[TowerTalk] 80 - 40 Meter Vertical Ideas

[Don Havlicek]

Dick,
Comments inserted below:

> Hi guys,
>
> I plan to homebrew a combination 80-40 meter vertical to place at the
> edge of  a saltwater river.   I am thinking of using one of the
> following options.   Your thoughts would be greatly appreciated.
>
> OPTION 1:  Use a 33' tower and extend a 33' length of aluminum tubing
> out of  the top section giving a combined height of aprx. 66'.  I could
> insulate the  tower from ground and base feed it giving me a 1/4 wave on
> 80 and a 1/2 wave on  40.  I would then need to match the base impedence
> for 40 meters.  What would  you recommend for matching the impedence?

This OPTION will involve lots of pruning and tuning .. and is NOT my
recommendation.

>
> OPTION 2: Use the same 66' structure as listed in Option 1 but ground
> mount  the tower.  Have 2 shunt feed systems: one for 40 and one for 80.
>  Can I have 2  shunt feed connected at the same time?

Yes .. just make certain that you use one feedline and remotely switch
between the two shunt feeds.  [my #2 choice]

>
> OPTION 3: Use the same 66' structure as in Option 1 but not only
> insulate the  tower from ground but isolate the top 32' section from the
> bottom.  This  would give me a 1/2 wave vertical dipole on 40.  When
> used for 80 meters I would  use a relay to connect the lower and upper
> halves giving me a 1/4 on 80.  What  would you recommend I use to switch
> in/out the two sections?

This sounds like the best option .. you can use a remote switch at the
midpoint of the antenna which could be operated by a low-voltage over the
coax when operating on 80m.  [my #1 choice]
>
> Ideally, I would like it set up for fast band changes.  (no time to fool
>  around outside during a contest!)

Contact me off the reflector for details on remote switching units which I
custom build.

>
> Any recommendations at to which option would provide the best field
> strength,  bandwidth, easiest match, etc. etc. etc. is much appreciated!
>
> 73, Dick- K9OM
> _______________________________________________

73
Don
N8DE
Connersville, IN