09-23-2018, 08:23 PM
For each of the sets that have a ground connection, use a common ground, each radio with its own wire, not daisy-chained. This ground must be short, direct to earth. Do not use an electrical ground at an outlet...
For the G-E find a way to put two or three turns of wire on the back of the radio as a loop. Or make a small frame of 1/4" MDF make five slots or more odd number of slots and wind at least two turns, weave around the slots. More turns if there is not enough coupling. Mount the MDF in a 2 x 3" block 8" long so it can be slipped out to add/remove turns. Connect the "loop" outside to antenna (6) and the inner to the ground like the other sets. This loop can magnetically couple to any AC/DC radio including a transistor set. Spacing away will reduce coupling. Since there is no electrical connection to the chassis it is safe.
There may be a noise issue with a set that has direct coupling of the chassis to the AC outlet ground. This will create a ground loop if a common ground is used. Even if an isolating capacitor is used it will not isolate noise from the home AC system... You may have to float the AC grounded radio with a ground adapter used without connecting its tab. Then ground the chassis via the "master" ground.
The Hallicrafters may also have a line coupling problem that may be solved by flipping the AC plug, that works unless it to has been creatively modified with the AC switch or/and or an additional safety cap installed. It too, even with AC cord putting neutral on the chassis can couple the AC via the internal bypass cap to the antenna. Resulting in an antenna that will give a tingle if contacted.
FWIK only some vintage boatanchors used a three wire cord. So the above won't apply unless the radio has been creatively modified
Consider a two pole antenna/ground switch if it can have a short ground connections.
Keep in mind the whole exercise is about getting an RF signal to each radio circuit such that the RF flows through the radio or coupling loop from antenna to ground and back. Negating all home AC as an RF ground system...
YMMV be SAFE!
Chas
For the G-E find a way to put two or three turns of wire on the back of the radio as a loop. Or make a small frame of 1/4" MDF make five slots or more odd number of slots and wind at least two turns, weave around the slots. More turns if there is not enough coupling. Mount the MDF in a 2 x 3" block 8" long so it can be slipped out to add/remove turns. Connect the "loop" outside to antenna (6) and the inner to the ground like the other sets. This loop can magnetically couple to any AC/DC radio including a transistor set. Spacing away will reduce coupling. Since there is no electrical connection to the chassis it is safe.
There may be a noise issue with a set that has direct coupling of the chassis to the AC outlet ground. This will create a ground loop if a common ground is used. Even if an isolating capacitor is used it will not isolate noise from the home AC system... You may have to float the AC grounded radio with a ground adapter used without connecting its tab. Then ground the chassis via the "master" ground.
The Hallicrafters may also have a line coupling problem that may be solved by flipping the AC plug, that works unless it to has been creatively modified with the AC switch or/and or an additional safety cap installed. It too, even with AC cord putting neutral on the chassis can couple the AC via the internal bypass cap to the antenna. Resulting in an antenna that will give a tingle if contacted.
FWIK only some vintage boatanchors used a three wire cord. So the above won't apply unless the radio has been creatively modified
Consider a two pole antenna/ground switch if it can have a short ground connections.
Keep in mind the whole exercise is about getting an RF signal to each radio circuit such that the RF flows through the radio or coupling loop from antenna to ground and back. Negating all home AC as an RF ground system...
YMMV be SAFE!
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
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