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Showing posts from February 9, 2012

I want my lazy BLX15 back!

I did replace my old BLX15 power transistor with a modern Power MOS device. The BLF177   the BLX15 has 6dB gain only at 70MHz. While the BLF177 should have over 20dB. After a few days  trying all I could think of to get stable power out of the BLF177 MOS   at 70MHz  the result was  2 melted tuning C's. It sure can generate power this device  but I did not manage to let it  work at the wanted frequency. Many combinations of L and C  where tested. The original circuit was  used for 50MHz relatively  close to 70MHz.  I did not expect major changes in the L and C's  in use. The   2 stage low-pass filter should be almost the same. Of course the bias circuit is different   but simple only a pot-meter to get about 3V at the gate for 500mA. The BLX15 needed the 0.7 PN diode in parallel to get a 500mA bias. I have  edited  an input file with the scattering parameters from the specificati...

PACC comes propagation leaves,,

423 km to OZ7IT 624km IO90 Will the sunspots left us just before the PACC?  28MHz closes just 2 days before the PACC? Last year just 1 day after the PACC  28 opened.. PACC  next weekend   but propagation  has been  very poor last 2 days.  only  VK6XT  was left  on 28MHz  and very  short open to USA.     80/160m  very poor     160m suffers  almost a radio blackout.    Hope it will improve for the weekend ..

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