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Detector Sensitivity Tests - The RadioBoard Forums Post by gzimmer » Wed Jan 04, 2017 Hi, For a long time now we've been discussing (and arguing about) the efficiency of the Diode Detectors in Crystal Sets. The difficulty in actually measuring the efficiency lies in the large number of variables: The size of the antenna, the degree of Selectivity, the Tuned Circuit loading, the sensitivity of the Headphones, and many others. So I've been thinking about a test set which could reliably measure the relative Sensitivity of different detectors, while eliminating the variables. I'm looking for definitive answers for the following questions: - Which diode types are the most sensitive? - What circuit impedances do they prefer? - Can battery bias improve Sensitivity? - How do Shunt Detecto…

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Designing class-A solid-state regen w/explicit AAC loop Post by qrp-gaijin » Wed Oct 30, 2013 Transistors, IC's and other new fangled devices forum qrp-gaijin Posts: 2822 Joined: Sun Feb 28, 2010 2:12 pmContact:Designing class-A solid-state regen w/explicit AAC loop vladn wrote: qrp-gaijin wrote:I assume there is nothing fundamental to the idea that would preclude a solid state implementation, correct? I just like playing with tubes. You can replace 6AS6 with a 3-transistor half-Gilbert cell and get more gain and long term stability. Is it possible to use JFETs or must BJTs be used? The fact that both ends of the hybrid feedback network are connected to grids, combined with the fact that grid current is flowing, leads me to believe that JFETs cannot be used in this configuration because then no current would flow through…

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Balanced autodyne mixer - The RadioBoard Forums

Post by qrp-gaijin » Sat Oct 07, 2017 7:21 This is my attempt at making a solid state version of vladn's balanced autodyne mixer described in viewtopic.php?f=3&p=76279#p76279 . Original tube circuit First, let's look at vladn's original circuit:

The image is a little fuzzy, but the idea is:

• Connect two tubes essentially in parallel.

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Auto regen "AGC" - The RadioBoard Forums by sixtynine » Wed Feb 08, 2017

Finally got some time over our long weekend to impliment an idea for simply AGCing a regen RX. My interest is in SW AM, and my old ears are allergic to large and annoying exursions in volume. The idea I think has merit and works very well given it uses three components only. Ill get a video up in the next few days to demonstrate it working. I decided to try to vary the gain of the regenerative amplifier, rather than controlling the input signal level. Looking at the schematic is a bog standard mosfet regen, TR1, is an RF buffer. Voltage amplification is performed in the coil due to transforrner ac…