my radio is an IC-9700 and i have gpredict running on a laptop doing the doppler tuning automatically but something feels off. like my downlink drifts one way and i push my uplink the other way and then i lose myself in the passband completely. been reading about how you lock onto a beacon first but AO-7 doesnt really have a useable beacon most of the time depending on which mode its in.

is there a better workflow for this? i feel like im missing something fundamental about how to set the rig up with gpredict. does anyone actually have the IC-9700 CAT control working smoothly for sat work or is it kind of a pain

my question is basically — do most people just let the tracking software handle the VFO correction automatically or is there some trick to doing it by ear? i was running gpredict linked to the radio via hamlib and it was doing something but honestly i couldnt tell if it was actually moving the frequency or if i had the port config wrong. the pass was only like 8 minutes and i spent the first 4 fumbling with everything.

also the inverting transponder thing caught me off guard. i knew about it intellectually but then in the moment i went the wrong direction tuning and that cost me another minute. any advice from people who have actually done this consistently would be really helpful

anyway the linear transponder stuff is where i got confused in practice. i understood the theory — you transmit on the uplink passband and your signal comes back on the downlink inverted, so LSB up means USB down or whatever. but i kept chasing my own signal all over the place. like i'd tune to where i thought i was and by the time i got there it had drifted again. not sure if that was doppler not being compensated fast enough or if i was just overdriving the transponder and causing the AGC to squish everything.

also heard what sounded like a few other stations on there but couldnt really pull any callsigns out, the passband seemed pretty busy for a weekday afternoon. is that normal for AO-73 or was i just in a bad geometry for the footprint? i didnt end up making any contacts but i got my own downlink signal which i guess counts for something. any tips from people who actually work these things regularly would be great.

the part im really struggling to wrap my head around is the doppler correction. i get that the sat is moving so the frequency shifts but like... if im using a linear transponder the uplink and downlink are on totally different bands right? so do i have to be manually tuning both at the same time? ive seen people say their radios are linked or something but i dont have a fancy rig, just an FT-817 and an old laptop. is there software that handles this or am i going to be spinning two VFOs at once trying to have a QSO. feels like it would be impossible honestly

also just to make sure i have this right - on a linear transponder if i transmit USB on the uplink my signal comes out as LSB on the downlink? ive read this a couple times but it still doesnt feel intuitive to me

my question is about the doppler correction. i've been using Gpredict to track the pass and it'll show me the doppler shift on both uplink and downlink separately but im confused about which one i should be manually correcting on my radio vs just letting the software handle. like do most people just tune the downlink and leave the uplink fixed, or are you constantly adjusting both? i feel like every time i try to actually make a contact im spending so much time chasing the signal that i cant coordinate an actual qso. probably a technique thing more than a gear thing but figured id ask here.

also what's a realistic expectation for how long a usable pass window is on a typical AO-73 overhead pass from mid-latitudes, like 45 degrees north roughly? some passes feel like i barely have time to get set up before its gone.

been messing around with AO-73 which i know still has the linear transponder active at least part of the time. my setup is a FT-818 running into a small 3 element yagi for 2m and a 7 element for 70cm, both handheld which i know is far from ideal. my question is basically do i need to be correcting doppler on BOTH the uplink and downlink simultaneously or can i get away with just tracking the downlink and leaving the uplink more or less fixed? ive seen conflicting stuff online and honestly some of it reads like it was written 15 years ago so im not sure whats still accurate for current ops.

also is gpredict good enough for tracking or do i need something else? running it on linux if that matters

my setup is a ft-847 with a pair of yagis on a G-5500 and im running gpredict for tracking. doppler correction is manual right now which is probably part of the problem. the az/el rotator seems to be following the pass okay but im not super confident in my antenna calibration. anyway the main thing is i cant hear myself in the passband at all even at like 10 watts. either im way off frequency or the bird just isnt hearing me, not sure which.

anyone work FO-29 recently and know if the transponder is even active these days? i feel like im chasing a dead bird half the time

my current setup is just a pair of handheld yagis, az/el is all manual which honestly isnt as bad as i thought it would be once you get used to anticipating the movement. the doppler on the downlink is the part that still trips me up — im running split mode and trying to correct on the fly but im definitely missing contacts because im slow on the VFO. anyone have a workflow for this that actually works without a full automated station

According to the documentation, low temperatures give higher frequencies, but I'm seeing the opposite behavior during my passes. Using a FUNcube Dongle Pro+ with the dashboard software, and my manual Doppler correction seems off by several kHz during peak thermal cycles.

Anyone else experiencing this? Would love to compare notes on thermal behavior vs transponder frequency stability.

the doppler correction alone was kind of a nightmare to keep up with manually. i was using gpredict for tracking which worked fine, but trying to actually tune my uplink and downlink at the same time while the frequencies are sliding around... i dont know how people do this without a rig that does it automatically. i've got an FT-818 for uplink on 435 and an SDRplay for downlink monitoring on 145 and keeping both corrected by hand during a 9 minute pass was just chaos.

i did hear myself in the transponder for maybe 30 seconds which was exciting but i was barely able to have any kind of qso. the other station i heard kept drifting out of my passband and i wasnt sure if that was him not correcting or me not correcting or both. ended up logging nothing which is a bit disappointing but whatever, first pass. i'm assuming the doppler on the downlink moves faster than the uplink since it's a different band? like the 145 MHz side shifts less per second than the 435 side? i think i read that somewhere but want to make sure i understand it right before my next attempt tomorrow evening.

i tried using gpredict for the tracking data and its pretty decent but syncing the doppler correction to my actual radio while also manually adjusting the uplink is just a lot to juggle. is there a way people usually handle this that isnt a full computerized rig with CAT control? i dont have CAT on my HT obviously lol. also is there a trick to just parking somewhere in the passband and staying put rather than constantly chasing the frequency? i feel like ive seen people mention this somewhere but cant remember where.

the passes where the max elevation is under like 20 degrees are basically useless for me right now, i think my antenna situation is part of that but still. any tips appreciated, been lurking here for ages and figured id finally just ask.

HRD claims to handle inverting transponder Doppler correction more accurately - it applies offsets from center frequencies then Doppler correction, rather than simple frequency tracking. The key difference seems to be proper handling of the inverted spectrum where LSB uplink becomes USB downlink.

For those running

• Linear transponder tracking with CAT control
• Multiple satellite operations
• Precision Doppler compensation for SSB/CW

What's your experience with software accuracy and ease of use?

my question is about the doppler correction — i get the concept, the satellite is moving toward you so the uplink frequency shifts one way and downlink the other. but when i use gpredict to track the pass and it feeds into my rig via hamlib, it seems like the offsets it applies are way more aggressive than what ive read about. like on a good overhead pass the total swing is something like 10kHz on 435 downlink? that seems like a lot but maybe im wrong

also the other thing thats confusing me is the inverting transponder thing on FO-29. so if i tune up in frequency on my uplink the downlink goes down? ive read about this several times and i sort of understand it mechanically but in practice when im on a pass im losing track of what im doing. does anyone have a tip for internalizing this that actually works or is it just muscle memory after a few passes

managed to track AO-73 last week using Gpredict on my laptop and i could actually hear the transponder which was exciting but i could never quite get my own signal through. i understand in theory that you need to adjust for doppler as the bird comes over but in practice im just fumbling around with the dial while trying to hold the antenna pointed at the right part of the sky and its a total mess

is there a way to lock the downlink frequency and just let it drift or do people really manually tune both the uplink and downlink simultaneously? i feel like i need three hands. also does it matter much which part of the pass i try, like high elevation only or can you work the low stuff too

anyway the doppler correction is what's killing me. i understand the concept, signal comes in higher frequency as the sat approaches and lower as it moves away, fine, i get that. but in practice when im trying to work a linear transponder i need to be adjusting both my uplink AND my downlink simultaneously? and they drift in opposite directions? that just seems incredibly annoying to manage in real time especially when the pass is only like 9 minutes long and you gotta actually make a contact in there somewhere.

using gpredict right now linked to my ft-818 via hamlib and it seems to be doing something but honestly i cant tell if its actually correcting or just showing me pretty numbers. did anyone else go through this learning curve or am i missing something obvious

i know the linear transponder is inverting so USB up means LSB down or whatever but i feel like im missing something fundamental here. do i need to be doppler correcting both VFOs independently or is there a smarter way to set this up with gpredict controlling the radio directly via hamlib. the passes here are only like 8-10 minutes and im spending half of it just chasing my own signal around

any help appreciated, been doing this for about 6 months overall but satellites are completely new to me

anyway i found the transponder passband and heard a couple QSOs in progress which was pretty exciting, managed to tune around and heard my own downlink which i know sounds dumb but that was kind of a revelation. the thing im struggling with is the doppler compensation. i understand the concept — uplink and downlink shift in opposite directions on a linear transponder — but my actual experience was kind of a mess. i was chasing my own signal around and i think i was overcompensating on one side and not enough on the other. Gpredict has the doppler tuning feature but i couldnt figure out if it was actually controlling both VFOs on the 847 independently or just doing one. does anyone have this actually set up and working? like what does your CAT setup look like for split doppler correction on a linear bird

i could hear the linear transponder fine, found my downlink on 70cm no problem, but i could not for the life of me figure out how to actually make a contact. like i was transmitting on the uplink and i could sort of hear myself come back down but by the time i figured out the doppler correction i needed to apply i missed the whole pass. the satellite was only above my horizon for like 6 or 7 minutes and i wasted most of it fumbling with my radio

been using Gpredict to track and that part actually works great, got the TLE data updated and the footprint display is really helpful. but whats the deal with doppler on linear transponders exactly — do i need to correct both the uplink and downlink or just one of them? i've seen different things online and some of it is from like 2009 so i dont know whats still accurate. any advice from people who actually do this regularly would be really appreciated

Has anyone else successfully copied the AO-109 beacon recently? My setup includes a 17-element 70cm Yagi with good preamp, so signal strength shouldn't be the issue.

Also wondering if the transponder is truly inverting - the documentation shows U/V mode but I want to confirm the sideband relationship before attempting any contacts.

The benefits of more bandwidth and the ability for multiple users to make QSOs simultaneously should allow for better frequency management than the FM birds. What's considered good practice for frequency selection and QSO length on the linear transponders? I know maximum uplink power should be 5 watts to a 7 dBi gain antenna (25W EIRP), but are there any unwritten rules about frequency etiquette?

anyway my main issue is keeping up with the doppler shift on both the uplink and downlink simultaneously. i was using gpredict on my laptop but its kind of a pain to be adjusting both radios at the same time while also trying to hold the antenna and talk. i've seen some people mention just tracking the downlink and leaving the uplink fixed or doing it in reverse, not sure which is the more accepted approach. also does anyone actually use the doppler tuning automation in gpredict connected to the radio via CAT or is that more trouble than it is worth for a single pass?

im running full duplex btw with the 818 on uplink and an sdr on the downlink side so i can hear myself, that part works pretty well actually.

i know about the doppler thing and ive been using Gpredict to get the shift values, applying them manually which is probably part of the problem honestly. when i key up i dont hear anything on the downlink, not even a squeal or anything to indicate im getting into it. the pass is usually around 12-15 degrees max elevation from my location so maybe thats killing me too. running about 3w into a pair of crossed yagis, Az/El capable.

is there a trick to initially finding yourself in there that im not getting? i read about tuning around a bit while transmitting but that seems like itd just walk over everyone else in the passband which doesnt seem cool

my problem is the doppler correction. i understand the concept, the satellite is moving so the frequency shifts, but when i actually try to work it in real time im fumbling with the radio while also trying to point the yagi and its just chaos. im using an FT-817 and a handheld yagi, nothing fancy. i tried the AO-73 linear transponder on a pass yesterday and i could hear some signals that sounded like SSB voices but they were drifting all over the place and i couldnt tell if that was me not correcting or other stations not correcting or both.

is there a way to set up gpredict to do the rig control automatically for doppler on the 817? i know it has CAT but i never really used it. or is most people just doing it manually and getting used to it over time? feels like im missing something obvious here