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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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20th Sep 2012, 12:33 pm | #1 |
Triode
Join Date: Nov 2009
Location: Darkest Northumberland.
Posts: 13
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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 |
20th Sep 2012, 1:05 pm | #2 |
Heptode
Join Date: Apr 2003
Location: Ayr, Ayrshire, UK.
Posts: 630
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Re: MOSFET Replacements
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20th Sep 2012, 2:23 pm | #3 |
Triode
Join Date: Nov 2009
Location: Darkest Northumberland.
Posts: 13
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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. |
20th Sep 2012, 6:36 pm | #4 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,801
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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 David
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21st Sep 2012, 8:34 am | #5 |
Triode
Join Date: Nov 2009
Location: Darkest Northumberland.
Posts: 13
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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 |
21st Sep 2012, 10:07 am | #6 |
Rest in Peace
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,872
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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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28th Sep 2012, 4:46 am | #7 |
Retired Dormant Member
Join Date: Sep 2012
Location: London NW4
Posts: 5
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Re: MOSFET Replacements
Cricklewood Electronics stock the BF180 at 25p. Please don't buy the lot!
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28th Sep 2012, 10:19 am | #8 |
Rest in Peace
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,872
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Re: MOSFET Replacements
BF180 is a BJT?
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4th Oct 2012, 2:51 pm | #9 |
Retired Dormant Member
Join Date: Sep 2012
Location: London NW4
Posts: 5
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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. |