The loop winding with most turns connects to pin #8 on your 12SA7 & tuner. Return of that winding connects to AVC. AVC must have a .05 cap or so to B-.
With that you will have a tuned circuit.
You mention touching 12SA7 grid. Does the radio act the same when you touch the loop?
Norm
: I have a delco R1174, a simple radio really, (12SA7, SK7, SQ7, 50L6, and 35Z5. It has a simple loop antenna, secondary is connected to grid of the SA7. With everything connected, good tubes, good B+, I get no reception, UNLESS I connect an antenna to the grid of the 12SA7. The antenna can be my finger or a length of wire. When I do this the reception is excellent. I have seen this problem numerous times in the past. Does anyone have any clues? (by the way the loop antenna primary and secondary is NOT open) Do I have a bad loop antenna?
Hi Joe
: The loop winding with most turns connects to pin #8 on your 12SA7 & tuner. Return of that winding connects to AVC. AVC must have a .05 cap or so to B-.
: With that you will have a tuned circuit.
: You mention touching 12SA7 grid. Does the radio act the same when you touch the loop?
: Norm
: : I have a delco R1174, a simple radio really, (12SA7, SK7, SQ7, 50L6, and 35Z5. It has a simple loop antenna, secondary is connected to grid of the SA7. With everything connected, good tubes, good B+, I get no reception, UNLESS I connect an antenna to the grid of the 12SA7. The antenna can be my finger or a length of wire. When I do this the reception is excellent. I have seen this problem numerous times in the past. Does anyone have any clues? (by the way the loop antenna primary and secondary is NOT open) Do I have a bad loop antenna?
Norm,
The loop is connected just as you say. When I touch the loop, I can barely hear the station, when I touch the 12SA7, grid, pin 8, the reception is much amplified. The only thing I haven't checked is the .05 cap to B-, but I didn't think it was critical or could be the problem. Any other ideas?
Your radio could depend on the AVC cap to ground for a loop coil return & tuned circuit. Are you sure the max number of turns are connected to the tuner & tube?
One wire from the loop goes directly to 12SA7. You should be able to touch either place and improve reception. Do you have an antenna coil you can try im place of your loop?
There are some loops with only a few turns made to work with an antenna coil. Hope you are using one of the radio backs with wire in a spiral?
Norm
: :Norm,
: The loop is connected just as you say. When I touch the loop, I can barely hear the station (I can't hear it at all without touching the loop), when I touch the 12SA7, grid, pin 8, the reception is much amplified. The only thing I haven't checked is the .05 cap to B-, but I didn't think it was critical or could be the problem. Any other ideas?
: Hi Joe
: : The loop winding with most turns connects to pin #8 on your 12SA7 & tuner. Return of that winding connects to AVC. AVC must have a .05 cap or so to B-.
: : With that you will have a tuned circuit.
: : You mention touching 12SA7 grid. Does the radio act the same when you touch the loop?
: : Norm
: : : I have a delco R1174, a simple radio really, (12SA7, SK7, SQ7, 50L6, and 35Z5. It has a simple loop antenna, secondary is connected to grid of the SA7. With everything connected, good tubes, good B+, I get no reception, UNLESS I connect an antenna to the grid of the 12SA7. The antenna can be my finger or a length of wire. When I do this the reception is excellent. I have seen this problem numerous times in the past. Does anyone have any clues? (by the way the loop antenna primary and secondary is NOT open) Do I have a bad loop antenna?
: Norm,
: The loop is connected just as you say. When I touch the loop, I can barely hear the station, when I touch the 12SA7, grid, pin 8, the reception is much amplified. The only thing I haven't checked is the .05 cap to B-, but I didn't think it was critical or could be the problem. Any other ideas?