[TowerTalk] Two 15M stacking

[donovanf at starpower.net]

>From Maryland, a 45 degree beamwidth will simultaneously cover the
following areas with large contester populations:

Azimuth    Coverage area

22-25      UA4 and UA9 zone 17
22-30      Northern LA  OH9  SM2  UA1Z
30-60      Continental Europe (DL, G, F, HA, HB, I, OK, SP, UA, YU etc)
60-68      Iberian Peninsula (CT1, EA)

Its wise to include in a few degrees of additional beamwidth for small beam pointing errors, pattern assymetry and skewed propagation paths.

50 degree beamwidth is a good choice, requiring boom lengths of one wavelength or less.

73!
Frank
W3LPL

---- Original message ----
>Date: Sun, 25 Feb 2007 12:27:38 -0500
>From: Michael Keane K1MK <k1mk at alum.mit.edu>  
>Subject: Re: [TowerTalk] Two 15M stacking  
>To: towertalk at contesting.com
>
>At 09:29 AM 2/25/07, TexasRF at aol.com wrote:
>>
>>One added thought that will help reconcile K1TTT's experience with others  on
>>this subject:
>>
>> From K1TTT into Europe, say a 3500 mile path,  a 54 degree angle 
>> will  have a
>>3dB coverage of about 3200 miles in width. From this part of the world,  that
>>path would be about 1500 miles longer, encompassing about 4500 miles in
>>width.
>>
>>Yes, I can see that more antenna movement will be needed from New England
>>for the same signal strength. Finally a factor that favors "the rest of  us"!
>
> From New England, Europe subtends approximately 40 degrees of 
>azimuth (35 deg (TF) to 74 deg (ZB) from Boston). There may be some 
>differences in opinion over how much additional coverage is necessary 
>to not exclude adjacent areas in Central Asia, N. Africa and the 
>Middle East, but it's difficult to see too narrow of a beamwidth 
>becoming a concern, even from New England, except perhaps for monster 
>Yagis (that 7-el 10m M2 on the 44' boom still has an HPBW of 43 degrees).
>
>Of course, putting a 40 degree wide pattern onto a 40 degree wide 
>target does place a premium on accurate alignment, particularly for a 
>fixed stack... which would include finding True North ;-)
>
>A trade study of going from 4-el to 7-el and whether the ~2 dB of 
>additional peak gain compensates for the ~10 degree reduction in HPBW 
>can be evaluated using a tool like VOAAREA to generate coverage maps.
>
>The difficulty in making such a comparison lies in having confidence 
>that the system models being compared (the antennas in a stack over 
>real terrain) are more accurate than the expected 2 dB difference 
>from the unit antennas.
>
>73,
>Mike K1MK
>
>Michael Keane K1MK
>k1mk at alum.mit.edu
>
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