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Old June 17th 08, 09:04 PM posted to rec.radio.amateur.antenna
Andy[_5_] Andy[_5_] is offline
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First recorded activity by RadioBanter: Apr 2008
Posts: 71
Default 40m centre feed dipole, I want to add 80m

Thanks for all your suggestions. When this wet weather clears I will try
them all out and see where I end up..

73 Andy


"Highland Ham" wrote in message
...
Andy wrote:
Hi,

I have a 40 meter centre feed dipole cut for 40 and feed direct with 50
Ohm coax. The house end is connected to the centre of the coax and the
pole end is connected to the braid. Seems to work best this way round.
The antenna is fixed tight to the house and the other end is tight to the
metal pole in a straight-line, diagonal across the garden, both ends are
insulated. The garden is about 64 feet give or take a couple of feet.

I cannot drop the ends down because of the house and metal pole at the
end of the garden being so close. I can only feed the antenna with coax.
The neighbours are OK with coax but not the ribbon feeder hanging down
and I don't want to upset them if I can help it.

My question. What are my options to enable me to operate 80 and 40m on
this same antenna wire?

===========================================
300 Ohms ribbon twin feeder is hardly more visible than coax feeder .
You don't have to use the 'wide' 450 Ohms ribbon type.
300 Ohms ribbon has an approx velocity factor of 0.8 ,so if you make half
the dipole + the feeder (roughly) an electrical 1/4 -3/4 -etc wavelength
at 80 meters ,you will be home and dry with an appropriate matching unit
or a choke balun in combination with a 'coax-in ,coax-out' matching box.

Frank GM0CSZ / KN6WH