N4KG comments below.
On Mon, 19 Oct 1998 20:29:31 -0600 (MDT) John Brosnahan <broz@csn.net>
writes:
>
>At 12:13 AM 10/20/98 -0600, Mike Lamb wrote:
>>
>>Eric: I just wanted to add a little emphasis to what you said about
>the
>>sound of the stack. When I first put my system on the air I was
>>astounded by the number of people that asked if I was using a
>different
>>microphone when I made the antenna change tests because the audio was
>>NOTICEABLY better with the stack. I can only surmise that there is
>less
>>selective fading and resultant distortion. In busting piles it is
>also
>>apparent because because of propagation often I am getting through on
>the
>>first call but getting no better report than the next guy in line.
>>
>>73/Mike, N7ML
>
>Mike (and Eric),
>
>When I first started playing with my four-stack of 8L Yagis on 10M
>40/80/120/160ft) and also had a single 8L Yagi on another tower (80ft)
>I was astonded at the differences in intelligibility the stack made.
>
>I started working Asiatic Russians that were S9 on the single 8L and
>were
>a bit stronger on the stack, but they were totally unreadible on the
>single
>8L (on ssb) due to "selective fading" but were without any sign of
>distortion
>on the stack.
>
>That is when I made the conclusion that the distortion was just that
>of
>multipath rather than some sort of "polar flutter". The stack, with
>its
>clean
>pattern which had no significant high angle lobes only received one
>path.
>The single 8L had higher angle lobes and was receiving two (or more)
>paths
>with different time delays--causing the "selective" fading.
>
>The copiability difference was totally astounding!
>
>John W0UN
>
>
When N4AR built a 4 high stack for 10M spaced every 30 ft,
he observed considerable "echo" on some signals from Europe.
The echo was not observed on a single 4L10 at 40 ft.
My conclusion was that the MUF was high enough to support at
least two modes (waveangles) and the stack had more gain at
the lower angle but most of the Europeans had more gain at the
higher angle due to (presumably) lower antennas.
When N4AR switched to his lower antenna with a higher waveangle,
the lower antenna more closely matched the stronger and higher
incoming waveangle.
You can never have too many antennas ! :-)
de Tom N4KG
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