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

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

Post by rigmo » Fri Apr 17, 2020 3:14 pm

Bton-FM wrote: Fri Apr 17, 2020 2:59 pm I like your progressive attitude Rigmo but I think some people on this forum are reluctant to give up their intellectual property for good reason.
Why we live? after all Nicola Tesla die to... but We live better. yes min 50% anther 50% is still in property, laws of lizards... !!!
I sniff and I find for 5 usd mosfet can make 300w PA.... but i will meke share when I finish the job... note earlier..
Education is for all receivers but ..what you can do with that after you receive that is your 100 responsibility...
business is evil.. they protect self-sufficiency.. and narcizam.. after all die like dog.. each of us equally... lif is to short for shit

p.s.
see story about NanoVNA edy555 and Hugen... stil friends.. developer parallel..

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

Post by rigmo » Fri Apr 17, 2020 3:23 pm

teckniqs wrote: Fri Apr 17, 2020 11:24 am I've seen some combine two of those amps and get about 350w out of them.
this is not cheep you need 2 this is 100e... and need to buy coax 75R PTFE... carbon dummy loads... bigger heatsink...
p.s. this one board can support up to 500 watt but need knowledge tools... etc.
LOT of WORK!

For less money ore equal you can get 300W and small board 10x10cm (80usd)with LPF and SWR bridge.. example MRF151G (80usd)

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

Post by rigmo » Fri Apr 17, 2020 3:34 pm

Lubomir73 wrote: Fri Apr 17, 2020 4:02 am Read posts on this thread, one year ago. April, May 2019.
I do not see this post but not to much interested... I explain why...
BEst REgards

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Re: Thought I'd try one of these..... Add a schottky?

Post by rigmo » Fri Apr 17, 2020 6:12 pm

Lubomir73 wrote: Sat Apr 27, 2019 8:56 pm Hello all. This is my first post as you can see... so go easy on me. I found this forum a couple days ago by searching for any suggestions on MRF9180/gate/protection. I know I'm a little late on this subject but I believe there is something else that needs consideration. A couple of months ago, I started a project using an MRF9180 to replace a MRF186 in the UHF version of this Chinese power amp board. After pondering the spec's and costs for various FET's, I realized that there is one huge, glaring difference between the MRF9180 and the MRF186 and many other devices... it's inability to tolerate negative gate voltage swing. Maximum Vgs for the MRF186 is -20/+20 volts. Maximum Vgs for the MRF9180 is -0.5 to +15 volts. That's a maximum of only minus one-half volt! Otherwise, Poof! The 9180 can't take a negative swing of the same magnitude as the positive swing needed to drive it in a Class B or AB configuration.
The diagrams of some FET's show a schottky diode drawn in the transistor case. I believe the 9180 lacks this gate diode and that maybe if you put one in at the gate connection, the input will be resistant to overdriving or as one commenter put it, "Breathing on it wrong." I also suspect that possibly Motorola, NXP Freescale and others, may have sneaked a schottky into their designs to make them more resilient. I would have done so. If, (and that's a Big IF) my assumption is correct you can bulletproof the 9180's input easily, by adding a diode.
I am still looking, but so far I think I have found a schottky barrier diode for this job. Panasonic DB2J50100L. Only 1.6 ns from reverse to forward conduction...suitable for UHF. Forward voltage (Vf) under 0.5 V, reverse voltage (Vr) of +50 V, and forward current max. 200 ma. Also a capacitance when reverse biased that is only 6 pf at a Vr of around +3 volts. You can buy them through Mouser, DigiKey or Newark for 10 cents a piece or less. For use at 440 mhz, I may need to reduce the FET's input capacitance to accommodate this diode. But for use at around 100 mhz, 6 pf may not be a big factor.
All kinda makes sense when I read an earlier post that he has to keep the drive less than 4 watts. If Pwr still equals E²/ R, then driving an input impedance of say 5 ohms with 4 watts gives an RMS voltage of 4.5 volts RF, with peaks at 6 volts. Take a volt or two away for input matching loss and you have about 4 volt peaks. Combining the RF with +3 volts gate bias gives you peaks of plus 9 volts and minus 1 volt going to the FET gates. I may be wrong, but I think that right there... that negative voltage swing is part of the reason why the 9180 FET's are dying so easily.
Also, remember the diode turns on when the input goes negative, and is reverse biased when the FET is forward biased. So the cathode connects to the FET's gate. I apologize for not having any proof of this concept. Anyone want to try this out? I am still working and lack the time and equipment. Any other ideas? All suggestions are welcome. Who's perfect? Not me!
maybe it is good to protect the input of the MOSFET?

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

Post by Bton-FM » Fri Apr 17, 2020 8:46 pm

rigmo wrote: Fri Apr 17, 2020 3:14 pm
Bton-FM wrote: Fri Apr 17, 2020 2:59 pm I like your progressive attitude Rigmo but I think some people on this forum are reluctant to give up their intellectual property for good reason.
Why we live? after all Nicola Tesla die to... but We live better. yes min 50% anther 50% is still in property, laws of lizards... !!!
I sniff and I find for 5 usd mosfet can make 300w PA.... but i will meke share when I finish the job... note earlier..
Education is for all receivers but ..what you can do with that after you receive that is your 100 responsibility...
business is evil.. they protect self-sufficiency.. and narcizam.. after all die like dog.. each of us equally... lif is to short for shit

p.s.
see story about NanoVNA edy555 and Hugen... stil friends.. developer parallel..
What is this 5 usd for 300W PA you speak of? :shock: :D

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

Post by Albert H » Fri Apr 17, 2020 11:31 pm

Friends of mine who were losing lots of rigs came up with a PA that used four VN88 FETs driven by one VN66 (total cost for the FETs was about $9). They built the PAs on aluminium I-beams that were used as parts of room dividers and made fairly good heatsinks. They made their own home-made capacitors out of pieces of transistor insulators, bent pieces of copper and bits of PCB material. They would build the PA with trimmers in it, then remove the trimmers and make fixed capacitors of the same values. Their PAs were good for between 50 and 60 Watts, and they used coax Bazooka aerials supported by bamboo canes. Their exciters were based on a simple CMOS PLL, built on etched PCBs. It took them about an hour to build one of these $24 rigs, and they kept a stock of ten or twelve of them. They used "local loop" phone lines to link, and achieved pretty good coverage of a good part of their city in mono.

Their big problem was repeated raids. However, they kept on the air for years every evening and all over each weekend.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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

Post by rigmo » Sat Apr 18, 2020 8:11 am

Bton-FM wrote: Fri Apr 17, 2020 8:46 pm What is this 5 usd for 300W PA you speak of? :shock: :D
I mean only about mosfet, ex BLF6G22-180PN

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

Post by rigmo » Sat Apr 18, 2020 11:46 am

600 watt test ( not mine )
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Re: Thought I'd try one of these.....

Post by teckniqs » Sat Apr 18, 2020 1:43 pm

As long as it works, but yeah the soldering isn't the nicest so I can see why the need to point out that it's not yours.

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

Post by Polecat » Sat Apr 18, 2020 2:12 pm

teckniqs wrote:As long as it works, but yeah the soldering isn't the nicest so I can see why the need to point out that it's not yours.
You're too funny Tekniqs
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Re: Thought I'd try one of these.....

Post by Bton-FM » Sat Apr 18, 2020 2:20 pm

:lol: :lol: :lol:

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

Post by rigmo » Sun Apr 19, 2020 9:10 pm

Hi Guy do any body try this baord withs short coax..
i have confirmation, i n that case perheps mrf9180 go 200W without diodes :)
mrf186 150W 22V input 3W
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Re: Thought I'd try one of these.....

Post by zeljko » Mon Apr 20, 2020 11:48 pm

BriansBrain wrote: Fri Jun 28, 2019 3:06 pm
zeljko wrote: Thu Jun 27, 2019 7:51 am Can someone tell me why can't see any .jpg on forum?
Hi Mr.zeljko ...

You should be able to see the jpgs now you have joined the Forum :roll:
hello my friend!
I'm retired, and not so good with this. But thanks anyway...copy now!!
Regards!

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

Post by zeljko » Tue Apr 21, 2020 12:07 am

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?
I fried 3 of them...but on my opinion is that on input MUST be attenuator....therefore must be termination 50 ohm. This LDMOS is for 900 Mhz, and on much lower freq, very easy can be unstable(I convinced myself). I purchase new item,but now i will put 50 ohm att. Will see. Must to say also...i have 180 W with 25V@ 9A without problem on 144Mhz...but my temper....uh..and good by 9180!

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

Post by johnnyB » Tue Apr 21, 2020 4:15 pm

Maximus wrote: Mon May 01, 2017 3:34 am With a few modifications, the amps have many other uses. Especially DAB, when combined with some good filtering on the output.


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Wondering what modifications you have done to make it work for DAB.
I have tried to use it, but could not get much power.
Any tips?

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

Post by rigmo » Sat May 02, 2020 10:12 pm

Hi, Today I play A lot with mrf186 and get 150W 26V idq 200mA... I do not wont try at 28V :)
This guy get power with self oscillating... opposite of mene work - expirance.. see link
Need to be end of coax Add 1nF on both channel 25R, China diy kit give only 4X120Pf ATC.. its to low value...

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

Post by rigmo » Fri Jun 26, 2020 10:59 pm

HI
all problem and speculation solved with high efficiency mrf186 150w & mrf9180 200w can run stable with good copper plate cooling. All problema lay on matching - fine tune. advice is for good long long nights 120w and 180w best regards folks ;) :tup

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

Post by Fgbokoiii » Wed Feb 03, 2021 6:21 am

Hi

Can i ask how much input power you give?

Thanks

Fgboko

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

Post by rigmo » Sat Feb 06, 2021 6:57 am

Fgbokoiii wrote: Wed Feb 03, 2021 6:21 am Hi

Can i ask how much input power you give?

Thanks

Fgboko
MRF9180 under 1w i cant remember... i think 600mW... ( form me this is best aspect ratio") 600mw in out 180
MRF151G 3-4W
MRF300 1.25W

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

Post by Fgbokoiii » Mon Feb 08, 2021 7:52 am

Hi!
Just to ask if this blue wire that i reciv with this chinese PA, is itc20 ohms or 50 ohms? ... not familiar with it, no device i could used to to test it...

Thanks

Fgboko
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