antenna

Is there an easy way for a novice to check an old antenna?
thanks
et

"et" wrote in message
...
Is there an easy way for a novice to check an old antenna?
thanks


I assume that you don't own any sort of antenna tester, so an SWR check is
not an option. Further assuming that we are talking about a previously
known-good aircraft antenna already installed on an aircraft, you could start
with a DC continuity test. You should have continuity (low resistance) from the
connector shell to airframe ground. If it is a metal whip, you should be able
to measure continuity from the connecter center terminal to the whip. From
there, connect a portable aviation radio and see what kind of performance you
get.

Vaughn

On Thu, 26 Jun 2008 20:39:09 -0700 (PDT), et
wrote:

Is there an easy way for a novice to check an old antenna?
thanks
et

use it connected to a radio.
the most likely issue will be corrosion to the screw threads on the
base which increases the resistance.
the base and threads should be brass which will clean up quite nicely
with brasso and a toothbrush.

....now of course you do have a mental picture of the antenna that I'm
thinking of dont you...

Stealth :-) Pilot

Describe the "old antenna" and how it is installed.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"et" wrote in message
...
Is there an easy way for a novice to check an old antenna?
thanks
et

On Jun 27, 8:07*am, "RST Engineering" wrote:
Describe the "old antenna" and how it is installed.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
* * * * --Aristotle

"et" wrote in message

...



Is there an easy way for a novice to check an old antenna?
thanks
et- Hide quoted text -

- Show quoted text -

It is a VHF com, similar to the AV-529 that AC Spruce sells.
Aluminum base, slanted whip off a late 60's pa-28. It is mounted on
an al. base about8"x10" in the rear of a Glasair fuse. The base is
connected to the a/c ground. I can turn on the runway lights from my
hanger with the PTT switch on the control stick[about 200']. When I
taxi tested for the first time, it wouldn't turn the lights on from
the end of the runway[about 1500']. I don't have the headset jacks
hooked up yet, just the PTT and a small speaker. I can recieve in
the hanger from a/c in and near the pattern.

et

A "whip" or monopole antenna such as this requires a ground plane to operate
properly. In general, a metal airplane with metal fuselage in all
directions will serve very well

In a plastic airplane, a "ground plane" of several (four is the accepted
number)radials quarter wave long (about 24") coming out at right angles at
right angles from the antenna is a requirement. A single 8x10 aluminum
bracket isn't going to cut it.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"et" wrote in message
...
On Jun 27, 8:07 am, "RST Engineering" wrote:
Describe the "old antenna" and how it is installed.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle

"et" wrote in message

...



Is there an easy way for a novice to check an old antenna?
thanks
et- Hide quoted text -

- Show quoted text -

It is a VHF com, similar to the AV-529 that AC Spruce sells.
Aluminum base, slanted whip off a late 60's pa-28. It is mounted on
an al. base about8"x10" in the rear of a Glasair fuse. The base is
connected to the a/c ground. I can turn on the runway lights from my
hanger with the PTT switch on the control stick[about 200']. When I
taxi tested for the first time, it wouldn't turn the lights on from
the end of the runway[about 1500']. I don't have the headset jacks
hooked up yet, just the PTT and a small speaker. I can recieve in
the hanger from a/c in and near the pattern.

et

RST Engineering wrote:
A "whip" or monopole antenna such as this requires a ground plane to operate
properly. In general, a metal airplane with metal fuselage in all
directions will serve very well

In a plastic airplane, a "ground plane" of several (four is the accepted
number)radials quarter wave long (about 24") coming out at right angles at
right angles from the antenna is a requirement. A single 8x10 aluminum
bracket isn't going to cut it.

Jim


Would perforated aluminum foil or aluminum screen embedded in the
skin and bonded to ground do the job? I'm assuming it wouldn't make for
a strong lamination, but as a ground plane it seems kind of tidy.

Dan, U.S. Air Force, retired

Electrically it would work just fine. The problem is how to get the
grounding bolts of the antenna base to mechanically connect to the aluminum
and not corrode over a long period of time. A secondary problem is that the
antenna gets as much "connection" to the metal skin of an airplane through
the capacitance between the metal base and the skin through a very thin
rubber gasket acting as a dielectric as it does with the metal screw
contact. WItness the fact that most of those fiberglass whip antennas have
a rather sturdy epoxy paint job on the base. 99 out of 100 times you take
the antenna off and you find that the paint in the bolt holes is still quite
intact, meaning that the screw never DID cut through that paint to give you
the ground you were hoping for.

Me? If it is a tupperware airplane or toothpicks and tissue paper airplane
I go down to the hardware store and buy some thin (1 or 2 mil) shim brass or
copper. Cut me a plate using the base of the antenna as a template and four
strips 22.5" long. Solder the strips to the brass plate near the center,
stuff the strips through a hole in the fuselage where the antenna is going
to go, leaving the plate on the OUTside of the fuselage, bolting the antenna
through the brass plate and through the fuselage, and then tidy up the brass
strips by "attaching" (glue, RTV, epoxy) them flat to the underside of the
fuselage.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"Dan" wrote in message
...

Would perforated aluminum foil or aluminum screen embedded in the skin
and bonded to ground do the job? I'm assuming it wouldn't make for a
strong lamination, but as a ground plane it seems kind of tidy.

Dan, U.S. Air Force, retired