MRF300 amp!

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Itrip875
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MRF300 amp!

Post by Itrip875 » Wed Oct 14, 2020 12:57 am

Anyone got the values for this board ? It’s so simple yet so expensive for what it is. Or is there any other design out there ?

The mrf101 amp is well documented on the net, but every amp containing the mrf300 seems to be paired up to create 600w.
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RF-Head
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Re: MRF300 amp!

Post by RF-Head » Wed Oct 14, 2020 8:38 am

That amp is not working good!
The input match is not good and it uses a 2 pole output so it won't be wideband
Stay away of it as most of the PCS-Electronics stuff

nrgkits.nz
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Re: MRF300 amp!

Post by nrgkits.nz » Wed Oct 14, 2020 10:46 am

I may look at doing a single ended MRF300 amp, if there’s demand for them.

Itrip875
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Re: MRF300 amp!

Post by Itrip875 » Wed Oct 14, 2020 12:55 pm

@RF Head. Ah that’s not good. I was gonna buy one but it’s so simple I thought I’d try and recreate it on copper first.

Would this be hard to try and guess with trimmers and air coils ? Or do you have an amp I could purchase from you ?

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Re: MRF300 amp!

Post by rigmo » Wed Oct 14, 2020 1:02 pm


Itrip875
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Re: MRF300 amp!

Post by Itrip875 » Wed Oct 14, 2020 2:33 pm

Yeh I saw them but you can’t buy them anywhere. I saw them on eBay months ago but now they have vanished.

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yellowbeard
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Re: MRF300 amp!

Post by yellowbeard » Wed Oct 14, 2020 7:21 pm

There are a couple of reference designs (81.36-108MHz & 87.5-108MHz) on the NXP website, but you need to login to access them. I am not arsed enough to give them my e-mail address, but you may be...
https://www.nxp.com/products/rf/rf-powe ... _Tools_Tab

:tup

RF-Head
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Re: MRF300 amp!

Post by RF-Head » Wed Oct 14, 2020 8:46 pm

Yes i have seen it and already test the AFT with MRF300 version and is not working good
They match not between the stages and the output is running hot and solder will melt by the coils :shock:

XXL
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Re: MRF300 amp!

Post by XXL » Wed Oct 14, 2020 11:04 pm

how can NXP have it wrong though? How much power was you getting out ?

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Bton-FM
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Re: MRF300 amp!

Post by Bton-FM » Wed Oct 14, 2020 11:12 pm

Large up NXP for opening the pandora’s box of insanely cheap 300 watt and 600 watt rigs! :D

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Re: MRF300 amp!

Post by XXL » Thu Oct 15, 2020 12:39 am

Iv seen someone put this chip on the mrf9180/186 boards. Do you need both AN and BN to get it working ? Or would it work using just 1 device to get 300 out ?

Albert H
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Re: MRF300 amp!

Post by Albert H » Thu Oct 15, 2020 1:03 am

On the boards designed for the twin FETs, you'd have to use two (ideally matched) devices. The match would be rather different - it's easiest to go for the NXP test circuit. It's proven. It works well (or NXP wouldn't publish it)
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Re: MRF300 amp!

Post by nrgkits.nz » Thu Oct 15, 2020 8:39 am

I’ve got a new 300W PA on the way which will be avail soon, it’s using a dual ldmos device, the pcb is Rogers 4350 32thou on a 6mm slab of aluminum - you’ll just need to supply a proper heat sink to bolt it onto.

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Re: MRF300 amp!

Post by Bton-FM » Thu Oct 15, 2020 10:09 pm

It might be an idea to get one of those Chinese push pull MRF300 amps and change the components/coax lengths to match the ones described in the NXP test circuit.

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Electronically
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Re: RE: Re: MRF300 amp!

Post by Electronically » Fri Oct 16, 2020 8:38 pm

Bton-FM wrote:It might be an idea to get one of those Chinese push pull MRF300 amps and change the components/coax lengths to match the ones described in the NXP test circuit.
Mrf300 is does get extremely hot. But however there is a work around this to cool it

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XXL
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Re: MRF300 amp!

Post by XXL » Sat Oct 17, 2020 6:50 pm

Water cool 😂

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Re: RE: Re: MRF300 amp!

Post by Bton-FM » Sat Oct 17, 2020 6:57 pm

Electronically wrote:
Fri Oct 16, 2020 8:38 pm
Bton-FM wrote:It might be an idea to get one of those Chinese push pull MRF300 amps and change the components/coax lengths to match the ones described in the NXP test circuit.
Mrf300 is does get extremely hot. But however there is a work around this to cool it

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Which circuit are you talking about that gets too hot? The one from NXP with a single transistor or the push pull one?

XXL
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Re: MRF300 amp!

Post by XXL » Sat Oct 17, 2020 7:04 pm

A mate of mine sent me this. At a guess what do we reckon these components are ?

XXL
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Re: MRF300 amp!

Post by XXL » Sat Oct 17, 2020 7:12 pm

Image
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Electronically
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Re: RE: Re: RE: Re: MRF300 amp!

Post by Electronically » Sat Oct 17, 2020 7:13 pm

Bton-FM wrote:
Electronically wrote:
Fri Oct 16, 2020 8:38 pm
Bton-FM wrote:It might be an idea to get one of those Chinese push pull MRF300 amps and change the components/coax lengths to match the ones described in the NXP test circuit.
Mrf300 is does get extremely hot. But however there is a work around this to cool it

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Which circuit are you talking about that gets too hot? The one from NXP with a single transistor or the push pull one?
Just heard from somebody that the single transistor gets hot I've no idea I haven't tried to find out for myself thought.

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