Hi Dick,
I suspect some sort of problem related to power wiring, and perhaps to
equipment bonding, is causing the equipment failures. I would check
every power outlet for wiring errors -- hot and neutral or neutral and
green swapped, stuff like that. I would also bond every chassis to every
other chassis with short, fat copper, including the computer, the
dongles, etc. One of these boxes (usually the power amp or rig) should
be bonded to the power system ground, the antenna entry ground, etc.
There are some pretty flaky dongles and sound cards in the wild. I had
some little $35 USB POS that sort of worked, but was junk. The two I
bought a couple of years ago work great. One, the Tascam US100, is
discontinued, and is what I use on my main rig. I paid about $75 from
B&H about 3 years ago. At the same time, I bought the cheapest stereo
Numark for about $35. It also works fine, and I use it on the second
radio for SO2R RTTY (and to a second laptop). Both are free of Pin One
Problems, they are equally good at decoding RTTY and JT65, both go 12 dB
farther down into the noise than the Thinkpad T4x-series built-in sound
cards. If I were buying a USB box today, it would be the lowest cost
Tascam replacement for a higher budget, or the Numark for low budget.
The advantage of the Tascam is that it has more gain on the line inputs,
so you don't have to crank the K3 as much.
73, Jim K9YC
On 4/9/2014 10:48 PM, Dick Frey wrote:
I have blown up computer motherboard audio line inputs on three computers
and two USB audio adapter dongles trying to run RTTY or PSK.
The Line Out is set at "nor 15". There was a direct connection from Line
out to the rear sound line in.There is a large ferrite 51 mix choke on the
cable. There was a ~20dB pad in line going to the mic input on the
dongles. The antennas are >150' away 75' up, and I am running 500W.
The line output is transformer-coupled, right? It appears there is some
sort of transient that's killing the input to the audio codecs.
Does anyone have experience with this problem?
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