My main design goal here is to use few parts and make the circuit as repeatable as possible, just incase anybody want's to try and give the rig a shot, but I'm not sure my design goal of a low-parts-count rig will allow that to happen. I know that I could use a source-follower and further amplify the signal and not pull the PTO - no problemo - but that's going to require more parts, which I'm trying to avoid. Unfortunately, my scope is still down (waiting on parts), so I'll just have to do things the old-fashioned way. ![]() I'm also going to try putting some 30pF trimmers on the input and the output port and see if I can dial in the correct values. Doing things this way probably has some obscure naming convention - named after the creator, I'd imagine - that I'm not familiar with it or something. Now I'm thinking that using two diodes and an anti-bias setup might work a bit better? I tried searching for a schematic that used this setup, but my searches on google have come up with nothing. ![]() Via empirical data, I've seen them turn on anywhere from. Hopefully, somebody out there has done some exhaustive research on the 1N34A, and then I'll know exactly what to design for, too. The highest number of degrees conduction per half cycle would be the goal. For switching purposes a square wave would be better, the higher level signal would switch it on quicker. At lower voltages the diode would still conduct in the non linear region. It was only then that I realized that it was not apparent to him that unlike tubes, most modern silicon transistors are very similar and in a properly designed circuit, the circuit's performance is largely independent of the transistor's characteristics. I remember on another thread an individual asking for bias resistor values for a specific transistor. Your electronic life will become much easier with the realization that in general, transistors are all very similar and with some exceptions necessary for power dissipation and higher frequencies, are largely interchangeable. If you examine the data sheets for most general purpose transistors, it will be discovered that their current gain, fT, input capacitance, output capacitance and Miller capacitance are very similar. Why is it necessary to alter the circuit? I might even be able to do a simple swap-out of the transistors and give that a shot (for the heck of it), but I'm thinking I'd be much better off using LTSpice and design the thing properly. Unfortunately, I don't have a 2N2907 in my junkbox, but I do have a LOT of 2N3904 and 2N3906 transistors, so I'm trying to alter the circuit to accommodate these devices. Guess I'll have to go read the tutorials again! God - how I hate being old and forgetful! LOL. I have most of it already input into LTSpice, but it's been so long since I've used the program that I've forgotten how to setup the AC voltage source and frequency. The PTO provides 400-500 KHz of bandwidth, and I'm hoping that, properly designed, I can keep the diode turned on enough to actually hear stuff decently. What I'm trying to do is see how well I can make a minimal-parts-count receiver play. I'm also thinking about adding an RF amplifier to the front end, just to see how she plays. I do have schottky diodes to roll my own passive, doubly-balanced mixer, though I'd like to experiment a bit to see how well I can get the diode detector/mixer to work. It's also important to point out that I'm trying to use a 1N34A diode as a mixer. Well, this is kind of a somewhat unique application, so, first and foremost, let me provide a link to a schematic: ![]() If it is a matter of voltage, and not dBm power, just use a broadband transformer wound on a ferrite core.
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