MRF101AN & MRF101BN

[XXL]

I do love a MRF101 as they are solid and it does what it says on the tin. but has anyone ever used 2 for 200W out ? It looks like it could work but cant find any on the net, only mrf300 x2. it would make a nice cheap amp. Thanks

[radium98]

add a combiner simply , i think fr4 can support 200w

[XXL]

It’s wasteful to use more components than needed.

[garada]

If you want 200w, better use an mrf300, it costs less than two mrf101s and the circuit is simpler as you don't need a combiner, you will also have more than 200w if you want, so I don't see any sense in it, that's why it's so difficult to find the mrf101b (inverted terminals)

[thewisepranker]

Interesting that the -BN is quite a lot cheaper than the -AN, probably because there's a significant amount of dead stock.

You could fit it upside down and re-jig the heatsinking...

I started typing out a load of commentary about mounting devices (like the -BN) upside down in single-device amps, and then doing it upside-upside down to make a push-pull but given the history of the OP blowing up pretty much everything within spitting distance, I can't be arsed!

[Albert H]

I do love a MRF101 as they are solid and it does what it says on the tin.

Electronically, the MRF101 is fine. It's also quite cheap. Unfortunately, it's in a ridiculous package. It's difficult to heatsink that kind of package effectively - this leads to problems like thermal derating: Your rig might start out at 100 Watts, but when the FET heats up, it reduces to 60 or 70 Watts.

Back in the early 80s, I used my first VHF FET - the Siliconix VMP4. It was capable of about 25 Watts, and we used then in a run of small rigs that went to Germany. The only way I found to kill a VMP4 is to give it too much drive!

[yellowbeard]

Garada has the right idea there, the MRF101AN/BN goes for about €30 each, the MRF300AN for about €60 - but you get 100 more Watts and a single-ended design, plus there are kits and PCB's available or NXP have a reference design if you want to do your own:

https://www.nxp.com/products/radio-freq ... -resources

[XXL]

Interesting that the -BN is quite a lot cheaper than the -AN, probably because there's a significant amount of dead stock.

You could fit it upside down and re-jig the heatsinking...

I started typing out a load of commentary about mounting devices (like the -BN) upside down in single-device amps, and then doing it upside-upside down to make a push-pull but given the history of the OP blowing up pretty much everything within spitting distance, I can't be arsed!

Why post negative bullshit ? I only post on here about things I’m having trouble with. What you don’t see is all the successful stuff iv built over the years as I don’t come on here bragging after iv finally figured it out, months down the line from all the wild goose chases people post online. If you don’t want to help why even bother commenting? Thankfully most people on here are helpful.

[XXL]

If you want 200w, better use an mrf300, it costs less than two mrf101s and the circuit is simpler as you don't need a combiner, you will also have more than 200w if you want, so I don't see any sense in it, that's why it's so difficult to find the mrf101b (inverted terminals)

Thanks. I tried the mrf300 in the mrf101 board years ago and didn’t last long. Lasted a few weeks before it died. It was doing 180w. Couldn’t get no more out of it.

This was all just an idea anyway.

[King Croccy]

If you want 200w, better use an mrf300, it costs less than two mrf101s and the circuit is simpler as you don't need a combiner, you will also have more than 200w if you want, so I don't see any sense in it, that's why it's so difficult to find the mrf101b (inverted terminals)

Thanks. I tried the mrf300 in the mrf101 board years ago and didn’t last long. Lasted a few weeks before it died. It was doing 180w. Couldn’t get no more out of it.

This was all just an idea anyway.

You need a decent copper heat spreader if you want it to live longer. Mines about 3" square on the heatsink.

I did successfully modify that enigma board for 300w out, you gotta get rid of that weedy 2.5mm trace and seriously mod the output stage so means redesigning a new pcb.

Only issue is its no longer broadband, but it bangs 300w all day long and runs super cool into a decent aerial load.

[XXL]

If you want 200w, better use an mrf300, it costs less than two mrf101s and the circuit is simpler as you don't need a combiner, you will also have more than 200w if you want, so I don't see any sense in it, that's why it's so difficult to find the mrf101b (inverted terminals)

Thanks. I tried the mrf300 in the mrf101 board years ago and didn’t last long. Lasted a few weeks before it died. It was doing 180w. Couldn’t get no more out of it.

This was all just an idea anyway.

You need a decent copper heat spreader if you want it to live longer. Mines about 3" square on the heatsink.

I did successfully modify that enigma board for 300w out, you gotta get rid of that weedy 2.5mm trace and seriously mod the output stage so means redesigning a new pcb.

Only issue is its no longer broadband, but it bangs 300w all day long and runs super cool into a decent aerial load.

Nice, wish I could work that out. Unless you could share or give me a clue lol ? I only build stuff for my own station. Yes that 2.5mm track is crap, it goes brown colour just using the mrf101 lol. I scrapped off the solder mask and added solder to it to thicken it up.

[Shedbuilt]

If you want 200w, better use an mrf300, it costs less than two mrf101s and the circuit is simpler as you don't need a combiner, you will also have more than 200w if you want, so I don't see any sense in it, that's why it's so difficult to find the mrf101b (inverted terminals)

Thanks. I tried the mrf300 in the mrf101 board years ago and didn’t last long. Lasted a few weeks before it died. It was doing 180w. Couldn’t get no more out of it.

This was all just an idea anyway.

If you want to put the MRF300 into the MRF101 board, apart from the other comments, you need to significantly change the output matching. The output impedance of the MRF300 will be significantly lower (factor of 3:1 since the supply voltages are the same). If you were driving it hard, it was probably that which caused it to only deliver 180W. In turn, that meant it was working inefficiently (probably trying to deliver a lot more than 180W), and also “seeing” a lot of reflected energy.

[XXL]

So is the input match the same ? Is it just everything after the output (drain) that’s needs to go ? Could I just use the old fashioned single pole hairpin match with a filter on the end ? Or is there a better way ?

[Shedbuilt]

The input impedance of the MRF300, is also much lower than the MRF101.which circuit are you currently using ?