Thanks. Yes - a long-wire was very the first antenna I used. Wish I had had a NanoVNA back then!

Thank you !

Thank you ! 73

Thanks ! Glad you enjoyed it .

Thanks. Enjoy the NanoVNA. It's an amazing instrument !

Sorry - don't have any good ideas for that. I'm not familiar with that ham radio. Maybe an external coax switch?

Thanks. Good point, and something that should be checked. But with the NanoVNA version I have at least, the checks I've done indicate the unit does interpolation of correction factors - and cal-checks in the new frequency ranges show the interpolation to work well, as long as one goes from a wider span to a more narrow span within the original frequency range. I've been amazed at this NanoVNA-F unit. Unlike the HP8753 units I've used in labs that do have a cal issue if not recalibrated each time, this thing seems to do the needed interpolation. Maybe the NanoVNA-F has different firmware than others? A good test is to look at S11 of an open (or short) on a Smith chart and confirm the point is still on the far right (or left, respectively) - and use a thru-cable and verify S21 is still 0 dB. Every time I've done this using my standard saved 50 kHz to 1500 MHz cal, it has passed these tests on new frequency ranges inside the 50k to 1.5G range. Of course if the cable length is changed, S11 will be rotated and a re-cal may be needed if S11 phase is important or the new cable has significantly different loss. That said, I totally agree, in general. Calibration checks are important to be sure measurements are meaningful !

Good question. I think I agree. But I would include losses in currents induced into the case-metal due to the magnetic fields stabbing through it at the ends of the coil. I think that will induce some image currents (like proximity effect, but not with the turns proper). Hard to say which of all of these is dominant...

Good questions. The answers come from tuned RLC circuits and Q (quality factor, which is related to bandwidth). A "high-Q" makes bandwidth less, but that results in larger currents ringing in the LC tank circuits in the T network, and higher power loss. Here's a video that goes into tuned circuits and Q in some depth: kzfaq.info/get/bejne/fstgYLtnq6mwfaM.html . In the case of the second question, it's actually a high-pass response. High frequencies pass through the two capacitors from input to output and the impedance of the shunt L to ground is high at high frequency, so it doesn't affect things much. But its more involved. It's highpass, but also bandpass. At intermediate frequencies, the response actually peaks at the resonant frequency of the back-to-back LC circuits. Around 20:30 in the video, we can see that the circuit is actually equivalent to two resonant LC circuits back to back. These resonate at the peak response frequency and perform the matching. At lower and higher frequencies, the tuner blocks signals or passes them without matching, respectively. Hope that helps. 73's

Thanks. I got it from Amazon. The board description there is: "SP1-50x50-G (Two Pack) SMTpads, Size 1, 50x50mil Pads, Unplated Holes to Ground Plane, 2 Sided PCB, Size 1 = 50 x 80mm (1.97 x 3.15in)" I really wish they had similar boards with 100x100 mil pads. That's what we used in our courses and they're easier to work with IMO. But they're hard to find and I ended up making some of my own (see the "Radio Design 101" episodes) 73's

Thanks. Here's a link to a page in the companion website that has all the class stuff. The antenna hand-out is the second item on this page. ecefiles.org/rf-circuits-course-section-11/ (It took me a while to find where it was in all the uploaded materials, but I think this is what you're looking for.)

Got them from Amazon. Search for "SP1-50x50-G (Two Pack) SMTpads". They have 50 mil pitch pads on the top and a solid ground plane on the bottom. Every 4th pad on the top has a plated-thru hole to the ground plane. They work for some things, but honestly you have to have good soldering tips, very fine solder, and magnifiers - otherwise the pads can burn off. But the concept is good for VHF+ radio work, given the ground plane. We used something very similar in our radio course designing/building FM receivers, although the pads were 80 mil on 100 mil centers. We drilled our own vias where ground connections were needed and stuffed them with a wire to the backside ground plane in lieu of a PTH. Worked well for building things with 0603 or 0805 parts, hand-wound inductors, and discrete SOT23 transistors (or old-style DIP chips with 100 mil spacings)...

@@MegawattKS thanks, they look great for smd prototyping indeed. I see that Mouser also has them, maybe I'll throw a few in for my next order there. The Amazon listing has quite a high shopping cost for ordering them to .nl

Good catch ! Definitely a typo in the schematic. I pulled the unit and on the A position, it ties the common to ground as it should. (FWIW, in the next vid on mixers I actually flagged an error in the SA602 IC's simplified internal schematic. It seems to have originated with Signetics in the early years, but still shows up in NXP's SA602 revised datasheet two decades later ;-)

Yes - looks like it is one of the handouts I put on the web for the students a while back :-) See 6th bulleted item here: ece.k-state.edu/about/people/faculty/kuhn/handouts.html

@@MegawattKS thanks, that's awesome.

While I agree that VSWR numbers are more familiar (until S11 is embraced and becomes familiar), both S11 and SWR measure the same thing fundamentally - the amount of signal voltage (or power) reflected from the antenna relative to the forward wave. Only the numbers are different. S11 in logmag (dB) format is convenient if one just looks for the frequency and amount of dip. This is the same as for SWR where we are also looking for the dip, but SWR values are different as you noted. A simple rule of thumb is that an S11 dip of 10 dB (one division down from 0 dB full reflection off-resonance, when in logmag mode with default scaling) is usually 'good enough'. The corresponding VSWR is 2:1. While I admit that 2:1 sounds not great (since I was trained early on to want 1.1:1 or 1.2:1), it's actually pretty OK. S11= -10 dB = 0.1 power ratio, which means only 10% of the power is reflected from the antenna, so 90% is radiated. That's only a fraction of an S-unit at a distant receiver. The transmitter may prefer something like S11 = -15 or -20 dB (1.4 or 1.2 VSWR) so the impedance it sees looking into the coax is closer to 50 Ohms, but generally -10 dB is OK for most finals. Hope that helps. 73s