Thanks john,
Caught a station ID and confirmed the station I am hearing on the
back is the same as on the front.
Closely watched the ground wave signal and there were a few DB of QSB.
Would indicate there was some sky wave mixing.
As you mentioned, when the reverse signal is ~ 8 S units down, the
arrival angle of any sky wave can vary the strength quite a lot.
Between you, Nick, and better monitoring, now understand what is happening.
Appreciate the help.
73
Bruce-K1FZ
On Mon, 20 Jun 2016 13:17:06 -0500, john battin wrote:
My observations using diversity reception with my 9 element
array and very long phased beverages was that on the back side the
qsb from the antennas was not in phase. My explanation is that the
nulls are very dependent on arrival angle and hence as the
propagation wiggles the arrival angles a bit, the signal goes up and
down. Only a few degrees of change in arrival angle can easily take
a 40db null down several db.
John K9DX
From: k1fz@myfairpoint.net
To: topband@contesting.com
Date: Mon, 20 Jun 2016 10:49:20 -0400
Subject: Re: Topband: Back Scatter ?
CC: nhp@ieee.org
Nick. The overall timing was irregular, but the slope of QSB took
a couple of seconds. This was at local noon time, so had not
considered other stations.
We do not have high power BCB stations here in Maine. Only a little
over 1 million residents that widely placed. Some 1 KW, 5 KW BCB
stations. It is however possible in mid-coast Maine to hear WBZ
1030 KHZ in Boston, at mid-day...
Thanks for the heads up. Appreciate your input. Will do more testing
73
Bruce-K1FZ
On Thu, 16 Jun 2016 05:41:41 +0000, Nick Hall-Patch wrote:
Hi Bruce,
Does the QSB vary regularly at say a 0.5Hz or 1Hz rate? Could it be
another station on the channel that is not exactly the same
frequency, not strong enough to deliver audio, but strong enough to
create a sub-audible beat note?
If it is irregular, shouldn't the traditional explanation of a touch
of high angle skywave interfering with the small amount of ground
wave remaining after nulling the station be sufficient to explain the
QSB?
73,
Nick
VE7DXR
At 15:20 15-06-16, K1FZ-Bruce wrote:
Been working to optimize the F/B on some antennas, using ground wave
stations in the upper BCB band. Noticed that some weaker ~20 mile
distant 5 KW stations that the back (reverse) signal
has QSB on them. Think we used to call it back scatter years ago.
Some are down in the noise and QSB up to about 1 S unit. We used to
think back scatter was reflective variations in the ionosphere. Is
there any more recent information ? Maybe carbon in varying cloud
layers ?
73
Bruce-k1fz
http://www.qsl.net/k1fz/beverage_antenna.html
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