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What are the symptoms of a multi-path problem?

204.34.199.252

Posted on June 23, 2004 at 10:49:47
Scholl


 
Are some tuners more prone to multi-path problems than others?

Thanks, Scott

 

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Re: What are the symptoms of a multi-path problem?, posted on June 23, 2004 at 12:54:13
AbeCollins
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Posts: 46200
Location: USA
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Contributor
  Since:
February 2, 2002
One symptom of multipath is audible distortion even though the signal strength is good. Multipath is just that... the antenna is picking up the signal from multiple paths... the direct signal as well as the signal reflected off hillsides, buildings, and other obstructions. This results in multipath distortion.

Some tuners (like some Magnum models) include a multipath meter.

 

Re: What are the symptoms of a multi-path problem?, posted on June 23, 2004 at 18:38:00
tesla
Audiophile

Posts: 3180
Location: San Diego County, California
Joined: October 25, 2000
Many of the older Marantz tuners have a O'Scope that can display Multipath

 

multipath, posted on June 24, 2004 at 22:38:09
skiroe
Audiophile

Posts: 194
Location: northern california
Joined: June 23, 2003
using a rotateable rooftop antenna can greatly improve reception and help virtually eliminate multipath. im sure a good tuner helps too. but the single most beneficial thing you can do for your tuner is not mods.. take the effort and install a rooftop fm only rotateable antenna.. the improvement is beyond belief. my upgraded accuphase T-101 has a multipath meter. when im tuned to a station i rotate the antenna untill the needle is buried in 0. this indicates that multipath is essentially not present. some of the best fm in the country is right here in s.f. bay area...otherwise you can listen to most of it maybe online.(try kfjc for starters)...thats the next step..how good can online be made to sound?...ive heard one particular tuner guru say that digital signal broadcasting does not sound as good as analog.. and a lot of stations are switching over..i dont know if digital would mean sound degradation... have to find out.

 

Scholl! yep, Capture Ratio is the indicative parameter, posted on June 25, 2004 at 16:57:55
Timbo in Oz
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Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
in the (tested / reviewed) specs.

BUT, this is highly dependent, on a good directional antenna, pointed in the best direction for sufficient signal strength (SS), and minimum multipath.


Many analogue tuners had / have two 'good' meters, SS is often a bit optimistic.

But it WAS common to allow the SS needle to flicker a tiny bit, if there was MP in the received signal, minimise that and yr fine.

NB some digitals, have quite good metering but you've got to read the manual, it may well be down two branches in the interface, for one or more buttons!

What's MP SOUND like? Sounds like birdies, but mainly sputters. If you have ever heard FM in a car break up going behind a hill, or down a concrete and glass canyon? YES! Well you have heard MP, at its worst!

MP is a timing problem, and effects Stereo badly, the waves that have bounced not only arrive out of time but out of phase/polarity, a horisontally polarised signal may now be approaching vertical.

There's a worst case scenario here in Canberra, just south of where I live, FM reception becomes impossible for the sub-city of Tuggeranong (the ....... Valley).

We are at the top of that valley, at its mouth, and just between two of its outlying hills, one being the highest in Canberra, barely 500 metres away. The Tugg'g Valley, is one big bowl of the Great Dividing Range / oothills of the Australian Alps, with several smaller bowls, re-entrants and a couple curvey canyons, with suburbs in them.

Almost all Canberra's FM Tx'ers (and TV) are powerful, and on ONE big telecom/restaurant/tower, which fires into the valley (down two openings!) and guess what happens to those strong signals? - bounce, bounce , bounce, boing, boing, boing........

We have got 4 UHF repeaters, for TV, all around the T'g Valley. Nothing for FM though.

SO a good antenna for YOU =>

SHALL,

- on all desired stations.

- drive your FM tuner into 'full limiting' on all desired stations, to minimise Noise and Distortion.

- Minimise Multipath effects, including Noise and Distortion.


NB 'desired' is yr budget V. value problem.


Timbo in Oz
The Skyptical Mensurer and Audio Scrounger
Peace

 

Thanks..., posted on June 26, 2004 at 05:38:57
Scholl


 
I don't think I have a MP problem. It was just a mis-aligned tuner that I had fixed.

In the fall I'll look at a yagi and rotor. It's to dang hot to work in the attic now.

Thanks for the great discription.

 

tah, posted on June 26, 2004 at 06:14:09
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
I can still write?

warmest,


Timbo in Oz
The Skyptical Mensurer and Audio Scrounger
Peace

 

though the reception sounds problematic......, posted on June 29, 2004 at 16:25:51
sober1
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Posts: 1536
Location: Chicagoland
Joined: August 9, 2000
the description of the terrian sounds beautiful!

pax

 

Re: though the reception sounds problematic......, posted on July 1, 2004 at 22:04:20
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
there are good sites ACT govt's in particular

act.gov.au

Timbo
Timbo in Oz
The Skyptical Mensurer and Audio Scrounger
Peace

 

we are/were also in the path of one of the fire storms that hit in Jan 2003, posted on July 1, 2004 at 22:06:42
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
the maelstrom bounced over our house, but there is till one empty block three houses down!


Timbo in Oz
The Skyptical Mensurer and Audio Scrounger
Peace

 

NB we're at the mouth of the valley, posted on July 3, 2004 at 16:55:17
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
to the NNE is big hill and ridge and the signal comes over the East side of that hill from the much higher but far away tower.

further South it just gets worse, a d'l antenna is IME&O vital where we are.
Timbo in Oz
The Skyptical Mensurer and Audio Scrounger
Peace

 

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