View Single Post
  #5   Report Post  
Old October 4th 10, 07:15 PM posted to rec.radio.amateur.antenna
Cecil Moore Cecil Moore is offline
external usenet poster
 
First recorded activity by RadioBanter: Aug 2006
Posts: 572
Default Is a screw driver antenna just a tuner with a wire attached to it?

On Oct 4, 9:12*am, John Ferrell wrote:
BTW, an SGC-237 tuner and a 28 foot whip will tune all of the HF ham
bands automatically and fast! *... you can consider that as an ideal
arrangement ...


The feedpoint impedance of a 28 foot whip on 3.8 MHz is ~5-j620 ohms
(according to EZNEC) which means considerable tuner/ground losses
(~9dB) = not ideal IMO, compared to a 1/4WL monopole. If one wants
reasonable performance on 80m, best to stick with not much less than
3/16WL = ~46'.

The Take-Off-Angle of a 28 foot whip on 28.4 MHz is ~43 degrees = not
ideal IMO, compared to a 5/8WL monopole. If one wants reasonable
performance on 10m, best to stick with not much more than 5/8WL =
~23'.

There's no single monopole length that is optimum from 3.5 MHz to 29
MHz. Just about the best compromise we can reach with an autotuner at
the base, IMO, is the 46' monopole for 80m-20m operation or the 23'
monopole for 40m-10m operation.
--
73, Cecil, w5dxp.com