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In Reply to: RE: Thanks posted by Jim Austin on October 09, 2015 at 10:46:43
FM just is directional, and is thus prone to multi-path - reflections ..... boing- boing, and when listening crackles and fizz. and weirdly strained phasey sound.
I do get what you are facing. Multi-path doesn't have to be grossly obvious to be affecting your received sound.
If you have a Significant Other who LOVES FM then you may be able to build one or more rhombics, and 'conceal' them.
Big tall city buildings. This is what DAB was developed for and for mountainous terrain, IE satellite radio firing down. HD radio isn't HD and doesn't sound better than good FM from a good antenna
The only reasons - two - for me to bother with FM and antennas are these two stations.
http://www.abc.net.au/classic/music-listings/?date=2015-10-10
a national free public broadcaster's classical network - Satellite based but the grnd txers are FM (and DAB).
http://artsound.fm/ which is far broader and local and for who I used to - and will return to - record live acoustic stuff in 2-mike stereo.
Antennas matter to me because ii) Canberra is inside the Great Dividing Range and we are between two Mt's in a strong signal area, and i) on my path to senior NCO rank in the infantry I had to learn to be a good signaller / radio man?! I had to become well above average at all the infantry specialist roles, in fact. Good reception is never where cover from observation or fire is good.
Happy to be a sounding board.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Follow Ups:
Tim(bo),
Thanks for this; it was fun to read and inspirational. This is a problem I intend to work on over the next few months. I'll post progress.
Cheers,
Jim
Two big problems.
Strong reflections, and aiming inside a ferro-concrete building? There are now GPS based compass apps for smart phones.
Mine seems to be unaffected by being indoors in our house which has a large number of (now redundant) AC-mains powered heating panels above the ceiling, which are still earthed, so are probably forming a partial Faraday screen.
Which reflection or main signal direction to aim at for station X?
I don't know if FM fool tells you the polarisation of each FM transmitter's signal. It is usually mixed ie some vertical and some horisontal or circular. A rhombic won't really 'care' about pol'n.
A T antenna mounted on a swivel either vertically on a sort of lazy-susan base / or horisontal may help you find the best axis for a rhombic. Use the signal-strength meter on the MR78 and listen. Or borrow a field-strength meter - if it's too optimistic. ? Lots of SS meters on tuners are, to make the tuner seem sensitive in the store.
Record the bearing that gives the least worst sound (best?) off the T-ribbon for each desired station. Then decide if you need a spread rhombic or two. It may depend on how many desired stations you have.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
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