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New Tranceiver, Old Electric

Jun 20th 2016, 21:21

K7RMA

Joined: Jan 10th 2013, 23:05
Total Topics: 0
Total Posts: 0
I enjoy a Yaesu FTDX-1200 and Samlex SEC-1235M power supply. Both worked excellently in my previous home, but since then I have moved into a 93-year-old home that still has knob-and-tube wiring. That means no ground wire, which is OK - I can run a ground outside. It also means the wiring can carry a higher load in terms of amps, but the insulation will be pretty toasty after all these years. My concern is whether the old wiring, which seems to be in decent shape otherwise, can handle the load the Yaesu and Samlex would place on it. Does anyone have experience with putting a modern transceiver on knob-and-tube wiring? If so, how did it work out?
Thanks.
Jun 21st 2016, 15:41

AA6E

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
The AC load of your radio gear will peak at 200 Watts, give or take, averaging less than probably 50W. Your AC circuits are probably fused for at least 10 Amps, way more than you will need. So you should be fine for your radio, as far as the basic wiring size goes.

The main worry I would have in your situation is AC safety. This is an issue for radio work, but also for lots of modern appliances that have 3-wire plugs. Running with 2-wire adapters and a dangling ground wire is dangerous. (A proper ground ensures that any AC fault in your gear is shorted to ground, blowing your fuse or breaker and saving your bacon!) I would seriously look at rewiring the house to modern standards.

Yes, you can provide your own ground for the radio, but be sure it's a good ground for AC (not over a couple of ohms resistance). Secondarily, it probably wants to serve as an RF ground and a lightning ground. Doing a good job for all 3 types of ground means low resistance (at 60 Hz), low inductance (at RF), and short runs (less than ~ 0.1 wavelength at RF is best). It can be difficult to satisfy all those conditions, but do the best you can.

For more, check the ARRL Web on Grounding.

73 Martin AA6E
Jun 27th 2016, 02:22

K7RMA

Joined: Jan 10th 2013, 23:05
Total Topics: 0
Total Posts: 0
Thanks Martin!

73, Rob / K7RMA

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