Fixing old 50ohm antenna

[roughshawd]

I asm fixing the old radio antenna off a boat.
The old antenna cable broke off at the mount, its a screw in antenna,fiberglass.
But it is so decomposing, I think I will put a new coat of fiberglass resin over it to rebuild the covering on it.
I took the antennas whip base, which is a male screw in antenna, into a female metal base,
out of the plastic antenna mount, and I want to put a new wire in it.
The antenna has a central core around a fiberglass stick.

The base has a small hole for the coax core, but no connection other than contact, for the ground.

The small + hole is too small for the core insulation around the coax core, so I am considering drilling the F.base' coax + hole to insulation size, then putting the coax ground onto the base with a little hole drilled for a screw.

The antennas contacts are shorted, in both the base and the antenna, but I remembered my basic antenna electronics and I have read something about antennas that are shorted out specifically and work that way on purpose...

Can anyone enlighten me on this shorted antenna design and how it is supposed to work so I don't short out my radio?

 

[Nanren888]

Sorry, can't picture it. Any chance of an image?
The coax outer should have somewhere to go, often for a whip, just a small groundplane, or a few radial wires.
A recent post response here contained some references to ARRL antenna pages.
https://www.electronicspoint.com/forums/threads/sleeve-antenna.293761/#post-1804235

 

[ratstar]

I asm fixing the old radio antenna off a boat.
The antennas contacts are shorted, in both the base and the antenna, but I remembered my basic antenna electronics and I have read something about antennas that are shorted out specifically and work that way on purpose...

yeh theres no ohmage on an antenna, the signal is so quiet nothing would get through a resistor - its got to go straight to the amp i guess. Maybe even adding a passive RC filter before the amp would kill it as well.

 

[Nanren888]

yeh theres no ohmage on an antenna, the signal is so quiet nothing would get through a resistor - its got to go straight to the amp i guess. Maybe even adding a passive RC filter before the amp would kill it as well.

I guess wire antennas will often look like opens as DC, but generally are something close to matched at their operating frequency for maximum power transfer. Circuits often try to match everything for 50 Ohm (at the operating frequency), but 75 and 300 Ohm is known where it makes sense.
.
Radio signals are often small, generally needing a preamplifier, often with low noise at the fornt, hence LNA, low noise amplifier.
Not sure that this aside helps the original poster.

 

[roughshawd]

Pic 4 is the coax base I dug out of the antenna mount.
The antenna screws right into the hole you are looking at.
Pic 5 is the coax base, upside down, standing on the antenna hole -- with a T-pin stuck in the coax tip wire hole that the center wire in the coax goes into. There is no connection for the shield ground, just contact.