Alternative to using 2n4427 for 1 watt drivers

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Bton-FM
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Alternative to using 2n4427 for 1 watt drivers

Post by Bton-FM » Sun Jun 07, 2020 12:06 pm

Hello everyone
I hope you are doing well.I’ve been building a driver board that I did a layout of a while ago and it got me thinking there must be a better alternative to using a 2n4427 for the 1 watt output on a driver boards.Its Ok paying 3£ for one but it’s a bit expensive for what it is.I think maybe the BFG35 is a good candidate but I doubt it can Crank out a watt by itself? What are your thoughts?

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by teckniqs » Sun Jun 07, 2020 12:24 pm

There are a number of alternatives but sometimes they can be a bit expensive compared to the price of a 2N4427.

....Personally I really like the 2SC730, it has a bit more gain and unlike the 2N4427 it runs really cool.

Others with a bit more gain include 2N3553, BLX65, BLY33, BLY34, MRF229, MRF629, TP8740, BFW16A, 2N5160.

There seem to be quite a lot of MRF alternatives but they are usually a lot more expensive.

My favouite 2N4427 replacement though has got to be the 2SC730, just drop it straight in and it should give you around half to over twice the power more than a 4427. (approx 1.5 to 2.5w)

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by Albert H » Mon Jun 08, 2020 2:22 pm

The BFG35 is a great little device, and has loads of gain at 100 MHz, but it's tricky getting rid of the heat. The 2SC730 is a very old device, but works well. I'm not as enthusiastic about them as Teckniqs, but they're a good choice. If run at a Watt out, you only need a small heatsink on them. If you try to push them for more power (and you can), you'll need a bigger chimney!

My favoured driver transistor is the old SD1127. It's roughly equivalent to an MRF237, and has the emitter connected to the can - you can bolt them down to the box that your exciter is in, and get rid of the heat. At Band II, you should get (roughly) 4 Watts out for 200mW in. My exciter circuit that used these had a pair of BF199s in parallel driving the 1127. If you shop around, you can get the 1127 (usually made by Mitsubishi) for around $2.

The other option (and the one that Stephen Moss preferred) was the 2SC1947. I found a large supply of these for $0.40 each (!), but they've all gone now. He and I used to get 5 Watts out of them easily for about 300mW drive. It's the device that was used for the final stage in the 4 Watt PLL Pro III board. There's a simple modification that can be done to that board (look at the tracks around the output transistor for clues!) that increases the gain of the stage.

At one point, there was a need for a few 10 Watt PLL Pro III boards, and I etched some modified ones that used a pair of '1947s for 10 Watts (easily) off the board. These were nicely boxed with Pro IV stereo coders, my little RDS modules and stereo limiters into 19" rack cases, and went to some religious types for R*m*d*n stations. I had two of them returned to my workshop last year (18 years after they were built) to have their frequency changed. They were still exactly "on the money" - 10 clean Watts on 87.7MHz. Nice little rigs!
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Re: Alternative to using 2n4427 for 1 watt drivers

Post by Bton-FM » Mon Jun 08, 2020 2:29 pm

Can you squeeze a watt out of the bfg35 comfortably?They are only a quid each which makes them a good candidate.Also it’s quite funny that as soon as I mention that device it gets scheduled for obsolescence - just my luck !

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by Albert H » Mon Jun 08, 2020 3:35 pm

You can get a Watt, but you also have to get rid of nearly a Watt of heat. It's a small device, so heatsinking it is a pain!

There's also the BFG135, which is good for about a Watt. It's also a surface mount device, but is more efficient than its older brother, so there's less heat to get rid of. It also operates at a lower supply voltage - I have a commercial PCB here somewhere that runs a pair of them at 7.5V supply in push-pull for 1 Watt out.
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Re: Alternative to using 2n4427 for 1 watt drivers

Post by Albert H » Mon Jun 08, 2020 3:38 pm

Really try to get some 2SC730s. You can find them on Ebay, and as they're old devices, there's no point in trying to fake them! They're good for a Watt at 12V.
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Re: Alternative to using 2n4427 for 1 watt drivers

Post by radium98 » Tue Jun 09, 2020 7:37 am

2n3866 what i use 1.2w out @15v

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by teckniqs » Tue Jun 09, 2020 8:33 am

2N3866 have less gain and usually only give around 0.6 to 0.8w and is probably the worst alternative. :tup

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by RF-Head » Tue Jun 09, 2020 8:36 am

If you get 1.2W out of a 2N3866 you have a chinese 2N3866 witch is the same as the chinese 2N4427 and 2N3553 BFW16A they all use the same transistor but only a other number on it :lol: :roll:

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by Bton-FM » Tue Jun 09, 2020 10:32 am

RF-Head wrote: Tue Jun 09, 2020 8:36 am If you get 1.2W out of a 2N3866 you have a chinese 2N3866 witch is the same as the chinese 2N4427 and 2N3553 BFW16A they all use the same transistor but only a other number on it :lol: :roll:
Are the Chinese clones alright to use?

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by Bton-FM » Tue Jun 09, 2020 10:38 am

@teckniqs I can’t find any 2SC730 on eBay for a reasonable price so I’ll bite the bullet and go with a 4427 for now. I was more trying to find something a bit more modern that I can have a reliable source of.

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by teckniqs » Tue Jun 09, 2020 1:32 pm

Fair enough, yeah like I said compared to the 4427 the alternatives are usually a bit more pricey.

....If you want something that is a bit more modern and a lot smaller you can always go for the surface mount MRF4427, you can pick these up for about 3 quid each, but it's still recommended to try and keep it cool and I think they are usually mounted underneath the board with some heat paste tight against the box to work as the heat-sink.
I just found 2 of them (2 sold in a pair) for just £3.39 on eBay here: https://www.ebay.co.uk/itm/123881939098

Probably best to just stick to the 2N4427, they are are very easy to always get hold of.
The genuine old Motorola 2N4427 seem to have the best gain, but BEWARE as there are many fakes.

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by radium98 » Tue Jun 09, 2020 5:14 pm

i tried both but they are expensive here and now i could not find any
a trucho 2n3866 with chiny body and the poor old oxidised 2n3866 from ph or motorolla all give good result in place of a 2n4427 that i can not find anywhere ,i have a used pair of c730 i will try them to see on a chassis and compare results.out of topic a bit ,any of you can give me what is the power of mrf227 and i need a replacement
,and what is the power of mrf517 can replace the mrf227 (in my place the mrf227 is driven a 2sc2695)
thanks guys for the generous answers.

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by Krakatoa » Wed Jun 10, 2020 9:03 am

There is a manufacturer "central semiconductor" that still makes de 4427 you will identify the transistor as it has a marking "CEN" on them. But the performance is a bit lower than the ST ones that used to exist beforr they ceased production of this transistor.
Maybe pushing the CEN one a bit more with an improved driver will get you the watts you expected.

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by nrgkits.nz » Wed Jun 10, 2020 11:22 am

Krakatoa wrote: Wed Jun 10, 2020 9:03 am There is a manufacturer "central semiconductor" that still makes de 4427 you will identify the transistor as it has a marking "CEN" on them. But the performance is a bit lower than the ST ones that used to exist beforr they ceased production of this transistor.
Maybe pushing the CEN one a bit more with an improved driver will get you the watts you expected.
Digi-Key sell them, and they’re expensive, they also didn’t work as a direct drop in replacement on an original NRG UK Pro3 board when I last tested - I got a lot less power out. There are 4427 copies on AliExpress at good prices which I’ve used and found to work very well, however these days I no longer use 4427’s in my designs as I’m using RD06 and RD15 FET’s instead, they also require significantly less drive. I was mainly using the 4427 as drive previously.

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by radium98 » Thu Jun 11, 2020 12:19 pm

radium98 wrote: Tue Jun 09, 2020 5:14 pm i tried both but they are expensive here and now i could not find any
a trucho 2n3866 with chiny body and the poor old oxidised 2n3866 from ph or motorolla all give good result in place of a 2n4427 that i can not find anywhere ,i have a used pair of c730 i will try them to see on a chassis and compare results.out of topic a bit ,any of you can give me what is the power of mrf227 and i need a replacement
,and what is the power of mrf517 can replace the mrf227 (in my place the mrf227 is driven a 2sc2695)
thanks guys for the generous answers.
Anyone reply me please thanks about the out of topic part

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by RF-Head » Thu Jun 11, 2020 5:28 pm

You also can use BLY33 or BFS22A and will also give a little more output

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by radium98 » Thu Jun 11, 2020 7:19 pm

my question is mrf517 can replace mrf227 for better power ?

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by teckniqs » Thu Jun 11, 2020 7:28 pm

radium98 wrote: Thu Jun 11, 2020 7:19 pm my question is mrf517 can replace mrf227 for better power ?
I'm not familiar with those devices, the best thing to do is take a look at the Datasheets and see which one has the most gain at your voltage. :tup

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Re: Alternative to using 2n4427 for 1 watt drivers

Post by radium98 » Fri Jun 12, 2020 7:25 am

Thanks tecknics

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