Thanks Andrey for your insights on one of Top-Bands favorite toys The Beverage
antenna. I think we agree on almost all points.
> Indeed, the signals reflected FROM the reflection transformer (
>that`s the single transformer end ) is traveling along the
>transmission line and DECREASED by its attenuation.
I certainly agree.
>BUT! how and where from, those signals (which we call reverse direction
>signals) are created? As I sad, "injected" from "nowhere" at two
>transformers end (via transformer?) and coming along the same
>transmission line (with its attenuation
>again) in the direction of a reflection transformers?
>To be twice the lines length attenuated in the last?
>NO.
>This is a common mistake I can hear often and my point was to clear it.
>.Sorry if I didnt made it clear in the first post.
I certainly agree.
I did not mean to imply that the signal ever travelled twice but that your
statement
of the attenuation level below confused me.
>The value of attenuation in a transmition line mode depends on
>the insulation material used by manufacture but seems to
>be near the same around the world and equals around 6 db per 300 feet
>at 1,8 mhz.
>Signals from the back direction will be around 9 db down from the
>forward direction at 600 feet.
To my way of thinking an attenuation of 6 dB in 300 feet of line would be
12 dB in 600 feet not 9. I must have missed your meaning in the above words.
>Your are lucky one! my noise level from Hydro Power Station (less then
>5 km away in a US direction) and a Nuclear Power station (less then
>20 km away in JA direction) is around S4 at BEST times ... and the
>city by it self ...
Yes, I feel very lucky as there is 4 hydropower Dams within15 miles of QTH.
One as close as 2 miles. Fortunately they are at the bottom of a deep canyon
that
shades me from their affects as near as I can tell. And, my city has only 1300
people and no stoplights. Lucky indeed.
> But in assumption that there is no common mode ingress what else can
>increase the matched input RX noise? And if the noise did increased,
>if its sounds as a normal band noise from that direction (and it is
>different at different times of the day and directions!) at that time
>and carrying also some signals sky waves propagated?
Agreed, at the time I made that statement I was trying to carefully
evaluate the
impedances reflected by the lossy line made of the WD-1A. I was misled by an
error in the calculation of the impedances that led me to believe there was a
huge
mismatch. There is not, so you are quite correct. I was wrong.
The reason I was looking for the impedances was I wanted to apply them back
as a
load resistor for the Eznec Beverage model. As it turns out there is very
little change in
line impedance (and Beverage load) as a result of the high attenuation so the
Eznec
model shows very little change in the pattern from forward to reverse as you
have observed.
My friend K7FIL has agreed to fly his airplane around my antenna farm in a
GPS
guided circle with a small TX. I really hope to get at least one pattern to
share on several
types of RX antennas. Hopefully more.
Lee K7TJR Oregon
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