That Lithium Ion board is "5S", so assumes 5 cells in series, about 21v when fully charged. Also, it does not have cell balancing, just protection from over-under cell voltage, over current. For stuff

I started out in this discussion recommending a $2 TCXO that doesn't jump around. Beyond that I hope nobody is taking me just too seriously. A rubidium standard would be fun to play with, but not wort

That's a lousy way to check the accuracy of a rubidium standard. They probably track due to experiencing the same number of neutrino hits or something. You need one of these: https://www.ebay.com/c/14

If you figure OCXO's aren't good enough and don't want to depend on GPS, a rubidium standard can be had for $250 on ebay. Accurate to around 0.1 ppb, so at 10 GHz it might be off by 1 Hz I'm sure the

I looked hard at building Don's binocular microscope. That probably would have been the best option. But not having much time, I instead opted for the AmScope SE400-Z And since Bezos is already plenty

Power grid frequency can slow a bit when they get hit with a big load. But they do try to keep the total cycle count per day a constant so clocks stay on time. The 1% error at 50.5Hz means if you are

Flux is used to remove oxides and such, exposing the surface of the bare metal to be soldered. Which means flux can be corrosive, even rosin fluxes can have acids added. All different kinds of fluxes

The old "qrp-tech" yahoo forum has been archived on groups.io, That group is locked down and inactive, just an archive. Everybody has moved over to "QRP Tech", with a new moderator. Here's a search fo

Jim, I mostly agree with what you have to say about lead acid batteries. Here's a datasheet for a wet cell flooded lead acid battery, much like an automotive starter battery except it has very thick l

Here's yet another possible option for those that wish to operate the amp at 24 volts. Though the suggestion from Hans to just turn down the bias might be a better bet, magnetics is not my strong suit

That's pretty cool, I've run into the Centronics interface many many times over the years. Even designed equipment to use it. Not many designs wind up getting used by so many. Jerry, KE7ER

Regarding resources required to run a C program: Not much. Back in the 90's, I designed hardware that used a Fujitsu SparkLite processor chip. When first getting the board to work (and later for use i

At work it was BSD Unix into the 1990's. But then the cheaper engineering tools were all moving to Microsoft, and I had to deal with it. Never felt comfortable on Dos/Windows unless I had a Unix like

Lots of different opinions here on soldering to magnet wire if you don't like mine: https://forum.allaboutcircuits.com/threads/best-method-to-strip-enamel-off-magnet-wire.29861/ I've used a hot butane

The kits from QRP Labs ship with magnet wire that has special solderable (or solder-through) insulation. A hot soldering iron and standard issue tin-lead solder (with flux included) should be all you

Parts may be cheap, but replacing them willy-nilly can be expensive if the board then no longer works due to trace damage and such. Maybe short across the output LPF, measure the power into a dummy lo

#qcx

Python is an ideal tool for anybody for doing these calculations of complex impedance. For example, assume we have a 1uH coil and a 10pF cap in parallel, and wish to evaluate at 10mhz F = 10e6 # frequ

#pa #u3s

A coil at a specific frequency can be evaluated as inductive impedance in parallel with any stray capacitive impedance, where the impedances must be evaluated at each specific frequency. The parallel

#pa #u3s

Curiouser and curiouser. Here's what looks like a college undergraduate chemistry text with a discussion of Graham's law. In the exercises for the student at the end of the section, exercise #1 uses G

That is indeed a very nice fact sheet on mylar. Figure 2 on page 3 shows that the permeability of hydrogen drops from 200 to 40 cc of gas per 100 square inch of mylar surface area over a 24 hour perio