BATC Forum

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.

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"

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

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

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

Here is another linear that could be useful if available at a reasonable price.
I found this here

https://www.nxp.com/products/rf/rf-powe ... RFEP24-300

Martin G8LCE

The active device costs around £100. It is a proven design as Achim DH2VA built one and it worked out of the box as advertised.

Brian G4EWJ and I investigated getting some boards made but the minimum sized sheet of material we could buy was enough for 60 PCBs
which was more of a financial risk than we were prepared to make.

Achim managed to get some boards made by the company that made the original NXP ones but when someone else contacted the
company recently they no longer seemed to have the information to make the boards.

I am sure someone with the right 'contacts' could do better!

- Charles

g8lce wrote: ↑

Sun Jul 21, 2019 8:21 am

Here is another linear that could be useful if available at a reasonable price.

If only... One for only those with very deep pockets, I think.

If anyone could get PCBs made, the device itself is more affordable, so could make for a nice QRO amp.

BATC shop might be able to help out with PCBs but probably not devices.

Do we have more details of this or the other designs that are going around??

73
Noel

Just a thought ..whilst we all crave these enormous powers ...What ERP are we actually allowed to transmit ?