That's why all this talk about HIGH POWER is kinda a non issue.... At least
for me. Except for not being gentlemanly and legal.
1500 watts is +62 and 5000 watts is +66 ...Then the guys that reportedly
run 5000 watts are 24dB over S9, and I'm a measly 20dB over S9....
Big deal!
73
Jim W7RY
On Sat, Apr 3, 2010 at 9:48 AM, James Colville <jimw7ry@gmail.com> wrote:
> Get your calculator out. 30dB down from 1500 watts is how much power?
>
>
> 1500 watts=+61.8 dBm minus 30 db (which is what the harmonic would be down
> normally) = +30dBm. +30dBm = 1 watt. Evenif the harmonic is only down 25
> db, that is only 3 watts.
>
>
> Not much power do dissipate is it?
>
> 73
> Jim W7RY
>
>
>
> On Sat, Apr 3, 2010 at 9:32 AM, David Cutter <d.cutter@ntlworld.com>wrote:
>
>> Jim
>>
>> Thanks for the tutorial.
>>
>> I've often wondered about the movement of energy in and around a stub.
>> Harmonic energy is delivered from the PA to the output feeder and onwards
>> to
>> the stub. Would I be right in saying that the harmonic energy is
>> reflected
>> from the stub back to the PA where it is absorbed in the output filter?
>> If
>> so, this energy is absorbed as heat, it has to go somewhere. Does any of
>> it
>> get back to the output device? A pi output filter is a low pass filter in
>> either direction, so, I'm guessing that harmonics are mostly absorbed
>> there,
>> but is there much attenuation in that direction?
>>
>> David
>> G3UNA
>>
>>
>> > On Tue, 30 Mar 2010 09:19:15 -0400, Carl wrote:
>> >
>> >>Those are fairly common for multi TX stations to knock down harmonics
>> and
>> >>phase noise.
>> >
>> > Yes. I'm currently working on a Q&A style tutorial on coax and stubs.
>> The
>> > first draft is at http://audiosystemsgroup.com/Coax-Stubs.pdf
>> >
>> > Comments are appreciated. I would especially appreciate additions to the
>> > table of amps and output circuits.
>> >
>> > W2VJN's book is excellent, and worth the money if you're doing any sort
>> of
>> > multi-transmitter station. Available from Inrad (the crystal filter
>> > people)
>> > for $20. There are also four excellent pieces in QST written by Ward
>> > Silver, N0AX. They are cited in my tutorial. And George has contributed
>> > some of his work on stubs to the 2010 ARRL Handbook.
>> >
>> > As to the effect of a stub on the current waveform -- a proper stub (or
>> > combination of stubs) should be invisible at the TX frequency, but a
>> short
>> > circuit at even order harmonics. If the amp has reasonable output
>> > filtering
>> > without the stub, the stub should have no significant effect on that
>> > current waveform.
>> >
>> > 73,
>> >
>> > Jim Brown K9YC
>> >
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>>
>
>
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