RE: " No tuner made can reject multipath." Discuss?

Posted by stellavox (A) on January 4, 2012 at 06:10:42

In Reply to: " No tuner made can reject multipath." Discuss? posted by Timbo in Oz on December 28, 2011 at 16:41:31:

Timbo,

Let's think about this and try to understand what you (and maybe I) mean by multipath, from the "poor" receiver's perspective.

At my antenna terminals I see two identical signals - on the exact same carrier frequency - one slightly delayed in time because it was reflected off of something. Let's call one the "direct" and the reflected, "delayed". The reflected signal should be weaker as it had a longer path to travel. Because they are on the same frequency, they should make it unchanged (although considerably amplified) through my RF and IF stages. So it's what happens once the signals hit my detector stage that we would "hear". I believe the FM detector stage's job is to change an incoming (instantaneous) frequency variation into an analog voltage equivalent. Now my thinking get's hazy - so let's try simplification - what if the transmission was a single 1Khz sine wave - wouldn't a "perfect detector" output two sine waves (if it were fast enough), the "delayed" one at a lower amplitude and "slightly behind" the direct. Having said that I have mo clue what I would "hear" on that simple or with a more complex waveform - Would my hearing mechanism try to mix the two together somehow and, wa-la, produce "jibberish"???

Having gone this far, I would opine that there is no way that my (or any?) detector could distinguish between the direct and reflected signal unless the reflected signal is significantly lower than the direct so it gets "buried in the noise". Even if you could apply some sort of digital processing, I can't see how you could reliably determine and continuously "lock on" to the primary signal. But then I don't (have to) design "spook" communication equipment.

Does this make any sense? New Years Cheers to down under.

Charles

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Follow Ups Full Thread

Topic - " No tuner made can reject multipath." Discuss? - Timbo in Oz 16:41:31 12/28/11 (16)

RE: " No tuner made can reject multipath." Discuss? - stellavox 01/4/1206:10:42 01/4/12 (0)

You're correct Tim..... - kootenay 00:29:47 01/4/12 (2)

RE: You're correct Tim..... - Brian Levy 12:41:08 01/30/12 (0)

If signal is strong 'cos it came from a directional antenna it 's unlikely to have much multipath content - Timbo in Oz 00:40:05 01/4/12 (0)

A most interesting thread. Thanks! (nt) - 1973shovel 10:24:34 01/1/12 (0)

Maybe no 'consumer' tuner... - AbeCollins 19:41:05 12/31/11 (1)

SDR? Yes I have heard about it. - Timbo in Oz 16:43:51 01/1/12 (0)

I'm going to agree - Awe-d-o-file 09:16:52 12/31/11 (0)

RE: " No tuner made can reject multipath." Discuss? - centaurfm 14:37:41 12/30/11 (2)

Hybrid Digital is very lossy digital, it isn't high definition by any assessment. - Timbo in Oz 16:24:02 12/30/11 (1)

Further digital RF either works or it doesn't, cell-phones and all else! - Timbo in Oz 01:07:08 01/4/12 (0)

RE: " No tuner made can reject multipath." Discuss? - Neff 11:37:43 12/29/11 (0)

RE: " No tuner made can reject multipath." Discuss? - hahax@verizon.net 21:42:02 12/28/11 (3)

AFAIK rejecting multi-path is a phase issue so capture ratio isn't much of a help - Timbo in Oz 01:42:28 12/29/11 (2)

Capture ratio is certainly relevant in reducing multipath - AbeCollins 13:00:23 12/31/11 (1)

It is my experience that a directional antenna with gain always sounds better than anything else - Timbo in Oz 01:03:55 01/4/12 (0)

Follow Ups

RE: " No tuner made can reject multipath." Discuss? - stellavox 01/4/1206:10:42 01/4/12 (0)

RE: " No tuner made can reject multipath." Discuss?

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