…I would like to mount it under the canard essentially in the nose compartment wheel well area…do you suppose this would work? What size should the aluminum ground plane be? Disk or square or egg shaped?!?!
With respect to the transponder antenna pointed down below the airplane (location under the back seat)…should I get rid of the current egg shaped ground plane or leave it as is?
This is just like being married…I tell my wife…just tell me what to do and I will do it…I don’t have to think that way!!!
..
Cheers!!!
Bill Hunter
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Monday, May 23, 2016 7:38 AM
To: aeroelectric-list(at)matronics.com
Subject: Re: Re: Transponder and ADS Antenna Mounting Location Questions For
There are two prime issues here . . . antenna performance with
respect to ground plane which is easily addressed by
reciting the physics behind the idea of ground plane.
(1) If your antenna is hanging out in the breeze or perhaps
located on top of a mast, there is no practical way to
provide the ultimate in ground planes . . . conductive
material radiating out from the base all the way to
the horizon.
Experience and measurement has demonstrated that a
artificial plane fabricated of 'radials' can be a useful
alternative to the acme of grounds . . . 4 or more RESONANT
radials at the base of the antenna. More that 4 can be
expanded upon to be an 'infinite' number of radials whereupon
you have generated a solid disk with a radius equal to
the height of the antenna.
Yes, there ARE proximity effects for location of the
antenna on unsymmetrical grounds . . . but you have
to go into an RF lab with REALLY good equipment to
identify/measure the effects.
On a composite airplane, mount it on the disk. On
a metal airplane, mount it to the skin . . . anywhere
pending other issues wrapped up on proximity to
a strong radiated signal . . . the transponder.
(2) ADSB receivers are listening to 100+ watt
digital signals from transmitters in line of sight
and 10 miles or less distant. That is a HUGE signal
compared to looking for a 25w marker beacon 50 miles
away and perhaps over the horizon.
A wet string hung under the fuselage would probably
do must fine in terms of performance for receiving
ADSB squitter. KISS . . . disk of aluminum with a
legacy monopole is cheap, easy, works good, lasts a
long time.
Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Mon May 23, 2016 2:01 pm Post subject: Transponder and ADS Antenna Mounting Location Questions F |
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There are two prime issues here . . . antenna performance with
respect to ground plane which is easily addressed by
reciting the physics behind the idea of ground plane.
(1) If your antenna is hanging out in the breeze or perhaps
located on top of a mast, there is no practical way to
provide the ultimate in ground planes . . . conductive
material radiating out from the base all the way to
the horizon.
Experience and measurement has demonstrated that a
artificial plane fabricated of 'radials' can be a useful
alternative to the acme of grounds . . . 4 or more RESONANT
radials at the base of the antenna. More that 4 can be
expanded upon to be an 'infinite' number of radials whereupon
you have generated a solid disk with a radius equal to
the height of the antenna.
Yes, there ARE proximity effects for location of the
antenna on unsymmetrical grounds . . . but you have
to go into an RF lab with REALLY good equipment to
identify/measure the effects.
On a composite airplane, mount it on the disk. On
a metal airplane, mount it to the skin . . . anywhere
pending other issues wrapped up on proximity to
a strong radiated signal . . . the transponder.
(2) ADSB receivers are listening to 100+ watt
digital signals from transmitters in line of sight
and 10 miles or less distant. That is a HUGE signal
compared to looking for a 25w marker beacon 50 miles
away and perhaps over the horizon.
A wet string hung under the fuselage would probably
do must fine in terms of performance for receiving
ADSB squitter. KISS . . . disk of aluminum with a
legacy monopole is cheap, easy, works good, lasts a
long time.
Bob . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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