Hi all:

Here's something I'm having trouble figuring out: My stereo FM receiver
has a "fried egg" static that's almost strong enough to drown out the
broadcast signal. I've tacked up a Radio Shack 300 ohm yagi in the attic
over the garage and the static seems even worse.

Meanwhile the two cars in the garage below get the same signal very
clearly. The yagi lead is coax all the way. The broadcast antenna is 15
miles to the west and the yagi is aligned north-south.

We'd appreciate any ideas, and Happy New Year!

Bob Johnson

Bob Johnson wrote:
Hi all:

Here's something I'm having trouble figuring out: My stereo FM receiver
has a "fried egg" static that's almost strong enough to drown out the
broadcast signal. I've tacked up a Radio Shack 300 ohm yagi in the attic
over the garage and the static seems even worse.

Meanwhile the two cars in the garage below get the same signal very
clearly. The yagi lead is coax all the way. The broadcast antenna is 15
miles to the west and the yagi is aligned north-south.

We'd appreciate any ideas, and Happy New Year!

Bob Johnson

Sorry, meant to say "folded dipole" instaed of "yagi".

A few comments;

Car FM radios tend to be far more sensitive than "Stereo's" that one
sees in the home. They are also better shielded against noise.

I'd suggest your receiver has some major sensitivity issue (like a blown
front end from a close lighting strike etc). Its unlikely but there
could also be a local interferring source causing a problem. This would
be very unusual on FM though. Can you hear other stations well?

As decribed the yagi is aligned at right angles to the station, where
minimum signal will be! A check of connections and matching (you said
300 ohms then coax) will also be in order.

Cheers Bob Vk2YQA

Bob Johnson wrote:


We'd appreciate any ideas, and Happy New Year!

How have you connected the 300 ohm dipole to the (assume) 75 ohm coax?
May I also assume you used a balun to properly make this transition?
Is your area served by more than one FM broadcast station? If so, are
the other stations also affected by the noise?

If so, you have a locally generated noise problem. Do this: Find a
small, portable, battery powered AM radio (like you'd take to the
ball-park to hear the play-by-play (!). Tune it to a very weak AM
radio station. Note: To do this, you may have to be some distance
*away* from you home, since we've already discovered it has RF noise
polution. As you approach you home, listen for the noise to increase,
while turning the receiver - that's turning with an 'r' - you're using
the receiver as a direction finder - listening for a peak in the noise.


In this way, you likely be able to pinpoint the noise source fairly
quickly.

Likely candidates include:

Light Dimmers
Fish Tank Heaters
Electric Blankets

MW