Many of the R-390As that exist today are in the hands of vintage amateur radio collectors and amateur radio operators who contend that few modern solid state communications receivers can equal its performance.
32.
The most common use of crystal filters are at frequencies of 9 MHz or 10.7 MHz to provide selectivity in communications receivers, or at higher frequencies as a roofing filter in receivers using up-conversion.
33.
Ceramic filters tend to be used at 10.7 MHz to provide selectivity in broadcast FM receivers, or at a lower frequency ( 455 kHz ) as the second intermediate frequency filters in a communication receiver.
34.
For really high-performance receivers, such as satellite communications receivers and military / naval receivers, two-stage ( " double conversion " ) and even three-stage ( " triple conversion " ) superheterodyne processing is frequently used.
35.
In order to meet their financial obligations, Hallicrafters produced radios for other manufacturers until they were financially able to begin production of their own line of communications receivers, starting with the SX-9'Super Skyrider', in late 1935.
36.
This was an ISA bus card which transformed a Windows-based computer into a wide-coverage communications receiver, making it possible to receive point-to-point communications ( ham radio, utilities, police, space research, etc . ) on an ordinary PC.
37.
Import and operation of radio scanners or radio communications receivers capable of listening to HF VHF UHF and satellite aircraft or maritime radio frequencies is tolerated if user has an appropriate amateur / maritime / aircraft radio licence.
38.
Listeners use inexpensive portable " world band " radio receivers to access the shortwave bands, and some advanced hobbyists employ specialized communications receivers featuring digital technology designed for optimum reception of shortwave signals, along with outdoor antennas to enhance performance.
39.
The terms " radio scanner " or " police scanner " generally refer to a communications receiver that is primarily intended for monitoring UHF landmobile radio systems, as opposed to, for instance, a receiver used to monitor international shortwave transmissions.
40.
Normal social influence research focuses on words or linguistic choices and scripts in order to effect a certain level of influence on a communication receiver or individual when in engaging in the act of inspiring change in a behavior or preconceived attitude.
