I have a Zenith Transoceanic, model A600. I recently replaced the Wave Magnet's 300 Ohm antenna lead-in wire, and noticed that the loop windings on the antenna's core are wound differently at either end. On the end where the lead-in wire is soldered to the loop, the windings are consistently spaced. However, past the middle of the core at the other end, the windings gradually spread out as you go from the middle to the end.
When listening to the BC band, I've noticed that the antenna has slightly different receive characteristics when the antenna is rotated 180 degrees on the same signal. It appears to have a bit more sensitive at one orientation as compared to the other. I also noticed that the effect isn't consistent, and seems to only show up when I'm using it on the counter next to the fridge, so it may be that proximity to the fridge is causing this.
The 300 Ohm lead-in is cut at the antenna end so that one lead is longer than the other. At first glance, this appears to accommodate the orientation and spacing of the internal connection points, allowing the lead-in wire to lie flat within the housing so that it exits the slot in the housing without kinking, allowing the wire to engage a small strain relief boss just ahead of the slot.
However, after experiencing the effect rotating the antenna 180 degrees caused, I started wondering if it might also be possible that the lead-in wire needs to be connected to the loop with a specific polarization in mind in order to accommodate the asymmetric windings? Besides the asymmetric loop windings, another clue I have to this is that the plug at the other end of the wire has three pins, two pins for the leads, and one open pin. You can only plug it in one way. Given all that, is it possible that the reason for the asymmetric loop winding was to equalize the receive characteristics of the antenna when the antenna gets flipped around 180 degrees, due to the characteristics of the radio's front-end circuitry?
The leads on the replacement wire came out of another radio, so their lengths were pre-cut when I installed it, presumably with the correct polarization. I have a copy of the schematic from a B600, which uses the same chassis as the A600, and I'm thinking that they use the same components as well. Looking at where the loop antenna comes into the radio, one leg of the lead-in connects to transformer L3, while the other leg connects to inductor L2. However, the way the band switches are depicted on the schematic, I'm having a hard time tracing how the signal goes through them in order to get to the RF amp.
I'm not really that proficient at reading schematics any more as it's been over 50 years since I've worked on anything like this, so I know just enough to be dangerous! Perhaps one of you might have some insight into this, as I'm wondering if reversing the lead-in wires at the antenna might eliminate the affect flipping the antenna appears to be having.
Edits: I always screw something up!
When listening to the BC band, I've noticed that the antenna has slightly different receive characteristics when the antenna is rotated 180 degrees on the same signal. It appears to have a bit more sensitive at one orientation as compared to the other. I also noticed that the effect isn't consistent, and seems to only show up when I'm using it on the counter next to the fridge, so it may be that proximity to the fridge is causing this.
The 300 Ohm lead-in is cut at the antenna end so that one lead is longer than the other. At first glance, this appears to accommodate the orientation and spacing of the internal connection points, allowing the lead-in wire to lie flat within the housing so that it exits the slot in the housing without kinking, allowing the wire to engage a small strain relief boss just ahead of the slot.
However, after experiencing the effect rotating the antenna 180 degrees caused, I started wondering if it might also be possible that the lead-in wire needs to be connected to the loop with a specific polarization in mind in order to accommodate the asymmetric windings? Besides the asymmetric loop windings, another clue I have to this is that the plug at the other end of the wire has three pins, two pins for the leads, and one open pin. You can only plug it in one way. Given all that, is it possible that the reason for the asymmetric loop winding was to equalize the receive characteristics of the antenna when the antenna gets flipped around 180 degrees, due to the characteristics of the radio's front-end circuitry?
The leads on the replacement wire came out of another radio, so their lengths were pre-cut when I installed it, presumably with the correct polarization. I have a copy of the schematic from a B600, which uses the same chassis as the A600, and I'm thinking that they use the same components as well. Looking at where the loop antenna comes into the radio, one leg of the lead-in connects to transformer L3, while the other leg connects to inductor L2. However, the way the band switches are depicted on the schematic, I'm having a hard time tracing how the signal goes through them in order to get to the RF amp.
I'm not really that proficient at reading schematics any more as it's been over 50 years since I've worked on anything like this, so I know just enough to be dangerous! Perhaps one of you might have some insight into this, as I'm wondering if reversing the lead-in wires at the antenna might eliminate the affect flipping the antenna appears to be having.
Edits: I always screw something up!
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