AMSAT NEWS SERVICE SPECIAL BULLETIN ANS-321
Downlink audio is 5 kHz deviation, as expected. Many will perceive that the audio is "low." This is an effect of the filtering below 300 Hz, which provides for the DUV telemetry, coupled with any noise on the uplink signal resulting from lack of full quieting or being off frequency. That makes for less fidelity than a typical receiver in terms of audio frequencies passed.
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It is important to remember that science is the reason behind the Fox-1 satellites. Not only does science help with the launch cost, it provides a great amount of educational value both from the science payload and in amateur radio itself. The data-under-voice (DUV) telemetry is an excellent way to provide the science without sacrificing the use of the satellite for communications, which would be the case if higher speed downlinks were needed. DUV provides constant science as long as the repeater is in use, which in turn provides more downlink data for the science - a mutually beneficial combination.
I designed the DUV telemetry system on Fox-1, with an important suggestion (use 8b10b coding for spectral shaping) from Tony, AA2TX. It's important to remember the severe design compromises imposed by the requirement that the satellite itself be an analog FM repeater, confining the telemetry to modulating frequencies below 300 Hz.
These design compromises would have been unnecessary with a fully digital communications payload, like those on every non-amateur satellite launched in at least the past decade or two. I've made it clear that this is my last telemetry design for an analog spacecraft. It's past time for AMSAT to move into the all-digital era.
--Phil, KA9Q