Re: LPF-Control PCB TX Logic at U3 & U7
|
I can't help because my system's been down for over a month and I haven't been able to do anything with the software. Jack, W8TEE
On Saturday, March 22, 2025 at 04:41:38 PM EDT, K9HZ <bill@...> wrote:
Its not a hardware problem.? The radio has been working fine until recently when some software mods were made. ? Use some sound deductive reasoning here.? This problem did not exist a month ago with any transceivers that were build.? Then work was done on the software in a mad dash to close it out for the next version of the T41 book.? All of a sudden, there are issues with most/ everyone¡¯s radio.? What conclusion and action would you take from that?? Bobb some hardware out of you radio?... or go back and check out an earlier version of the software? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? From: [email protected] <[email protected]> On Behalf Of Rick Price via groups.io
Sent: Saturday, March 22, 2025 3:14 PM To: [email protected] Subject: Re: [SoftwareControlledHamRadio] LPF-Control PCB TX Logic at U3 & U7 ? Oliver,? I was having some kind of feedback/oscillation problems a couple of weeks ago and traced it back to the T/R switch also.? The relays and associated parts all checked out but, when I removed the 3-"0" ohm resistors that were there in place of?the Low Pass Filter (160M) and inserted the parts for the LPF the problem stopped.? I wanted to go back and remove the filter parts and place just two "0" ohm parts at c14-c16 and a single cap at c-15 but never did.? Wondering if the oscillation problem boards have the "0" ohm resistors and not the LPF filter in place.? Maybe, I will try it later just thought I would mention what I had, when you suggested a possible feedback issue. Rick, KN4AIE ? ? From: [email protected] <[email protected]> on behalf of Oliver KI3P via groups.io <oliver@...> ? The situation I think we might have is that both TX_BPF_SEL and RX_BPF_SEL are HIGH during SSB transmit. This lets a little bit of the transmitted signal leak through the TR switch back into the amplifier input through the BPF selection stage, like this: ? ? These two lines are controller by GPIO register bank A: ? ? This register is set by the function call ; the code there looks correct and unchanged. Scanning the code, it all appears to be correct. Some judiciously placed statements like this will confirm: Debug("Set LPF GPA state: "+String(LPF_GPA_state,DEC)); ? The fix that I implemented (major change to radio layout) to cure the short that caused the burning smell has created a display freeze issue, so I'm not able to test this myself right now. ? ? ? ? ? -- Jack, W8TEE |
jjpurdum