Skin depth is larger in aluminum but not enough to balance out its lower conductivity, copper is better material taking all into account, in practice both are good. If opposite was true we’d use lead or zinc for conductors. There are satellite microwave parts made out of aluminium (low weight) coated sequentially with zinc (bonding layer), copper (better conductivity), thin layer of silver (even better conductivity) and then gold (actually not thick enough to contribute, this one is for corrosion protection)

the thing with using aluminum tape is that you can get away with very small thickness, because current flows only in top tens of micrometers depending on band. you can just roll up, say, 5cm wide, 0.5mm thick aluminum tape and have riveted/brazed/spot welded short length of 2mm thick bar to the ends for connecting capacitor. the problem is with mechanical stability of this setup, which is why you see pipes and thicker bars, bicycle rims etc, and here you would need some kind of horizontal bars for loop to more or less keep shape

with braid you get a lot of contacts between wires, and i’m not sure that resistance of them would be low unless tire is fully inflated. keep in mind that copper in contact with some grades of rubber develops copper sulfide film. maybe you can put short U-turn within loop at end opposite of capacitor and have adjustable shorting bar there. adjustable capacitor is more common by far, because if you can adjust it widely enough, you can get to different bands

if you’re going for portable operation, wire dipole is probably the better way to go. cheaper, lighter, more efficient, you can roll it up and fit in your pocket. if you’re operating out of a car, you don’t need to fold magloop just lay it flat in the trunk

“has potential” and “could” but never “is”

90% of drugs that enter clinical trials, fail them

“All day Astronomy” seems to be a weird place to take medical news from

i’d expect shield to fray and core to bend with arrangement like this. if you just slide piece of pipe (can be rectangular, or U-shaped) it should be more durable. you’d be surprised at voltages developing there, even with 4W online calculators suggest something in 1kV range. 100W is over 5kV (voltage scales as square root of power)

btw if you don’t need it collapsible, consider using bicycle rim as loop, or some kind of wide aluminum tape, as it has much higher equivalent diameter than coax (less losses)

you can add in parallel small adjustable capacitor, made from two or maybe four coax cores with some kind of sliding conductive sleeve around them all (piece of copper pipe moved by screw) this way you should be able to tune to any channel within cb band

additionally, you made your loop suitable for higher power than was previously (magloops tend to be limited by voltage across capacitor). if you use coax with foam core, capacitance per mm will be lower still. for adjusting, you can get away with only clipping away shield with nail clippers

real. every prediction i got from computational chemists was wrong

Ferrite beads allow you to use old calibration. If you make 1:1 balun just by threading coax through toroid, you can use old calibration as well provided it’s the same coax. Keep in mind minimum bending radius of coax. There are other designs, like using twisted pair on toroid, then you have to include balun in calibration as well (it adds some electrical lenght). If you noticed changes after making air core, this suggests that you do have some common mode current, this will make your measurements sensitive to random changes as rf current flows on the outside of cable where it shouldn’t

I’ve seen people using PE-Al-PE pipe for variables, this gives you layer of good dielectric (polyethylene) (but not as good as air) in dimensionally stable form. One connection is aluminum layer inside the pipe, and for the other you’ll have to figure it out on your own. Retuning might be required anyway within the band (magloops are narrowband) Common way to make variables is to bolt two of them in series, so that no sliding contact is used, moving part is the same for both. This is good for high voltages also but i’m not sure if you’ll need it

Yeah this lower one looks better but still probably your capacitor value in loop is way off, try to find frequency where impedance is real (purely resistive; green line on smith chart crosses horizontal line in the middle) and work from there, then you’ll know whether to increase or decrease it. what LH0ezVT said makes more way sense than that, i forgot how magloops work. but you still might want variable capacitor

resonance is narrow so you might miss it. there’s a reason why magloops are made with variable capacitors (sometimes retuning is required due to changes in ex. humidity)

how have you made your capacitor anyway?

you can put some ferrite beads on your coax close to feedpoint in order to eliminate common mode currents. better yet, use a balun. this might help you in getting more reproductible results

e: note how swr gets much higher when off resonance with properly calibrated nanovna. when measuring antenna with cable, you’re seeing loss in cable as a degree of lowered swr but only with high swr, because energy is lost in cable when it bounces around and never goes back to nanovna

i’ll add that in a way SWR chart is more resistant to misuse, because if nanovna is calibrated with wrong length of 50 ohm feedline, or without feedline at all, then smith chart will be rotated by angle depending on difference in length of that feedline, while SWR chart should look the same. for example, if real part of impedance at resonance is too low (ex. 20 ohm), and feedline is quarter wavelength different from what nanovna was calibrated with, then impedance will be still real but too high (ex. 125 ohm), while SWR chart should look the same (1:2.5 SWR minimum) (barring losses in feedline). (this works the same way as quarterwave long feedline impedance matching scheme). for different feedline length differences (non-multiple quarterwave) impedance will be complex at antenna resonance. this problem is avoided by calibrating nanovna with feedline

idk how you have done that, maybe i have older version but for me this marker just reads CH0 SWR 1.00/(value), this is some random vhf/uhf dipole that i found

you can pull up a smith chart, this will tell you whether impedance is too low or too high, since it’s still not matched at resonance. if matched it’ll be much milder for your transmitter but make sure that nanovna is calibrated (with feedline)

you can get away with very inefficient antennas on HF reception, so i wouldn’t take SDR reading very seriously. (atmospheric noise dominates all noise, so amplification will get you useful signal with amplifier not introducing significant noise on its own. reverse is true on vhf, and especially on uhf and up)

resonance should happen no matter what power level. do you mean SWR 50 or 50 ohm? i’m not even sure if nanovna can measure SWR that high. it sounds like you have a short or open somewhere it shouldn’t be? you need to calibrate it after changing tested frequency range, have you done that? (calibration can be saved). at the vhf-ish frequencies, it would make sense that your loop becomes full wave or even larger. circular loop has impedance of some 100 ohms, but you have capacitor at the ends of it so it’s gonna be different

with magloops, with set size of loop, tune is via changing capacitance, match is via changing position (closer or further from loop, tilt away from plane of loop), shape or size (cross sectional area) of feed loop, you can match it exactly this way. coax stub can be lossy, if it’s just 4W then probably not a problem but with higher powers check if it’s not overheating

no no no no it’s on by default so it’s opt-out, and switch for that isn’t even implemented yet

at least he didn’t say he “fell on it” and it was totally an accident

in this economy?

it can be bought in italy as a cleaning agent without going through entire process as for reagents purchase iirc

nah. loam is, for example, 40% sand, 20% clay, 40% silt and it’s close to middle of that polygon, on top of letter O

for example, draw a line from 50% sand point on edge to 50% clay point on edge, the first one is 50% sand 50% silt because that axis for sand is also 0% for clay, the second one is 50% sand 50% clay because it lies at the line that is 0% silt

I meant weaker per kg of body weight, not in absolute terms

Square-cube law means that as they get bigger they need to hunt less (lower rate of heat loss per kg of birb) and get less powerful compared to their size

some common friend spilled the tea in advance perhaps

for ccgt it’s more like 2/3 for gas turbine, 1/3 for steam turbine split, even more uneven for diesel/steam because diesel exhaust is much colder