UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Questions on 160/80 metre AM transmitters.

AdrianH · 26th Dec 2022, 12:40 am

Re reading Ian's post #81 and looking at the diagram of the modified circuit, especially around where the 100mA meter has been moved to the anode side of the output valve, I think I can see an issue with the Key 'click' filter.

To my mind it would have worked with the resistance and inductance of the meter in the cathode line, but without the meter I can not see any shaping with KEY DOWN. I can see it with KEY UP, but if the key has a very low resistance I can not see anything to shape the RF/Current rise time. To me some resistance needs to be between the Cathode pin and the Key socket?

Wonder if anyone else is considering building for Top band and 80?

Adrian

26th Dec 2022, 12:40 am	#98
AdrianH Octode Join Date: Mar 2020 Location: Blackburn with Darwen, Lancashire, UK. Posts: 1,573	Re: Quick question on the CODAR AT5, if anyone has one to hand. Re reading Ian's post #81 and looking at the diagram of the modified circuit, especially around where the 100mA meter has been moved to the anode side of the output valve, I think I can see an issue with the Key 'click' filter. To my mind it would have worked with the resistance and inductance of the meter in the cathode line, but without the meter I can not see any shaping with KEY DOWN. I can see it with KEY UP, but if the key has a very low resistance I can not see anything to shape the RF/Current rise time. To me some resistance needs to be between the Cathode pin and the Key socket? Wonder if anyone else is considering building for Top band and 80? Adrian __________________ Asking questions and learning, or trying to! Youtube EF91Valve