I currently have an Igate setup with an old Windows XP computer. Old Pentium 4 and 1 GB of RAM. I just received a USB sound card and I'm still running into the same issue. I can received packets that are near by, around 12 miles or so but anything further won't be decoded by SoundModem. Signals will show up on the waterfall but nothing gets decoded unless you close. Eventually, the setup will be done with a Raspberry Pi (USB to serial and the USB audio device I already mentioned.) To link the radio to the computer, I'm using an EasyDigi I bought of eBay. I soldered everything myself with some oversight from another ham. I used cat5 cable to interface the EasyDigi to my Kenwood TM-281a. Everything works, PTT, RX audio and TX audio. It's just the RX rang sucks. My antenna is currently in my attic. I'm using LMR 400 cable, about 100ft of it, about 25ft too long. Any suggestions? I've tried adjusting the microphone audio with no luck.
A little late but I've worked on a similar setup (sadly still on the bench waiting for an antenna...) Is there any way for you to monitor the sound levels being received? It could be a noise issue, it's getting through as long as it's strong and clear but once the signal weakens a bit from further out, it's still clear but not so much as to overpower the noise. I had issues with noise on my Easy-Digi, due to setting it up incorrectly. First the resistors are very easy to install backwards, that makes a huge difference as I found out. Second, there is a ground for PTT and an audio ground. Initially I connected them together for simplicity, but then assigned them to their proper assignments on the cable to the radio. This reduced noise but if it was a huge factor or not I'm unsure. I had mine set up and it would receive packets, I never did get it in a live signal setting from outside the room, but I noticed my noise levels were way too high. (Direwolf software TNC will warn you of the issue in the readout.) After moving the grounds and reversing the transformers, it settled right in where it needed to be.
Doh, my bad. They are transformers, not resistors. Not that I know any more about directional disposition of transformers.....I just know when turned around one way they worked better than the other.
This book would be a good read. It will help you understand what a transformer is doing and why there is a primary and a secondary set of windings. https://www.arrl.org/shop/Understanding-Basic-Electronics
