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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 specification data for  RFSimm99 I need a working circuit with practical L and C values to continue.

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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