<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: Times New Roman; font-size: 14pt; color: #000000'><P>Test.</P>
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<P><BR>----- Original Message -----<BR>From: "David McKenzie" <k1fsy@vhfwiki.com><BR>To: "144.450 Mailing List" <450@lists.vhfwiki.com><BR>Sent: Monday, December 20, 2010 4:52:27 PM<BR>Subject: [450] Fwd: [VHF] Close Vertical stacking distances [was: Horizontal stacking distance question]<BR><BR>Interesting reading re: stacking for those of you not on the VHF list<BR><BR></P>
<DIV class=gmail_quote>---------- Forwarded message ----------<BR>From: <B class=gmail_sendername>Ev Tupis</B> <SPAN dir=ltr><<A href="mailto:w2ev@yahoo.com" target=_blank>w2ev@yahoo.com</A>></SPAN><BR>Date: Sun, Dec 19, 2010 at 7:02 AM<BR>Subject: [VHF] Close Vertical stacking distances [was: Horizontal stacking distance question]<BR>To: Stanford VHF email Remailer <<A href="mailto:VHF@w6yx.stanford.edu" target=_blank>VHF@w6yx.stanford.edu</A>><BR><BR><BR>I've taken the liberty of re-presenting Jay's informative plots. Thanks to Jay,<BR>we can study data rather than shooting from the hip.<BR><BR>I can clearly see that the text attributed to Kent's observation held true:<BR><BR>------ Original Message ----<BR><BR>> > Kent WA5VJB did some experiments that were presented at Central States this<BR>> > year. He found that when single Yagis for different bands were stacked on<BR>> > one mast, they could be practically on top of one another (as little as 5<BR>> > inches apart, I think) and had virtually no effect on one another. When two<BR>> > Yagis for one band were used on the same mast, this did not hold true.<BR>----------------------------<BR><BR>The "purist" will say "I told you that there would be interaction!" And, of<BR>course there is. The "practicalist" will say, "so what? it is so insignificant<BR>I don't care."<BR><BR>See what I mean, below...<BR><BR>I've restated Jay's post a little differently below...<BR><BR>Note: "ascii figures" are NOT to scale and are left-justified. The assumption is<BR>that all antennas are centered on the mast instead. I'm including this as a<BR>visual aid only.<BR><BR>Antenna Scenario #1<BR><BR><A href="http://s509.photobucket.com/albums/s339/K0GU/K0GU%20MISC/?action=view¤t=222-5wl.jpg" target=_blank>http://s509.photobucket.com/albums/s339/K0GU/K0GU%20MISC/?action=view¤t=222-5wl.jpg</A><BR><BR><BR>The stack lays out like this:<BR><BR>----------------------- (222-5wl w/23' boom)<BR> two feet<BR> spacing<BR>------------------------------- (17b2 w/31' boom)<BR> two feet<BR> spacing<BR>------------------------------- (6m7jhv w/31' boom)<BR><BR>Jay's modeling shows a slight "upward" skew to the 222 beam's main elevation<BR>pattern. However this is only when compared to the same pattern in "free space"<BR>w/o any ground interaction at all. Even so, the difference is only fractions of<BR>a dB between the 222 antenna in free space vs within 24" of a 17b2 "ground".<BR><BR>Overall 222 MHz gain in elevation is -0.18 dB vs. free space<BR>Overall 222 MHz gain in azimuth is +0.04 dB vs. free space<BR><BR>Mast needed above the tower: 4'<BR><BR>Of significant note: The wind survivability of a 4' mast is greater than that<BR>of a mast that is long enough to conform to "perfect" stacking distances for<BR>these antennas.<BR><BR>Cheers,<BR>Ev, W2EV<BR>------<BR>Submissions: <A href="mailto:vhf@w6yx.stanford.edu" target=_blank>vhf@w6yx.stanford.edu</A><BR>Subscription/removal requests: <A href="mailto:vhf-request@w6yx.stanford.edu" target=_blank>vhf-request@w6yx.stanford.edu</A><BR>Human list administrator: <A href="mailto:vhf-approval@w6yx.stanford.edu" target=_blank>vhf-approval@w6yx.stanford.edu</A><BR>List rules and information: <A href="http://www-w6yx.stanford.edu/vhf/" target=_blank>http://www-w6yx.stanford.edu/vhf/</A><BR></DIV><BR><BR>_______________________________________________<BR>450 mailing list<BR>450@lists.vhfwiki.com<BR>http://lists.vhfwiki.com/cgi-bin/mailman/listinfo/450<BR></div></body></html>