DMA wrote: So you are that legendary guy with 1200W transceiver? What's your current setup? xwhatsit or soarer? Any EMI shielding?
Well, not sure about the legendary part, but yeah, I was the guy asking for ideas for reducing RF interference on an XT board a while back. Same problem with this F122. Both were just simple Soarer's converter mods, with no additional shielding or anything. I have tried some large ferrites on the cables as a test, but the problem seems to be the controller or keyboard PCB picking up the RF rather than the cable.
My station puts out around 1300W on voice peaks and the antenna feedpoint is only about 30ft above my office, so I get a pretty decent amount of RF 'in the shack', as they say. This would most likely be a combination of direct feedpoint radiation along with RF travelling back down to the equipment on the shield of the coax. Radiation exposure falls within safety guidelines from a human health standpoint, but isn't so great with poorly shielded electronic devices, lol.
I could probably greatly reduce the RF on the coax by adding a nice big choke balun at the feedpoint, instead of trying to put 'band-aids' on affected devices (such as this keyboard). Until recently the cold weather made it a hassle to get the antenna down for servicing. Now that Spring is finally here, I may get to that and try to mitigate the source of the RF somewhat.
I have a couple of tricks in my sleeve made with you in mind.
IIR is tunable
This configurability is really excellent to have, and should allow me to tweak things to work the best for my situation. Thank you for this!
I would be more worried about transceiver inducing so much voltage it fries the circuitry. F122 makes for a pretty good Faraday cage - you'll probably need to construct paper/vinyl(to prevent shorts) + foil case for the controller section. I'm actually interested in what you have right now and what you tried for shielding if anything.
I honestly don't think there is a need to worry about induced voltage. I'm not setting off an EMP here, and in truth the RF fields are really quite weak by the time they reach the keyboard. It's just enough to disrupt the careful balance and trigger key presses.
My impression is that the F122 isn't particularly well shielded, though. The PCB hangs off the back and is fully open to RF through the plastic edges of the case. Each key sensor is also pretty much wide open. Every key / barrel is, from an RF perspective, an unshielded hole directly to the PCB. Yeah, I could probably put a tiny foil piece between each keycap and stem, but that's just getting crazy with the band-aids, and still leaves a lot of RF holes near the base of the barrel, rofl.
I think I will give the 'tin-foil hat on the controller' approach a try, and run some tests to see if it has any effect.
Thanks for all the nice input on this. RF is a tricky thing to deal with sometimes.
...which makes me wonder... Did IBM ever make a Tempest hardened F122? Hmm...
In theory you can even go 127/128 safely - but that will be quite inconvenient in practice.
