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I've noticed that the enclosure of my HP 4342A Q meter can seriously degrade the Q of a physically large coil. I wrote a Windows program that lets you extend the meter terminals with a parallel wire transmission line. You suspend the coil a foot or more above the enclosure, run parallel wires to the meter terminals, and record Q and capacitance. The program solves the telegraphers equation and provides the coil inductance and Q as if no transmission line were present. It uses the Getsinger equations to account for transmission line end-effects. Results for a small coil with no enclosure interaction with and without terminal extension were very close. The program is part of the Q meter utilities listed in the middle of the following page. Another utility compensates for the Q of an auxiliary capacitor used to extend Q meter range. It calculates the Q the meter would indicate if the auxiliary capacitor had no loss. See the end of the page for downloading instructions. http://ham-radio.com/k6sti/mu.htm Brian

Years ago I found graph of Input Z of a transformer vs the multiple of the primary inductance to the drive impedance. Most amateurs us a 4 time multiple, as in 50Ω drive, the transformer primary would require 200Ω at the lowest frequency of operation. I'll post the graph at the end. My transformer is 1 to 1 ratio, with a 2 turn primary and secondary on a BN72-202 binocular core. I'm using a basic voltage divider circuit to measure the input impedance of the transformer. I'm on my second iteration of my test jig but have not found a great change in my numbers. My primary has a 59.3?H primary. This is 50Ω XL at 134,300 Hz or 1X. 4X is 200Ω at 537,000 Hz. You will need to recalculate these frequencies for you primary inductance. I have a jig as shown. A drawing describing the method and the graph showing the 4 X rule. I'm a little disappointed I can not get my transformer to look like 50Ω with a 50Ω load. At multiple of 10X I get 48.68Ω 4X I get 46.77Ω 3X I get 46.77Ω Notice 3X and 4X are the same, I have found this consistent over about 15 tests. 2X I get 46.15Ω 1X I get 39.29Ω At 0.5X I get 26.14Ω Can I get anyone to verify my figures? Use any method you want, a VNA, an NanoVNA, etc. You can also use any core you want, would be interesting to see how a toroid does. Mikek

I have had the above Qmeters for some time, which I have not attempted to use. Is there a way to test the thermocouples to see if these units are worth trying to restore? Your attention is appreciated. Ray, W4BYG -- "If you want to build a strong house, I'll give you my engineer's number. If you want to build a strong life, I'll introduce you to my carpenter." Lebron and Heather Lackey Virus-free.www.avg.com

I have been working on the design of a data logger that will run unattended for several months from three AA cells. I needed a “Battery Low” indicator that would run for a few days on cells nearing depletion, and came across this flashing LED circuit based on an AtTiny85 microprocessor. It requires only three components, has a very small footprint and draws about 5μA when quiescent by making use of the CPU’s sleep capability and watchdog timer. The supply can be anywhere between +2.7 and +5.5V. As described in the source code at [1] the LED is on for around 25ms in 4 seconds. The LED current is set by the resistor and supply voltage, but the value shown results in good visibility of a 3mm LED with a 3V supply. The cycle time can be set over a wide range and the output pin can be chosen (in the code) to be either side of the CPU body, making circuit board layout straightforward. Note that the code shown in [1] allocates the output to physical pin 3! Change int pinLed = 4; to int pinLed = 1 to move the output to physical pin 6. A CMOS 555 offered the next best solution but that had several more components and drew around 300μA quiescent current which would have drained the battery comparatively quickly. There used to be dedicated ICs for flashing LEDs, but these seem to have vanished from the market. PeterS G8EZE [1] https://arduinoelettronica.com/2014/01/06/ultra-low-power-led-flasher-con-attiny/

Has anyone any thoughts about how one make an LCR meter that works at low frequencies (below 20 Hz)? I need to measure the complex impedance of a capacitor of a few hundred pF. This presents a pretty high impedance at low frequencies. My HP 4284A goes down to 20 Hz, but a few hundred pF presents an impedance in the MΩ range which is higher than the optimal range. But ideally I would like to make a measurement at 10 Hz. I do have an EG&G DSP based lock in amplifier which could possibly be bought into a setup. Dave

Following my July post [1], I got round to realising the exciter in a 100 x 100 x 50mm extruded aluminium enclosure powered by an external 7 - 12V "wall wart". Power draw is about 2.5W. RF output 40kHz to 55MHz is more than +14dBm, all harmonics and spurs <30dBc, adquate for my purposes with the TF1245A injection transformer modification [2]. ALC provides a constant output level across the whole frequency range which really simplifies searching for a resonance by frequency. Tuning is continuous in 1Hz to 1MHz decade steps with up-down buttons to change the step size on the fly. Signal source: AD9850 DDS Filter: 7 section elliptic, 62MHz corner frequency Amplifier: AD603 variable gain amplifier, 2N3904 fixed gain driver with some frequency compensation Power amplifer: 2 x 2N5109 White follower run from +13.6V rail Levelling loop: AD8307 log detector, LM358 amp/comparator (overkill, but provides very fine adjustment) Power conditioning: +13.6V boost, +5V buck converters with additional filtering on outputs Controller: 8MHz Arduino Pro-mini The design is based on elements I had to hand or had prototyped for other projects, there are probably better and/or lower cost ways to realise it. That said, the result is a Q meter outfit that is a pleasure to use with respect to amplitude and frequency stability/readability/repeatability without taking up much space. It also preserves a fine piece of Marconi engineering as a working instrument that I had purchased as scrap to break up for its RF deck. Now I want a Marconi power indicator lamp holder and bezel to improve its appearance... PeterS G8EZE [1] Marconi Q meter exciter post #1811 July 2023 [2] Marconi Q meter exciter posts #1703, 1709 May 2023

I may be a little wordy, but I want the concept to reach the measurement. I want to measure the input impedance of a Norton Noiseless Feedback amp. It has been proposed that the input impedance of the amp is a function of the load on the output of the amp. Specifically the input is 60% to 80% of the output resistance. I made a crude attempt outlined in the picture below. However, I have been told thatthis is inaccurate, especially if the input has reactance. With the next measurement I do, I want to be able to change the source resistance just to verify that my first test is wrong. It shows the input resistance changes when the source resistance changes. Even though that doesn't make sense, I want verify that doesn't happen. How do I make an input impedance measurement and then change the source resistance, for a second test and still have accuracy? Thanks, Mikek PS, for those that want to see a schematic or details of the article, it is here. https://web.archive.org/web/20070226191335/http://www.kongsfjord.no/dl/Amplifiers/Ultralinear%202N5109%20And%202N3053%20Amplifiers.pdf

This is not an electronics project per se, but as it is specifically intended for drilling front panels, etc. I thought I'd give a heads up on the radio oriented lists. Travel is slightly larger than 3" x 6" which should suffice for getting holes in a straight line. Have Fun! Reg ----- Forwarded Message ----- From: Reginald Beardsley via groups.io <pulaskite@...> To: "[email protected]" <[email protected]>; "[email protected]" <[email protected]> Sent: Thursday, January 11, 2024 at 02:35:04 PM CST Subject: [projects-in-metal] A $5 2 axis DRO for a small drill press It's been a long time since I posted anything, but my shop now has lighting and by summer should be fully operational after being "storage only" for 7-8 years as I was inundated by Dad's stuff. The drill press being one of several he left me. A pair of $2 "carbon fiber composite" 0.1 mm/0.1" digital calipers and some bits of aluminum angle and screws.Three holes drilled and tapped 8-32 in the vise. This setup is for drilling PCBs and enclosure holes for switches, knobs, etc for small electronic projects. Obviously, one of many such "DRO" setups, though I think I can claim the cheapest at least for the next few minutes. The Clausing lathe and mill will be getting nicer readouts. Have Fun! Reg

All those verniers cried for something to do, so I built a box with banana jacks and 100k and 1M linear pots. Not sure I'll ever use it, but I had all the stuff on hand. Took a *lot* more time than I expected. Have Fun! Reg

An update on these: https://www.aliexpress.us/item/3256804374910172.html The range of rotation is ~300 degrees with clutched stops at the ends. They take a 6 mm shaft, so drilling out is needed to accommodate 1/4" shafts. They are intended for single turn pots. So you only get 0-60 in 180 degrees. However, with laser engravers common, a custom dial shouldn't be a problem. So for anyone who is fond of pure analog radios they are a steal. I've attached one to an existing breadboard variable and also showed the bracket which is included with an air trimmer in position, but not attached. The air trimmer shaft just isn't long enough. There are a slew of other sellers, possibly at better prices. It changes constantly. This is all I have to say on this thread unless someone has a question. I thought I should give people a heads up that these were available at such reasonable prices. Have Fun! Reg NB link repeated because I forgot to copy the test list.

I've spent the last couple of weekends working on an open-hardware power rail oscilloscope probe: connect it to a low-impedance source via a 50Ω cable/termination and it applies an adjustable offset, allowing you to view ripple on relatively high voltage rails. Commercial probes are quite expensive (~$4k), so I've taken a first pass at a low-cost version based on an existing public design. Currently it's just a schematic, but it's been a few years since I went this deep on a low-noise design (and my maths is terrible) so I'd appreciate any early review people here can offer. You can find the schematic and analysis at https://github.com/blinken/power-rail-probe. Feedback appreciated on-list or via GitHub issue. Kind regards Patrick Coleman Technical Director BLINKENLIGHT Ltd web. https://blinkenlight.co.uk

Before I realized I was old and could afford the good stuff, I was very focused on low cost T&M kit. Here's my current absolute cheapest acceptable quality RF suite: Hanmatek DOS1104 F***Elec FY6900-50 Frequency counter ??? nanoVNA H tinySA BSIDE ESR02 Pro diode noise source OXCO <10e-9 TQP3M9037-LNA -60 db x 1 dB JFW step attenuation DC-2 GHz. or similar The DOS1104 only has 20k of memory, so not good for serious embedded work, but it also gives very fast and accurate FFT updates though with incorrect labeling if you are aliased. But it's also 1/2 the price of the deep memory Owon version which really isn't competitive in the $400 range. Can anyone think of anything else to add? Have Fun! Reg

Is there any interest here in circulating a set of RF related references? The voltnuts on EEVblog are now in the 3rd round. A set of voltage references, resistors and a temperature and humidity logger are sent hub and spoke so that each time it's sent out it's been checked. I have in mind a set of capacitors, inductors and resistors, power meter calibrator, OXCO/GPSDO, SMA and N cal kits, etc of sufficient accuracy to calibrate common hobbyist instruments. Have Fun! Reg

https://www.aliexpress.us/item/3256805245384099.html The actual unit is around $33 USD. Typical misleading landing pages. Rather annoyed they don't say what chip, but it's obvious from the BW and range. I just can't remember. I just received one I bought for evaluation. I have ready to hand an 8648C and 438A with appropriate sensors. And an 8340B if it looks promising. I have an ample supply of step attenuators of varying resolution and unknown accuracy. JFWs being my favorites for general convenience. Initial thought is to calibrate a splitter by reversal and then measure a series of frequencies and levels showing the 8348C, 438A and AD???? eval board values. Any suggestions of more devious tests? Have Fun! Reg.