Is my antenna working?
 

Forgive me for being a completely ignorant novice, but I built a
simple ground plane antenna which seemed to cure my directional
broadcast problems (broadcasting over my yard), but I unplugged it for
a while, and now when I try to broadcast the signal is very weak, and
doesn't change even though I unplugged the antenna. In other words, I
was listening to the broadcast right at the Ramsey FM10a transmitter,
and when I unplugged the antenna cable, the signal didn't change. Am
I right in thinking that the coax connection to the antenna is broken
somewhere and that the transmission is coming completely from the
antenna jack of the transmitter?

Thanks for your help.

Clueless in Seattle

J.S. Snpw wrote:
"---I unplugged the antenna cable, the signal didn`t change."

You need to measure carrier level to determine FM signal strength. Once
the "FM improvement threshold" signal is reached, very little increase
in audio level results from increases in RF. It`s the magic which makes
RF repeaters work well. All signals, weak and strong, are nearly as
strong in audio levels.

Next. If you build kits, you probably have a way to test continuity.
Check your antenna circuit for opens and shorts in all the right and
wrong places.

Best regards, Richard Harrison, KB5WZI

Next. If you build kits, you probably have a way to test continuity.

Well, duh. Shoulda thought of that!

Thanks


--
John Snow
"Pull hard and it comes easy"

John Snow wrote:
"Now I need to address hum."

It is likely the FM kit is 100% solid-state. Filament wiring and leakage
are out of the question.

Shielding is necessary on low-level, high-impedance audio wiring.
Continuity of shields and their supposed connections is mandatory.

Low ripple is needed in the d-c power supply. The placement of the
supply and its components must be isolated so that these do not induce
a-c into sensitive circuits.

Ground connections within the FM circuit must be sequenced and arranged
so that a low-level circuit is not sharing the ground return of a
high-level circuit. This imposes high-level noise (hum) in the low-level
circuit. This is sometimes called a ground loop.

I recall solving the phono oscillator hum problem just by putting enough
distance between the oscillator and the receiver.

Best regards, Richard Harrison, KB5WZI