Recent Posts

1

Programming / Re: Linux Dependency Black Hole

« Last post by selvaklnc on Today at 11:35:43 am »

It's interesting to hear about your transition from using Linux in engineering to being a hobbyist in ham radio. Dependency issues can indeed be frustrating, especially as they seem to have become more prevalent in recent years.

One factor contributing to this escalation could be the increasing complexity of software and the rapid pace of development in the open-source community https://developer.wikimint.com/p/about.html#open-source. As projects evolve and grow, dependencies can become more numerous and interdependent, making it challenging to maintain compatibility across different versions and distributions.

One strategy to mitigate dependency issues is to leverage package managers effectively. Tools like apt, yum, or pacman can help manage dependencies and ensure that software installations proceed smoothly. Additionally, containerization technologies such as Docker can provide a more isolated environment for running applications, reducing the risk of conflicts.

Keeping your system updated regularly can also help prevent dependency-related headaches. By staying on top of software updates and package versions, you can ensure that your system remains compatible with the latest applications and libraries.

Overall, while dependency issues can be a nuisance, they're also a testament to the vibrant ecosystem of open-source software. Embracing tools and practices that streamline package management can help you navigate these challenges and continue to enjoy your Linux experience, whether in engineering or as a hobbyist in ham radio.

2

Beginners / Re: Why are thermal jumpers so expensive?

« Last post by Doctorandus_P on Today at 11:34:46 am »

I did a bit of poking before I posted, and did find AIN in high power SMT resistors, but was not sure about the "common" small resistors.

These higher power resistors also seem to be around 50ct, (or much more expensive for high accuracy ones) so similarly priced to these thermal jumpers.

3

RF, Microwave, Ham Radio / Re: High bandwidth FM signal generation

« Last post by radiolistener on Today at 11:33:56 am »

Cellular network operators do have the personnel and resources to find people jamming their networks - I worked with them for years - but most of the time this jamming is unintentional

if I understand correctly, for 5G it will be more easy than for 2G/3G/4G, because they using phased antenna array to rotate beam, so it will works like radar and allows to get more precise position of transmitter with triangulation, isn't it?

Just wonder is it possible to use some kind of synchronized array of transmitters distributed all around the base stations and transmitted signals in that way so their interference signal at base station location gives false position of the transmitter or just spamming it with a bunch of virtual transmitter positions to make it hard to find which one is real? Are such kind of jammers are used in practice?

4

FPGA / Re: Help on translate schematics to Verilog.

« Last post by caius on Today at 11:33:26 am »

[

If you use Quartus and have made a schematic, then while the schematic are selected you can click "File"/"Create/Update"/"Create HDL Design File from current file" (the schematic)  select verilog, give it a name, quartus will then make a verilog version of your schematic.

Thanks, I did it.I have these other two KiCad symbols that I'm try to identify, are they a D flip flop and a D latch with enable?Not sure though.

5

Buy/Sell/Wanted / Re: FS: Affordable DMM Checkers: AC Reference, DC Reference, OHMS Reference, etc.

« Last post by watchmaker on Today at 11:31:26 am »

[

If you limited the claimed to, for example, "...verify the function of 3.5 digit Digital Multimeters", then the points wouldn't even arise.

What you claim here (or "elsewhere") is irrelevant; what you claim in the advert is what matters.

This is basic measurement theory. While you need higher resolution than the manufactured reference to measure its calibration error, that same calibration reference can then be used on on lower resolution instruments (assuming it is stable).  If you only work in mA, you do not care what is going in pA.

So a lot depends on claims for where it should be used.  And the reliablity of the maker.

FWIW, I bought one of the current and voltage references from AliExpress.  It includes a sketchy paper claiming the actual values as measured by some reference down to the 7th decimal point.  Turns out these measurements were within a couple counts on my Fluke 45, Fluke 8842, HP 358a and Keysight 1252.

Have no idea why I bought it since all my instruments already agreed, but it was cheap and I am a measurement junkie (work down to 500 micro meters).

6

Beginners / Blocking Phantom Power 48V from Audio output

« Last post by Saimoun on Today at 11:20:08 am »

Hi

I have a simple audio output circuit, the audio comes from an opamp with no negative rail, so the signal is from 0 to 3.3V (centered around 1.65V), so I have a coupling cap to bring it to zero volt.
How could I make the output blocking +48V phantom power? Would it be enough to add a 63V cap (in the opposite polarity as the current caps) just before the output?

What about if the plug is a TRS instead of XLR, thinking that pluging the cable in and out will momentarily create some shorts?

Thank you!

7

Projects, Designs, and Technical Stuff / Re: Heated Ferrite == Useless Ferrite

« Last post by mag_therm on Today at 11:17:18 am »

Refer to Fair-Rite "Product Life"
When re-using salvaged cores, it might be necessary to know at least whether it was a MnZn ( low freq, power transformer etc), or Ni Zn (high Freq)
Both types can be permanently damaged by excess magnetic field strength H swing   and mechanical stress , NiZn may be more susceptible to those.
Both types should recover after being heated above Curie Temperature.
MnZn Cores usually work most efficiently  at around 90 C There are graphs for the material types showing this. So design for 70 to 80 C helps counteract thermal runaway effects.

For hobby here I have hand wound about 20 power transformers, and  inductors using surplus  (new old stock) MnZn cores from electronics surplus suppliers.
For components in the 10's MHz range needing NiZn I would always buy new cores. I have had good success just using basic design methods although some I have done with FEM.
I hav e FairRite Type 61 toroids running at 14MHz as power transformers for ham radio. They run too hot to touch, and they are efficient enough. It is a  bit difficult to measure temperature and performance in situ  at that frequency.

If a new core set is around $2 I wonder why salvage attempts  would be worthwhile.

8

Metrology / 20khz instrument amplifier with 1000X gain - or some other approach?

« Last post by veeti on Today at 11:12:57 am »

Hello

Any thoughts to interface with torque sensor which output is highspeed differential signal (few millivolts aprox 20khz)?

Or atleast that is the way I figured out how to use this kind of sensor, inside electric bicycle?
There was samekind thread https://www.eevblog.com/forum/metrology/reading-a-magneto-elastic-torque-sensor-with-high-resolution/ in few years ago - but the post seem dead, so I started new one.


But like in the old thead the sensor has two identical coils, each with 15ohm resistance - and one end connected together.
Inside the coils is foil  which has cut outs, mirrored to eachother. My gues is that when the foil is twisted by torque the cut out somehow move to increase one coil impedance and decrease the other.

The problem is that even I  apply quite a lot torque, I can only measure few % variation in my test circuit.
Example without torque I have 300mV difference, with all what I can twist with couple of big wrenches I get 294mV

The frequency has to be high so that the skin effect causes the foil only to affect the measurements.



Can I just put instrumenal amplier? with 1000X gain to get few volts output?

And another question, can I supply the coil with sinusoidal DC - or do I have to use AC. DC just would make easier for power supply setup 

9

Beginners / Re: Why are thermal jumpers so expensive?

« Last post by tooki on Today at 11:09:40 am »

Next question:

What are the most common ceramics used for SMT resistors?

It looks like AIN is a fairly common ceramic for thick film stuff.

AlN only used on very high-power ones. Most are alumina, and cheaper ones unspecified “ceramic”.

10

General Technical Chat / Re: A serious (as in not troll) requestfor help w/ultrasonic transducer

« Last post by watchmaker on Today at 11:09:33 am »

I'll be happy if you find something that can extend the life of these machines. I just want success for people's endeavors here, nothing owed lol.

Engineering used to be about problem solving, figuring it out. Like doing a crossword puzzle. You never worried, just kept chipping away and learning. Some searching, the right keywords and I can somewhat understand the machine enough to help a bit. Physics, MecE, EE (multidiscipline) knowledge needed for this Tempo make it difficult.

Today, young engineers literally have a panic attack if they don't know something. There seems to be a stigma with "not knowing", even in business and management. I find it funny, being free of such worry. Electronics gives a constant humiliation for those types of people, the "know it all" types especially.
If you don't know enough, then ask - I've learned to reach out to manufacturers and sometimes they have great expertise.

I am so frigging tired of people who WANT to fail.  So I passed on your post to both of the service businesses; the one responded saying emphatically that you cannot buy donuts!  Have not heard back from the person who actually bought all of L&Rs inventory.  He is likely much more confident.

That is what people told me before I had all the breakable parts for the Hamiltn M21 made and 100s of mainsprings for my bread and butter aircraft clocks.  Paid those back 5 times over in the last 30 years.

Most people are too damned timid to seize an opportunity.  They say "no" when a life altering adventure is right in front of them.  In all my years, I have encountered very few ventures or adventures where saying "yes" resulted in my death.  Most of my regrets involve saying "no".

Fortune favors the bold.  While the meek may inherit the earth, nothing was said about the timid!