Re: strange issue with 20m classic; ideas invited
|
Hi Jim
I did not forget... But in his original post in this thread, Julian said he had already replaced the LPF capacitors. Well he mentioned three of them and I assumed that was a simple erroneous omission. I didn't think it necessary to mention something he had already tried.
73 Hans G0UPL http://qrp-labs.com
-------- Original message -------- From: Jim Allyn - N7JA <jim@...> Date: Mon, Nov 1, 2021, 7:06 AM To: [email protected]Subject: Re: [QRPLabs] strange issue with 20m classic; ideas invited I'm a bit surprised that Hans didn't remember this: a number of people had low output power on 20 meter QCXs.? This was traced to the 390 pf capacitors in the low pass filter.? Several people replaced the stock caps with silver micas and others that they had on hand, and the power came up to where it was supposed to be.? As I recall, this is what inspired Hans to switch to Vishay caps.? A search for '390 pf' turns up 35 hits, many of which say something along the lines of hey I only had 2 watts out, but I changed the 390 pf caps and now it's up to 4 or 5 watts.? One guy even posted an IR photo of the low pass filter area, and it was clear that those 390 pf caps were dissipating some power.? Replace those 390 pf caps with something of better quality, and you should be in business.
|
