Several months ago, Georges F6DFZ sent me pictures of a Manhattan project he had just completed, using Rex’s MeSQUARES, and I have waited far too long to share it with you. It began life as a copy of the Ten Tec 1253 regen, but George said that the results and usability were very poor. One thing that must be said about regens is that the ones which don’t work well are very dispiriting. However, when you come across a good design and build it well, the performance can be very satisfying indeed. Luckily, Georges didn’t let his initial regen experience put him off, and he ended up turning the project into a receiver based on the Kitchin-inspired Scout Regen. He normally uses PCB software to design custom boards for his projects, but decided to try Manhattan construction for this receiver.
I like how his project was obviously the result of considerable careful planning –
The slow motion drive came from a very old French military surplus rig. George says that it tunes very smoothly with no backlash, and has 2 ratios – 10:1 and 100:1. The operator pulls on the tuning knob to shift to the slow tuning rate –
The front end is taken from the Scout regen. Georges added an RF preamp stage. You can see the RF board and tuning capacitor in this photo. I am guessing that the polyvaricon is for fine tuning –
A closer view of that RF board –
From above –
The AF stage in the Scout design uses an LM386 with the ubiquitous 10uF capacitor between pins 1 and 8 for a stage gain of 46dB. While offering high gain with a low component count (and a low quiescent current), this circuit configuration also introduces a lot of hiss. Georges used a more complex, and lower noise audio chain. A MAX293 device provides 8th order low-pass filtering for good audio selectivity, and feeds an LM380 AF output stage. Using a relatively low noise device such as the LM380 makes listening much more pleasant, in my experience. Both my Sproutie and Sproutie MK II regens use one, and I regularly listen to them both for hours at a time. Good filtering, such as the arrangement that Georges has used, also does a lot to reduce unnecessary static and noise that can make listening for long periods fatiguing. Here are the AF stages, located underneath the chassis –
Another view of the topside of the chassis –
Georges also added an S-meter, which he got from a QRP book by Doug DeMaw –
This receiver operates on 80M and 40M. The band coverage on each band is 3.48 – 4.8MHz, and 6.95 – 8.5MHz respectively. Everything was done with hand tools, and a sheet metal brake which was made from an article in QST – this was indeed an admirably home-brew project! It even has dial lights –
I love how Georges fabricated his own custom chassis from sheet aluminum, and paid attention to all the mechanical aspects of the design, making sure to include a dial and slow motion drive. These are the aspects of making your own equipment that can be very time consuming but which ultimately, make the project more enjoyable to use, and helps to ensure that it will occupy pride of place in the shack for years to come.
Incidentally, Georges wrote an article that appeared in the Oct 2014 issue of QST, on a CW adapter for the Collins KWM-2A transceiver. You can view it here if you have an ARRL membership. Thank you very much to Georges for being willing to share these pictures and details of his wonderful regen. I find it very interesting to see how other people build their projects, and I know a lot of others do.