Pro Crastination

Pro as in very high skill level of doing nothing but looking busy. HAHA, Well i really should be building the hand held, I have the boards here and its just a matter of assembly and giving them a go. But, for some unknown reason I was digging in my box of arduino crap and came across these 2 modules. The first is an Analog Devices SSM2167 variable compressor and noise gate, the second is Maxim Integrated MAX9814 which is an AGC mic amplifier.

And this got me thinking because after the hand held build the very next thing will be a superhet receiver which will start life as a receiver to mate with the CW transmitter and later will become a ssb transceiver. Part of that build will be a single unified front end board, that has on it a micro controller, in this case its going to be an ESP32, a bunch of peripherals, like keyboard interface, SD Card slot, real time clock, SI5351 PLL Synth, a few push buttons for various radio functions, a couple of LCD screens, rotary encoder etc.

Also on the board will be the entire audio chain, which, when i designed it originally contained an pre amp with agc, select-able ssb or cw active filters and an LM386 AF amplifier because i was not thinking ahead of myself. I have a better AF amp ic that i can be using and it has a shutdown pin, so i can send logic level from the micro and mute the AF amp on transmit. And now, i have these 2 modules.

I can now see using 2 sets of these in an SSB transceiver build. First in the receiver, audio coming out of the product detector is routed into the compressor and noise gate, then into the agc before it is sent off to the audio filters and then to the AF amp. Seeing that I would have quite a bit of gain just in these 2 modules, I would not need to lots of gain from an LM386 and I could then use a much better sounding and higher wattage audio amp.

And then on the transmit side, have the exact same thing, compression, noise limiting and agc on the mic. Lets be honest here, how many home brew transceivers actually incorporate such luxuries as these. Each of these modules is around $5 aud off ebay, the Analog Devices IC i can buy for a couple of bucks and the passives I have, its a TSSOP package and something i can solder, so it is something i can integrate without mounting the module. The Mic AGC is a leadless package and not something i can really deal with at home, well i could, but i really do not want to. So that module will have to be mounted to the board.

People have been saying that 2020 is going to be a very interesting year for home brew, and from the way things look to me, it looks true. From the QSX probably making an appearance to novel items like AGC, compression and noise gates being incorporated, to other unique SDR based receivers like this one over on Circuit Salad things are already looking rather interesting indeed.


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