[email protected] wrote:
In a message dated 4/12/00 10:16:44 PM GMT Daylight Time,
[email protected] writes:
<< Very few signals generated by such amplifiers and used by radio amateurs
have
a pure sine wave output after one 5 pole LPF, except at very low power
levels, >>
Hello.
I think you will find that the relative level of harmonics (dBc) will depend
on the characteristics of the LPF and source / load impedances i.e. the
correct filter terminating impedance, and not the applied power levels.
Equally: The relative level of radiated harmonics (dBc) is generally
speaking independent of antenna whether it's at 130 feet or a long wire a
"few feet off the ground"
"amateurs....push class D/E amplifier too hard" - With square wave drive the
harder they are driven, the better they are.
No one has a pure sinewave output.
A low pass filter will not remove key clicks as they are within the passband
of the LPF.
90% of multikilowatt MF broadcasters use class D/E etc.
Surprisingly, the UK amateur radio licence allows up to 1% of energy to fall
outside the amateur bands, so this would not be of any interest to the RIS.
In anycase 250Hz is 'inband' and would be considered a problem to be resolved
by the band's users. - If it was considered a problem at all.
On any other amateur band it would be considered a problem if it
interfered with
other amateur transmissions so what is special about 136 khz. It would
certainly
concern me if every cw transmission had a 250 khz spread of key clicks.
Dont
suppose you are a regular cw operator.
I think the RIS would be very interested if there was a complaint.
You misread my original message and getting confused about key clicks
and
harmonics.
Key clicks are one thing and harmonics another.
1. I was making the point that the transmission had key clicks and
needed to be
checked.
2. I was saying that because of the intensity of the signal, the odd harmonics
also needed to be checked to avoid interference to other services and use
several poles of LPF'S to avoid harmonic radiation, especially if an erp of 100
w is to be used.
Using a computer and spectran / gram clearly demonstrates the larger
bandwidth occupied by fast CW transmissions. As the band is very narrow,
should we put an upper speed limit on CW - to limit the occupied bandwidth?
You dont have to worry David there is no chance of you exceeding the
speed limit
!!!!!!!!!!
(Hi)
Goodness Mal. They only had a mast bigger than yours.
The difference is that I bought and installed my own mast !!!!!!!!!!!
"Oswald Mc Donald Jr"-----
Nothing like owning your own MERCEDES instead of borrowing a friends
!!!!!!
"So many negative vibes" - Donald Sutherland.
Was Donald able to explain to you why your signals were not getting as
far as Scarborough in spite of all the rhetoric from your qth.
73
David
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