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

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Maximus
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Re: Thought I'd try one of these.....

Post by Maximus » Fri Jul 20, 2018 1:54 pm

Electronically wrote:mrf9180 26v from enigma I've used a few of there chips never had an issue with them either .How long have you tested it to see how well it goes without getting to warm maximus?
Maximus wrote:I think part of my fault with blowing the outputs was not having them bolted down properly with heatsink compound.

The Freescale version of the transistors from Enigma are bulletproof.

I once forgot to connect the dummy load for a couple of minutes and nothing happened. It just got hot.


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I had the transistor on test 24/7 for over a month @ 24v with no problems. Even after forgetting to connect the dummy load in the early testing stages.

Make sure you have the biasing set correctly.


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

Post by Maximus » Fri Jul 20, 2018 1:56 pm

Electronically wrote:
Electronically wrote:mrf9180 26v from enigma I've used a few of there chips never had an issue with them either .How long have you tested it to see how well it goes without getting to warm maximus?
Maximus wrote:I think part of my fault with blowing the outputs was not having them bolted down properly with heatsink compound.

The Freescale version of the transistors from Enigma are bulletproof.

I once forgot to connect the dummy load for a couple of minutes and nothing happened. It just got hot.


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with your antenna plugged in long did you get it to stay cool for before it goes to warm ?

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Just like any ordinary transistor. It depends on the size of your heatsink.


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Re: RE: Re: Thought I'd try one of these.....

Post by Electronically » Fri Jul 20, 2018 1:57 pm

Maximus wrote:
Electronically wrote:mrf9180 26v from enigma I've used a few of there chips never had an issue with them either .How long have you tested it to see how well it goes without getting to warm maximus?
Maximus wrote:I think part of my fault with blowing the outputs was not having them bolted down properly with heatsink compound.

The Freescale version of the transistors from Enigma are bulletproof.

I once forgot to connect the dummy load for a couple of minutes and nothing happened. It just got hot.


Sent from my iPhone using Tapatalk
Sent from my SM-G900F using Tapatalk
I had the transistor on test 24/7 for over a month @ 24v with no problems. Even after forgetting to connect the dummy load in the early testing stages.

Make sure you have the biasing set correctly.


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brilliant maximus .do you suggest I buy kit from eBay or elsewhere?

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Re: RE: Re: Thought I'd try one of these.....

Post by Electronically » Fri Jul 20, 2018 2:16 pm

Maximus wrote:
Electronically wrote:mrf9180 26v from enigma I've used a few of there chips never had an issue with them either .How long have you tested it to see how well it goes without getting to warm maximus?
Maximus wrote:I think part of my fault with blowing the outputs was not having them bolted down properly with heatsink compound.

The Freescale version of the transistors from Enigma are bulletproof.

I once forgot to connect the dummy load for a couple of minutes and nothing happened. It just got hot.


Sent from my iPhone using Tapatalk
Sent from my SM-G900F using Tapatalk
I had the transistor on test 24/7 for over a month @ 24v with no problems. Even after forgetting to connect the dummy load in the early testing stages.

Make sure you have the biasing set correctly.


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I've took note of the biasing .Thanks for the tip maximus

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Re: RE: Re: Thought I'd try one of these.....

Post by Electronically » Fri Jul 20, 2018 2:17 pm

Maximus wrote:
Electronically wrote:
Electronically wrote:mrf9180 26v from enigma I've used a few of there chips never had an issue with them either .How long have you tested it to see how well it goes without getting to warm maximus? Sent from my SM-G900F using Tapatalk
with your antenna plugged in long did you get it to stay cool for before it goes to warm ?

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Just like any ordinary transistor. It depends on the size of your heatsink.


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I'm going to have a wide and thick heat sink .

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

Post by Mike-Delta » Mon Jul 30, 2018 7:16 pm

Hi Guys,
I'm new to this forum and hopefully welcome.

I have also built one of these kits with an MRF9180.
At first everything seemed to work well. I started with less drive and gradually removed the attenuators until I reached 1 watt. Output 100 watts, SWR < 1.1 on a dummy load. The FET was cool. I have done some tests, switched it off and on, TX on and off, suddenly, I do not know why, no output anymore.
It turned out that one channel of the FET is damaged.

Now, I would like to test again with a MRF186 because it is cheaper.

I read that the SWR protection circuit could be a problem?
Or maybe that I did not always give drive ....
I dont know.
Maybe you can take a look at my board and see if everything is right before I destroy another FET?
Are there any tricks to prevent self-oscillation?
IMG_20180727_172106.jpg
IMG_20180727_172315.jpg
IMG_20180727_172325.jpg
IMG_20180727_172338.jpg

I am grateful for any help!
Thanks.
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Re: Thought I'd try one of these.....

Post by MC Spanner » Tue Jul 31, 2018 12:30 am

That's a common failure mode for the FETs provided with that Chinese board - the gates are very fragile. Those 9180s, and the MRF/XRF186's provided with the same PCB in a cheaper kit, are mostly ancient Motorola devices hacked (literally!) out of old cellular base stations and aren't known for being particularly robust. If you're going to replace your FET, don't buy the second hand devices floating round eBay, aliexpress etc from the Chinese market, they came from the same source as the ones provided with the kits. Try and get a newer one. Consensus is that the Freescales are best. Enigma have some Freescale 9180s in - after most of the last ones got bought up by one of our friendly builders South of the river!! ;-)

Your board looks tidy. There is no "SWR protection" but the directional coupler on the output does work. You might need to mess with the termination resistors to get any useful output (try 180R). There are also tweaks to overcome more obvious problems like output filter response, bias stability (replace the pot with a proper one, incorporate an NTC resistor in the bias network) and the input match, you can replace the three 1nF caps in series with a single one. I think 33pF does the job. I only know one builder who claims to have had that amp self oscillate though. Do you think this was why your FET blew up? Doesn't look like you've modded the board. How are you driving it?

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

Post by OgreVorbis » Mon Aug 06, 2018 6:40 am

I'm amazed that I just managed to push 280W out of one of these MRF9180's.
It was a Motorola brand one no-less.
It still hasn't popped. I wonder how high it can go. I can keep my finger on top of it for about 5 secs, so I don't think it's too hot. Of course I don't plan to run it at this power 24/7, but considering this one only cost $13, I don't really care too much.

The bias is set at 2.2V. Quiescent current is 170mA. No first harmonic. Second harmonic is -15db (no third) - so technically I am making about 271W. This is with about 2.5W of drive. How much can this thing really do and will it be stable?

Also, this is measured with no LPF.

Something else to note is that I am not using the kit. I bought the pre-assembled board fitted with an MRF186 and removed it. I came to find that the included LPF coils are way too thin. I almost popped it trying to run through the filter, but with it removed, does much better. I need to get some thicker wire to make coils out of. The other thing is that the output loops on this are much smaller than all the ones I'm seeing posted here.

So maybe if you want more power: Try getting bigger coils and try shortening the white cables. Maybe this will give more power.

EDIT: 300W out with 3W in. :lol:

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

Post by nrgkits.nz » Mon Aug 06, 2018 7:51 am

To get that kind of power from this Chinese devices, your input and output matching must be very good. Be careful touching the device, I hope you're not doing that while it's running?

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

Post by Electronically » Mon Aug 06, 2018 1:46 pm

I've actually ran one of these at 100 watts but trouble is I can't mind what the transistor I had on it .But anyways I ran 70 volts and the amps where 1.4 amps . geez should of seen this thing on a sinewave .I don't know how they use 26 volt transistors it baffles me should go higher I wouldn't use 26 volt transistor try double that .

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

Post by Electronically » Mon Aug 06, 2018 2:20 pm

for instance could try this operated at 50 volts with transistor .forget about the cheap China transistor .Have a look at this picture !!!!
2018-08-06 14.17.23.jpeg
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Re: Thought I'd try one of these.....

Post by Electronically » Mon Aug 06, 2018 2:23 pm

and it could handle 600 watts

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

Post by Electronically » Mon Aug 06, 2018 2:24 pm

and the info for it

https://www.nxp.com/products/rf/rf-powe ... tation_Tab

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

Post by OgreVorbis » Mon Aug 06, 2018 8:06 pm

Yeah, all the new MRF devices are much superior compared to the MRF9180. But for the pricepoint, it's amazing. I think the Freescale brand ones are more stable and not very expensive either. Maybe I could get even more power using one of them.

Right now I'm wondering if there are any other of these retired GSM type MOSFETs. Because they are now obsolete, I can't really seem to find a list of the product line that they came from, but I'd be interested if there are any others aside from the 186 and 9180.

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

Post by OgreVorbis » Mon Aug 06, 2018 10:42 pm

I looks like there's also the MRF9120 and MRF372. The 9120 seems like it should be very similar to the 186 (it could be a bit better). The only real difference is that it's rated for 800mhz instead of 1ghz (which is more like the 9180). The price is about the same as the 186, so it could easily be tested.

The MRF372 is 180W, but it's more expensive than the 9180, so probably not worth it.

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

Post by Mike-Delta » Fri Aug 10, 2018 7:27 pm

MC Spanner wrote:
Tue Jul 31, 2018 12:30 am
That's a common failure mode for the FETs provided with that Chinese board - the gates are very fragile. Those 9180s, and the MRF/XRF186's provided with the same PCB in a cheaper kit, are mostly ancient Motorola devices hacked (literally!) out of old cellular base stations and aren't known for being particularly robust. If you're going to replace your FET, don't buy the second hand devices floating round eBay, aliexpress etc from the Chinese market, they came from the same source as the ones provided with the kits. Try and get a newer one. Consensus is that the Freescales are best. Enigma have some Freescale 9180s in - after most of the last ones got bought up by one of our friendly builders South of the river!! ;-)

Your board looks tidy. There is no "SWR protection" but the directional coupler on the output does work. You might need to mess with the termination resistors to get any useful output (try 180R). There are also tweaks to overcome more obvious problems like output filter response, bias stability (replace the pot with a proper one, incorporate an NTC resistor in the bias network) and the input match, you can replace the three 1nF caps in series with a single one. I think 33pF does the job. I only know one builder who claims to have had that amp self oscillate though. Do you think this was why your FET blew up? Doesn't look like you've modded the board. How are you driving it?
Thank you for your answer.
I was surprised why the Mosfet works first and suddenly dieed without reason. But yes, that seems to happen more often.
Do you think it would be better to remove the directional coupler if I do not need it?

The output power was fine in my opinion. ~ 0.8W in 100W out. Which terminating resistor do you mean? Thanks for the other tips. But there are no obvious reasons for the loss of the Mosfet?
I do not believe that self oscilation was the reason but I had no obvious explanation.
I was driving it with an yaesu handheld radio on 144 MHz.
I will drive it next time with the exciter on the radio band.

Sorry for any grammatical mistakes. I am no native speaker.

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

Post by MC Spanner » Sat Aug 11, 2018 1:38 am

Mike-Delta wrote:
Fri Aug 10, 2018 7:27 pm
Thank you for your answer.
I was surprised why the Mosfet works first and suddenly dieed without reason. But yes, that seems to happen more often.
Do you think it would be better to remove the directional coupler if I do not need it?

The output power was fine in my opinion. ~ 0.8W in 100W out. Which terminating resistor do you mean? Thanks for the other tips. But there are no obvious reasons for the loss of the Mosfet?
I do not believe that self oscilation was the reason but I had no obvious explanation.
I was driving it with an yaesu handheld radio on 144 MHz.
I will drive it next time with the exciter on the radio band.

Sorry for any grammatical mistakes. I am no native speaker.
I'm sure your English is far better than my attempts at your language would be - unless you're Dutch ;)

Your observations are about right, I'd say. The amps I've built with MRF9180 easily achieve 150W with around 1.1W of drive in band II. I just found that the transistors supplied with the Chinese kits are fragile. When I first discovered these circulating on eBay I bought a couple of each to look at the design and to work out how they were doing it so cheap. It's a while ago now but here are my experiences as far as I can remember.

First board I built was a 100W effort which came with an XRF186. Worked OK and I was easily getting 100W with a couple of Watts in. FET was robust. I managed to crank it up to 120W very briefly. It's still alive although I don't use the board, I wasn't happy with the harmonics performance even after sorting out the filter response, but I'd never intended to put the thing on air. I was impressed enough to buy a couple of extra second hand Chinese MRF186's though, to use in an improved version of the amp.

On the next 100W board I popped an MRF186 by overdriving it, trying to get a feel for the device parameters on Band II (data sheet is obviously geared to 800MHz). I was using a driver board with an RD06 and was getting careless with the twiddler - I was being lazy when I should have been using a pad instead of trusting my instincts with too many parameters in play. Don't know if a "proper" MRF186 would have survived this, although I suspect the XRF186 in the first board might have done.

So, obvious precaution. The 186 in particular doesn't like being overdriven. I forgot to ask also, how much quiescent bias current you were using but from what you say, it doesn't sound like you were overbiasing and it looks like the 9180 can take a fair Idq anyway (1400mA?). This is the quoted figure from their tests on UHF though and you may find you need less. I wasn't using anywhere near 1400mA as I recall, and gain/harmonics were as expected.

The first board I built with the MRF9180 ran great for a few seconds and then died. Subtle fault, and completely invisible to the eye. What had happened was, the solid outer of the 50Ω cable had sheared all the way around. A tiny gap meaning the outer wasn't connected to the board at one end. I'd probably been over zealous with the wire strippers and bending it into the loop had finished it off. Obviously therefore, a serious mismatch killing the FET. Others have reported the newer Freescale MRF9180s standing up to this kind of abuse, but I expect that without realising there was a problem, they would have died eventually - perhaps not as quickly as mine. I killed one of my spare Chinese MRF186's before I diagnosed the fault too, it died even quicker than the 9180. Lesson learned - check the output transformers and matching carefully with a multimeter even if they look fine!

By the way, every time I popped a FET, one side died.

There's no harm in the directional coupler. If you don't need it, you don't have to populate the components on the coupled lines (diodes, capacitors and resistors). It won't affect the amplifier performance - as far as the output of the amplifier is concerned it's just going through a small 50Ω microstrip transmission line. For this type of PCB, the dimensions of that central line look about right (around 3mm width for 50Ω). The terminating resistors I was talking about are the resistors to ground at one end of each coupled line (the tracks running parallel to the microstrip carrying the RF output). Each coupled line (forward and reverse) can be considered part of a 2 port network with the main transmission line. Optimal power transfer to the sensing network will occur when the line is terminated with its characteristic impedance, which, in the case of my board, the designer had assumed to be 50Ω. I assumed not, as the tracks were somewhat narrow, and I obtained more output from the coupler by increasing the termination resistance to 150 if memory serves. This allowed me to drive my control board properly (yes, I admit I built a rig with one of these boards :oops: ). All kinds of factors affect not only microstrip, but this kind of coupler circuit so if you do want to use the coupler, you might find you can optimise it by experimenting and the value of that terminating resistor is significant, so it's a good place to start.

As I said, I've never had one of these boards self oscillate under any circumstances, but it's easy enough to spot (still getting power out after you drop carrier). I'd be surprised if you're getting self oscillation using a good 2m handheld and assuming a proper patch lead, connectors etc. Your construction looked spot on!

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

Post by Electronically » Mon Aug 13, 2018 4:40 pm

I can just say I've ran this for 4 days solid now at 9 hours a day .With mrf9180 .
However my power supply is at 22volts .
With 3 watts driving it to give me 169 watts output.if I bring my pll down to 2 watts I'm getting 113 watts .Don't go above 4 watts keep it at 3 watts .If you put 4 watts in you'll certainly blow this faster than you think .If the real world put it at 2 watts to push around 113 watts if you feel you don't want to push it at 3 watts for 169 out.

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

Post by Albert H » Thu Aug 16, 2018 12:59 pm

I found two dud 9180s here. Both had one side popped. As a single FET in a conventional circuit, at 24V, I'm getting 50W out for 600mW in at 108 MHz. I built another 60MHz PA with the other one, and now have a nice 20 Watt link transmitter for use in the Middle East! So don't chuck out your damaged FETs - they can sometimes be repurposed for lower power stuff.
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Re: Thought I'd try one of these.....

Post by MC Spanner » Fri Aug 17, 2018 12:55 am

Albert H wrote:
Thu Aug 16, 2018 12:59 pm
don't chuck out your damaged FETs
I've been known to do exactly that - out the window! Why didn't I think of this!! :ugeek:

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