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

[SOTS 87 7]

Back on the subject of the MRF186, I came across this interesting animal earlier and just had to share it with everyone. This has 2 MRF186's in it and a very primitive looking power combiner with a 100 ohm flange mount resistor. The combiner has 87.5 - 108 MHz written on it. This says to me that the MRF186 could be a general purpose device. Power supply is at 24 volt. I hazard a guess its a 200 watter. I'm going to test it tomorrow.
It has a massive heatsink.

[RF-Head]

That board is not complete it's missing the input combiner
I sold that module on ebay without fets and only on a heatsink without lpf
I think the buyer put it on a other heatsink and made a rig with it
Orginal the in-out combiner where from italy
For the input combiner you can use also 2 pieces 75e coax 1/4 wave
The module is normal made for 2 x BLF278

[SOTS 87 7]

Hmmmm, I thought it maybe. Well, I'm going to fire it up into a 50 ohm load and see what happens.
Will keep you posted on the result.
What's the worst that can happen?

[SOTS 87 7]

Actually, I've just noticed on further inspection, Mr. RF Head you said the input combiner is missing, there is a very weird input matching board that has been made up on Veroboard using 3 vericaps that I assume connects to the 2 inputs on the amp. Can't see how it'll work. The whole thing is mounted in a 3U rack case.
Confusing I must say.

[OgreVorbis]

Does anyone have the size, number of windings, and wire for the input transformer on this amp. The chinese didn't include either of the ferrite beads with mine. Could I get the dimensions of these two? maybe a link to buy? Also what are those two pcb pieces on either side of the input transformer? do I need that?

[pjeva]

It is so-called binocular ferrite core. Inside holes are two small copper pipes connected with two small pcb pieces with two holes on both sides. On one side pcb is full copper (and you apply bias voltage here), and on the other it is split between holes (see image). This acts as ONE turn through transformer. In this case, it is secondary winding. Through this small pipes you should put wire (isolated) and make 2 turns through holes.
RF transformer winding ratio of 2:1 gives impedance transformation ratio of 4:1, which means that it will transform 50 ohm input impedance to 12,5 ohm.
Since secondary of this transformer is connected between gates of dual mosfet, and not between one gate and ground, output impedance will be split to 6,25 ohm (and in opposite phase at each gate).

It is bit hard to explain in words, take a look at the picture and ask if there is still something unclear...
Cheers!

rf1200.jpg

[Analyser]

You can buy the transformers here...

http://enigma-shop.com/index.php?option ... ransformer

Get some ordinary hook-up wire (7/0.2 or whatever) and wind three turns inside the core. If you've done it right you'll only see two turns on the input side and three turns at the output near the FET gates. Before you feed the wire on to the core, solder the FET gates to the side of the transformer with the PCB which is split down the middle . The other end with only one PCB is normally grounded or used to supply bias. Have a look at the photos earlier and see how others have done it.

[radio-berlin]

Ive got loads of the little pcb part to put either end of the binoculars. Through plated aswell and fit standard 3.2mm brass pipe. Ill stick a couple in the post if you wanna cover postage.

However how you gonna hook up a small transformer, it will have long wires to reach each pcb unless you etch up a small pcb. Id personally use two length of 75ohm cut to frequency as some kind of splitter

[thewoodstarr]

Hi,
That is a fantastic little Amp. It took a little time to come through, and came with no schematic, and no instructions whatsoever, not even a component list! Not a problem because the component list is widely available. This amp easily replaces the BLF 244 / SD1407 line up. We have found it to run at 110 Watts with a 300 mW drive. And its as cool as cucumber! Harmonics are not a problem either, its better than 60 dB`s down relative to carrier. I know a few people has said, the filtering looks a wrong? I say if it ain't broke, don't fix it.
Its a good find, I am off to buy more!
Easy all.....

[teckniqs]

I bought one of those and after waiting ages for it to turn up and then leaving it in tucked away for a couple of months, I then discovered there were loads of components missing from the kit!
....So it's going to cost me more for the cost to replace the missing parts than what I paid for the whole board.

[SOTS 87 7]

Well, the one I constructed when I started this thread is still working well as are the other two.
Absolute little bargain.

[teckniqs]

Have you been using it for Fresh Sounds Oxfordshire?

[SOTS 87 7]

Now would I do a thing like that.
I have something much better for that. Will upload a pic asap.

[shuffy]

We have found it to run at 110 Watts with a 300 mW drive.

Really? Are you sure? What voltage are you thrashing it with?

[SOTS 87 7]

Have you been using it for Fresh Sounds Oxfordshire?

WP_20150726_001.jpg

Now would I do a thing like that.
I have something much better for that. Will upload a pic asap.

[thewoodstarr]

God posting on this is like going back in time, to Windows 95! Sort your code out! I was going to show you a finished rig using this device, not possible to upload images direct to the site. however I can tell you, the test results are excellent! If you have the skill to build it, and the eyesight for that matter, and a decent Exciter, totally sweet. Some of you may also have noticed that is possible to change the Transistor to a more powerful device, most will just slot in, but change the output capacitors for a higher value for over a 150 Watts.... Happy Days....

[thewoodstarr]

To be honest why would you lump 2 together to get 170 Watts, when all you need to do is to install a BLF*** in 1 board, not forgetting to upgrade the output Caps, and get 300 Watts from less than 3 Watts drive..?
Simple.....

[thewoodstarr]

Yes. I'm not disagreeing with you, but I get the impression you think I am. The comment about it not being designed for Band 2, was in answer to you asking why they would use 2 turn coils in the LPF; ie because the LPF is designed to cut off much higher. As long as the transistor works ok in thy design, and it's stable it should just be a case of changing the LPF, which is why I posted the LPF. The component values could be used in the LPF section of the Chinese board - with appropriate component ratings etc.....

Hell no, I fully agree with you, the point I was trying to make was that it could be a good little amp that don't cost a lot of money. Only drawback is SMD components if your not so confident with soldering. The thing that threw me was using the MRF 186 which is essentially a UHF device, but it appears to work fine.

Hi,
Not being funny, as most are on this forum, but you have posted a low pass filter for a 2n4427 Transistor, it may work on that device, but not on this device! We have this tested this amp, harmonics are at least 60 db down relative to the carrier, we could not find any spurious emission that would cause any worry. If it ant broke don't fix it!

[thewoodstarr]

We have found it to run at 110 Watts with a 300 mW drive.

Really? Are you sure? What voltage are you thrashing it with?

With our own exciter, which can deliverer 15 Watts, but set @ 1 Watt. And on a switch mode @ 27 Volts... 120 Watts, but that is it, there is no more...... Next Question?

[teckniqs]

So you are driving it with 1000mW and not 300mW???