🎓 Doc Freemo 🇳🇱 @freemo@qoto.org

Whats your favorite rechargeable battery chemistry.

#EE #Electronics #Chemnistry #Battery #Batteries

Hacked together an ultraportable HF antenna system to work well between 3.5Mhz - 200 MHz (80 meters - 2m) frequencies. Basically took a coil loaded GRA-1899T antenna with telescoping antenna, added some off-the shelf BNC adapters and did some minor hacking. To make it work I had to remove the center connector from two of the BNC adapter s(marked with an X in the diagram). Then added a short-circuit BNC connector, which connects the otherwise floating center connector from the bottom half to ground/shield enabling the counterpoise. Added two additional telescoping elements for the counterpoise and we have a complete system.

The thing I like about the approach is the modularity. For example I can remove or add normal t-connectors to change the number of counterpoises used. The setup pictured uses 2 counterpoises but it would be trivial to setup 1 to 4.

Also the short circuit connector (pictures here as the black and teal connector with the short circuit in it) can allow me to do multiple things if i want to get more complicated. For example if I want to remove the short circuit I can replace it with coils or capacitors for additional tuning. I can also leave it as is but connect an earth ground to it to improve the effectiveness of the counterpoise.

A final note, the loading coil attached to the radiating part of the antenna has a jumper with 6 different positions. This lets you manually adjust the size of the loading coil for different frequencies. Fine tuning is accomplished by changing the length of the antenna itself.

#Science #electronics #RF #radio #Amateur AmateurRadio #HAM #HAMRadio ## @Science

You know you are a nerd when you by a textbook for over a hundred dollars and at twice the price just to get it new and then cant sleep the night before because your excited to get it....

@Science #science #physics #math #maths #mathematics #EE #electronics

Some pictures of my APRS station brought back to life. Currently being heard in Ireland, Canada, Germany, and Washington state (I'm on the opposite coast).

#ham #hamradio #radio #RF #EE #Electronics #AmateurRadio @Science

Sweet, just brought back up my APRS radio station transmitting on both VHF and HF frequencies. Looks like it is working great I am being heard in both Ireland and Canada on the HF side!

Can't wait to get back to coding PEAK (the APRS software I run that runs a next gen version of APRS I am developing).

https://aprs.fi/info/WI2ARD

@Science #ham #hamradio #radio #RF #EE #Electronics #AmateurRadio

You know you are getting old when you have lived through an transmitted during 2 solar cycles.

Kinda excited to see the solar cycle peak again over the next few years. Already back on the rise!

@Science #ham #hamradio #radio #RF #EE #Electronics #AmateurRadio

YAY! The Siru.box I ordered just came in. Havent used it yet but its basically a usb controlled and powered power supply. Lets you control the voltage and/or current and even has a very simple API so you can control it programatically. Not sure if/when I will have a use for this but it was cheap enough and cool enough I figured I'd snatch one up.

@Electronics #electronics #EE #science

Finally got my station back on the air!

@Science #Ham #HamRadio #RF #radio #amateurradio #EE #electronics #kenwood #yeasu

For anyone who still has devices with old AA, AAA, C, D, or 9V type batteries in it I highly recommend you move over to the USB chargable Li-ion type of the same format.

Most of those devices dont work with traditional rechargable batteries like NiMH because the voltage is a bit lower. Even if they do work they tend to last only a short period of time because as they discharge the voltage drops even further. So your device will often die even with 70% of charge still in those batteries.

With the newer USB rechargeable Li-ion type batteries of the same form factor, however, you have a drop-in replacement that doesnt have those issues. They basically are a LI-ion battery with a built in charger but more importantly with a DC-Dc converter to keep the voltage fixed at the desired voltage (1.5V or 9V) for the entire life of the battery. So they work in any device that they can fit in and lasts a long time as they deliver 100% of their power before cutting out (at which point it drops from 1.5V directly to about 0V).

The only downside is if your device reports a battery percentage then it will report 100% battery right up until it hits 0.

Anyway I replaced all my devices with batteries like this and they last longer than regular batteries in some cases (especially with 9V)... so I am sold!

#Electronics #Batteries

Found this in my notes from a while back. Shows how to calculate the values for a balun to match a transmission line to an antenna.

#Ham #HamRadio #radio #rf #EE #electronics #ElectricalEngineering #Science #math #maths #mathematics @math

Self assembling "wires".. sooooo cool

https://youtu.be/PeHWqr9dz3c

#EE #electronics #ElectricalEngineering #HV #HighVoltage #Science @Science

lol dude builds a 555 timer out of vacuum tubes.

https://youtu.be/bjAlzA4Cyys

@Electronics #electronics #ee

Dude builds a VGA card on a breadboard using simple logic chips.

https://youtu.be/l7rce6IQDWs

@Electronics #Electronics #EE #ElectricalEngineering

You know shit is about to get serious when i bust out my 25 kV variable vacuum capacitor.

#ElectricalEngineering #EE #electronics #science @Science

Any Electrical Engineer will understand this one...

@funny #EE #Electronics #ElectricalEngineering

Man I wish the American economy still had small stores like this... Radioshack put them all out of business then stopped selling it when places like digikey put THEM out of business.. now you can only order from a catalog and its just not as satisfying.

https://ledpixelart.com/shenzhen/

#Electronics #EE #Engineering #ElectricalEngineering #Science
@Science

Ham radio operators be like...

#Science #Ham #HamRadio #amateurradio #radio #rf #EE #Electronics @Science

@Science

So here is a question some of my EE and radio friends disagree on... Is a purely resistive matched load, like a 50 ohm dummy load, considered "resonant". In the strictest sense of the word is that a valid term here?

While it would seem odd I'm leaning towards yes, and would be the simplest example of resonance.

#EE #Electronics #Ham #HamRadio #amateurradio #adio #rf #science #physics

For this weeks #FollowFriday I am going to do a groups addition.

* @Electronics - An Electronics Group
* @theamazingweb - A group about interesting and novel things on the internet.
* @vim - A group for everything VIM
* @funny - A group for humour and memes
* @mnmlsm - A group devoted to discussing unix and related topics
* @calligraphy - A group devoted to sharing and discussing calligraphy & handwriting
* @FreeSoftware - A group for discussing Free and Open-source software
* @math - Everything math!
* @dogs - A group for sharing pictures of dogs, for any reason.
* @Science - A group to discuss Science topics.
* @photography - A group for sharing or discussing photograph.

So its been about a month since the QOTO Moderated Groups Server came online at groups.qoto.org. It adds group capability to the fediverse with an owner capable of moderating membership in the group unlike previous group servers which were completely unmoderated and open.

We have had some amazing groups form and overall the server seems to be the most popular on the fediverse, I'm seeing more activity than the open-group servers which is great!

As such I wanted to share a list of a few groups I know of so far in case anyone is looking for a group to follow. Just follow the group as you would a user and you will be in the group and receive group posts in your timeline!

#Electronics #EE #VIM #Funny #Humour #meme #memes #unix #linux #Calligraphy #Handwriting #OpenSource #FreeSoftware #math #maths #mathematics #dog #dogs #doggo #Science #Photography #Pictures #FF

@Electronics

LOL @sharow@fosstodon.org just brought this meme to my attention, and it is perfect!

@funny #Ham #HamRadio #amateurradio #EE #Electronics #RF #RFEngineering #Engineering #Science