"Len Over 21" wrote in message
...
In article , "Dan Finn"
writes:

"Len Over 21" wrote in message
...

On most modern HF transceivers, the 3rd harmonic has the strongest
content of RF. The 3rd harmonic of 3.5 to 4.0 MHz is 10.5 to 12 MHz
and there aren't many "ham listening frequencies" there, are there?

For most modulated sine waves, the 3rd harmonic is usually the strongest
*harmonic* although it depends upon several factors. Generally, the odd
harmonic components add and the negative components subtract with
modulated
sine waves.

Oh my, such interesting math (which wasn't shown)...:-)

If you do not know this to be true without seeing the math worked out for
you, then you should not be discussing harmonics in a technical context.

That isn't quite the case in any real world OR the theoretical world.

Your saying so does not make your statement true. We are talking technical
issues here which are a matter of common knowledge to the RF community so
your flames are irrelevant.


First of all, in the real world, you must be presuming some absolute
zero phase shift for each harmonic to make your statement. That just
doesn't exist.

Oh God...Earth to Len....harmonics *are* phase shifted. If you reduce the
phase shift to zero, then you have eliminated the harmonics, stupid.

I can do the numbers on the series formulas for AM, FM, or PM no
problem but so few in here can follow even the beginnings of such that
I won't care to put it in public view...:-)

Having said that, most modern rigs that produce FCC quality
signals will filter such harmonics several 10's of dB rendering reception
almost impossible except in the near field.

Really?!? They work PERFECTLY ACCORDING TO SPECIFICATIONS
ALL THE TIME?!?!?!

Pretty close, most of the time, dummy.


That's not a realistic view, but feel free to indulge if you've laid
out a
big
plastic for a couple kilodollars worth of transceiver. :-)

That old standby tube output matching circuit, the "Pi-network" is only
good for about 18 db per octave attenuation above cutoff frequency.

Since 3dB is half the power, you cut the power in half 6 times. 18dB is not
bad over one octave.

Not
all modern transceivers have such "lowpass filters" since they rely on
Class B or AB linear amplifiers with rather broadband transformers
matching PA to load.

They had better filter it so that you do not have a significant signal at
12MHz when transmitting in the 75 meter band.

A typical 100 W RF transceiver has a fundamental power output of +50
dbm. If there is as much as "60 db harmonic attenuation" in it, the
harmonics can be -10 dbm into the load. That's 100 microWatts and
DOES radiate and rather beyond the Near Field...the level is a lot
higher
than most "40 db over S9" signals (depending on who assigned what
levels to a local transceiver S meter).

0.1mW? Hardly a significant signal.


I thought I needed to correct
this BS, that emanates from someone who claims to understand modern
amateur
technology theory.

Feel free to do your numbers in public, senior

That would be a rather boring and somewhar ominous excercize to do on a
newsgroup, dummy.

Call it all the "BS" you want to. When you can actually MAKE a linear
(of any class) go as low as 40 db down on total harmonic output, I'll
be
giving you a round of applause.

Hams transmitting signals of any significance on 12MHz
will not be hams for long.

Oh? Were there any recent NALs published at the FCC or ARRL sites
on such things?

Not that I know of. Not for transmitting harmonics on 12MHz using 'modern'
transceivers, as you called them.

Let us know, please, I've not seen any of those
concerning out-of-ham-band interference due to harmonic generation.

Neither have I. Most NAL's are for in band interference, referred to as QRM.

de KR4AF

LHA