Sunday, May 30, 2010
Here is a block diagram of my vacuum tube home theater system. Thought this might be interesting to share.
Sunday, May 23, 2010
Interested in repairing an old tube radio that you purchased at a garage sale? How about connecting your ipod to it?
Wednesday, May 19, 2010
another model 20B that he has purchased. This one is much different
than mine, where, there are no front doors and the output tubes are
push/pull type 45's rather than my single ended variant (photo 2).
In addition to this, it does not have doors on the front.
A great find! Can't wait to see it working.
Sunday, May 9, 2010
pair VFO from the 2010 ARRL handbook, scaled to a frequency range of
10-10.5 Mc and combined with a surplus VFO chassis/vernier dial gear
reduction that i salvaged out of an old FAA modulation tester.
Photos from the top:
3. connected to the rest of the modules that make up my 20 M SSB
Works great! I found that cheaper 2n4124's (or equivalent) NPN
transistors work better than UHF low-noise transistors. This was
indicated in the ARRL handbook, but, i chose to ignore it and hoped
to improve phase noise performance by using the low-noise UHF
transistors. The problem with the UHF transistors was that they
would output broad-band oscillations on occasion causing instability
in the VFO. So, best approach is to follow the directions from the
handbook and go with the cheap transistors for this type of VFO.
Saturday, May 8, 2010
reference oscillator from his 1997 book on PLL synthesizer design.
In this i used a new low-noise NPN transistor, with an NF=1 dB.
Oscillator signal chain includes: oscillator circuit -> mmic
amplifiers -> LPF -> RF out at 10 dBm.
Photos (from top down):
1. inside of the oscillator
2. outside of oscillator
3. oscillator connected to SSB radio signal chain. works great!