Fox-1B

{{short description|American amateur radio satellite}}

{{Use American English|date=January 2021}}

{{Use dmy dates|date=January 2021}}

{{Infobox spaceflight

| name = Fox-1B

| names_list = AO-91
AMSAT OSCAR 91

| image =

| image_caption =

| image_size =

| mission_type = Communications

| operator = AMSAT{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2017-073E|title=AO-91|publisher=NASA GSFC|date=14 May 2020|access-date=7 January 2021}} {{PD-notice}}

| COSPAR_ID = 2017-073E

| SATCAT = 43017

| website =

| mission_duration =

| spacecraft =

| manufacturer = Vanderbilt University
Radio Amateur Satellite Corporation

| dimensions = {{cvt|10|x|10|x|10|cm}}

| launch_mass = {{cvt|1.3|kg}}

| power =

| launch_date = 18 November 2017,
09:47:36 UTC

| launch_rocket = Delta II 7920-10C
(Delta D378)

| launch_site = Vandenberg, SLC-2W

| launch_contractor = United Launch Alliance

| last_contact =

| decay_date =

| orbit_reference = Geocentric orbit{{cite web|url=https://www.n2yo.com/satellite/?s=43017|title=FOX-1B (RADFXSAT AO-91)|publisher=n2yo.com|accessdate=2018-06-24}}

| orbit_regime = Low Earth orbit

| orbit_periapsis = {{cvt|461.3|km}}

| orbit_apoapsis = {{cvt|823.7|km}}

| orbit_inclination = 97.70°

| orbit_period = 97.40 minutes

| apsis = gee

| programme =

| previous_mission =

| next_mission =

}}

Fox-1B, AO-91 or AMSAT OSCAR 91 {{cite web|url=https://amsat-uk.org/2017/11/18/radfxsat-fox-1b-ao-91|title=RadFxSat (Fox-1B) Launched, Designated AMSAT-OSCAR 91 (AO-91)|date=18 November 2017 |editor=Trevor Essex|publisher=AMSAT-UK|access-date=2018-06-24}} is a United States amateur radio satellite. It is a 1U Cubesat, was built by the AMSAT-NA and carries a single-channel transponder for FM radio. The satellite has a whip antenna for the 70 cm and 23 cm bands (uplink), and a second antenna for the 2 m band (downlink). Fox-1B is the second amateur radio satellite of the Fox series of AMSAT North America.

To facilitate a satellite launch as part of NASA's Educational Launch of Nanosatellites (ELaNa) program, the satellite carries a student experiment conducted by Vanderbilt University's Institute for Space and Defense Electronics. The RadFx experiment at this institute hosts four payloads for the study of radiation effects on commercially available electronic components. So it should be tested electronic components "off the shelf" under space conditions. The payload of AMSAT North America is a single-channel FM converter from Ultra high frequency (UHF) to Very high frequency (VHF). After successful launch, the satellite was assigned the OSCAR number 91.