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Post by vladn » Thu Dec 22, 2011

Most wideband regen RXs require substantial adjustment of regen level as you tune across the band. For example most common BCB regens using Armstrong/Hartley/Colpitts topology usually require advancing feedback at the low side of the band. This is the result of frequency dependence of both tank Q-factor and feedback path gain. But there is a solution that allows compensating at least the linear term (tilt) of the regen feedback adjustment dependence on frequency. There are at least 3 class of oscillator feedback network types (I wrote about it earlier) that have substantially different frequency dependence of the feedback gain: class 1: Armstrong, Colpitts, Hartley class 2: Vackar (basic form, fig5 in original Vackar paper [1]) class 3: Clapp/Gouriett Within …

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One Transistor Loudspeaker Superhet! - The RadioBoard Forums

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Multi-band regenerative loop antenna - The RadioBoard Forums Post by qrp-gaijin » Sun Jan 26, 2020 I'm planning a multi-band regenerative loop antenna, controlled by computer (specifically, a Raspberry Pi). I want to cover 500 kHz to 30 MHz. Here's what I've come up with so far. Comments would be welcome. ml.png (18.87 KiB) Viewed 1243 times The basic idea is to have a multi-turn loop antenna with taps on the various turns. The loop will be fairly small, maybe 20 cm in diameter (the width of a standard piece of paper -- similar to the dimensions of the Kiwa Loop, http://www.dxing.info/equipment/kiwa_mw_loop_plimmer.dx). Unused turns would be left floating. The portion of the coil that is in use is selected by the switches (only one of which is closed) on the …

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Low-power BJT converter stage for superhet Post by qrp-gaijin » Wed May 13, 2015 I'm working on another low-voltage, low-power superhet design and, after a few evenings of messing around on the breadboard, have the RF converter working. Previously I had done some experiments with a single-transistor autodyne converter, but that was too hard to get working reliably, so this time I'm splitting the oscillator and mixer: Screen Shot 2015-05-13 at 10.29.23 PM.png (34.26 KiB) Viewed 2852 times I hooked up the IF output port on the IF transformer to my FT-817's antenna input, tuned my FT817 to the IF of 2 MHz, and was able to tune in several shortwave stations with good audibility, so it's working so far. Q1 and Q2 form a differential pair oscilla…