[RFI] Spurious signal levels
Bob Wanderer
Bob Wanderer <aa0cy@nwrain.com>
Wed, 20 May 1998 20:34:40 -0700
When I had a spurious problem on 14 MHz back in the late 70's, I
called the FCC (Laurel, Md. Lab) to find out whether the
measurement was into a
dummy load or into the antenna itself (as the levels were
different and into the dummy load less than the limits discussed below).
They couldn't answer. I eventually was able to solve the problem (brought
SWR from 3:1 to 1.7:1 by modifying the angle of the radials on the trapped
1/4-wave vertical). I lost a bit of respoect for the Commission's technical
representatives. Anyway, what's the answer?
73, Bob AA0CY
----------
From: Hare, Ed, W1RFI[SMTP:ehare@arrl.org]
Sent: Wednesday, May 20, 1998 1:58 PM
To: Ian White, G3SEK; rfi
Subject: RE: [RFI] Spurious signal levels
Hi, Ian,
They are found in the Code of Federal Regulations, Title 46, Part 97,
Section 307 (97.307) of the FCC regs, but they are a bit cryptic. Let me
translate into plain English (or at least the American version of same. :-)
).
On HF, spurious emissions must be attenuated below the transmitter mean
power output:
5 W or less mean power output: 30 dB
>5W mean power output: 40 dB
The additional requirement is that no spurious emission may exceed 50
milliwatts mean power output, so above 500 W, the attenuation increases by
the formula: attenuation (dB) = 13 + 10 log (Pwatts).
On from 30-225 MHz, the requirement is even more convoluted.
The rules state that attenuation from 30-225 MHz shall be at least 60 dB for
transmitters using more than 25 watts mean power output.
For transmitters using less than or equal to 25 watts mean power output, the
required attenuation is 40 dB, but no spur is permitted to exceed 25
microwatts, but no spur need be attenuated to less than 10 microwatts. The
combination yields::
P < 0.1 watts, attenuation = 50 + 10 log(P)
P > 0.1 watts and p < 0.25 W, attenuation = 40 dB
P > 0.25 W and P < 25 W, attenuation = 46 + 10 log(P)
P > 25 W, attenuation = 60 dB
Above 225 MHz, there is NO specific attenuation specified, only the general
requirement that the emission purity be in compliance with good engineering
and good amateur practice.
In addition, on all frequencies, if a spurious emission causes harmful
interference to another radio service, the amateur must take whatever steps
are necessary to eliminate the interference.
73 from ARRL HQ,
Ed Hare, W1RFI
ARRL Lab
The actual text of the rules can be found at
http://www.access.gpo.gov/nara/cfr/cfr-table-search.html. Search
http://www.access.gpo.gov/nara/cfr/cfr-table-search.html.
Here is the applicable section:
ec. 97.307 Emission standards.
(a) No amateur station transmission shall occupy more bandwidth than
necessary for the information rate and emission type being transmitted,
in accordance with good amateur practice.
(b) Emissions resulting from modulation must be confined to the band
or segment available to the control operator. Emissions outside the
necessary bandwidth must not cause splatter or keyclick interference to
operations on adjacent frequencies.
(c) All spurious emissions from a station transmitter must be
reduced to the greatest extent practicable. If any spurious emission,
including chassis or power line radiation, causes harmful interference
to the reception of another radio station, the licensee of the
interfering amateur station is required to take steps to eliminate the
interference, in accordance with good engineering practice.
(d) The mean power of any spurious emission from a station
transmitter or external RF power amplifier transmitting on a frequency
below 30 MHz must not exceed 50 mW and must be at least 40 dB below the
mean power of the fundamental emission. For a transmitter of mean power
less than 5 W, the attenuation must be at least 30 dB. A transmitter
built before April 15, 1977, or first marketed before January 1, 1978,
is exempt from this requirement.
(e) The mean power of any spurious emission from a station
transmitter or external RF power amplifier transmitting on a frequency
between 30-225 MHz must be at least 60 dB below the mean power of the
fundamental. For a transmitter having a mean power of 25 W or less, the
mean power of any spurious emission supplied to the antenna transmission
line must not exceed 25 <greek-m>W and must be at least 40 dB below the
mean power of the fundamental emission, but need not be reduced below
the power of 10 <greek-m>W. A transmitter built before April 15, 1977,
or first marketed before January 1, 1978, is exempt from this
requirement.
(f) The following standards and limitations apply to transmissions
on the frequencies specified in Sec. 97.305(c) of this part.
(1) No angle-modulated emission may have a modulation index greater
than 1 at the highest modulation frequency.
(2) No non-phone emission shall exceed the bandwidth of a
communications quality phone emission of the same modulation type. The
total bandwidth of an independent sideband emission (having B as the
first symbol), or a multiplexed image and phone emission, shall not
exceed that of a communications quality A3E emission.
(3) Only a RTTY or data emission using a specified digital code
listed in Sec. 97.309(a) of this part may be transmitted. The symbol
rate must not exceed 300 bauds, or for frequency-shift keying, the
frequency shift between mark and space must not exceed 1 kHz.
(4) Only a RTTY or data emission using a specified digital code
listed in Sec. 97.309(a) of this part may be transmitted. The symbol
rate must not exceed 1200 bauds, or for frequency-shift keying, the
frequency shift between mark and space must not exceed 1 kHz.
(5) A RTTY, data or multiplexed emission using a specified digital
code listed in Sec. 97.309(a) of this part may be transmitted. The
symbol rate must not exceed 19.6 kilobauds. A RTTY, data or
[[Page 700]]
multiplexed emission using an unspecified digital code under the
limitations listed in Sec. 97.309(b) of this part also may be
transmitted. The authorized bandwidth is 20 kHz.
(6) A RTTY, data or multiplexed emission using a specified digital
code listed in Sec. 97.309(a) of this part may be transmitted. The
symbol rate must not exceed 56 kilobauds. A RTTY, data or multiplexed
emission using an unspecified digital code under the limitations listed
in Sec. 97.309(b) of this part also may be transmitted. The authorized
bandwidth is 100 kHz.
(7) A RTTY, data or multiplexed emission using a specified digital
code listed in Sec. 97.309(a) of this part or an unspecified digital
code under the limitations listed in Sec. 97.309(b) of this part may be
transmitted.
(8) A RTTY or data emission having designators with A, B, C, D, E,
F, G, H, J or R as the first symbol; 1, 2, 7 or 9 as the second symbol;
and D or W as the third symbol is also authorized.
(9) A station having a control operator holding a Novice or
Technician Class operator license may only transmit a CW emission using
the international Morse code.
(10) A station having a control operator holding a Novice or
Technician Class operator license may only transmit a CW emission using
the international Morse code or phone emissions J3E and R3E.
(11) Phone and image emissions may be transmitted only by stations
located in ITU Regions 1 and 3, and by stations located within ITU
Region 2 that are west of 130 deg. West longitude or south of 20 deg.
North latitude.
(12) Emission F8E may be transmitted.
(13) A data emission using an unspecified digital code under the
limitations listed in Sec. 97.309(b) also may be transmitted. The
authorized bandwidth is 100 kHz.
[54 FR 25857, June 20, 1989; 54 FR 30823, July 24, 1989, as amended at
54 FR 39537, Sept. 27, 1989; 60 FR 15688, Mar. 27, 1995]
----------
>From: Ian White, G3SEK
>To: rfi
>Subject: [RFI] Spurious signal levels
>Date: Wednesday, May 20, 1998 5:40PM
>
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>Message-ID: <Cx7zXbAydwY1EwO0@ifwtech.demon.co.uk>
>Date: Wed, 20 May 1998 17:40:18 +0100
>To: rfi@contesting.com
>From: "Ian White, G3SEK" <G3SEK@ifwtech.demon.co.uk>
>Subject: [RFI] Spurious signal levels
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>Please can someone point me toward the FCC regulations on spurious
>signal levels from transmitters for the amateur service?
>
>Are they on the FCC web site?
>
>73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
> 'In Practice' columnist for RadCom (RSGB)
> http://www.ifwtech.demon.co.uk/g3sek
>
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