(Richard Harrison) wrote in news:29905-4198FBFC-
:

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



Yep, there was a short in my coax. Fixed it and the signal improved 1000%.
Now I need to address hum.

--
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