Jottings on HEXFET power amplifiers

Hi all,
HEXFETs are quite popular with hams as HF linear stages . I too attempted to make some linear amps with them and that too with pretty promising results . Here is the outcome . The first FET that I tried was a IRF540 . The circuit used is given below .

I had to place some component in TINA as a choke , so I put a 1m choke . In reality , I used a torroid with some 20 winding . I could pull some 2~3W into a 50 ohm dummy load ( which I used as a termination in front of the CRO ) at 1MHz , but at higher freq , power output dropped drastically . The power calculation was carried on the basis of the voltage that I measured across 50 ohm load . The voltage peak to peak was 40V . So that gives me around 2W power . Next , I'm gonna try IRF530 , IRF610 etc  

Some thoughts on DDS VFOs

Hello all !
I recently homebrewed a Direct Digital Synthesis Variable Frequency Oscillator (DDS VFO) . The reason for this was quite strong.Almost all the VFOs that I had attempted suffered from stability issues.Besides,it was impossible to know the frequency of oscillation precisely and accurately (with atleast 100Hz precision).It was then I came to notice the AD9850 DDS modules in ebay.They are cheap,easy to use,stable and have a large tuning range (from ~1Hz to 40Mhz) which makes them a good alternative to analog VFOs.On another note,VU2MV,OM Venu once commented " You need the grace of God to make a stable analog VFO !".
The VFO design is simple.I use an Arduino as the controlling board. The frequency tuning is carried out using four push buttons,arranged in a navigation button style. The code for Arduino and the inside view of VFO shall be posted soon along with the ckt diagram. For the time being,I'm posting the pics of the completed VFO and the video of its smoke test :) . Thankfully no smoke appeared !
I frequently use this VFO to tune into the 40m morning nets . The output of this VFO can be mixed with the antenna input (using a ring modulator or a balanced modulator) to get the audio from SSB transmissions , using the direct conversion principle.

VFO display 

VFO testing

VFO smoke test video .