60m operation is limited to 50w pep relative to a
1/2WL dipole. Since a typical 60m mobile antenna
would be much less than 50% efficient, seems it
would it be OK to run an IC-706 at its normal 100
watt output level. Am I reading the rules right?
--
73, Cecil, http://www.qsl.net/w5dxp

Cecil Moore wrote in news:sFoDh.262$M65.0
@newssvr21.news.prodigy.net:

60m operation is limited to 50w pep relative to a
1/2WL dipole. Since a typical 60m mobile antenna
would be much less than 50% efficient, seems it
would it be OK to run an IC-706 at its normal 100
watt output level. Am I reading the rules right?

What are the actual words used in the rules?

If this is based on ERP, and uses the term Effective Radiated Power to mean
relative to a dipole (rather than say, EIRP), then the ERP would be
calculated from transmitter power output and antenna gain wrt a dipole, or

ERP = TxPower*AntennaDirectivity/DipoleDirectivity*Efficiency.

So the terms you left out were AntennaDirectivity and DipoleDirectivity,
but I should think that most HF whips would have Directivity lower than a
dipole, so you may be ok.

Owen

Cecil Moore wrote:
60m operation is limited to 50w pep relative to a
1/2WL dipole. Since a typical 60m mobile antenna
would be much less than 50% efficient, seems it
would it be OK to run an IC-706 at its normal 100
watt output level. Am I reading the rules right?

I think your interpretation is correct, but the key is:

"A half-wave dipole antenna will be presumed to have a gain of 0 dBd.
Licensees using other antennas must maintain in their station records
either manufacturer data on the antenna gain or calculations of the
antenna gain."

Meaning you probably need to keep an EZNEC printout in your glove
compartment. ;-)

Chuck

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"Cecil Moore" wrote in message
...
60m operation is limited to 50w pep relative to a
1/2WL dipole. Since a typical 60m mobile antenna
would be much less than 50% efficient, seems it
would it be OK to run an IC-706 at its normal 100
watt output level. Am I reading the rules right?
--
73, Cecil, http://www.qsl.net/w5dxp

That is the way I see it. The 1/2 wave dipole would be the 0 db refferance
point. I doubt any practical antenna on a car would be anywhere near 50% of
a dipole.
YOu seem more able than most to calculate the number of db below the dipole
so you can calculate the ammount of power you would have to run to get up to
the same level of the 1/2 wave dipole. I am not sure even the legal limit
of 1500 watts would get you there with some antennas. Maybe the 1500 watt
rule does not apply on this band if you have a very poor antenna.

YES! You are reading the rules correctly.

There are many 60 meter mobiles running 300 to 400 watts into a 10% efficient
antenna relative to a 1/2 wavelength dipole.

Get on 60, It;s is a great band.

Cecil Moore wrote:
60m operation is limited to 50w pep relative to a
1/2WL dipole. Since a typical 60m mobile antenna
would be much less than 50% efficient, seems it
would it be OK to run an IC-706 at its normal 100
watt output level. Am I reading the rules right?

So, hows does an armchair operator (one who doesn't have $10K worth of
test equipment) determine the efficiency of the antenna?

Scott
N0EDV

Dave wrote:

YES! You are reading the rules correctly.

There are many 60 meter mobiles running 300 to 400 watts into a 10%
efficient antenna relative to a 1/2 wavelength dipole.

Get on 60, It;s is a great band.

Cecil Moore wrote:

60m operation is limited to 50w pep relative to a
1/2WL dipole. Since a typical 60m mobile antenna
would be much less than 50% efficient, seems it
would it be OK to run an IC-706 at its normal 100
watt output level. Am I reading the rules right?

Scott wrote:
So, hows does an armchair operator (one who doesn't have $10K worth of
test equipment) determine the efficiency of the antenna?

Radiation resistance/Feedpoint resistance?
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote in news:rUCDh.2296$re4.1031
@newssvr12.news.prodigy.net:

Scott wrote:
So, hows does an armchair operator (one who doesn't have $10K worth of
test equipment) determine the efficiency of the antenna?

I am guessing that as an armchair operator, you would use a commercial
antenna.

Given your licence conditions on 60m, it would be very reasonable to ask
your supplier for a written statement (that you can file to fulfil your
licence obligations) of the gain of their antenna in installations like
yours so that you can calculate the maximum input power allowed. If that
is too hard, perhaps a written statement of the permitted maximum input
power for compliance with the licence.

Some of this in tounge in cheek, I just can't see antenna manufacturers
'fessing up to a range of gain figures for typical HF mobile antennas /
installations.

In time, the regulator will wise up to the challenge and specify things
more simply, eg if you use an antenna of less than 8' in length, you can
run up to 100W, otherwise up to 50W. That is more understandable to our
(eg VK) new six hour hams with their shack on their belt.

Owen

But...how does one measure those, or is it done by calculating them and
then applying to the formula below?



Cecil Moore wrote:
Scott wrote:

So, hows does an armchair operator (one who doesn't have $10K worth of
test equipment) determine the efficiency of the antenna?


Radiation resistance/Feedpoint resistance?

Scott wrote:
But...how does one measure those, or is it done by calculating them and
then applying to the formula below?

EZNEC will give an estimate of the radiation resistance.
Feedpoint resistance can simply be measured.
--
73, Cecil http://www.w5dxp.com