SA>Doug, I've also had similar experiences with my hytowers. I posted the
SA>following to the newsgroup but didn't get any responses. Since you're
SA>also into hytowers, I'll repeat for your opinion:
SA>First the hytower has some mechanical weaknesses as shown:
SA> |
SA> |
SA> | ---- 1.25" OD tapering to .25" tubing
SA> |
SA> || ---- 2" OD to 1.25" OD joint will fail
SA> ||
SA> 40m - |_ ||
SA> stub || |- 2" insulators \
SA> || | can arc over \
SA> || | \
SA> | | | 80m \
SA> | |--|-- wire to 3 Rohn BX sections
SA> | | | base / 24 ft tall
SA> | | | /
SA>base | | | /
SA>weld | | | /
SA>fails - o-------
SA> \/ \/ - Base insulators can arc over
SA>Because of the load that the base can stand and the 2" to 1.25"
SA>joint (to reduce wind loading), top loading the hytower can be a
SA>real mechanical problem.
SA>So considering windloading, here's a form of linear loading:
SA> ~
SA> | - 80m wire
SA> |
SA> | |----- - 3 ft Alum tube attached to top BX section
SA> | | |
SA> | | |
SA> | | | - 24 ft wire to 160m matching network
SA> | | |
SA> | | |
SA>baseplate ------- |
SA> | (
SA> | _( - 160m matching network (tapped coil to gnd)
SA> |_ | |
SA> \ / gnd - 80m/160m switch
SA> |
SA> Coax to transmitter
SA>This system would meet the mechanical criteria. 80m would remain more or
SA>less intact. A simple changeover switch would get on 160m. I'm not sure
SA>about 40m (it would probably be lost). Construction/designing would be possi
SA>for an average joe (like myself).
SA>Any comments as to its efficiency vs baseloading? If it is worth pursuing?
SA>73, Dick - K5QY
Hi Dick,
Your compromise preserves 80M without retapping the coil, I guess, but
the result is still an inverted L with only 27' or so of vertical, a
small improvement over the inverted L using the Hytower MK-160A add-on
that preserves 80, 40, 20, all the bands. I've never heard of the
base insulators arcing over. They're at a low voltage point so I don't
think that's a problem. However, the insulators at the top tower
section are at a high voltage point and, Hygain recommends running only
100 watts to the Hytower on 160M. I live in a very windy area and have
never had any problems with the mechanical strength of the aluminum
tubing section.
I think the Hytower is an excellent antenna on 40 and 80, and can be
pretty good on 160 as a base loaded vertical. You're right, there's no
easy way to top load the Hytower that I know of.
I guess the Hytower is a linearly loaded antenna with the 24' tower
section, and 24' 80M wire and 26' tubing above it fed in parallel. Is
that your understanding? Can anyone help me here? I'm not sure I
understand the linear loading, if indeed it is that. If I ever get
time, I'll try to model it on YO.
I have considered adding an 8' section of tower to increase the total
height to 60'. I think it would perform better on 160M, but am not
sure I would be able to get it to resonate on other bands?
73, Doug W2CRS
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