When matching a very short whip one gets a big reading but
further down the road is could all be dissapeared.

Can a closeby fieldstrenght measurement be done ?
The magnetic field is also great with a short whip.

If you are changing nothing except the impedance matching, you can put
the field strength meter anywhere, and the highest reading will mean
you've adjusted it for the strongest signal at any distance.

Roy Lewallen, W7EL

Norbert M. wrote:
When matching a very short whip one gets a big reading but
further down the road is could all be dissapeared.

Can a closeby fieldstrenght measurement be done ?
The magnetic field is also great with a short whip.

On 6 ene, 09:55, "Norbert M." wrote:
When matching a very short whip one gets a big reading but
further down the road is could all be dissapeared.

Can a closeby fieldstrenght measurement be done ?
The magnetic field is also great with a short whip.
Hello Norbert

A similar question appeared some days ago in a Dutch amateur radio
newsgroup.

As Roy also mentioned, when you do not change the antenna (inclusive
any ground system) and also not change the E-field meter position and
orientation, but only change the matching, every dB increase in the
near field, will give the same dB increase over distance. Assuming
that your matching network does not produce significant E-field.

Determining the radiated power from near field measurements is
theoretically possible, but not easy in real world for most
amateurs.

You might measure the field strength at a certain (near field)
distance. Run an EM simulation for your antenna construction
(inclusive ground system if present). Compare the simulated (near
field) E-field with the measured value. From the radiated power (in
the simulation) you can calculate the radiated power from your
antenna.

Best regards,

Wim
PA3DJS
www.tetech.nl

Wim, PA3DJS wrote:
"Determining the radiated power from near field measurements is
theoretically possible, but not easy in the real world for most
amateurs."

My experience in tuning commercial 2-way HF radios for maximum power
radiated. It could be obtained by placing my multimeter (using crystal
rectifiers for a.c. scale rectification) with its test leads attached on
the hood of the vehicle containing the radio and tuning for maximum. The
measured performance proved as good as any other tuning method.

Best regards, Richard Harrison, KB5WZI

On 6 Jan, 16:06, (Richard Harrison) wrote:
Wim, PA3DJS wrote:

"Determining the radiated power from near field measurements is
theoretically possible, but not easy in the real world for most
amateurs."

My experience in tuning commercial 2-way HF radios for maximum power
radiated. It could be obtained by placing my multimeter (using crystal
rectifiers for a.c. scale rectification) with its test leads attached on
the hood of the vehicle containing the radio and tuning for maximum. The
measured performance proved as good as any other tuning method.

Best regards, Richard Harrison, KB5WZI

But that doesn't change anything that Wim stated which is entirely
correct.
You did not "determine" radiated power.......period
Art

art wrote:
"You did not 'determine" radiated power.....period"

Exactly right. Power in the near field is largely reactive. To determine
radiated power you measure the in-phase volt-amperes with a wattmeter.
The multimeter on the hood maximizes output same as a Bird wattmeter for
practical results, but you hanen`t quantified watts out.

Best regards, Richard Harrison, KB5WZI

On 7 ene, 04:25, (Richard Harrison) wrote:
art wrote:

"You did not 'determine" radiated power.....period"

Exactly right. Power in the near field is largely reactive. To determine
radiated power you measure the in-phase volt-amperes with a wattmeter.
The multimeter on the hood maximizes output same as a Bird wattmeter for
practical results, but you hanen`t quantified watts out.

Best regards, Richard Harrison, KB5WZI

Hi Richard,

You can determine radiated power and radiation pattern by near field
measurements (theoretically). Please search for "poynting theorem"
and "Huygens principle", "Huygens Source" or "Fresnel diffraction
theory". Most texts require differential vector calculus.

Because determining radiated power based on E- and H-Field measurement
is generally not feasible for amateurs (and even for many
professionals), I suggested another approach based on E-field
measurements and EM simulation.

As absolute E-field measurement and EM simulation are within the reach
of amateur radio operators, one can both tune for maximum field and
determine absolute radiated power.

Of course you don't know how much power is dissipated in nearby
structures (buildings, etc).

Best regards,

Wim
PA3DJS
www.tetech.nl