Message 26477 in TECH.WW
From: G8MNY
Date: Thu, 23 Jul 26 08:55:00 Z
Newsgroups: TECH.WW
Subject: Understanding a Multipath
Message-ID: <69_GB7CIP>
Path: N2MH4|N3HYM|IW2OHX|GB7CIP
R:260723/0857Z 34233@N2MH4.#SENC.NC.USA.NOAM LinBPQ6.0.24
R:260723/0857Z 10789@N3HYM.#FRDK.MD.USA.NOAM BPQ6.0.25
R:260723/0856Z 8925@IW2OHX.ILOM.ITA.EU BPQ6.0.25
R:260723/0855Z @:GB7CIP.#32.GBR.EURO #:69 [Caterham Surrey GBR] $:69_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (New Feb 06)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
If you Rx a RF signal by more than 1 path this is what you get..
Reflection or Tx
tropo refraction. /'
The angle BC is / '
proportional to . . B / '
frequency with .' ' / '
refraction or . / . ' Path A is
Rx _ _ _ _ ___ up to +6dB
/' `\ /' `\ /' `\ /' `\ enhancement
The affect of reflection, | | | | | | | | over 1 path
make the tropo beam 300 400 500 600 700 800 Frequency
heading appear to change
with frequency! Of cause _ _ _ _
as the anomaly moves `\ /' `\ /' `\ /' `\ /' ` Path difference
or down as well, changes 300 400 500 600 700 800 Frequency
in dual path amplitude
will cause the null depth _ _ _ _
to change, from not \ /' `\ /' `\ /' `\ /' `\ Unequal signals
300 400 500 600 700 800 Frequency
LENS EFFECTS
My experience with a group of well scattered users of 23cm GB3HV ATV repeater
at High Wycombe, may put more light on the subject. During a Wx front it became
apparent that large lens of heavy damp air was moving through many viewers Rx
paths....
GB3HV
_..._
/'' ``\
( DENSE AIR )
BASINGSTOKE \.._ _../
0dB """
READING CROYDON
-20dB -3dB
ALTON
+20dB
Signal were lost in some palaces and much enhanced in others by getting on for
hour or so.
Why don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
← Return to Bulletin List