Hans K0HB wrote:

Mike Coslo wrote


What is the basis for 50 watts?



NCRP Report No. 86, "Biological Effects and Exposure Criteria for
Radiofrequency Electromagnetic Fields", Copyright 1986, National
Council on Radiation Protection and Measurements, and ANSI/IEEE
C95.1-1992, "Safety Levels with Respect to Human Exposure to Radio
Frequency Electromagnetic Fields, 3 kHz to 300 GHz", Copyright 1992,
IEEE, Inc.

And that 50 watts affects calss A different than Class B?

I seriously doubt that a person that cannot handle 100 watts shild have
any license. Maybe class A shouldn't be alloed to have antennas over 10
feet off the ground either. Nasy falls.

- Mike KB3EIA -

"Mike Coslo" wrote

And that 50 watts affects calss A different than Class B?

Of course not. (This is another of those 'novel' questions.)

But my intention is that the Class B (learners permit with training wheels)
test be ultra simple, to allow as many applicants as possible. For that
reason, requiring qualification in esoterica like "Biological Effects and
Exposure Criteria for Radiofrequency Electromagnetic Fields" is
inappropriate. Thus the 50W power level recommended by the NCRP and
ANSI/IEEE ensures a modicum of safety for these beginners.

In the process of preparing for Class A (without training wheels) license,
the candidate would need to explore the RF-exposure safety issues which
would be on the qualification test. Then we could expect that they'd have
some appreciation of the hazards and how to ensure that their station is
engineered in compliance with the MPE criteria mandated by 97.13(c).

73, de Hans, K0HB

KØHB wrote:

"Mike Coslo" wrote


And that 50 watts affects calss A different than Class B?


Of course not. (This is another of those 'novel' questions.)

But my intention is that the Class B (learners permit with training wheels)
test be ultra simple, to allow as many applicants as possible. For that
reason, requiring qualification in esoterica like "Biological Effects and
Exposure Criteria for Radiofrequency Electromagnetic Fields" is
inappropriate. Thus the 50W power level recommended by the NCRP and
ANSI/IEEE ensures a modicum of safety for these beginners.

I would counter that it is a good idea for the initiate to know right
off the blocks that RF has some potential problems associated with it.

And while everyone talks about RF exposure, there are other problems
associated with RF that a person should know before they are allowed to
legally operate a rig. I had a problem trying to tune a longwire once,
and my trusty MFJ tuner nailed me good - bad knob design - it shouldn't
have the metal rim on the knob, which allows for some capacitive
coupling, so it seems. RF burns hurt! Power was probably around 50 watts.

I think the responsible thing to do, if safety is a concern, would be
to get those safety guidelines out of the way BEFORE going to advanced
licenses.


I also hope that your regulations would prohibit the Class B hams from
making or using a magloop antenna. I just did some calcs on a small
magloop for 40 meters, and at 50 Watts there is almost 5 kV across the
tuning cap. Ouch!


In the process of preparing for Class A (without training wheels) license,
the candidate would need to explore the RF-exposure safety issues which
would be on the qualification test. Then we could expect that they'd have
some appreciation of the hazards and how to ensure that their station is
engineered in compliance with the MPE criteria mandated by 97.13(c).

I think the candidate needs to know the safety issues long before this.
If the potential ham is smart enough to learn them for class A, they
should be smart enough to learn them for class B. If safety is first,
they shouldn't learn it second.

In article , Mike Coslo
writes:

Hans K0HB wrote:

Mike Coslo wrote

What is the basis for 50 watts?

NCRP Report No. 86, "Biological Effects and Exposure Criteria for
Radiofrequency Electromagnetic Fields", Copyright 1986, National
Council on Radiation Protection and Measurements, and ANSI/IEEE
C95.1-1992, "Safety Levels with Respect to Human Exposure to Radio
Frequency Electromagnetic Fields, 3 kHz to 300 GHz", Copyright 1992,
IEEE, Inc.

Hans dropped in a nice bibliographic note but did NOT say HOW
he arrived at his magical 50 W limit. :-)

Way too many variables in the amateur radio "station" arrangement
to say with some kind of certainty that 50 W is THE limit for any
class. FCC already showed that with a survey of some typical
California ham stations along with measurements of fields courtesy
of a couple of other government agencies and the hams who let them
all prowl around their property.

And that 50 watts affects calss A different than Class B?

I seriously doubt that a person that cannot handle 100 watts shild have
any license. Maybe class A shouldn't be alloed to have antennas over 10
feet off the ground either. Nasy falls.

100 Watts in a 50 Ohm system has an RMS RF Voltage of 70.7.
That's on the verge of burning human skin tissue.

50 Watts in a 50 Ohm system has 50 V RMS RF...still on the verge
of burning human skin tissue, although not as badly.

100 W of RF is little, piddly stuff to what I'm used to...like 15 KW up-
close-and-personal on HF, including walking around in antenna
fields of many and varied HF emitters...and 40 KW PEP HF stuff in
antenna fields in 1955. Most of us being personal with such powers
weren't suffering ill effects and almost all of us weren't licensed in
any "classes." We got the messages through.

---------

For some really in-depth looks at radio frequency radiation, go to the
Brooks AFB website and the documents at the USAF School of
Aerospace Medicine. The following is the cover page for one of the
shorter documents released in 1996:

http://www.brooks.af.mil/afrl/HED/he...uman-exposure/
cover.gif.html

That document title number is AL/OE-TR-1996-0035. It was
prepared in 1994. Be prepared to do a little math to find the
permissible RF field strengths...not much, just a little.

There's also FCC Office of Engineering and Technology
Bulletins 56 and 65 available on the FCC RF Safety webpage.
Only a few ANSI standards are free for download (if available),
the same with the IEEE site.

Maybe Hans will reveal what kind of aluminum suit he wears when
he fires up his "2.5 KW with increased drive" HF amplifier. :-)

LHA

(Len Over 21) wrote in message ...

100 W of RF is little, piddly stuff to what I'm used to...like 15 KW up-
close-and-personal on HF, including walking around in antenna
fields of many and varied HF emitters...and 40 KW PEP HF stuff in
antenna fields in 1955. Most of us being personal with such powers
weren't suffering ill effects and almost all of us weren't licensed in
any "classes." We got the messages through.

I have no doubt whatsoever that your proximity to high RF sources
has made you the "man" you are today, Lennie.

No doubt what so ever!

Steve, K4YZ

PS: Perhaps this is why we hear you talking about child rearing but
never hear about YOUR child-rearing experiences???

SR