60m mobile operation
 

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

60m mobile operation
 

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

60m mobile operation
 

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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60m mobile operation
 

"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.

60m mobile operation
 

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?

60m mobile operation
 

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?

60m mobile operation
 

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

60m mobile operation
 

On Feb 23, 7:06 am, Scott wrote:
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?- Hide quoted text -

- Show quoted text -

Hmmm, one could go to Terman, et. al... Lots of heavy math... ughhhh
One could ask the mobile whip manufacturer what the relative gain of
his product is - On second thought that's unlikely to get an answer
other than 42... (See: HitchHikers Guide To the galaxy)

Or one could do the bone simple, farm boy stupid, yet amazingly
effective method of comparing the relative length of the mobile whip
to a quarter wave vertical...
First, the quarter wave vertical is half the length of a dipole so you
immediately have a multiplier of 2...
(Awwww right you nit pickers, DOWN! - Yes I know about vertical-P
loss compared to horizontal-P, but I'm farm boy simple for this one)
Assume the 1/4 Lambda vertical is 45 feet (rough number, I'm a farm
boy, remember) and the whip is 8 feet... Then 45/8 = 5.6 ratio...
So 2 times 5.6 = 11.2 ratio so far...
Therefore 11.2 times 50w = 284 watts...

Now the efficiency of a mobile whip that is just over 20% tall (of a
quarter wave) is roughly 8%-10% (swag) Lets call it 10% for rough
numbers therefore we can expand the 284 watts by dividing 0.1 into
it... or 2840 watts.... Which will make your IC-706 sweat a bit...

OK nitpickers, have fun...

denny / k8do

60m mobile operation
 

Scott wrote:

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

Scott
N0EDV

SNIPPED

There are two easy methods and one rule of thumb method that will get you into
the ballpark.

1) As Cecil replied, divide the radiation resistance by the feedpoint
resistance. EZNEC will give a reasonable value for radiation resistance and an
MFJ 259B [~$250] will give a measure of the feedpoint resistance.

2) A freeware program, mobile antenna, will also calculate the efficiency.

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.

/s/ DD

60m mobile operation
 

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

60m mobile operation
 

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

60m mobile operation
 

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

60m mobile operation
 

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

60m mobile operation
 

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?

60m mobile operation
 

OK, I take that answer...now, why did the FCC go with an ERP as that
would require calculation rather than a measurement. Hard to measure
ERP as far as I know...

Oh well, go figure!

Scott
N0EDV

Dave 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?

Scott
N0EDV

SNIPPED

There are two easy methods and one rule of thumb method that will get
you into the ballpark.

1) As Cecil replied, divide the radiation resistance by the feedpoint
resistance. EZNEC will give a reasonable value for radiation resistance
and an MFJ 259B [~$250] will give a measure of the feedpoint resistance.

2) A freeware program, mobile antenna, will also calculate the efficiency.

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.

/s/ DD

60m mobile operation
 

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

60m mobile operation
 

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.

60m mobile operation
 

On Feb 23, 7:57 pm, Scott wrote:
OK, I take that answer...now, why did the FCC go with an ERP as that
would require calculation rather than a measurement. Hard to measure
ERP as far as I know...


Because ERP (or EIRP, depending on the application) is how most
licensing works, because that's what's important for spectrum
management in a shared band. Ham radio is somewhat unique in that the
rules are applied on power somewhere in the middle of the system (i.e.
in the feedline from Tx to antenna), with no limits (except for RF
safety) on the radiated field strength. If you can build a 60dBi
antenna and radiate 1.5 GW EIRP, you can do it. (part of that
'encouraging experimentation and advances in the radio art').

yes, commercial broadcast is regulated in terms of power output, but,
since you have to do a "proof of performance" and demonstrate that you
have a certain field strength at a distance, it's really regulating
ERP. Change your antenna gain, and they can conceivably make you
change your Tx power.

60m mobile operation
 

On Sat, 24 Feb 2007 03:57:24 +0000, Scott
wrote:

OK, I take that answer...now, why did the FCC go with an ERP as that
would require calculation rather than a measurement. Hard to measure
ERP as far as I know...

Hi Scott,

This never intimidated the FCC when they handed me tests for
RadioTelephone Second and First Class. In this group, we can account
for ERP by using modeling tools such as EZNEC. This and other
modeling tools generally agree with measurements found in the field.

73's
Richard Clark, KB7QHC