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
_______________________________________________
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