Dave wrote in
:

....
3) [Rule of thumb] The gain is proportional to the effective aperture
in square wavelengths. So, as mentioned in another reply,
approximately, the ratio of length of the mobile antenna [~8 feet] to
the length of a 1/2 wavelength antenna for 60 meters [~93 feet] yields
8.6% efficiency. So, 100 watts from an IC-706 [series] yields ~9 watts
effective radiated power. Conclusion, 50 watts ERP on 60 meters with a
9% efficient antenna would require 555 watts into the antenna.
....

It certainly is ROT that in the general case, and in this case, that you
can run a tape measure over an antenna to calculate the aperture area and
in turn calculate gain.

Can you explain how your method deals with capturing the effects of a high
loss loading coil vs a low loss loading coil in such an antenna?

Owen

I'll rely on the calculation from the freeware program "Mobile Antenna". That
program allows variation in coil designs to be specifically input as a variable.

If you have a better answer or method then please provide it.

The original post is basically asking if 100 watts can be run from a 706 in a 60
meter mobile. The answer is YES. Why? Because an eight feet long antenna is
substantially less than the reference dipole. [Typically it is -10dBd].

/s/ DD, W1MCE

Owen Duffy wrote:
Dave wrote in
:

...

3) [Rule of thumb] The gain is proportional to the effective aperture
in square wavelengths. So, as mentioned in another reply,
approximately, the ratio of length of the mobile antenna [~8 feet] to
the length of a 1/2 wavelength antenna for 60 meters [~93 feet] yields
8.6% efficiency. So, 100 watts from an IC-706 [series] yields ~9 watts
effective radiated power. Conclusion, 50 watts ERP on 60 meters with a
9% efficient antenna would require 555 watts into the antenna.

...

It certainly is ROT that in the general case, and in this case, that you
can run a tape measure over an antenna to calculate the aperture area and
in turn calculate gain.

Can you explain how your method deals with capturing the effects of a high
loss loading coil vs a low loss loading coil in such an antenna?

Owen

Dave wrote:
The original post is basically asking if 100 watts can be run from a 706
in a 60 meter mobile. The answer is YES. Why? Because an eight feet long
antenna is substantially less than the reference dipole. [Typically it
is -10dBd].

For a 10' whip, EZNEC says the radiation resistance
on 60m would be ~1.3 ohms. Doubling that for center-
loading yields ~2.6 ohms. Dividing by an estimated
feedpoint resistance of 20 ohms gives an efficiency
of about 13%. Assuming an efficiency of about 90% for
a 1/2WL dipole, I should be able to run
50w*90/13 = 346w. 100 watts should certainly be
justifiable. Heck, I might even fire up my SG-500
at 300 watts. Now the next question. Is anyone using
60m?
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Dave wrote:

The original post is basically asking if 100 watts can be run from a
706 in a 60 meter mobile. The answer is YES. Why? Because an eight
feet long antenna is substantially less than the reference dipole.
[Typically it is -10dBd].


For a 10' whip, EZNEC says the radiation resistance
on 60m would be ~1.3 ohms. Doubling that for center-
loading yields ~2.6 ohms. Dividing by an estimated
feedpoint resistance of 20 ohms gives an efficiency
of about 13%. Assuming an efficiency of about 90% for
a 1/2WL dipole, I should be able to run
50w*90/13 = 346w. 100 watts should certainly be
justifiable. Heck, I might even fire up my SG-500
at 300 watts. Now the next question. Is anyone using
60m?


YEP!!! Quite active here in NE and along the East of the Mississippi River. It
is 1700Z and I'm listening to QSOs on 60-4 and 60-5 from SC and TN. BTW, I'm in NH.