modify a wondershaft?

[bob85]

after looking at the francis patent and the different permutations of multiple conductors i thought it would be fun to try modding my shakespeer wondershaft or my avanti 1/4wave fiberglass antenna,
maybe its a crackpot idea but what do you guys think of fixing several different diameter conductors radially to the outside of a regular fiberglass antenna and either cutting it back to get a match to the coaxial or maybe use a dollar match at the feedpoint,
if it worked i could cover the whole antenna in thin heatshrink to hold the wires in place,

could this work and give better bandwidth or a perceptable increase in gain providing i get it resonant then match the antenna to the feedline?????

whats the best way ( or easiest ) to ensure resonance before i start trying to get a low vswr??
since a resonant 1/4 is rarely 50ohms at the feedpoint when mounted on a vehicle then throwing an antenna on the car and trimming for low vswr seems like a cockeyed way of doing things for best pattern and efficiency even though thats how everybody i know does it,
if i do it like that i cannot get a very low vswr with any unloaded 1/4 wave on my car, how can this mount and trim method give the absolute best performance??.

 

[W5LZ]

bob85,
Sounds like it might be fun to 'play' with. The only things I can think of to suggest is to wind those wires all in the same direction, and don't expect miracles.
Why the same direction? First, the finished product won't appear quite as 'lumpy', and that winding coils in opposite directions tend for them to cancel each other out, sort of. If they 'cancel' each other, why have them there to start with?
Document everything! Won't be a 'best' seller if the thing doesn't work out substancially better than the original, but would certainly help prevent the next one who tries the same things.
Have fun!
- 'Doc

 

[bob85]

hello doc, i was thinking about linear wires straight up the side of the fiberglass antenna but mounted radially about the vertical shaft using different diameter wires as in the francis amazer then covering the whole lot with heatshrink, maybe the heatshrink that has glue inside,
the idea was to keep the relative distances between wires fixed,
i would only use it on a stationary vehicle,

the main advantage if the idea worked would be bandwidth,
i go as low as 27.025 but our legal band is 27.60125 to 27.99125, having to swap stingers on the 10k is a pita when you have to do it several times in a couple houres of dx and local talk,
an antenna that would work well at 025 555 and our legal band would be cool,
if the idea worked i would do both my fiberglass 1/4's so i can cover 025 to 10mtrs with 2 antennas,
something to play with when the weather warms up a little.

 

[Captain Kilowatt]

Why use wires at all? If you want bandwidth then slip a piece of c o p p e r braid from some old RG-8 coax over it.Much easier to deal with and better looking when the job is done.I really can't see it making THAT much of a differance but it may be worth a try. I have been playing around with an HF antenna for the mobile and plan to use c o p p e r braid over a fiberglass shaft for the lower part below the loading coil.

On editdamn word filter) :evil:

 

[bob85]

i think the idea of wires of different diameter is to have multiple parallel radiators tuned to different center frequencies to broadband the antenna,

can this idea create a 1/4wave that is resonant and 50ohms when mounted on a car if you get the correct dimentions i don't know,

another idea is something i have seen on our original bullwhip antennas, they had a log wound base loading coil 18 inch long,

an old timer told me that type of winding gives a broader bandwidth due to increasing interwinding capacitance in a logarithmic fashion towards the top of the coil,
i dont know if that is true or not but the antenna did exhibit a broader bandwidth than comparable length even spaced wound antennas on a slightly wider diameter former,

could that idea if its true be combined with different diameter wires for even more bandwidth???

i have seen the braid idea before on our version of a goldenrod top loaded 1/4wave, that had a central rod covered in woven braid and transparent plastick with a tight wound top loading and tuning tip similar to the firestick antennas use.