[Lowfer] Lowfer Final Transistors.

[Andy - KU4XR]

Hi Lee:

Good luck with the new transmitter construction. I use the transistors
that John mentioned. MPS6502/MPS6652...they are definitely better than
the 2907/2222 pair. The biggest reason for the 2907/2222 combination is
probably they're easily obtainable. The MPS pair will require a little
searching on the net for a source, and possibly having to purchase from
2 different sources. But, they are worth finding in the long run.
I have not built a Class " E " final so can't give any experienced pros,
and cons, but just from all the reading I have done, it might come down
to complexity versus simplicity. The 2907/2222 setup is very simple to
construct, is very forgiving to impedance mismatches, and will easily
obtain 90% efficiency in Class " D " configuration. The Class " E " 
design is not as forgiving to impedance mismatches. The construction
requires more detail to matching or you'll probably be popping the
transistor more than you would like. There are many good articles on
Class " E " transmitters on the net should you decide that you want to 
go in that direction..... Again, good luck in whatever direction you
choose to go. Hope you can get one on the air soon.  73 for now :



Andy - KU4XR - EM75xr - Friendsville, TN. USA
LOWfer Beacon " XR " @ 185.29875 KHz ( QRSS-60 )

*** Temporarily OFF, while constructing a new antenna ***

Coordinates:  N:  35º 43' 54" - W:  84º 3' 16"
http://www.myspace.com/beaconxr


--- On Sat, 7/31/10, LEE BAHR <pulsarxp at embarqmail.com> wrote:

> From: LEE BAHR <pulsarxp at embarqmail.com>
> Subject: [Lowfer] Lowfer Final Transistors.
> To: "Discussion of the Lowfer (US, European, & UK) and MedFer bands" <lowfer at mailman.qth.net>
> Date: Saturday, July 31, 2010, 6:31 PM
> I am in the process of trying to
> build up a transmitter for my Lowfer Beacon 
> I plan to get on the air this Fall.  I see that most
> of the examples on the 
> internet use a pp scheme with a PN2222A and PN2907A
> transistors.  In really 
> days of old the ancients used IRF single Hexfets.  The
> present day articles 
> say, use PN2222A and PN2907A because they are cheap,
> but......  a 
> NTE-129/NTE -128  combo might produce slightly better
> results.  Well, NTE 
> transistors today are not all that popular and readably
> available as in the 
> past. (I realize they still are
> available).   All the present internet 
> articles were written a few years ago.  There must be
> some really modern 
> transistors available today that would make good
> replacements for the "in 
> every ditch PN2222A/PN2907A" units with generic numbers.
> 
> I'd like to know what others are using today besides the
> PN2222A/PN2907 
> combo that might be as good as the NTE transistors in TO-39
> cases.
> 
> I'd appreciate any comments.
> 
> Lee, w0vt
> Texas 
>