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Re: GS-31B 50mhz Amplifier Project..
Posted: Sun Oct 06, 2013 11:21 am
by VK2OMD
VK3ZL wrote:Thanks for the link Owen..I will peruse it carefully...Bob..
I see Tom has written on the subject, I think after our discussion some years ago. See
http://www.w8ji.com/tuned_input_circuit.htm .
It looks unfinished, and the page was last worked on a few months ago... so I suspect it is fairly new.
Owen
Re: GS-31B 50mhz Amplifier Project..
Posted: Sun Oct 06, 2013 4:21 pm
by VK3ZL
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..
Re: GS-31B 50mhz Amplifier Project..
Posted: Sun Oct 06, 2013 6:27 pm
by VK6OX
Looks like another superbly finished PA Bob...well done!
I'm sure the on-air test will be just as designed!
Re: GS-31B 50mhz Amplifier Project..
Posted: Sun Oct 06, 2013 7:47 pm
by VK2ZRH
Great stuff, Bob.
I
want one
73, Roger Harrison VK2ZRH
Re: GS-31B 50mhz Amplifier Project..
Posted: Sun Oct 06, 2013 9:14 pm
by VK6OX
VK2ZRH wrote:Great stuff, Bob.
I
want one
73, Roger Harrison VK2ZRH
Well you can't have mine Rog !!!
Re: GS-31B 50mhz Amplifier Project..
Posted: Mon Oct 07, 2013 10:03 am
by VK3ZL
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..