Sunday pm...Hi all...Well I have completed this project today...I will put some RF into it tomorrow and tune it up then run it for a few hoursto test reliability...
Pics show the finished amplifier..
Bob..VK3ZL..
Attachments
Finished amplifier..
On the work bench switched on into operate mode idling at 150ma...
Good morning all..Well I connected this amplifier up this morning to tune it up..I used an Oskerblok meter to monitor through and drive vswr..Under 1.2-1 ..On the output I am using a Bird watt meter with a 1kw slug into a Bird 500 watt dummy load..
First tuning I just had to adjust the T input capacitor to achieve 1-1 drive vswr...The rest tuned up perfectly..Using 25 watts of drive the Bird says around 550 watts output with the amplifier fully tuned...Drive vswr under 1.2-1..Amplifier efficiency is around 55% so that's pretty good for the GS-31B..I am not interested in driving the tube any harder as the new owner is just looking for a legal limit amplifier..I have no doubt the amplifier will run more than 1kw..This project is now complete...I only have to finish the cabinet sides with a final coat of paint and give the amplifier a good run test over the next couple of days to check reliability..
I checked the tube anode for heat after 5 minutes of carrier at 400 watts output with my infra red temperature gun...Tube anode core nut and cooler measures 74C so cooling is more than ample..
Thanks to all those with their encouraging posts and emails..I am now going to do a bit more work on a 70cm amplifier, complete but requires further work...Then my next project is another 2 meter amplifier..
Pics are the metering results this morning..
Bob..VK3ZL..
Attachments
Oskerblok showing bypass vswr..
Oskerblok showing amplifier drive vswr..
Oskerblok and Bird watt meter readings...Drive vswr less than 1.2-1 and Bird meter showing around 550 watts output with 25 watts of drive..
