----- Original Message -----
Sent: Sunday, October 18, 2009 2:49
PM
Subject: LF: Re: AF Amps at 136
Chris
Do not use audio amps for RF. Build a class
D or E amp and operate trouble free. Audio amps were tried by some in the
early days but never worked properly.
Read the horror stories of yesteryears about
using audio amps for RF applications. Buckets of burnt out FETS.
73 De Mal/g3kev
----- Original Message -----
Sent: Sunday, October 18, 2009 2:13
PM
Subject: LF: AF Amps at 136
Hi All,
Just started constructing TX for 136kHz,
noticed Maplin do a Velleman audio PA kit that is rated at 200W (100W RMS
into 4R). OK there's no mains transformer or heat sink, but reckon it's good
value at £14.99. Point is the specs also say the minus 3db frequency
response is 3Hz / 200kHz.
The RSGB books 'LF Today' refer to using audio
amps as PAs at 136 with 'a few modifications'. Does anybody know where these
modifications are documented? I guess there's nothing major, reduce a few
cap values? Remove Zobel Network etc.?? If anyone has experience with this
approach I would appreciate some hints. Thanks.
Chris, G4AYT, Whitstable.
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