Gorman Redlich Manufacturing Co CRW-S 사용자 설명서
WARRANTY
For a period of 2 years from date of shipment, Gorman-Redlich will repair or replace, at its option,
any Model CRW-S receiver that fails in normal service without a charge for parts or labor and with a
flat $25 fee, prepaid by purchaser, to cover shipping and handling. Receivers can only be accepted
for adjustment under Warranty following notification by letter, telephone or e-mail. Receivers
showing evidence of modification or abuse, in the judgment of Gorman- Redlich, cannot be accepted
for repair under Warranty, but will be repaired for a reasonable fee, with the consent of the purchaser.
any Model CRW-S receiver that fails in normal service without a charge for parts or labor and with a
flat $25 fee, prepaid by purchaser, to cover shipping and handling. Receivers can only be accepted
for adjustment under Warranty following notification by letter, telephone or e-mail. Receivers
showing evidence of modification or abuse, in the judgment of Gorman- Redlich, cannot be accepted
for repair under Warranty, but will be repaired for a reasonable fee, with the consent of the purchaser.
NOAA WEATHER RADIO
The National Weather Service (NWS), a branch of the National Oceanic and Atmospheric
Administration (NOAA), operates a network of stations broadcasting around-the –clock weather on
seven frequencies, spaced at 25 KHz intervals from 162.4 MHz to 162.55 MHz. About 890
stations are in operation as of April 2004. Modulation is narrow-band FM, and polarization is
vertical.
In addition to local and national weather, other information tailored to the locality, such as soil
conditions and marine information, is broadcast by NWS. If a severe storm, flood, or nuclear
attack threatens, three bursts of coded FSK is followed by a 1050 Hz signal tone transmitted for ten
seconds by NWS. The Model CRW-S will be demuted after 6 seconds of 1050 tone for automatic
warning of impending danger.
The FCC has authorized rebroadcast of NWS transmissions by commercial AM, FM and TV
stations, provided: 1) rebroadcast must be within one hour of receipt, 2) commercials aired during
rebroadcast must not convey an endorsement by the government, and 3) credit must be given to
NWS.
GENERAL DESCRIPTION OF MODEL CRW-S RECEIVER
The RF section of the Model CRW-S is a double-conversion superheterodyne, with both oscillators
crystal-controlled. First IF is 21.4 MHz and second IF is 455 KHz. Receive frequency can be
selected to be any one of the seven NWS frequencies between 162.4 and 162.55. The passband of
the receiver is controlled by a four-pole crystal filter at 21.4 MHz and a four-pole ceramic filter at
455 KHz to produce a response characteristic with a nearly ideal rectangular shape about +/- 15
KHz wide and sufficient skirt selectivity so that adjacent channels at +/- 25 MHz are attenuated
about 70 db. The RF amplifier (Q1) and the first mixer (Q2) are dual-gate MOSFETS, having
excellent cross-modulation rejection. The second mixer and the second local oscillator are part of
U1. Most of the receiver gain takes place at 455 KHz in a limiting amplifier that is part of U1. U1
also contains a product detector for demodulation of the narrowband FM signal, and an operational
amplifier that is used to shape the audio passband and to provide a low-impedance audio output.
Audio pre-amplification and power amplification take place in U9, U10, U11.
crystal-controlled. First IF is 21.4 MHz and second IF is 455 KHz. Receive frequency can be
selected to be any one of the seven NWS frequencies between 162.4 and 162.55. The passband of
the receiver is controlled by a four-pole crystal filter at 21.4 MHz and a four-pole ceramic filter at
455 KHz to produce a response characteristic with a nearly ideal rectangular shape about +/- 15
KHz wide and sufficient skirt selectivity so that adjacent channels at +/- 25 MHz are attenuated
about 70 db. The RF amplifier (Q1) and the first mixer (Q2) are dual-gate MOSFETS, having
excellent cross-modulation rejection. The second mixer and the second local oscillator are part of
U1. Most of the receiver gain takes place at 455 KHz in a limiting amplifier that is part of U1. U1
also contains a product detector for demodulation of the narrowband FM signal, and an operational
amplifier that is used to shape the audio passband and to provide a low-impedance audio output.
Audio pre-amplification and power amplification take place in U9, U10, U11.