Boredom got the best of me: AA5 hum and loop antenna

[JohnCT]

Originally Posted by Kevin Kuehn

John,

Sorry for making three posts to answer one question. This thread with pictures sheds more light on the situation.

https://antiqueradios.com/forums/vie...307249&start=0

Are you kidding? Dad always told me that beggars can't be choosers!!! I'll take advice any way it's packaged.

I think I understand now. The point of the unattached segment on the loop board is to be able to add an external antenna while providing isolation from the chassis, yes?

Thanks again.

John

[Kevin Kuehn]

Originally Posted by JohnCT

I think I understand now. The point of the unattached segment on the loop board is to be able to add an external antenna while providing isolation from the chassis, yes?

John

Yes that's my understanding as well. And if you notice on the schematic they show an earth ground symbol for the external antenna, which is not chassis ground. In theory when it's wired correctly you would have your antenna on one end of the isolated loop and earth ground(water pipe) on the other. Doing that should isolate anyone touching those two connections from shock hazard. Unless of course there's a capacitor shown on the schematic connecting those two grounds, which I didn't notice with my quick scan over. Make sense?

[JohnCT]

Originally Posted by Kevin Kuehn

And if you notice on the schematic they show an earth ground symbol for the external antenna, which is not chassis ground. In theory when it's wired correctly you would have your antenna on one end of the isolated loop and earth ground(water pipe) on the other. Doing that should isolate anyone touching those two connections from shock hazard. Unless of course there's a capacitor shown on the schematic connecting those two grounds, which I didn't notice with my quick scan over. Make sense?

I'm not sure what you mean.

The antenna fiberboard has three wires exiting the board: two form the continuous race track loop, one end of each ending up at the grids of the osc tube and first IF tube like most AA5s. Typical stuff at this point.

The third wire on the antenna fiberboard is a single trace that lays alongside the edge of the racetrack loop. One end of that wire is terminated and literally buried into the fiberboard where no electrical connection can be made to it. Looks like it was punched in with a tool. The other end is connected to a wire which presumably is the wire that would serve as the external antenna lead in.

Do you mean that single lead would go to an antenna, or to an earth ground? It wouldn't be possible to connect that isolated track on the antenna board to both an antenna and an earth ground.

Thanks again.

John

[Kevin Kuehn]

Originally Posted by JohnCT

I'm not sure what you mean.

The antenna fiberboard has three wires exiting the board: two form the continuous race track loop, one end of each ending up at the grids of the osc tube and first IF tube like most AA5s. Typical stuff at this point.

The third wire on the antenna fiberboard is a single trace that lays alongside the edge of the racetrack loop. One end of that wire is terminated and literally buried into the fiberboard where no electrical connection can be made to it. Looks like it was punched in with a tool. The other end is connected to a wire which presumably is the wire that would serve as the external antenna lead in.

Do you mean that single lead would go to an antenna, or to an earth ground? It wouldn't be possible to connect that isolated track on the antenna board to both an antenna and an earth ground.

Thanks again.

John

I assumed that your back looked like this one from the ARF thread. It appears to have 4 connections, which would match what's shown on the schematic.
Basically one loop with another around the perimeter. But maybe I'm seeing things. If that's not what's going on there then I'm a little lost myself, because that's normally how an antenna matching transformer is designed. Let me go study that schematic again.

[Kevin Kuehn]

From Riders 17-26 in the general notes, it says

All models have self-contained antennas and do not require additional antenna connections. For permanent home installations, however, if it is desired to improve reception of weak stations, an additional outdoor antenna may be used. For this purpose a lead has been brought out in the rear near the line cord. Use NO ground connection

But then in the alignment directions 2 and 3 it specifies to connect the signal generator

High side to the external antenna lead. Low side to external ground lead

Those alignment directions are what through me, as there's apparently no external ground lead. Possibly it's typo and they meant chassis ground? In any event I'm sorry I confused the matter.

[Kevin Kuehn]

I think these are the intended connections for the antenna as pictured below. The outside antenna wire and ground form a single turn around the perimeter of the internal spiral loop. Internal loop connects between AVC line and the grid of the 12BE6. The outside antenna ground should be left disconnected or returned to an earth ground, but not the AC chassis ground, unless you don't mind having a shock hazard.

[JohnCT]

Originally Posted by Kevin Kuehn

I think these are the intended connections for the antenna as pictured below. The outside antenna wire and ground form a single turn around the perimeter of the internal spiral loop. Internal loop connects between AVC line and the grid of the 12BE6. The outside antenna ground should be left disconnected or returned to an earth ground, but not the AC chassis ground, unless you don't mind having a shock hazard.

Yeah, that's unlike what i have:



In this radio, there's only three connections on the antenna board, the two for the loop and the third (blue wire attached) which is not connected to the loop in any way. You can also see that the third runs inside the loop, and is pinned into the fiberboard.

It can be connected to an antenna, to an earth ground, but not both.

John