250W Linear PA using Ampleon BLC2425M9LS250 mosfet

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g7ntg
Posts: 15
Joined: Sat Feb 17, 2018 7:07 pm

250W Linear PA using Ampleon BLC2425M9LS250 mosfet

Post by g7ntg » Sat Jun 15, 2019 7:27 pm

I have just started building a PA using the Ampleon BLC2425M9LS250 mosfet which is designed for CW operation in microwave ovens. It is rated at 250W at 32volts 20 amps and 18dB gain. I am using the same layout as the test board shown in the data sheet so I will see what happens!
The device is £64 including postage and the rest will be 3 x 12v 30a power supplies in series and turned down to 10.6v, a huge heatsink and a big fan!
I will post more details as I progress.

g7ntg
Posts: 15
Joined: Sat Feb 17, 2018 7:07 pm

Re: 250W Linear PA using Ampleon BLC2425M9LS250 mosfet

Post by g7ntg » Sat Jun 15, 2019 7:38 pm

I regret I can't supply pcb's as the one I am using is hand carved with a scalpel.
Power measurement is via a 30dB high power directional coupler and my dummy load will have to be a patch antenna out the window as I don't have a dummy load that big!
The pcb's are fitted to a 3mm copper pallet fixed to the heatsink with 16 screws
I will post pictures on Facebook in "OSCAR-100, QO-100, Es'Hail, satellite operators and experimenters"

darrenrainer
Posts: 13
Joined: Thu Aug 09, 2018 12:40 pm

Re: 250W Linear PA using Ampleon BLC2425M9LS250 mosfet

Post by darrenrainer » Fri Jun 28, 2019 12:28 pm

I have also got hold of the BLC2425M9LS250 device. Where did you get the pcb material from ? I will have a go at carving a test pcb layout and see if I can get it working.

73s

Darren G4VTQ

g7ntg
Posts: 15
Joined: Sat Feb 17, 2018 7:07 pm

Re: 250W Linear PA using Ampleon BLC2425M9LS250 mosfet

Post by g7ntg » Sat Jul 13, 2019 9:42 am

PCB is the hardest part - look at https://wiki.batc.org.uk/Transmitting_O ... Amplifiers. I am trying to source material - this can be Rogers 6035HTC or Arlon 25FR 0.762mm thick 1oz copper

G4WIM
Posts: 227
Joined: Thu Jan 29, 2015 8:36 pm

Re: 250W Linear PA using Ampleon BLC2425M9LS250 mosfet

Post by G4WIM » Sat Jul 13, 2019 8:27 pm

looks like we're going down a similar path - in my case using MRF24300.

Just been doing some tests up to 150 watts output as I'm PSU current limited and have found that a temperature compensated bias supply is to be advised to prevent run away with a fixed bias voltage.

https://www.ampleon.com/documents/appli ... _10032.pdf

Only problem I had was with RF getting into the sense transistor - a bit of screening and filtering fixed the problem.
I also soldered the PCB down to the heat spreader around the FET and RF connectors.

I also had to snow flake the input match as it was centred on 2450MHz .

One slightly odd effect I've noticed is the proximity of metal (or even a human hand !) causes the output power to vary as much as 30 watts when running at 150 watts out - I may have to install a shield round the PA.

The output coax gets quite warm !

I have an 868MHz telemetry system built in for remote monitoring and control.

Over all very pleased so far and hope to be air testing in the next few days.

Regards Tim

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