06-07-2010, 08:10 PM
How many loop antennas does the 41-255 have? My set is missing the back cover and I didn't know if it had a bc band loop on it. Looks like the loop that is there is for the sw bands.
Terry
Terry
06-07-2010, 08:10 PM
06-07-2010, 09:01 PM
Just one, and it serves for AM and SW. Two turns, tapped at one turn.
06-08-2010, 09:13 AM
The 41-255 didn't have a back cover. The loop spirals around the inside of the cabinet. It is constructed of uninsulated solid copper wire, #10 gauge, I think. The loop begins at the bottom of the cabinet approximately in line with terminal 4 on the antenna block, about 1/2 inch from the back edge of the cabinet. It spirals to the right around the inside of the cabinet twice, and ends approximately in line with terminal 2 on the antenna block. The direction of the spiral is toward the inside of the cabinet. The three short terminal wires are soldered to each end of the loop and at the center tap point, which is in line with terminal 3.
The spirals are 3/4 inch apart, measured from the wire centers. The wires of the loop were clamped between thin but rigid fiber plates riveted together. There is one flat clamp at the top and one at the bottom of the cabinet, and one with a 90 degree bend at each corner. The clamps are screwed to the cabinet, except the one at the top, which is just held in place by the wire. It should be easy to fabricate something out of heavy cardboard that will work as clamps.
The wires run parallel with the edge of the cabinet at the top and the bottom, and slant outward on the sides, so that the top outside wire is just 17/32 from the back edge of the cabinet.
The spirals are 3/4 inch apart, measured from the wire centers. The wires of the loop were clamped between thin but rigid fiber plates riveted together. There is one flat clamp at the top and one at the bottom of the cabinet, and one with a 90 degree bend at each corner. The clamps are screwed to the cabinet, except the one at the top, which is just held in place by the wire. It should be easy to fabricate something out of heavy cardboard that will work as clamps.
The wires run parallel with the edge of the cabinet at the top and the bottom, and slant outward on the sides, so that the top outside wire is just 17/32 from the back edge of the cabinet.
06-08-2010, 05:27 PM
The reason it 'looks' like a SW loop with only a few turns is because it is only part of the total inductance for the circuit to achieve resonance. There is still a main antenna coil on the chassis that accounts for the bulk of the inductance.
Clever scheme, works well.
-Bill
Clever scheme, works well.
-Bill
06-08-2010, 07:51 PM
Tnx Guys
I thought that the copper loop wouldn't have enough inductance for the bc band
but having it connected to another coil makes sense. I only saw the one loop on
the diagram but just want to be sure.
Terry
I thought that the copper loop wouldn't have enough inductance for the bc band
but having it connected to another coil makes sense. I only saw the one loop on
the diagram but just want to be sure.
Terry