Neil Well, so far the whole thing has been 'ugly' construction in some form or other. The good thing is that I've built and rebuilt the important circuits several times, several ways, so I'm confident it's reproducible. Stay tuned... ----- Original Message ----- From: Neil Martinsen-Burrell To: minima@xxxxxxxxxxxxx Sent: Wednesday, December 10, 2014 11:47 AM Subject: [minima] Re: A New Approach Joe, As a minima lurker and beginning homebrewer, I greatly appreciate your comments and contributions here. I think we are all better off if there is another modern BiDi SSB transceiver design in the world. There are many different ways to skin this same cat as you and Allison have taught so many of us. I, for one, would love to see a schematic, even a somewhat incomplete one. I am more likely to try building something that is Manhattan- or ugly-style with leaded parts, but again there's the thing about cats and their skins. Presumably your design would work with that technique as well, perhaps with some necessary part substitutions. Thanks again for everything you have contributed here for the learning of all of us. -Neil N0FN On Wed, Dec 10, 2014 at 8:53 AM, Joe Rocci <joe@xxxxxxxxxx> wrote: For the last several months, I've been quietly and slowly developing the components for a different approach to the Minima. I've written about some of the concepts here, but I never really laid out the whole thing. At the risk of creating a major fork in this group, I'm going to describe where I'm going. If there's serious interest, I'll put all this up on my own web site, along with a discussion forum for anyone who wants to follow along. Here are the key components: 1) A high-level front-end mixer based on my Quad FST3257 bus switch design. It accepts Si570 or Si5351 drive levels. 2) An IF at 9 mhz, but changeable according to the builder's tastes. I'm considering an optional dual xtal filter for SSB/CW, using bus switches for filter switching. 3) A totally different BiDi amp architecture. This one uses a single Hybrid Cascode amplifier with a complimentary NPN-PNP output stage. It easily develops 30 dB of gain, up to +10dbm of uncompressed output power, excellent input and output match, and about 3.5db noise figure according to LTSpice. It only draws about 18 ma. It has well over 70 db of voltage-controlled gain range that can be used for TX ALC as well as Rx AGC. This single amp is turned around from the Rx direction to the Tx direction with another FST3257 bus switch. It works very nicely. 4) A product detector made with another FST3257. It also accepts Si570/Si5351 drive levels. 5) Audio amplifier chain that is made with a single package of low-noise op-amps. This amplifier chain is used for Tx as well as Rx and is turned around with some left-over switches in the product-detector bus switch package. 6) Detectors for audio-derived Rx AGC and RF-derived Tx ALC. Both of these are optional. 7) Should be possible to use the Minima control system as a control foundation with relatively simple changes I've done some preliminary bench testing of the whole RX chain (minus input filters) and the 10db sensitivity is in the sub-1uv range. In Tx mode, it's putting out about 3-5 dbm. There are two easy to make binocular core transformers in the mixer (possibly one can be eliminated) and another in the product detector. Other than the FST3257 bus switches, everything else is done with a few 2N3904's & 2N3906's, a J310 and a pack of quad op-amps. Overall, I don't think the parts count is much/any higher than the Minima. This basic Xcvr sub-system can be finished off in several ways: 1) The input filters, which will be a separate board, can be individual switched bandpass filters (my preference) or a pair of low-pass filters as in the Minima. Based measurements I'm seeing, I'm pretty sure the LPF approach is workable with the 9mhz IF, although the IF can be built for other frequencies. In either case, I plan to use more FST3257 switches to select input filters. 2) AGC/ALC can be left out at the builder's desire. I'm calling this design the "BSS-1", standing for "Bus Switch Special". I started to draw the schematic in Eagle with the intention of making a PCB. Due to my own design tastes, I'm doing the first layout with SMD components. This generally results in smaller size and better performance. Although I fully intend to take this to fruition on my own, I sometimes get sidelined for long periods of time, so a group effort would keep things moving. If there's enough interest, I'll put up the forum I mentioned. Joe W3JDR