LF: Re: AF Amps at 136

["Hugh M0WYE" <m0wye@radiouk.com>]

Hi Chris,

I used an OMP 100W amp for my brief sortie onto 136kHz. I never blew up any FETs, but never managed to get more than 50W out of it either.

Unless you want a linear mode go for the switching-on-and-off things they're much more efficient.

Hugh M0WYE

----- Original Message -----

From: Chris

To: RSGB LF Group

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.