<199909251008.GAA26893@contesting.com>
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit
Content-Transfer-Encoding: 8bit
Sender: owner-topband@contesting.com
Precedence: bulk
X-List-Info: http://www.contesting.com/topband.html
X-Sponsor: W4AN, KM3T, N5KO & AD1C
A followup on my notes about my trying to come up with a better way
to compare the receive noise (eg static) reduction capabilities of
diverse receive antennas. I felt a little embarrassed when listing
the relative noise figure for my 3 parallel Beverages planned for
this year since it wasn't much better than last year's 2 parallel
Beverages. While I still planned revision to the design before
installation (crops not harvested here yet) I thought that I was
close to the final revision. My reaction to this was, "Let's put
this new number to use and see if I can use it to improve my design."
While heavy on the numbers, I think that observing the progression
of changing one parameter (the phase of the wide spaced Beverage)
is useful in that it shows a variety of things happening with my
Beverage array:
RELATIVE
PHASE NOISE AZ dBi BW F/B EL ELBW COMMENTS
0 -8.08 40 -8.16 54.3 24.97 24 41.6 Prior listed #
25 -8.21 46 -8.47 52.8 26.86 22 40.5 + minor #1 adj
50 -8.35 49 -9.07 50.7 28.25 21 39.5
75 -8.51 52 -9.99 48.2 29.60 20 38.2
100 -8.62 55 -11.26 45.5 28.70 18 36.0
125 -8.45 58 -13.03 43.1 26.06 17 34.7
150 -7.43 60 -15.29 44.9 22.21 16 32.9
90 -8.60 53 -10.59 46.8 28.35 19 37.3 Chosen design
AZ = Center of azimuth lobe
dBi = dBi value of above lobe
BW = -3 dB bandwidth of azimuth lobe
F/B = Front of back of main lobe (NOT to "back" of Beverage)
EL = Center of elevation lobe at peak azimuth
ELBW = -3 dB bandwidth of elevation lobe
Note that while the Beverages all stay with a 40 degree azimuth
that the main lobe shifts clockwise with increasing phase delay
to Beverage #3 (the wide spaced one). Being able to adjust the
phase of that Beverage (via a MFJ-1026) will be very useful!
Looks like I'll be shifting the Beverage wire azimuths to around
30 degrees to compensate. Note that the 90 degree "Chosen Design"
numbers also include a minor change to the phase of Beverage #1.
Looking at the pattern as my receive noise figure improved, I
thought that becoming a "less clean" looking pattern would result
in a worse figure. However, the decrease in the main lobe width
obviously made up for that. Also apparent was there's a limit
to only observing main lobe width figure.
This changes my prior summary to:
RELATIVE
ANTENNA NOISE COMMENTS
Any omni ant 0 dB
2 ele vert -3.14 Classic 90ºspace/90ºphase array for comparison
My xmit ant -5.28
584' Bev -6.31 Haven't helped me much over in-line w/xmit ant
881' Bev -7.31
2 x 881' Bev -7.86 6' spacing, stagger fed 1/4 wavelength
3 x 881' Bev -8.08 Above, plus third spaced 0.4 wavelength (planned
for this season)
3 x 881' Bev -8.60 Today's revision of the above
Note the minor changes to the Beverage lengths above correct my
"rounded numbers" previously listed.
While still subject to further revision, I think that his year's
European Beverage is now very close to its final design...
73, Bill K0HA
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|