|[AMRadio] AM Transmitter Advice??|
John E. Coleman (ARS WA5BXO)
wa5bxo2005 at pctechref.com
Sat Feb 18 18:39:31 EST 2006
I have heard rumors of a citation or two but only in extreme cases such as
10 or 20 KW PEP and I don't know if the rumors are true.
As I understand it the trick, that the FCC was to prevent, and someone was
trying to get away with, was to run a 304TL with about 100 Volts on the
plate in a GG configuration. Forward bias it to a high plate current like 1
Amp, so that it acts like a switch that is on. Then drive it with 5 KW PEP.
It may have been some other some scenario as this but I think you get the
An Now, For Something Completely Different.
Then there was the trick that a gentleman up in 3 land, I think, was
going to run the high level double sideband reduced carrier generator type
rig but he was not reducing the carrier just increasing the SBs via an extra
upside down tube, as it was commonly called. The sideband power would
continue to go up without distortion (if copied on a proper synchronized
product detector) after the first tube was over modulated in the negative
direction. The voltage and power would be diverted to the upside down tube
where sideband power would continue. There was trouble with the specific
rule interpretation at the time in the FCC. Of course any of us today, would
be able to see that the upside down tube's audio plate current and audio
voltage must also be counted as part of the input power. But the FCC was
having trouble deciding, at least as I understand it. At any rate, I think
they got him for being outside the 40 meter band limits. You may remember
more of the specifics on this Don.
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Donald Chester
Sent: Saturday, February 18, 2006 4:41 PM
To: amradio at mailman.qth.net
Subject: RE: [AMRadio] AM Transmitter Advice??
>My understanding was.
>Under the old rules stage or stages, that provide output to the antenna,
>total power should not exceed 1000 watts DC input. This includes the sum
>the driver and final in the case of GG output circuit.
>I think that rule was tested.
I recall that was the rule. But it seems to me it was much ado about
nothing. At most, the feedthrough power would be 10% of the total output
power. How much signal strength gain could you get from increasing your
Of course, back in those days the FCC was very nitpicky about the ham rules,
as they still are with broadcast stations. But they have shifted to the
opposite approach with ham radio. Riley's efforts have rooted out the
rottenest of the apples, but I suspect ham radio enforcement is still pretty
low on the FCC's priority list, as long as the violations don't cause
interference to other radio services.
Since they changed the power rule, I have never heard of a SINGLE case of a
ham receiving a citation for running too much p.e.p.
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