Does anybody know the bandwidth of the Voyager 2 radio receiver's front-end?
I know that the current data rate of the receiver is of order tens of bits per second, and I have one estimate of 18 Hz. Could that be correct?
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This is an interesting but challenging question. I've found the following footnote on page 39 of Voyager Telecommunications, DESCANSO Design and Performance Summary Series, Article 4 Section 7.2.6 Voyager 2 Procedures to Compensate for Voyager 2 Receiver Problem and so am posting as a partial answer for now. I will have to dig deeper and then update accordingly.
4The term “best-lock frequency” in a phase-locked loop refers to the frequency the loop would naturally oscillate at with no input. When the receiver loop is receiving an uplink carrier exactly at BLF (the center of its band- width), the loop would indicate a zero static phase error telemetry measurement. The bandwidth of a healthy Voyager receiver is about 100 kHz, as compared with 100 Hz for the receiver with the failed tracking loop.
This does not mean the received signal can be 100 kHz wide, but I think it means that if a narrow signal were within this range, and the receiver were working properly, it could be locked on to and decoded.
Again, partial answer only for now...
Experts feel free to comment, edit, or post a better answer.
Does anybody know the bandwidth of the Voyager 2 radio antenna?
Well there are different bandwidths for different functions. This summary of Voyager's telecommunications systems by JPL's Deep Space Communications and Navigations Systems Center of Excellence (DESCANSO) claims Voyager has 4 main functions for communication. They are carrier tracking (Doppler), command, telemetry, and ranging. NASA's webpage on Voyager's Instrument Information states,
. . . the carrier tracking loop bandwidth was 18 Hz, and the ranging channel noise bandwidth was 1.5 MHz.
EDIT: I initially thought that the OP was asking about the frequency of Voyager's communications system. So I might as well add that information too.
The uplink frequency Voyager receives (Earth to Voyager) is 2113.3 MHz. These are the downlink (Voyager to Earth) frequencies of both Voyager 1 and 2:
Voyager 2 uses a frequency of 2295 MHz (S-band) or 8415 MHz (X-band).