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noms1reqd(at)yahoo.com
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 Posted: Mon Jun 12, 2017 4:15 am Post subject: Multiplexer or new antenna |
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Hello. I've added a new comm radio on my RV4. I currently have a Comant CI-122 bent whip. Space is limited on the belly of the RV4. Would it be OK to use a multiplexer and share the antenna or try to find a spot for another antenna? What multiplexer would you recommend?
Thanks.
Jeff Bertsch
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nuckolls.bob(at)aeroelect
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| Posted: Mon Jun 12, 2017 5:30 am Post subject: Multiplexer or new antenna |
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At 07:13 AM 6/12/2017, you wrote:
| Quote: | Hello. I've added a new comm radio on my RV4. I currently have a Comant CI-122 bent whip. Space is limited on the belly of the RV4. Would it be OK to use a multiplexer and share the antenna or try to find a spot for another antenna? What multiplexer would you recommend?
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Having two or more appliances share a single antenna
is problematic . . . and as Heinlein noted, "There ain't
no such thing as a free lunch".
There are various ways that the energy being received
or transmitted by an antenna may be split into multiple
pathways . . . but the first effect is attenuation of
said energy(ies). The second consideration is ability
to isolate one pathway from another . . . a transmitter
dumping thousands of milliwatts into the feedline
is a severe performance risk (if not destructive) of
other appliances where a pathway is conducting microwatts
of energy.
There ARE power dividers for driving up to two VOR and
two glideslope receivers from a single VOR antenna . . .
but the performance of ALL receivers downstream of
the signal source is degraded . . . and, of course,
NO transmitters are expected to share this system.
The short answer to your question is no. Separate
antennas go to maintaining both PERFORMANCE and
REDUNDANCY of the two transceivers.
Bob . . .
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Mon Jun 12, 2017 5:32 am Post subject: Multiplexer or new antenna |
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Find a place for second antenna. If there isn't room on belly, consider
locations on top of fuselage, or.. I've had success locating a CI-122 on
an inspection plate on underside of a wing. I'm not aware of any
reasonable device that allow sharing a transmitting antenna with
adequate protection from frying the receiver on the other radio.
On 6/12/2017 5:13 AM, Jeff Bertsch wrote:
| Quote: | Hello. I've added a new comm radio on my RV4. I currently have a
Comant CI-122 bent whip. Space is limited on the belly of the RV4.
Would it be OK to use a multiplexer and share the antenna or try to
find a spot for another antenna? What multiplexer would you recommend?
Thanks.
Jeff Bertsch
|
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
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noms1reqd(at)yahoo.com
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| Posted: Mon Jun 12, 2017 8:26 pm Post subject: Multiplexer or new antenna |
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Thanks Kelly.
Follow up question... I can put a second comm antenna about 3 feet from the existing antenna, but that will place it about 1 foot from the transponder antenna.
Would that be OK since the transponder is so much higher freq?
Jeff
On Monday, June 12, 2017 8:47 AM, Kelly McMullen <kellym(at)aviating.com> wrote:
--> AeroElectric-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>
Find a place for second antenna. If there isn't room on belly, consider
locations on top of fuselage, or.. I've had success locating a CI-122 on
an inspection plate on underside of a wing. I'm not aware of any
reasonable device that allow sharing a transmitting antenna with
adequate protection from frying the receiver on the other radio.
On 6/12/2017 5:13 AM, Jeff Bertsch wrote:
| Quote: | Hello. I've added a new comm radio on my RV4. I currently have a
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| Quote: | Comant CI-122 bent whip. Space is limited on the belly of the RV4.
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| Quote: | Would it be OK to use a multiplexer and share the antenna or try to
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| Quote: | find a spot for another antenna? What multiplexer would you recommend?
|
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nuckolls.bob(at)aeroelect
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| Posted: Tue Jun 13, 2017 4:10 am Post subject: Multiplexer or new antenna |
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At 11:25 PM 6/12/2017, you wrote:
| Quote: | Thanks Kelly.
Follow up question... I can put a second comm antenna about 3 feet from the existing antenna, but that will place it about 1 foot from the transponder antenna.
Would that be OK since the transponder is so much higher freq?
Jeff |
If it is a problem, the difficulty will manifest in
misbehaviors by the comm radio. You may hear a burst
of 'buzz' every time the reply light comes on. Baring
that, proximity to the antenna should not be a problem.
Bob . . .
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Tue Jun 13, 2017 5:18 am Post subject: Multiplexer or new antenna |
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I would rather see you get the separation by putting a com antenna under
a wing. It may be okay, but what is backup plan if it doesn't work and
you have a hole to patch in the fuselage? It is much easier to make an
inspection plate mounting that can be discarded if you don't like the
results.
On 6/13/2017 5:09 AM, Robert L. Nuckolls, III wrote:
| Quote: | At 11:25 PM 6/12/2017, you wrote:
> Thanks Kelly.
> Follow up question... I can put a second comm antenna about 3 feet
> from the existing antenna, but that will place it about 1 foot from
> the transponder antenna.
> Would that be OK since the transponder is so much higher freq?
>
> Jeff
If it is a problem, the difficulty will manifest in
misbehaviors by the comm radio. You may hear a burst
of 'buzz' every time the reply light comes on. Baring
that, proximity to the antenna should not be a problem.
Bob . . .
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD |
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