Thought I'd try one of these.....

[Fgbokoiii]

Hi

Can i ask how much input power you give?

Thanks

Fgboko

MRF9180 under 1w i cant remember... i think 600mW... ( form me this is best aspect ratio") 600mw in out 180
MRF151G 3-4W
MRF300 1.25W

Hi rig,

Thanks you.

Fgboko

[radium98]

you need a vna that you can test with .or try to use a calculator for diameter in and outer

[ronald001]

You guys are too funny. I wish I knew this Gotts guy. I think you had too much fun playing hide and seek with him. Albert, I'm glad the schottky diode trick is working out for you. I considered the Bat42/43, but saw the forward voltage increased above 0.5V after about 20 ma. The DB2J50100L stays below 0.5V even up to 200 ma. Plus it has a peak reverse voltage of 50V and a recovery time of 1.6 ns. The Bat42 is a little slower at about 5 ns.

I am doing DAB experiments with this FET, with IDQ set to 2000mA.
Albert, what diode can you advise me that can handle this drain?

[Albert H]

DB2J50100L works OK, but the damn FET still dies sporadically. They seem really susceptible to static - the gate is incredibly sensitive. I killed one just by connecting the input coax feed - there must have been some small static build-up!

These devices may be really cheap, and if you're lucky, you'll get lots of lovely Watts for not much input power. However, they are ridiculously fragile. I discovered that one manufacturer of cellphone PAs puts a graphite pad underneath the gate terminal on their boards, presumably to leak static away to earth!

I've completely abandoned this series of devices, and have been looking for more robust but cheap replacements. Luckily, I found a few MRF150s in a box under the bench, and built a couple of twin PAs using them. They were just quickly thrown together, and after setting up the bias to each FET, I got a cool 250 Watts out of a pair at 48V supply with a drive from a 2SC1971 of about 6 Watts. They really do have plenty of gain. They were the first of that series of devices, and - to my mind - the best. Perhaps Motorola put more work into getting the early ones right!

[ronald001]

That's exactly what happened to me - just by touching the input it died...

Found another model that originally operates in the 800-900Mhz band @3Mhz bandwidth - so perfect for DAB - and it is way later manufacturerd than the 9180, so hopefully more robust.

Noticed some projects on indonesian websites, where they use the same FET for FM broadcast rated at 350W @ 28V