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

Cecil Moore wrote:
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.


Which is why the whips that SGC sells (and others use) are typically two
monopoles in one.. I have fairly good luck with a 9ish foot CB whip with
about 25-30 feet of wire roughly spiraled up it. The precise length
isn't real critical, as long as you don't wind up with an anti-resonance
in a ham band making it hard to match.