[AMRadio] AM Transmitter Advice?? (meter time constant)

Jim Wilhite w5jo at brightok.net
Mon Feb 20 17:50:14 EST 2006

Hi Don:

Damn topic!  This started me wondering about measuring PEP and Carrier Power 
today.  So I went to the FCC website to look for the standards that apply. 
Well I finally found it.  Here is a link to Chapter 1-FCC, Subpart J, 
Section 2.1046, if anyone is interested in reading it.  I hope the link 


This was originally 39 FR 5919, 2/15/74    Redesign and amended at 63 FR 
36599, 7/7/98

Good reading if one wishes to be compliant.

73  Jim

----- Original Message ----- 
From: "Donald Chester" <k4kyv at hotmail.com>
To: <amradio at mailman.qth.net>
Sent: Monday, February 20, 2006 11:00 AM
Subject: Re: [AMRadio] AM Transmitter Advice?? (meter time constant)

>>From: "Bob Bruhns" <bbruhns at erols.com>
>> > Bacon, not trying to be contrite, but where in the
>> >old rules did the .25
>> > second time constant appear?  I have a copy of the
>> >old rules and don't see
>> > it.  It says only that "have the means".
>>Hi Jim... Hmm, it came from my sometimes flakey
>>memory...  I'm pretty sure there was a 0.25 second spec
>>for the metering somewhere... maybe it was simply
>>assumed that the meter time constant would be about
>>0.25 seconds.
>>From ARRL's "Single Sideband for the Radio Amateur," p. 14, 1958 edition:
>                            S.S.B. POWER LIMIT
> ...We quote from a Commission letter addressed to ARRL:
>   The following . . . may be considered as a presently acceptable method 
> for determining the d.c. plate power input to the final r.f. stage of a 
> single-sideband amateur transmitter:
>   The maximum d.c. plate power input to the radio frequency tube or tubes 
> supplying power to the antenna system of a single-sideband 
> suppressed-carrier transmitter, as indicated by the usual plate voltmeter 
> and plate milliammeter, shall be considered as the "input power" insofar 
> as Sections 12.131 and 12.136(d) of the Commission's rules are concerned, 
> provided the plate meters utilized have a time constant not in excess of 
> approximately 0.25 second, and the linearity of the transmitter has been 
> adjusted to prevent the generation of excessive sidebands.  The "input 
> power" shall not exceed one kilowatt on peaks as indicated by the plate 
> meter readings.
> Don k4kyv

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