Today's Message Index:
----------------------
1. 07:12 AM - Ground plain (Bob Gibfried)
2. 07:56 AM - Re: Ground plane (Craig P. Steffen)
3. 07:58 AM - Re: Ground plain (Charlie England)
4. 10:44 AM - Re: can I use a nav triplexer for duplexer (CardinalNSB@aol.com)
5. 02:08 PM - Finding Grimes (Rick)
6. 03:41 PM - Re: Ground plain (Doug McNutt)
7. 07:58 PM - Re: Finding Grimes (William Gill)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
--> Avionics-List message posted by: "Bob Gibfried" <rfg842@cox.net>
Quick question. Have my glass antennas mounted on the alum wing fairing
strips on the top of my Tripacer. Some have said that the fairings do not
provide a very good ground plain (or is it plane)?
Would a ground strap from the antenna to the large, alum gas tank cover
improve the ground plain or would the antenna have to be mounted to the
center of the cover. This would be impossible because the cover fits too
close to the top of the tank to allow the connection on the bottom of the
antenna.
Bob, Wichita
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Ground plane |
--> Avionics-List message posted by: "Craig P. Steffen" <craig@craigsteffen.net>
Bob,
> Quick question. Have my glass antennas mounted on the alum wing fairing
> strips on the top of my Tripacer. Some have said that the fairings do not
> provide a very good ground plain (or is it plane)?
Plane. Um...so what's a "glass" antenna?
First question here. Is the antenna a quarter wave antenna ("whip"
antenna) or a dipole antenna? You can tell by the length, if nothing
else. For VHF voice band (120-ish MHz), quarter wave antenna is about
23 inches, dipole is about 46 inches.
A "ground plane" is required for a quarter wave antenna. That's the
sort that you see sticking up from the top of the fuselage on a metal
airplane. The metal skin forms a pretty decent ground plane.
A ground plane isn't required at all for a diple antenna.
> Would a ground strap from the antenna to the large, alum gas tank cover
> improve the ground plain or would the antenna have to be mounted to the
> center of the cover. This would be impossible because the cover fits too
> close to the top of the tank to allow the connection on the bottom of the
> antenna.
I don't really understand the physical situation here. Can you put up
a photo or something?
In a quarter wave antenna, the ground braid (shield) of the signal
cable from the radio must be bonded to the ground plane next to the
antenna. A separate ground "strap" probably wouldn't help so much.
Unfortunately, grounds at RF frequencies have different requirements
than grounds as part of the DC power system. A quarter wave antenna
needs to stick up from its ground plane at 90 degrees, at a point
where the ground plane goes out in all directions.
Craig Steffen
--
craig@craigsteffen.net
public key available at http://www.craigsteffen.net/GPG/
current goal: use a CueCat scanner to inventory my books
career goal: be the first Vorlon Time Lord
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Ground plain |
--> Avionics-List message posted by: Charlie England <ceengland@bellsouth.net>
Bob Gibfried wrote:
>--> Avionics-List message posted by: "Bob Gibfried" <rfg842@cox.net>
>
>Quick question. Have my glass antennas mounted on the alum wing fairing
>strips on the top of my Tripacer. Some have said that the fairings do not
>provide a very good ground plain (or is it plane)?
>
>Would a ground strap from the antenna to the large, alum gas tank cover
>improve the ground plain or would the antenna have to be mounted to the
>center of the cover. This would be impossible because the cover fits too
>close to the top of the tank to allow the connection on the bottom of the
>antenna.
>
>Bob, Wichita
>
1st, are the fairings strong enough to handle the wind load of the
antennas? I'm more familiar with homebuilts where the fairings are only
strong enough to 'fair', not structural.
2nd, if the tank is more or less centered under the antenna, it might
work fairly well as a ground plane anyway since it's grounded to your
airframe. Fly it & see. (Better is the enemy of good enough.)
You can make an adequate ground plane by making 4 'radial' arms that
form a cross or 'X' with the base of the antenna sitting on the center
of the 'X'. Make each leg roughly the same length as the antenna &
ground them to the shield of the antenna wire. Aluminum strips, welding
rod, coat hangars etc will all work for the arms. Obviously, they can go
inside the fuselage/wing if it's fabric covered. You can get a lot more
elaborate than this, but I'll bet you will be happy with the performance
of this simple setup.
Charlie
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: can I use a nav triplexer for duplexer |
--> 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 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
--> Avionics-List message posted by: Rick <n701rr@yahoo.com>
I have a Grimes 14VDC rotating beacon pulled from my first aircraft, a 1946 Cessna
140. I would love to put that lil red beacon on my homebuilt Zenith 701.
The beacon draws about 6.5 Amps, that I imagine is fine. However she is really
loud and surges from time to time. I guess she at least needs brushes and
bushes...anyone know where I can get this sentimental little beacon rebuilt?
Thanks,
Rick
ps (ok to laugh now)
Rick
Orlando, FL. USA
http://www.geocities.com/n701rr/index.html
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Ground plain |
--> Avionics-List message posted by: Doug McNutt <douglist@macnauchtan.com>
At 09:09 -0600 3/12/05, Bob Gibfried wrote:
>ground plain (or is it plane)?
It helps to think if the ground plane as a flat mirror. The quarter wave antenna
above it is reflected in the plane that is the mirror. The reflection acts as
the other half of the fictional half-wave antenna that doesn't need a ground
plane by itself.
Metal acts like a mirror to radio energy. Fabric and wood do not.
If you're in the middle of Kansas building a 640 kHz antenna for AM broadcasting
the ground plane is the flat terrain below. Perhaps it is a plain.
--
--> From the U S of A, the only socialist country that refuses to admit it. <--
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
--> Avionics-List message posted by: "William Gill" <wgill10@comcast.net>
Hello Rick,
Honeywell purchased Grimes Aerospace a couple of years ago. Try the
following link For their Repair & Overhaul facility
http://www.honeywell-lightingandelectronics.com/services/repair/csscap.j
sp
Best regards,
Bill
-----Original Message-----
From: owner-avionics-list-server@matronics.com
[mailto:owner-avionics-list-server@matronics.com] On Behalf Of Rick
Subject: Avionics-List: Finding Grimes
--> Avionics-List message posted by: Rick <n701rr@yahoo.com>
I have a Grimes 14VDC rotating beacon pulled from my first aircraft, a
1946 Cessna 140. I would love to put that lil red beacon on my
homebuilt Zenith 701. The beacon draws about 6.5 Amps, that I imagine
is fine. However she is really loud and surges from time to time. I
guess she at least needs brushes and bushes...anyone know where I can
get this sentimental little beacon rebuilt?
Thanks,
Rick
ps (ok to laugh now)
Rick
Orlando, FL. USA
http://www.geocities.com/n701rr/index.html
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|