Jeff Duntemann's Contrapositive Diary Rotating Header Image

Odd Lots


  1. Bob Fegert says:

    I have not looked closely at U16 but it sounds like what is commonly called a COB (Chip-on-Board) that is usually underneath those blobs of black epoxy that every geek has noticed…they forgot the blob

    One fun test to run on the RDA1846 would be to send it the control codes to operate on 6 meters and see if there is both RF output from the chip and good sensitivity to a weak RF input to its receiver section. The chip is certainly able to operate outside the ranges detailed in the spec sheets… one proof of that is the commercial FM band ability it has. Generally, SDR reaches a limit in the upper bound while the lower bound goes nearly to there is hope for 6 meters on the RDA1846. Replacing the original microcontroller with something that can be programmed and altering the RF output section might result in a 6 meter/144 handie. You would have to wind and encapsulate a custom duckie though.

    The cheapo but very capable RDA1846 makes one wonder just what sort of tiny SDR wonder chips the NSA has cooked up in their not-so-secret chip FAB…. and what the heck are they doing with the tech!? I have a few ideas about what they are doing.

  2. TRX says:

    If I remember right, “back in the day” I saw an article about making a photodetector out of an old RAM chip with the ceramic cover cracked off… back when RAM chips had two-piece ceramic cases, anyway.

    For that matter, when reprogramming my truck’s computer I use ultraviolet light to erase the EPROMs. Eventually even ambient light will eventually do the job, which is why I keep a supply of old 5-1/4″ floppy write-protect tabs…

    1. Michael Black says:

      There was talk in the magazines about taking the top off a to-3 transistor to make it light activated. The catalogs around the same time offered a similar device, but I don’t know if it was issued from the factory that way, or a third party did the mod.

      There was an article in Ham Radio for a 6metre synthesizer, and the author had problems with hum. He eventually realized that the diode he was using as a varactor had a clear glass case, and the desk lamp was light modulating it.

      Sam Harris’s first article about the parametric amplifier in CQ warned that the hardest part would be getting the varactor (this was the late fifties). He urged anyone wanting to build one to try diodes on hand, which often has been the case later.

      RAM was used as an “eye”. Pry off the top (much easier with the ceramic cased ones) and the bits would react to light. Very low pixels. You’d refresh the dynamic ram to get the image.

      The Cyclops in Popular Electronics in early 1975 used RAM this way, a “computer eye” to fit into the Altair. The authors went on to form Cromemco”. I can’t remember if they bought RAM intended for this purpose or modified RAM.

      Later other projects used ram in this way, but there was definitely a point where RAM was selected and packaged with a window for this purpose. The higher density RAM, the higher the pixel count.


  3. TRX says:

    > What’s going on in the Martian atmosphere

    Well, *obviously* it’s Anthropogenic Global Warming. Duh!

    You should eschew the evils of electricity and fossil fuels, and heat your home only with carbon-neutral peat and animal dung!

  4. Jim Dodd says:

    The plumes in the Martian atmosphere are the first sign of the Martian invasion of Earth, of course, and H. G. Wells warned us about it. Maybe if we trick them into eating Activia, the bacteria will get them like it did in War of the Worlds.

    1. …or at least it’ll make them “regular.”

Leave a Reply

Your email address will not be published. Required fields are marked *