There were two issues associated with connecting and ANAN radio running with either Thetis or PowerSDR software using VAC to a VARA modem.
One was a very isolated corner case when SNRs are high which enable high VARA speeds and VARA enters an IDLE state where neither station is transmitting. With high speeds and in the IDLE state, ANAN VAC timing would cause the connection to drop after one minute. Special thanks to Jose for posting an update to VARA on his website that addresses this issue. This new VARA update does not change the version number. You just need to copy this new version of VARA.exe into your VARA folder.
The second issue is more complex. I won't try to rehash it here. Check this Apache Labs ANAN forum thread for more info. Be prepared to have your eyes glaze over.
With both forward error correction and ARQ, the VARA modem is very robust and handles errors caused by digital audio sample rate differences between the radio and computer. I just turn off the resampler without any degradation to packet error rate or bit rate for small chat messages and larger file transfers.
So were you seeing issues with the resampler On or Off?
When Jose made the change for the timing issue, he didn't go to a new version number. Take a look at the release notes which have been updated. You can "install" the new version to a different folder on your PC and then copy just VARA.exe from there to your previous VARA folder.
Regarding the ANAN VAC, take a look at the recent ANAN forum exchanges with WU20. Every situation is unique so what works for each combination of radio and PC will be different. My experiments show no VARA bit rate or packet error rate difference between VAC resampler on or off. The VARA modem with forward error correction and ARQ will handle small audio imperfections caused by turning off the resampler (ticking the Force boxes). This might not apply to other digital modes or to voice.
I like to use metaphors to help explain complex concepts and I think I have one that fits this situation.
There was an "I Love Lucy" episode where Lucy and Ethel were working in a pie factory. Their job was to take pies off the conveyor belt and put them in boxes. As the conveyor belt sped up, comedy ensued.
Modify the Lucy scenario to include two conveyor belts separated by about 6 feet. Pies come in on one belt evenly spaced and must go out on the other belt also evenly spaced. Since the two belts are running at slightly different speeds, there is a table where pies can be placed to even out the transfers.
Any more info on this new VARA HF? Still just a full installer on Jose's website.
Interesting. I have not seen this problem myself. I actually had several VarAC connects with WU2O today, with some 6+ minutes. Wonder how your VAC settings differ than mine? Also on Jose's website is just the 4.6.3 but as a full installer.