Semi - NORDO in a Champ to Oshkosh - Misc questions

As I remember, the 7AC has a metal fairing between the fuselage and the wing
to join the fuselage, windshield, and wing. Please confirm.

If this is so, I will design and send you the parts for an external antenna
that you can mount by drilling a half inch hole in that metal fairing. In
essence, it is a 22" brass welding rod soldered into (and hot glue filled) a
BNC-M connector. A BNC-FF bulkhead connector is inserted into a half-inch
hole drilled into the metal fairing just aft of the leading edge of the
wing. A coax cable with BNC-M connectors on either end then connect the
bulkhead connector with the radio. Simple, cheap, and effective. VSWR
bandwidth is nothing to write home about, but it will work one hell of a lot
better than the rubber resistor.

The "ground plane" for this antenna is the metal fairing. If you want to
make a marginally better ground plane, you can make a short jumper wire
between the fairing and the metal fuselage tubing. Use a metal cable clamp
to connect to the tubing and a screw-nut-crimp connector to connect to the
fairing.

You want to take it off to make the airplane look more "stock"? Unconnect
the antenna and cover the bulkhead connector with another BNC-M connector
filled with hot glue. Paint the connector to match the metal fairing and 99
out of 99 people will never notice it. If they do, just tell them it is a
new design for communicating with aliens.

Payment for the parts? How about a beer at Friar Tuck's?

Jim

A new shielded harness was put into my 7AC before I bought
it, and I've had pretty good luck for typical CDAS and CTAF
comm. I found that handheld location was pretty important,
so I don't hold my handheld in my hand :-) I've got a PTT
setup with the handheld in a cradle mounted well forward,
high on the left tubing. I'm debating adding an external
antenna, but the only real comm difficulty I've had seems to
be on the ground in certain orientations.

RST Engineering wrote:
As I remember, the 7AC has a metal fairing between the fuselage and the wing
to join the fuselage, windshield, and wing. Please confirm.

If this is so, I will design and send you the parts for an external antenna
that you can mount by drilling a half inch hole in that metal fairing. In
essence, it is a 22" brass welding rod soldered into (and hot glue filled) a
BNC-M connector. A BNC-FF bulkhead connector is inserted into a half-inch
hole drilled into the metal fairing just aft of the leading edge of the
wing. A coax cable with BNC-M connectors on either end then connect the
bulkhead connector with the radio. Simple, cheap, and effective. VSWR
bandwidth is nothing to write home about, but it will work one hell of a lot
better than the rubber resistor.

The "ground plane" for this antenna is the metal fairing. If you want to
make a marginally better ground plane, you can make a short jumper wire
between the fairing and the metal fuselage tubing. Use a metal cable clamp
to connect to the tubing and a screw-nut-crimp connector to connect to the
fairing.

Pretty much what we did, only with a different connector and attachment.
The coax and mount cost $20.
This is what I use.
You will want to rivet a doubler plate to the fairing where you attach
the antenna base. You can then screw on the antenna and cut the whip to
the frequency you desire. The coax enters the cabin at the wing leading
edge meets the top of the windscreen. This is also where the coax is
coiled and stowed when not in use.

http://www.antenna.com/lm_cat/lmrpg37.html

Motorola Style Mounts
Model KRM66
Similar to K-66 except Motorola style mount and 14 ft (4.3 m) of
RG-58/U cable and PL-259 connector.
Model KRMX66
Similar to K-66 except Motorola style mount and 17 ft (5.2 m) of RG-58/U
for ASP-7450 and ASP-7650 series. Connector available separately.
Model KREMX66
Similar to K-66 except Motorola style mount and 17 ft (5.2 m) of
PRO-FLEX PLUS low loss cable. Connector available separately.