okay so ive been trying to get Winlink working for about three weeks now and im at the point where i want to throw the whole thing out the window. quick rundown of what im doing: running Winlink Express on a windows 10 machine, IC-7300 connected via USB, using the built in VARA HF modem. i can see the RMS gateway list just fine and i pick one thats showing green, start the session, it handshakes, and then just... drops. sometimes i get as far as seeing the RMS banner before it disconnects. other times it drops right after the initial connect.

my SNR looks decent, usually sitting around 15-18dB on the IC-7300 display during the attempt. the gateway im usually trying is about 400 miles away which shouldnt be a problem on 40m in the evening. ive tried a few different gateways with similar results. tried bumping VARA down from 500 to 250 and it doesnt seem to make a huge difference.

one thing i noticed is my ALC is jumping around quite a bit. i backed off the power to about 50 watts thinking maybe the gateway doesnt like being hammered with 100 but still same issue. is there something obvious im missing here? also not sure if my PTT timing is off or something, i have it set to the default in Winlink Express. been reading the Winlink documentation and honestly its not super helpful for actual troubleshooting.

the ALC jumping is almost certainly your problem. that is the number one killer for VARA sessions and most people dont realize it because the radio sounds fine for voice. for digital modes especially VARA HF you really want that ALC meter barely moving if at all. what you need to do is go into IC-7300 menu and find the data mod level settings, then back off your audio drive until the ALC is basically flatlined. you might end up running way less power than you think — sometimes 20-30 watts is plenty and youre actually getting cleaner signal than at 80 watts with ALC pumping.

also check your USB audio sample rate, the 7300 can be finicky about that. make sure its set to 48000hz on both ends. and yeah PTT timing — i had mine at default too and it was clipping the start of my transmissions. bumped the lead-in to 500ms and it helped a lot. the gateway has to hear your preamble cleanly or it just bails on the session.

so anyway this is kind of a tangent but when i was setting up my own gateway (im running one on 40m here in the midwest) i noticed a lot of failed inbounds that turned out to be people with exactly this problem. you can actually see it on the gateway side — the session starts, modem tries to negotiate, and if the client audio is clipping or the timing is off the RMS just moves on. it doesnt wait around.

one thing i dont see you mention is whether youre using the radio's built in soundcard or a separate interface. the 7300 internal USB audio is fine but i know some guys have had better luck with a SignaLink or similar just to get cleaner audio path. probably not your main issue here but worth knowing. the ALC thing the other guy mentioned is definately the first thing to fix though.