DESIGN NOTES K7DYY SUPER SENIOR 160 80 - AB2RA

1. Early models had a 5 KHz tuning step. This was upgraded to 1 KHz per step. While this was an improvement, it took a long time to change bands. The manual posted here is for the early 1 KHz step unit. I believe this required a hardware change.

I suggested to Bruce that it could be changed in software for adaptive tuning. In other words, if the knob was rotated fast for a long time, it would automatically switch to 5 KHz per step. Once you stopped turning for a bit, it would automatically revert to 1 KHz per step.

There were some rigs that got confused with the encoder and the tuning stuck. I found that a power down reset cleared the fault on mine. This may have been fixed with a different shaft encoder.

It is my understanding that parts availability dictated selecting a new shaft encoder when the existing one was no longer available.

2. Early 160 - 80 models had a weaker capacitor on the Low Pass Filter Board for 80 meters. This was upgraded.

3. Early models allowed modulation in low power tune up mode. I suggested to Bruce that he change the switch to DPDT and mute the audio in tune mode. This prevented overmodulation protection trips during tune up in a noisy shack.

4. I suggested to Bruce that he include a simple LED on the front panel to indicate excessive negative modulation peaks, which would cause a protection trip. This would give more information if it did trip (since the display indicated SWR for any kind of fault). It was not adopted.

5. The manuals posted here reflect an earlier model, but they are larger size and higher contrast and resolution. Maybe you can extrapolate these to the more modern style that was posted on the official K7DYY website.

6. I have heard rumors that the 160 80 was modified later in production to be more similar to the 80 40. This may be related to the known power level upward drift problem. All models have been updated around 2024 with a compensating circuit that reduced carrier level drift.

7. On the early production units I have, the 160 80 was able to get positive modulation peaks of +120% when carrier level was 300 watts, still within the 1500 watt limit. The 80 40 will not do that, it needs to be +/-100% symmetrical audio modulation. This is due to the more restrictive protection circuits in the 40 meter model.

8. Upper frequency limit of the 160 80 is in excess of 10 KHz audio band width. The 80 40 is more like 8 KHz. The lower frequency limit is less than 5 Hz. I measured it. I had to buy a low distortion HP oscillator that went that low.

9. The original FETs became obsolete. I bought some offshore to have some on hand. Documentation for the correct substitute is provided elsewhere on this web site. It also would be wise to obtain driver chips and other critical parts NOW if you can, to avoid problems. These FETs are in an INSULATED case and require on mica washers to insulate them from the heatsink. See the full discussion.

10. Early models used a different connector on the rear for the muting relay and PTT connections. The newer 8 pin connector also had terminals that directly went to the microprocessor control. I disconnected the microprocessor wires to protect the chip. Yeah, I blew the chip plugging in the connector. Then I took out some insurance.