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Old 20th Sep 2012, 12:33 pm   #1
Gridleak
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Default MOSFET Replacements

Hello All,
Can anyone either suggest a supply of the BF981 or perhaps a replacement part / equivilent. Seem like some of the older devices are getting harder to source. I would like to upgrade my old MickMouse Transverter.

Regards Paul G4HDS
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Old 20th Sep 2012, 1:05 pm   #2
radioman
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Default Re: MOSFET Replacements

Jab Electronics Components have them listed
http://www.jabdog.com/semi-tra2.htm


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Old 20th Sep 2012, 2:23 pm   #3
Gridleak
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Default Re: MOSFET Replacements

Hi, Andy

Thanks for the Info, also found another place that selling them... so got myself 10 whilst they still exist.... Should keep me in front ends for a while

Are there any more upto date devices with a lower noise fig that you may be aware of?

Regards And thanks again Paul , G4HDS

Last edited by Gridleak; 20th Sep 2012 at 2:37 pm.
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Old 20th Sep 2012, 6:36 pm   #4
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Default Re: MOSFET Replacements

For 2 metres, stick to Silicon. GaAs is noisier until you get to 70cm.

There's not a lot much quieter because market demand has changed. All the semiconductor houses are churning out specialised devices for low voltage supplies (5v and 3.3v and lower) to make tiny batteries in tiny devices last longer. Some odd techniques have come along like the BF904 with a second scale model FET as a current mirror to get the gate voltage threshold varience out of the bias current control system.

Some MMICs aren't bad for noise, but otherwise you'll have to look at the exotica in the Avago and NEC catalogues. Have a look at what the 2m moonbouncers are using, and have a look in 'Dubus' - a great magazine. I don't read German, but I look at the pictures

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Old 21st Sep 2012, 8:34 am   #5
Gridleak
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Default Re: MOSFET Replacements

Hi David
Thanks for the update, i guess that he market must be driving the development of such devices as you mention for consumer product i.e. iphones etc etc, I will follow you suggestion and see what the moonbounce boys are using.. I just hope that any intersting devices are of human proportion so i can solder them !!!! my days of using solder stations and surface mount are behind me....

best regards Paul G4HDS
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Old 21st Sep 2012, 10:07 am   #6
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Default Re: MOSFET Replacements

In most cases at 2m your total noise figure is likely to be set as much by the input circuit as the MOSFET. Little point in looking for a better MOSFET.
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Old 28th Sep 2012, 4:46 am   #7
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Default Re: MOSFET Replacements

Cricklewood Electronics stock the BF180 at 25p. Please don't buy the lot!
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Old 28th Sep 2012, 10:19 am   #8
G8HQP Dave
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Default Re: MOSFET Replacements

BF180 is a BJT?
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Old 4th Oct 2012, 2:51 pm   #9
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Default Re: MOSFET Replacements

Ahem! I wondered if anyone would spot that deliberate mistake.
They stock quite a few dual gate mosfets at reasonable prices as well.
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