I've been away (from this hobby) for quite a long time (maybe 2 years). But recently, I've just been browsing the web for 300W pallet amps and I can get pretty obsessed with that. Well, it looks like the chinese have a new used 300W mosfet they are using now. I remember the MRF186 and MRF9180. Now I'm finding this weird 300W device that appears to be an SRF that they soldered a copper thing onto the bottom of. And a very convenient placement of the bar code sticker. . . Anyone know the name of the FET?



So has anyone been using these lately? I couldn't find anything with the search. I'd assume that these FETS are probably even less reliable than the MRF186.
I'm also thinking that maybe this is the amplifier pallet used inside this thing: viewtopic.php?t=2907

Wrong package for an SRF, surely? Given the alleged power and the look of the thing (width of tabs) I've no concrete ideas at the moment what it might be. I know you're only trying to work out what the FET is but if anyone is thinking of taking a punt on that board, my advice would be to stay well clear.

Probably 2 or 3 years back, I tested a version of that amp, sold as 170W. Almost certainly the same PCB manufacturer though. No markings or label on the FET and it didn't last long before going pop. Due to their popularity at the time I assumed it was an MRF9180 and a genuine Freescale replacement worked OK in the board giving 170W, but IIRC I rebuilt the filter as the caps were underrated.

If you do a search on that image, you'll see it show up as a 150W (eBay) and a 300W amp (Aliexpress). So I wouldn't assume that's a 300W device shown.

I also know that at the moment, there are a lot of fake, and unreliable MRFE6VP* devices around. Those Chinese amps (at least the ones described as 300W) are listed at around £200. I'm pretty sure you could source a genuine MRFE6VP6300H or BLF278, plus everything else you need including the RF caps and transformer coax for that! Why take the risk!

Yes it’s the SRF261. Apparently meant to do 300w but never tried it.

You live and learn eh! Never seen one of those.

Yep - the SRF261 will do about 300W (if you're careful). However, they're not too robust.

That is an output filter on it, and a directional coupler for SWR. Why would you take a chance on that when you can get a proper, rugged amplifier from Holland for less money
https://dutchrfshop.nl/en/amplifier-mod ... er-v2.html
You will need an output filter for that one though...

Also this one made in the UK... Can be driven with lower power 1W exciters.
High efficiency exceeding 70% (typically 75%).
On-board low pass filter, low harmonics (always less than -70dBc).
The amplifier is supplied completely assembled and tested on a heatsink.

FM Broadcast High Power 300W Amplifier Module
https://enigma-shop.com/products/fm-bro ... ier-module

BriansBrain wrote: ↑Fri Jan 19, 2024 12:35 pm

Also this one made in the UK...
E-300W.JPG

Can be driven with lower power 1W exciters.
High efficiency exceeding 70% (typically 75%).
On-board low pass filter, low harmonics (always less than -70dBc).
The amplifier is supplied completely assembled and tested on a heatsink.

FM Broadcast High Power 300W Amplifier Module
https://enigma-shop.com/products/fm-bro ... ier-module

I had loads of issues with this build. Using everything from enigma shop, firstly the swr protection IC wouldn’t work, they sent me another IC but was the same. I checked everything and It did still power up without it which was fine. With 1w applied it would do 300w but would slowly die down to 150w after 5 mins and ran red hot even on a huge heatsink. I tried re-seating it, changing the driver board, power supply, anything you can think of iv done it. Still ran hot so chucked it up a tower block doing 150w. Didn’t last long before council removed it but good riddance. Stupid thing.

I think you mean the kit version with 2SC1971 and BLF278
Never had problems with the Enigma amp
used many of them but maybe something with overdrive from you driverboard
The first stage give lots of gain and sometimes 400-600mW is the max or you will overdrive the BLF278 and the 33E resistor will be realy hot and will detune the amp.
The SWR strip can give problems when you have ground problems on your board/heatsink or cables.
RF is not a easy thing and can only be done good when you realy know what you doing

BriansBrain wrote: ↑Fri Jan 19, 2024 12:35 pm

Also this one made in the UK...
E-300W.JPG

Can be driven with lower power 1W exciters.
High efficiency exceeding 70% (typically 75%).
On-board low pass filter, low harmonics (always less than -70dBc).
The amplifier is supplied completely assembled and tested on a heatsink.

FM Broadcast High Power 300W Amplifier Module
https://enigma-shop.com/products/fm-bro ... ier-module

Have been using these for years! Won't use anything else