Topband: w7iuv preamp.

Michael Tope W4EF at
Sat Feb 17 16:46:04 EST 2007

----- Original Message ----- 
From: "Larry Molitor" <w7iuv at>

> If the 2N5109 is operated at my recommended current,
> without a heat sink, it will get very hot. In
> non-engineering terms, if you put your finger on it,
> you will get burned! However even with a small
> heatsink, the operating temperature is low enough to
> be able to put your finger on the thing and hold it
> there. The heat sink I use is a snap-on thing with 10
> small fins and an outside diameter of about 3/4 inch.
> Don't ask for a part number, I don't have one, they
> came in a box of junk I picked up 30 years ago!

Digi-Key has a whole assorment of little heatsinks for
various standard device packages (TO-39, TO-220,
etc). The are very cheap. I am sure they have something
similar to the ones you pulled from your junkbox.  

> Since I run these preamps 24/7 most of the time, I
> have way over 10,000 hours of total operating time on
> the devices with no failures or degradation of
> performance. Now we can debate reliability as applied
> to manned space flight or weapon systems, but we are

I was in a room full of people doing just that last week, 
Larry. I'ts great to go back to the ham radio paradigm
where the reliability criteria is "how long can you hold
your finger on it" and if the device fails, you just go 
solder in another one (no failure investigation boards are 
convened) -:)-:)

73, Mike W4EF..............................

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