[TowerTalk] Bobtails
Don Moman
ve6jy@freenet.edmonton.ab.ca
Sat, 29 Aug 1998 00:55:39 -0600 (MDT)
Currently I am using 3 bobtails, 2 on 80m and 1 on 160m. They are the
conventional 3 verticals, connected across the top, overall roughly a
wavelength long and 1/4 wave high. All are bottom fed thru the usual
tapped LC network. There are only between 4 and 8 radials under the center
wire, which is likely less than optimum.
Having the two 80m ones at right angles, I can comment on their pattern -
some nights there isn't much difference but typically I observe 3 to 5 S
units (FT-1000mp) with Carribean signal vs a European one, less for
closer in stations. For DX they are nearly always better than the delta
and various inv Vees. The 4 el yagi is under construction and hopefully
will be up this season, giving soemthing else to compare against.
On 160, I have other antennas to compare against - dipoles at 160', a
couple of delta loops (one with apex at 180', and one sloping delta as the
apex is only at 140' feet), and at least on receive the bobtail hasn't
shown much to get excited about. It favours the east coast/carrib and
Japan off the other side. It has just been up this last season so I really
haven't done enough tests to get a good feel for it, but it has rarely
been the best antenna of the bunch. Perhaps it needs more radials, and
also I am somewhat concerned that the two supporting structures may be too
close to the outside two verticals - they are maybe 30 -40 feet away. Is
this a concern? They are not trees but guyed towers. The antenna looks
thru several other towers to the east coast but has a clear shot into
Japan.
73 Don
VE6JY Don Moman email: ve6jy@freenet.edmonton.ab.ca
Box 127 Lamont, Alberta email forwarding: ve6jy@rac.ca
T0B 2R0 (403) 895-2925
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