Design
Well, I've pretty much put the finishing touches on my secret QRP project for a well-known QRP club. The beta testers are currently working on building it, and hopefully the club can make an announcement about the kit fairly soon. It's not a very complicated circuit, but it's somewhat novel and has a bit of [...]
Last week, I was informed that everyone in our company would be receiving a temporary (but indefinite) 10% reduction in pay. To make matters worse, it looks like we will be taking more mandatory shutdown days in the current quarter; we've got five coming up over the next few months. This is also another open-ended [...]
You can never have enough low frequency decoupling in an audio amplifier with 100 dB voltage gain. You can never have enough voltage regulation on the VXO you are using to feed your diode mixer. Not enough and you get all kinds of nasty low frequency oscillations in the receiver.
As I mentioned in a previous post, I did the calculations to change the AF filter in the Willamette from a low-pass filter with a 3.3 kHz cutoff to a peaked low-pass filter with a cutoff frequency nearer to 1 kHz. I finally got around to implementing the mod last night and got a chance [...]
I finally got a few days of decent sleep (decent meaning more than 4 hours), so I had a little energy to work on the simple DC transceiver. A few days ago, I got the remainder of the audio chain working. The emitter follower on one of the outputs of the differential mixer was yanked, [...]
Yes, its a post about another simple, low-performing direct conversion receiver. However, I think that this one is slightly unique. I was inspired to give this a try based on the Flea minimalist transceiver that was introduced on the EMRFD Yahoo group. These little rigs are fun to build in an evening, but just how [...]
Even though a homebrew return loss bridge is a relatively simple piece of gear to build, I've never gotten around to building one until now. Which is truly a shame, and something I don't really have an excuse for, except perhaps laziness. I'm excited to add this essential gear to my stable of test equipment, [...]
Continue reading about Dual Gate MOSFET Investigations - Return Loss
Some days I feel like I can't see the forest for the trees. After submitting my last dual gate MOSFET experiment to the EMRFD group for review, I got a nice note from Henning suggesting that I needed to bypass gate 2 directly. Of course, like a three-year old who has to constantly ask "Why?", [...]
Continue reading about Dual Gate MOSFET Revelations from W7ZOI
Having determined some basic characteristics of the biasing of the BF998 dual gate MOSFET in a previous experiment, it was now time to look into the gain and AGC performance of the amplifier. A few changes were made to the original circuit to turn it into a proper RF amplifier. Test Equipment Power Meter: M3 [...]
Continue reading about Dual Gate MOSFET Investigations - Gain and AGC
While digging around the avrfreaks.net forums, I found this very interesting tidbit in a message from a gentleman who was working on using an AVR microcontroller for SAME decoding. One poster mentioned using the Goertzel Algorithm as a way to perform tone detection on a sampled signal. The algorithm is supposed to be simple enough [...]
