Mysterious mosfet SRF261 from FREESCALE 300w

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rigmo
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Mysterious mosfet SRF261 from FREESCALE 300w

Post by rigmo » Sun Apr 18, 2021 9:36 am

Hi I just make experiment with mystirus freescale mosfet popular called SRF261
I get fine tune and result is very good... for the moment is not broadband board.. but is not important for the this task / request (If we wanted broadband... we must forget the higher efficiency....)

This PLL drive board is best i see on market.. 0/6W without harmonics... and also almost a flat power through scale 88/108

26.5V
13.8A
300W RF OUT
1.25W RF drive
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Last edited by rigmo on Sun Apr 18, 2021 10:01 am, edited 3 times in total.

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Bton-FM
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Re: Mysterious mosfet SRF261 from FREESCALE 300w

Post by Bton-FM » Sun Apr 18, 2021 2:56 pm

Nice work!

Could you share the schematic? I’d be interested to try this.

What is the efficiency like if the circuit is board band?

I could swear that driver used an all in one chip for the oscillator but maybe the design has been changed

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Re: Mysterious mosfet SRF261 from FREESCALE 300w

Post by radium98 » Sun Apr 18, 2021 7:16 pm

Good work rigmo

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Re: Mysterious mosfet SRF261 from FREESCALE 300w

Post by rigmo » Wed Apr 21, 2021 8:50 pm

Bton-FM wrote: Sun Apr 18, 2021 2:56 pm Nice work!

Could you share the schematic? I’d be interested to try this.

What is the efficiency like if the circuit is board band?

I could swear that driver used an all in one chip for the oscillator but maybe the design has been changed
is not so much difference then for mrf9810. Each tune matching is individual... nothing special / secret..
standard protocols..
start with 0v BIAS... lover drive and PSU voltage... calculate efficiency i fined best match. lower then 75% is not good at all...

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Re: Mysterious mosfet SRF261 from FREESCALE 300w

Post by rigmo » Fri Apr 23, 2021 6:17 pm

LPF support up to 600W
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Re: Mysterious mosfet SRF261 from FREESCALE 300w

Post by radium98 » Fri Apr 23, 2021 9:48 pm

wonderful rigmo

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Re: Mysterious mosfet SRF261 from FREESCALE 300w

Post by iykee » Sun Oct 01, 2023 3:22 pm

Can someone post a detail finished work with schematic for this FET srf261? Am not getting any good output. Died several with try and error, please neep help. Thanks.

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Re: Mysterious mosfet SRF261 from FREESCALE 300w

Post by rigmo » Sat Oct 07, 2023 7:29 am

iykee wrote: Sun Oct 01, 2023 3:22 pm Can someone post a detail finished work with schematic for this FET srf261? Am not getting any good output. Died several with try and error, please neep help. Thanks.
based on experience, it is difficult to say final values. you have to deal with that yourself. it also depends on the quality of the coax... it needs final tuning. adding capacitance or longer coax... if you zoom in on the pictures, you'll see what I'm talking about.. this is a 400w test, but it's not SRF261...
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Re: Mysterious mosfet SRF261 from FREESCALE 300w

Post by iykee » Sun Oct 08, 2023 9:13 pm

rigmo wrote: Sat Oct 07, 2023 7:29 am
iykee wrote: Sun Oct 01, 2023 3:22 pm Can someone post a detail finished work with schematic for this FET srf261? Am not getting any good output. Died several with try and error, please neep help. Thanks.
based on experience, it is difficult to say final values. you have to deal with that yourself. it also depends on the quality of the coax... it needs final tuning. adding capacitance or longer coax... if you zoom in on the pictures, you'll see what I'm talking about.. this is a 400w test, but it's not SRF261...
Thanks very much for your contribution, i have mrf9180 kits from china 3 years ago and I want to use srf261 because the mrf9180 got burnt just 3 days in operation. Secondly the srf is very cheap, what changes should I make on the board since you said there are no much difference between these two mosfet. Thanks.

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Re: Mysterious mosfet SRF261 from FREESCALE 300w

Post by rigmo » Mon Oct 09, 2023 9:07 am

iykee wrote: Sun Oct 08, 2023 9:13 pm Thanks very much for your contribution, i have mrf9180 kits from china 3 years ago and I want to use srf261 because the mrf9180 got burnt just 3 days in operation. Secondly the srf is very cheap, what changes should I make on the board since you said there are no much difference between these two mosfet. Thanks.
a picture says 1000 words, right? if your MRF9180 burn, it means that you have not made protection, etc... it is very sensitive.. if the work is done well, she has no fear.. my last experimental one worked for 5 days at 180W without failure.

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Re: Mysterious mosfet SRF261 from FREESCALE 300w

Post by Albert H » Mon Oct 09, 2023 9:39 pm

I found that the MRF9180 worked well at 900 MHz when wound down in power, but was fragile at 100 MHz. Fortunately, there are cheap FETs that are much more robust that are widely available these days!
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