Re: Use of a small amp to boost the 5 W Paraset output


Timothy Fidler
 

If you use the 50 W CW  KIT amp from Qrp Labs (about $30 USD) you will get 14 W true out on 40 M with a 14 V supply. that 's another 5.5 dB of signal at the far end.   That amp will produce 45 W but only on a 22 VDC supply.  It is specifically designed for QSK CW work though mods to make it a SSB amp are possible.

If  you equip it with "bend pin "  RD16HH mosfets you will get up to 20 W of clean  CW rf out  on 40 mtrs. THe efficiency will be about 55 percent.  The RD16HHs can be got for about $12 a pair from Ebay Schenzen etc  (if you go too cheap you will get fakes ) . Hans Summers ex  Qrp labs does  not sell those parts  . THe RD16s are vastly better from a thermal  point of view.

NB you need to get  an RX / TX 5V  TTL signal out of the BJ to the  power amp to control it the rx tx switching . that could be an issue - you may need to fit a TDO timer (CMOS 555) based on the CW key  down so you will get only semi qsk in that case. 

The 50W CW amp is one off the deals of the century in  terms of what you get for the money.  The only ones that don't work  are the ones where someone on cocaine wound the RF transformers  or soldered the puppy up.  If you do build one,  consider fitting  dpdt relays and a second filter set so you  make it dual band. 

regards, TEF 

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