Today's Message Index:
----------------------
1. 03:29 AM - Re: Re: can I use a nav triplexer for duplexer (Denny Mortensen)
2. 12:30 PM - Re: Horizontal antennas (TeamGrumman@aol.com)
3. 12:55 PM - Better question (Bob Gibfried)
4. 02:02 PM - Re: Horizontal antennas (Doug McNutt)
5. 08:29 PM - Re: Horizontal antennas (TeamGrumman@aol.com)
6. 09:30 PM - Re: Horizontal antennas (John Rippengal)
Message 1
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| Subject: | Re: can I use a nav triplexer for duplexer |
--> Avionics-List message posted by: "Denny Mortensen" <dennymortensen@cableone.net>
If you have ever heard the term educated guess then you will know where
I come from as it has been a long time since school however the
"terminator" that you refer to, I think we used to call it thin net is
indeed 52 Ohm and is there fore what you want. As far as the three way
splitter, yes this should work just fine however the 3 way splitter will
present a slightly higher loss in your signal strength then a 2 way
would. Not being an avionics expert I can not tell you how many DB
difference this will make but it should not affect things to much. If
your in a pinch go for it.
Denny
-----Original Message-----
On Behalf Of CardinalNSB@aol.com
--> Avionics-List message posted by: CardinalNSB@aol.com
Hello, I have a triplexer (2 navs and a glideslope output)-I will only
be
using one nav with glideslope, can I "cap" the unused nav output from
the
triplexer, and use it as outputting one nav and one glideslope? I have
some of
the bnc caps used on the old style computer bnc networks, I forget what
ohm
they are. What ohm would I need to "cap" one of the nav outputs from
the
triplexer? Thanks Skip Simpson
Message 2
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| Subject: | Re: Horizontal antennas |
--> Avionics-List message posted by: TeamGrumman@aol.com
I have a question regarding horizontally mounted antennas.
Years ago, I mounted a broadband 1/4 wave fiberglass wound antenna inside a
fiberglass dorsal fin. I didn't notice ANY reduction in transmit or receive
quality. I could still talk to and receive from stations 80-100 miles away.
I could talk to aircraft up to 300 miles away.
Last year, thinking I would save a little time fitting the antenna, I used a
bent wire antenna which is normally mounted on the bottom. This antenna
doesn't seem to be as effective as the fiberglass antenna. Is there something
I
could do to bump up the signal of this wire antenna?
Is the ground plane requirement different for the wire antenna than the
fiberglass antenna?
Gary
PS, it's mounted on a Grumman Tiger.
Message 3
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--> Avionics-List message posted by: "Bob Gibfried" <rfg842@cox.net>
I should have been more explicit. I'm using the Conant CI-121, white
fiberglass com antennas. Mounted on the Tripacer wing to fuselage alum
fairing using a 4 X 4 65 thousand doublers underneath the fairing to stiffen
the mount area. There is a gap of some six inches to the alum cover over
the 18 gal wing tank on each side.
Trying to teach my kids some instrument flight in an old (1956) aurokabe
with steam boiler equipment. Do have a double I, ground and air but pretty
outdated.
Just trying to stretch the Icom com and Narco Escort II Navcom as far as
possible.
Bob, Wichita
Message 4
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| Subject: | Re: Horizontal antennas |
--> Avionics-List message posted by: Doug McNutt <douglist@macnauchtan.com>
At 15:29 -0500 3/13/05, TeamGrumman@aol.com wrote:
>I have a question regarding horizontally mounted antennas.
>
>Last year, thinking I would save a little time fitting the antenna, I used a
>bent wire antenna which is normally mounted on the bottom.
Bent wire antennas are pretty good but they fall off rapidly above the 90 channel
limit at 126 MHz. Some bent wire jobs have a matching box at the base with
a coil and capacitor. They're probably better.
The fiberglass jobs go out to 136 MHz. They typically use a copper foil element
inside. The width allows for some control not available with bent metal.
But HORIZONTAL? Comm signals are vertically polarized and the antenna needs to
match unless you like flying on the knife edge. VOR and ILS signals are horizontal.
--
--> If you are presented a number as a percentage, and you do not clearly understand
the numerator and the denominator involved, you are surely being lied to.
<--
Message 5
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| Subject: | Re: Horizontal antennas |
--> Avionics-List message posted by: TeamGrumman@aol.com
In a message dated 3/13/05 2:02:52 PM, douglist@macnauchtan.com writes:
> But HORIZONTAL? Comm signals are vertically polarized and the antenna needs
> to match unless you like flying on the knife edge.=A0 VOR and ILS signals=20are
> horizontal.
>
I believe that the signal bends to match the curvature of the earth so, the
signal will be horizontal after a few miles. Now, the only drawback is the
strength of the signal toward the rear (no transmission off the tip). As I
said, I've not had any problem with transmission or reception (other than to the
rear).
My question was regarding the wire antenna and if there were a way to make it
stronger. You answered that question with the 126 Mhz upper limit.
Thanks.
Message 6
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| Subject: | Re: Horizontal antennas |
--> Avionics-List message posted by: "John Rippengal" <j.rippengal@cytanet.com.cy>
Well you should terminate that belief as soon as possible. While it is true
that energy radiated with one polarisation can 'leak' a little, so to speak,
into some small component of another polarisation, nevertheless the main
component stays as radiated. This happens by reflection and diffraction from
obstructions near the transmit antenna and possibly due to minute amounts of
scattering. But to base your comm antenna on anything else but Vertical just
does not make sense.
As for bending round the earth, there is a small refraction effect but this
is minimal in most weathers and in anycase how does that change the
polarisation??
John Rippengal
>
> I believe that the signal bends to match the curvature of the earth so,
> the
> signal will be horizontal after a few miles. Now, the only drawback is
> the
> strength of the signal toward the rear (no transmission off the tip). As
> I
> said, I've not had any problem with transmission or reception (other than
> to the
> rear).
>
> My question was regarding the wire antenna and if there were a way to make
> it
> stronger. You answered that question with the 126 Mhz upper limit.
> Thanks.
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