#1478

[@aduedc]

Very good clip, thanks. I did not know about transformer type coupling. In some power amplifiers, they use couplers to sample the output power so they can per-distort the input signal to cancel out non-linearity of the amplifier .

[@aduedc]

I did some online research on this and found something interesting. Checkout ADL5920, which is a directional coupler in a chip based on opamp.

[@ka2pbo]

@@aduedc And there is an Arduino shield/ evaluation package for it at Mouser Electronics. 9khz to 7 ghz...Yikes !

[@robinbrowne5419]

Interesting as usual. Although most of it is black magic voodoo for me, I always learn a few nuggets of RF wisdom. Thanks 👍

[@jspencerg]

Thanks. That was a great variety of introductory examples. Appreciating your macro views.

[@pyrokinetikrlz]

Delicious black magic! For me the tough part is achieving coupling without disturbing too much the main rf path (as well as getting good impedance match)

[@byronwatkins2565]

The electric field around a wire is mostly radial. The part parallel to the wire only generates IV heat losses. The EM field inside the wire decays exponentially beginning at the surface; this is the 'skin effect.'

[@robinbrowne5419]

I like your microscope pictures. Glad you are able to use it now.

[@tahlularose9267]

WOW, just wow, beautiful explanation. Thank you for your time...

[@DS-vu5yo]

That thing that looks like ferrite may be a cast carbon resistor. It looks like a high power coupler so the combination of surface area and non-inductive resistance makes a lot of sense for both heat dissipation and bandwidth.

[@bobdoritique7347]

Merci, and thank also for the joint videos about it.

[@AndrewJones-tj6et]

That microstrip coupler on the power amplifier is actually reading the forward output power of the amplifier and is probably used as part of a power control loop.

[@IMSAIGuy]

oh, you are right. I also noticed that the main line is 50 ohms and they used a 100 ohm coupled line. had not see that before.

[@taylormayhew369]

Man that's a sweet Tektronix mainframe TM 503 function generator and oscilloscope

[@KeritechElectronics]

Check with your DMM if there's continuity between the L-shaped rod and the ground, because the pin going through the ferrite is there to contact the end of the rod. Lovely HF engineering there! It's still all Klingon to me, but hey - I'll learn it someday. Ha.

[@alklapaxida850]

and they are so handy to boot ! nice vid.

[@Mark-hb5zf]

Imsai Guy, Maybe the blue coupler's ferrite material is really a wideband resistor? That would make more sense since it would follow the typical coupled line construction (i.e. 50 termination on one end). And I suspect the resistor's topology results in very low parasitics, permitting a very high upper frequency.

[@joeteejoetee]

@15:25 The wide un-plated trace is of unknown impedance. The green trace above it has a 100 Ohm resistor termination, so we know what the impedance (100-Ohm) is very likely to be. It could be a 1:2 ratio, or in the case of Toroid based (low power) couplers with 1 thru-turn through it could be a 1:20 or higher ratio, depending on the Toroid secondary turns ratio. Many QRP SWR meters use Toroids just to get enough voltage to measure... ...but mostly via Op-Amplification of the half-wave rectification.

[@herbertsusmann986]

More RF magic. Doesn't get much better than this! The two transformer based ones are not that difficult to understand. One transformer measures the current on the transmission line and the other measures the voltage. If you do the math as W2AEW did it comes out fairly easily in terms of forward and reflected energy on the line. See his excellent video for details.

[@thomasmaughan4798]

The transmission line devices do the same. Capacitive coupling from the center rod to the adjacent rods establishes the voltage on the center conductor and it will be in phase with the voltage of the center conductor. Inductive coupling reveals the current on the center conductor; this coupling turns into a voltage on the parallel rods BUT the phase is reversed. That means one of the sensing rods will take its measure where the induction and capacitance reinforces; the other sensing rod is where the inductance opposes the capacitance. Only in the case the termination is 50 ohms will the resulting current exactly cancel the capacitively coupled voltage. Really that's all it does. It has no idea of "direction" and it isn't, strictly speaking, a directional coupler.

[@mstover2809]

Awesome video. Back in video #749 you made "Improvements" to an old Antenna Tuner. IT had on of the "SWR Bridge" units in it just like the "Archer" unit in this video. SOMEWHERE around my house I have one of these units - I THINK it is a Vanco unit. Main thing I got from this video is the difference between a "Coupler" and a "Detector (like the SWR Bridge) and it made things much easier to differentiate between the two. Have to used the Toroid thye coupler (see #749b) with an Arduino WITHOUT the Log Amp? Did it work ok?

[@IMSAIGuy]

no, should be OK as most SWR bridges in ham radio transceivers don't use a log amp. you won't have a lot of dynamic range

[@TheRcEngineer]

I would guess, a Coupler couples the signal out, a bridge has only in and out and does the measurement internaly

[@mrtechie6810]

I have a 6GHz dummy load. How can I get a proportional sample into the TinySA from the transmission line to get an accurate power measurement?

[@theMlab23]

The set up doesn't seem to yield results for me. Is there a 50Ω resistor on the insulated line? And whats the frequency of the sine wave?

[@IMSAIGuy]

No resistor. 1MHz

[@theMlab23]

@@IMSAIGuy I gave it a shot, but I don't have the same results (No coupling), the two wires I'm coupling are also the same in length. Maybe the Vpp? Any ideas?

[@IMSAIGuy]

@@theMlab23I used a 10x scope probe on the insulated wire.

[@jjoeygold]

Why a 101 (100ohm) resistor rather an a 50ohm?

[@IMSAIGuy]

two 100 in parallel. one on one side one on the other

[@jjoeygold]

Ah.. the hidden resistor

[@akiko009]

That's just pure black magic. Careful as you might get burned at the stake.

[@peterhansen8216]

Is that in bird watts? jk

[@IMSAIGuy]

birds aren't real

[@ab-bd1kt]

I have no idea what I'm looking at