The 'Shack' used carry three 'filters'/transformers of this type. One was as shown, one was a 600/600 ohm, and I can't remember exactly what the third one is/was. They came in very handy in a number of ways, interfacing radios/computers was only one of them.
One of the earliest PC/radio interfaces was only a transformer (one of the above) and a 0.01 ceramic disc capacitor in series with one of the leads. Which transformer? Just depended on if you knew what the impedance of the inputs/outputs were, sometimes 'we' didn't, so whichever one seemed to work okay. (The one shown worked good, typically because it had more than one 'tap' so could be 'adjusted' some.) That 0.01 capacitor was sort of for the more difficult cases of RF. If you were really 'bothered', you could go to a 0.1 cap, but it had some 'benefits' that didn't always end up with very much 'fidelity'. [A very common way of interfacing in the "early days" of computer SSTV, JV-FAX, etc It worked!]
Another thing that you had to watch out for was 'grounding'! Computer sound cards are/were usually NOT operated at zero 'ground', they 'float'. If you ground them, you just crashed the computer
. No 'blue screens', they just turned off. That was so much fun the first time it happened! Or maybe the first several times??
Also don't expect much 'power' handling ability with any of those transformers. Not something usually worried about with audio circuits, but something to think about.
And like most other things dealing with RF, a five gallon bucket of torroids really does come in handy!
Have fun.
- 'Doc
If you're really desperate, you can build one'a them interfaces into a 25 pin RS-232 port connector. But who uses them things any more??
What kind of inline filter are you talking about? Lowpass TVI filter perhaps?? Nothing connects to your PC or uses phono cables if that is the case. They use regular SO-239 connectors. Maybe you are talking about some sort of audio filter/EQ unit?? More info please. Tell us what you are talking about.
