16-04-2013, 07:43 PM
(16-04-2013, 07:11 PM)Skywave Wrote: Not a lot of £ for what it is and does, is it?
I can think of two useful applications for that, (in addition to the obvious ones and those listed) :
(a) as an enhanced calibrator for a short-wave radio;
(b) as a tunable local oscillator for a superhet radio.
Or . . . buy two: and do both!
Al.
I am tempted to have one of those, I always wanted to do a hybrid DCR with a DDS VFO, talking of which I built a DCR many many moons ago based on Spaargarens design but I can't for the life of me remember the coil details for the balanced mixer, so far as I can remember the coil I made was trifilar wound, primary was RF in, the two secondaries were connected as a center tapped winding which along with two diodes and a balancing pot formed the single balanced mixer, I remember that AM envelope detection could be virtually eliminated by balancing the mixer with the pot.
My design used valves and I think an EB91 or something similar was used for the balanced detector diodes
The link below is all I can find regarding Spaargarens design.
Can anyone remember this?
http://www.epanorama.net/sff/Radio/Commu...rt%201.pdf
Lawrence.
