[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Hearing AO-40 MB at 150 deg. squint? <ANSWERED!>



I have observed the "mountain" diffraction mentioned below  - a friend
called it "multi-path". This was on my 70cm UHF repeater when it was on one
of the larger mountains in North Georgia.You could hear the repeater almost
anywhere, even when the only direct path was completely blocked by another
mountain.

73's

Don Woodward
KD4APP
443.200 and 53.45 - Pine Log Mountain (Northwest of Atlanta)
53.45 (back on air in 2 weeks)

----- Original Message -----
From: "Steve Diggs" <w4epi@mediaone.net>
To: <amsat-bb@AMSAT.Org>
Sent: Saturday, June 16, 2001 12:45 AM
Subject: [amsat-bb] Hearing AO-40 MB at 150 deg. squint? <ANSWERED!>


> Thanks to Dom I8CVS, an obvious RF smart-guy, there is a textbook answer
to
> my question. I have included Dom's message to me for reference. At first,
I
> thought "diffraction" as a misspelling. <grin> NOT SO! Check Page 21.3 of
> the 2001 ARRL Handbook, and you will read an excellent piece on "knife
edge
> diffraction", a fairly well understood RF anomaly.
>
> It seems what was happening was that a side lobe of the helix antenna was
> striking the edge of AO-40, between the bottom and side, and caused a
> "shadow zone" of RF to wrap around the spacecraft.
>
> Also, thanks again to the ham on this mailing list that spotted the fact
> that Borders Book Stores was selling 2001 ARRL Handbooks for about $10 or
> so. What an outstanding reference, and an incredible price. (It had to be
a
> mistake)
>
> Regards,
> Steve Diggs, W4EPI
>
> (Here's hoping DOM will send me a reply QSL card for our AO-40 contact; I
> even sent him an IRC...hi..hi..)
>
> -----Original Message-----
> From: i8cvs [mailto:domenico.i8cvs@tin.it]
> Sent: Friday, June 15, 2001 5:55 PM
> To: w4epi@mediaone.net; AMSAT-BB
> Subject: R: [amsat-bb] Hearing AO-40 MB at 150 deg. squint?
>
>
> Hi  Steve,
>
> Probably  a  strong side lobe of the AO40  helix is diffracted against the
> corner edge of the satellite metallic structural radiating back to the
> earth.
>
> Propagation of MW by diffraction on the crest of mountain i.e. Monte
> Bianco,is currently used  for QSO between Italy and Switzerland.
>
> Tank you for your very interesting remark
>
> 73 de i8CVS Domenico
>
>
> ----- Original Message -----
> From: Steve Diggs <w4epi@mediaone.net>
> To: <amsat-bb@AMSAT.Org>
> Sent: Friday, June 15, 2001 3:01 PM
> Subject: [amsat-bb] Hearing AO-40 MB at 150 deg. squint?
>
>
> > OK, guys I have a question here:
> >
> > I am sitting here listening to a very weak AO-40 MB, with Nova
indicating
> > squint is over 150 degrees. Distance is 6,100 miles, and elevation is 33
> > degrees.
> >
> > How can this be? The antenna is pointed away from me, and I have a big
> chunk
> > of satellite between the antenna and me. Is the signal bouncing off
> > something and then coming back to me? I don't understand how the signal
is
> > propagating in such a manner that I can hear it in this configuration.
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home