How to improve FM reception?

[planet10]

Originally posted by c.d.s.
I have had excellent results with J-pole antenna's.

I have one of those in my project queue... i'll mount it up on the tin roof, which will give it a good ground plane & more height. The little dipole i'm currently using does surprisingly good, even thou it is under that same tin roof.

dave

[jackinnj]

both the ARRL and RSGB have excellent antenna designs in their handbooks -- in particular, the ARRL Antenna Handbook comes with an CD-ROM which allows you to tailor the gain and response to your heart's content.

[Damon Hill]

My jpole measured 1:1 at 88MHz and 2:1 at 92MHz at 50 ohm impedance; that's reasonable bandwidth. I may trim it to the middle of the band and try another one with 3/4" tubing to see if the bandwidth can be increased.

I've done this project 'by the book' so far and don't
understand how the antenna actually works; it should be possible
to tune it for a 75 ohm impedance though for receiving purposes
this isn't critical. The actual impedance reading was more around
40 ohms, but I'm not familiar how this instrument (MFJ Enterprises,
MFJ-249) works so I may have misinterpreted something. One meter
reads SWR, the other reads impedance and the subject is a bit
complex.

As much as I'd like to have a big log periodic on a rotator, this
is a more practical answer for now. Ben Franklin would accuse me
of making a lightning rod, and I did make sure it was well-grounded.
It's a rugged and simple design, and I recommend it if you can't
get a directional antenna installed. I also ran across a modification that will turn a jpole into a kind of Yagi vertical
antenna that has some front-to-back ratio.

No serious attempts to DX, hoping to pull in a Portland station or
two. The reception is solid on the three local stations I like:
KWJZ (smooth jazz), KING (classical), and KPLU (traditional jazz and blues, NPR) Alas, no one in the region carries Hearts of Space...

Need to replace the burnt-out lamps on my tuner display so I can
read it!

[ALW]

In the UK is a firm advertising in a UK Hifi journal that has a nice one. Sorry don't recall the names

Elso,

Are you thinking of the Ron Smith Galaxie range? They are excellent but very large.

http://members.fortunecity.com/g7nnt...s/galaxie.html

For good FM in most places you want a good, high-gain directional antenna to help eliminate multipath, which is a killer for sonic performance.

There are large benefits to be had from having excessive gain in the antenna (almost always better than a booster amp, with their potential noise and overload problems), good high-quality low-loss feeders (use double-screened satellite-grade coax) and then attenuators at the tuner end to bring the signal into the correct order for the tuner. You want the signal level to meet the full quieting sensitivity of the tuner you use.

The advantages of this approach are the attenuator improves matching, provides some isolation and attenuates the multipath pick up from the cable itself.

Andy.

[planet10]

Originally posted by Damon Hill
and KPLU (traditional jazz and blues, NPR)

That's my station -- i listen to it 90% of the time.

dave

[Damon Hill]

Andy:

In my many years of playing with outdoor FM antennas,
those Rod Smith Galaxies are the most outrageous I've ever seen.

I want one. Badly.

At one time I had a JFET preselector and a switched RF
attenuator which helped my mediocre Heathkit AJ-29 plow
through local signal overload. Since I moved to Seattle,
I haven't had much opportunity or money to play that
game. For the present, this Jpole will have to do.

--Damon, who once had a stack pair of JFD's biggest log periodics
and still has a useable Finco FM-4G. Both companies are
long gone.

[ALW]

I want one. Badly.

I knew there's be a closet antenna fetishist who'd drool over that

Andy.

P.S. I often got good results with a 'SLIM JIM' folded J antenna, when fed from a suitable balun these give excellent results in a compact antenna.

[AuroraB]

Just to clear up a few matters for non RF inclined readers....

The J-pole and Slim Jim are vertically polarized , and more important- horizontal omni directional antennas,......... doing very good for omni directional reception.....

For weak signal reception you need a good directional antenna, like a yagi. Drawback is of course that it is directional,... and may need a rotor if you want reception in more than one direction.

A good quality masthead amplifier will do well for all types of receiving antennas.

Polarization of FM broadcast used to be horisontal, and are thus more compatible to the traditional yagi FM antenna. Receiving with opposite polarization gives what is known as "polarization loss", reducing the signal.

Qiute strange it is, though , this modern fashion of tugging home a receiver and expecting good reception without any form of antenna!


QRT de LA5**

[ALW]

A good quality masthead amplifier will do well for all types of receiving antennas.

This is the only area I'd disagree with you on. There's no substitute (in terms of noise figure / ultimate performance) for a higher gain antenna.

Whilst there may be good masthead amps out there, most that people are likely to come across aimed at this market are noisy and exhibit poor overload / intercept performance.

In our increasingly noisy RF environment, I'd only use a masthead where absolutely necessary.

Andy.

[AuroraB]

Concerning the masthead amp, - I won't disagree either!

One problem though is that most modern receivers seems to be designed for living next door to the transmitter,- most of them have rather poor sensitivity. This can be remedied by a high quality masthead amp, - but again I agree with you, - most masthead amps of today are of a rather poor quality, - and the good ones are likely to be expensive, if you can find them.
Indeed, - if the tradeoff is between a larger antenna or small antenna/amplifier, the larger antenna is the the bettter way., but even with a large antenna, a masthead amp can be a good compensation for long cable runs.
Another problem, maybe not so common, is wind load on laarger antennas. In my neighbourhood, large antennas have a very short lifetime, unless being exceptionally rigid mechanically.
( I do occasionally get wind gust at 70 knots + .......... )