2N3866 Transistor power query - UK Vintage Radio Repair and Restoration Discussion Forum

Damo666 · 25th Oct 2015, 9:52 pm

Hi all,

I've been searching Google looking for a simple amplifier to home brew for the 2m (145Mhz) band, and while browsing I've found a few circuits utilising the 2N3866 NPN Transistor.

The circuits I've found claim to be able to produce 1W from a 13.8v supply, however, by scrutinising datasheets for this Transistor - which I'm not particularly good at, I can't see that this output power is obtainable. I can only gather that this RF level is obtainable at 28V.

Please would somebody be so kind as to give one of these datasheets a once over and work out if I'm wrong and the aforementioned is possible or not, and if not, what is a realistic output power at the quoted 13.8V at 145Mhz?

My Transistor claims to be a genuine Motorola, but I bought these a while ago and can't confirm they're actually genuine OEM.

Here is a link to the datasheets, and many thanks for your valued input in advance. http://www.alldatasheet.com/view.jsp...66%20datasheet

Herald1360 · 25th Oct 2015, 11:38 pm

The device seems to be good for 400mA Ic and several watts dissipation suitably heatsunk, so 1W at 150MHz sounds feasible as long as the collector load is low enough impedance. It would likely need stepping up to match 50ohm output load.

Are you after a linear or class C amplifier?

Tyso_Bl · 25th Oct 2015, 11:42 pm

I've used these driven by either a BSX20 or BF199, at car battery voltages you should expect around 800/1200mW output. Very much depended on how gainy the specimen was. I'd used them to drive a 2SC1971 final to around 10/12W. the 2N4427 is gainier, butless robust. An MRF237 will give around 5W, but needs really good layout to be stable.

Damo666 · 26th Oct 2015, 3:27 pm

Thanks for the replies, guys.

I'm looking at using the said Transistor in Class C for 2M FM purposes, Herald1360.

By looking at the datasheets, what would you say the sweetspot frequency is for best gain - as I wouldn't mind perhaps also building a QRP transmitter on HF or a UHF class C amplifier?

I do apologise about these questions, but some of the info' I find on datasheets goes right over my head.

David G4EBT · 26th Oct 2015, 4:03 pm

The 2N3866 is widely used in QRP circles and designs abound, which generally claim up to 1 Watt output. They benefit from a clip-on heat sink.

There's a simple 1 Watt VHF FM transmitter design here (though tuned to the FM broadcast band!):

http://circuit-zone.com/?cat=fm_transmitters

There’s a simple SSB QRP Transceiver here (Chapter 6), which makes use of 2N3866s:

https://books.google.co.uk/books?id=...ojects&f=false

A 1 Watt PA:

http://www.hobbyprojects.com/T/trans..._circuits.html

The ‘Ham-Can’ 40M minimalist transmitter:

http://www.4sqrp.com/kits/HamCan/hamcanmanual.pdf

I used a 2N3866 in the PA of the PW 'Severn' 40M CW transceiver, designed by Rev George Dobbs, G3RJV back in 1983. It gave a good account of itself.

Hope that's of some interest.

Herald1360 · 26th Oct 2015, 4:52 pm

2N3866s (and 2N3553s) featured in the lower power stages of Racal Solid State HF TXs back in the '70s when I was there. No problem using them at HF.

Damo666 · 27th Oct 2015, 1:41 pm

Thank you all for your knowledgeable input, it's very much appreciated.

25th Oct 2015, 9:52 pm	#1
Damo666 Hexode Join Date: Jan 2010 Location: Blackburn, Lancashire, UK. Posts: 399	2N3866 Transistor power query Hi all, I've been searching Google looking for a simple amplifier to home brew for the 2m (145Mhz) band, and while browsing I've found a few circuits utilising the 2N3866 NPN Transistor. The circuits I've found claim to be able to produce 1W from a 13.8v supply, however, by scrutinising datasheets for this Transistor - which I'm not particularly good at, I can't see that this output power is obtainable. I can only gather that this RF level is obtainable at 28V. Please would somebody be so kind as to give one of these datasheets a once over and work out if I'm wrong and the aforementioned is possible or not, and if not, what is a realistic output power at the quoted 13.8V at 145Mhz? My Transistor claims to be a genuine Motorola, but I bought these a while ago and can't confirm they're actually genuine OEM. Here is a link to the datasheets, and many thanks for your valued input in advance. http://www.alldatasheet.com/view.jsp...66%20datasheet

25th Oct 2015, 11:38 pm	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: 2N3866 Transistor power query The device seems to be good for 400mA Ic and several watts dissipation suitably heatsunk, so 1W at 150MHz sounds feasible as long as the collector load is low enough impedance. It would likely need stepping up to match 50ohm output load. Are you after a linear or class C amplifier? __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

25th Oct 2015, 11:42 pm	#3
Tyso_Bl Hexode Join Date: Jul 2014 Location: Magor, Monmouthshire, Wales, UK. Posts: 436	Re: 2N3866 Transistor power query I've used these driven by either a BSX20 or BF199, at car battery voltages you should expect around 800/1200mW output. Very much depended on how gainy the specimen was. I'd used them to drive a 2SC1971 final to around 10/12W. the 2N4427 is gainier, butless robust. An MRF237 will give around 5W, but needs really good layout to be stable. __________________ Adapt, Improvise, Oh Bother.....

26th Oct 2015, 3:27 pm	#4
Damo666 Hexode Join Date: Jan 2010 Location: Blackburn, Lancashire, UK. Posts: 399	Re: 2N3866 Transistor power query Thanks for the replies, guys. I'm looking at using the said Transistor in Class C for 2M FM purposes, Herald1360. By looking at the datasheets, what would you say the sweetspot frequency is for best gain - as I wouldn't mind perhaps also building a QRP transmitter on HF or a UHF class C amplifier? I do apologise about these questions, but some of the info' I find on datasheets goes right over my head.

26th Oct 2015, 4:03 pm	#5
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,761	Re: 2N3866 Transistor power query The 2N3866 is widely used in QRP circles and designs abound, which generally claim up to 1 Watt output. They benefit from a clip-on heat sink. There's a simple 1 Watt VHF FM transmitter design here (though tuned to the FM broadcast band!): http://circuit-zone.com/?cat=fm_transmitters There’s a simple SSB QRP Transceiver here (Chapter 6), which makes use of 2N3866s: https://books.google.co.uk/books?id=...ojects&f=false A 1 Watt PA: http://www.hobbyprojects.com/T/trans..._circuits.html The ‘Ham-Can’ 40M minimalist transmitter: http://www.4sqrp.com/kits/HamCan/hamcanmanual.pdf I used a 2N3866 in the PA of the PW 'Severn' 40M CW transceiver, designed by Rev George Dobbs, G3RJV back in 1983. It gave a good account of itself. Hope that's of some interest. __________________ David. BVWS Member. G-QRP Club member 1339.

26th Oct 2015, 4:52 pm	#6
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: 2N3866 Transistor power query 2N3866s (and 2N3553s) featured in the lower power stages of Racal Solid State HF TXs back in the '70s when I was there. No problem using them at HF. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

27th Oct 2015, 1:41 pm	#7
Damo666 Hexode Join Date: Jan 2010 Location: Blackburn, Lancashire, UK. Posts: 399	Re: 2N3866 Transistor power query Thank you all for your knowledgeable input, it's very much appreciated.