🎓 Doc Freemo 🇳🇱 @freemo@qoto.org

Finally completed the 6th and final directional Coupler utilizing all the tricks I learned from the series. She is beautiful isn't she.

Half of the final prototype for the directional Coupler complete. Isn't she pretty!

The only 10 year challenge I will ever do.

@Surasanji While it does have a shield, that would be true of anything carrying an RF signal really. But yes in this situation the outside of the boxes you saw do act as shields.

But aside from that it is not a "shield" just happens to use one. The shield isnt too important for the operation other than to make the output a bit cleaner. It actually works more like a transformer.

There are many ways to build a directional coupler. In my case I'm using a circuit called a "Tandem Match" circuit. Its basically two transformers. One on the main line carrying the high power (up to 1500W in this case). That transformer is a 1:20 ration with the "1" just being the high power line running straight through the middle of the toroid, and the toroid having the 20 turns around it. this is matched on the other side with a "mirror image" between the two coupled ports (the ones where a smalls sample of the forward and reverse waves come out). In this case however the transform is reversed from the direction it was in on the main line. The two transformers balance each other such that the main power line doesn't get effected very much so the DC wont disrupt the existing signal in any meaningful way (though it will loose a tiny bit of power). The two transformers also serve to "sense' voltage and current seperately.

This then spits the waves out the two smaller ports in a rather clean way.

Now WRT shielding there is some special shielding going on here that you wont usually see. It doesnt result in the actual function but as i said just makes the signal cleaner. Youll notice in all of my designs the thick wires running through the center of each toroid has a wire mesh around the outside and is grounded ONLY on one end. In addition in the copper case based designs there is an additional vertical wall separates the two toroids, this is another level of shielding.

Also a sort of form of shielding is the fact that the two toroids are positions at 90 degree angles to each other. This eliminates some parasitic inductance (not capacitance) and prevents the two transformers themselves to affect each other as inductors would (instead of as capacitors).

It would work fine with none of this shielding it would just be less predictable (it would respond to slight changes in frequencies by slightly changing its sensitivity a bit). That because when you have two wires running near each other they accidentally create a very low value capacitor between them. This is called "parasitic capacitance" and is undesirable and causes the issues. all this extra shielding i just mentions eliminates a lot of parasitic capacitance and gives a really clean output.

Thats why i didnt go to the same lengths of shielding on the silver boxes. They were prototypes so not worth the effort. Its only on attempts at final designs (the copper boxes) I add the extra level of shielding to create a final product.

@Surasanji A directional coupler itself seperates out electrical waves traveling in opposite directions down a wire into the forward and reverse components so they can be analyzed. This alone is useful for things beyond just radio.

the purpose for me however is as a component to my ROES meter I've posted before. You seperate out the waves going to your antenna from your radio, and those moving from the antenna to the radio (the ones reflected back by the antenna). By comparing these two waves using specialized chips in the ROES it is possible to analyze the efficiency of your antenna as well as know what you have to do to improve your antenna system (how to get your antenna to transmit more power rather than to waste it).

Started the final draft of the directional Coupler. Building in extra levels of shielding and a 20:1 winding ratio. I'm stoked to finally have the design locked down

#RF #EE #Electronics #Engineering #Science #ElectricalEngineering #RFEngineering #HAM #HamRadio

Over the past few days I built 5 different Directional couplers. Each one uses either a new design even tierly or a new winding ratio. After all the testing I've finally figured out the ideal design for the frequency range I'm targeting. Time to build the final prototype.

#RF #EE #Electronics #Engineering #Science #ElectricalEngineering #RFEngineering #HAM #HamRadio

@ab3xu Sadly the final design (just finished a few seconds ago) had its self resonance kick in at too low a frequency. Probably going to have to go back to a modest 20 turn setup.

It took me 3 hours but I rolled two perfect 126 turn Toroid inductors. These will be two halves of the two transformers in a Tandem Match Circuit (Directional Coupler). Should have infinitesimal insertion loss

#RF #EE #Electronics #Engineering #Science #ElectricalEngineering #RFEngineering #HAM #HamRadio

@hal@slime.global It was real yummy :)

@Afal Can you explain your shirt. I dont get it and am curious.

So i stuck a piece of hot pepper cheese in the dehydrator for shits and giggles... this is actually working. It is drying out, solid (was liquidy for a quick minute), and the little sample i took it tasted good. This might actually work...

Just a reminder, even if big game hunters are assholes for their desires, the truth is it is the #1 most effective way to fund conservation in many third world countries.

It has done more to save species than much of anything else we tries.

So next time you want to ban trophy hunting just remember like most things all that does is drive it to the black market and denies an effective revenue source used almost exclusively for conservation.

https://www.nationalgeographic.com/magazine/2017/10/trophy-hunting-killing-saving-animals/

#conservation #animalrights #animals

@Meachamus_Prime Ok so the vitamin episode was slightly off.

They assert vitamins are useless because you can get everything you need easily from food. Truth is even if you eat a ton of veggies there are certain vitamins almost everyone is deficient on (like potassium).

But most of it was on spot, just a small nitpick. Lets see if this trend continues...

@Meachamus_Prime Since I already know about 95% of these facts or more I should be able to pick up on it. so good so far though.

I finally got to watching "Adam Ruins Everything". I'm on the eigth episode and really digging this.

I'm usually pretty critical of mainstream "fact" shows because even when they are sorta close to accurate, they frame it in a way that is often misleading or with an agenda.

This show however is spot on. No left or right lean, controversial facts are delivered really accurate. this is completely on spot. Really digging it.

Hell even i am learning shit. They are talking about the hymen and definitely threw me some new info.

While I luckily don't suffer from any of these diseases myself I have spent a lot of time trying to help those that do. This meme is spot on, peoples judgments are always more a mix of ignorance and hate rather than any sense of real understanding.

If the little mermaid was reality.

The plot of spiderman really kinda had to work out the way it did. The alternative would be kinda boring.