The ISS is large and relatively low, so it experiences a bit more atmospheric drag than most satellites. They periodically raise the orbit, which requires new orbital information. AMSAT updates the nasabare.txt information for the ISS as required. So depending on the source of information and when it was updated, you can get noticeable differences between prediction sites and tracking programs. As JoAnne said, go with the AMSAT site when in doubt.
73,
Alan WA4SCA
<-----Original Message----- <From: AMSAT-BB [mailto:amsat-bb-bounces@amsat.org] On Behalf Of <JoAnne K9JKM via AMSAT-BB <Sent: Friday, February 14, 2020 10:35 AM <To: amsat-bb@amsat.org <Subject: Re: [amsat-bb] Newbie Questions - ISS < < > 4. N2Y0 says up/down is 437.550/437.550, ASFK, inactive. HeavensAbove < > says 145.825/447.550 FM active. Who is right? How can I get correct < > frequencies to listen to? < <Latest list of frequencies posted at: <https://www.amsat.org/amateur-radio-on-the-iss/ <The 145.825 MHz packet is most common operating mode. It has its on/off <days depending on crew activity and radio health. < <Watch the amsat-bb for ARISS school contact announcements. For example <there is a school contact scheduled for next week - direct with a school <in Ohio. The 145.800 MHz downlink will be good copy over a lot of the <northeast and parts of the midwest. < < > Why the [time] difference? < <Often related to differences in using local time and UTC on different <sites. I'd go with the amsat predictor for now. < <-- <73 de JoAnne K9JKM <k9jkm@amsat.org <_______________________________________________ <Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available <to all interested persons worldwide without requiring membership. Opinions <expressed <are solely those of the author, and do not reflect the official views of AMSAT- <NA. <Not an AMSAT-NA member? Join now to support the amateur satellite <program! <Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb