10
votes
Accepted
Why are there differences in antennas that depend on electrical component and magnetic component of a radio wave?
In free space, the electric and magnetic fields are always in a fixed ratio, a physical constant called the impedance of free space, about 377 volts per ampere. The two are always in phase (and thus ...
- 50.8k
7
votes
Why are loopstick ferrite antennas commonly wound with Litz wire?
The advantage of Litz wire —lower loss than solid wire— is realized below about 1 MHz. It is of little use above 160 meters.
From https://en.m.wikipedia.org/wiki/Litz_wire
Litz wire is a particular ...
- 7,605
7
votes
How do I rewire a simple a.m. loop antenna that became unwound?
There is no special precise construction to these antennas — they are just wire wrapped around an inert plastic frame. It does not matter (significantly) how the turns (wraps) lay next to each other. ...
- 23.7k
6
votes
Accepted
How do active loop vs. passive loop differ in terms of noise rejection?
Loops (active or passive) don't have the RFI rejection capabilities they are often claimed to have. RFI is electromagnetic radiation just like the signal, and it's not possible to design an antenna ...
- 50.8k
5
votes
Accepted
Loop antenna layout and radiation?
Summary: substantial advantage can be realized for every meter increase in the height of the loop. Other parameters, including the metal roof, are much weaker factors in performance.
I simulated a 3....
- 7,743
5
votes
Accepted
Choke at feed point of delta loop with Q match
The choke should go at the transition between unbalanced and balanced, which is where the RG-6 meets the ends of the loop wire.
You talk of coiling coax: I suggest you coil it around a ferrite core ...
- 50.8k
4
votes
Antenna tuner design
So, yes, to tune a resonant antenna, you'll need an adjustable capacitor or inductor. You'd usually go the capacitor route, since adjustable caps are smaller, cheaper, and more exact, usually.
Bonus: ...
- 14.7k
4
votes
How do active loop vs. passive loop differ in terms of noise rejection?
Poor Loop Gain
The small (<0.1 wavelength in circumference) loop antenna has very low gain. While the size somewhat lowers the directivity, the primary reduction in gain is due to inefficiency as ...
- 18.3k
4
votes
Basic antenna matching theory?
Does this mean this antenna can't be tuned to the 160M band, or does this just mean that the impedance is so different from 300 ohms that the SWR is useless?
A little bit of both. If you get an off-...
- 10.7k
4
votes
Choke at feed point of delta loop with Q match
Forget about air-core chokes. G3TXQ's page that Phil links to in his excellent answer here shows just how much superior ferrite chokes are than air core choke baluns.
Please visit k9yc.com and ...
- 7,605
4
votes
Why is self-resonance important in a loop antenna?
"self-resonance" sounds like not quite the way to describe the issue.
The problem is more simply that if the circumference is not very small relative to the wavelength, the antenna is no longer a ...
- 50.8k
4
votes
Multi-turn large/full-wave loop antennas?
Small loops and full-wave loops are very different antennas.
There isn't a well-defined distinction between "small loops" and "large loops", but a typical rule of thumb is a loop ...
- 50.8k
3
votes
Why is self-resonance important in a loop antenna?
VK1OD compared several small transmitting loop antenna calculators. The author concludes that there are serious errors in the ARRL analysis which have made their way into some (most?) of these ...
- 7,743
3
votes
Why are there differences in antennas that depend on electrical component and magnetic component of a radio wave?
Whether an antenna is called an "electrical" or "magnetic" antenna, the generated and captured far-field electromagnetic photons of the same wavelength are identical. The difference in the two ...
- 1,646
3
votes
Can a Loop Antenna send and receive 10,000 miles away
Very unlikely. 100W SSB over 9,000 miles is already a challenging path, but these antennas are very inefficient which will make it nearly impossible. Let's simulate with VOACAP.
This is 100 W SSB, ...
- 50.8k
3
votes
interdigital (finger) capacitor bank for fine tuning of differential loop antenna
Great idea.
Why not just make a single two-wire transmission line, called an open circuit stub, and cut it to length with a knife.
$Z=-jZ_0Cot(\beta l)$ or
$C=1/{\omega Z_0 Cot(\beta l)}$
where $\...
- 9,599
3
votes
maximum distance omnidirectional antenna
Antennas don't have ranges. The maximum range of a link is determined by many factors in addition to the information you have about the antenna, among them:
the power output of the transmitter (not ...
- 23.7k
3
votes
Why are variable capacitor plates made from aluminium?
Copper indeed would be better. Silver would be better yet. These materials, however, are heavier and less rigid than aluminum. So there is that. To aluminum's advantage, it can be laser cut at very ...
3
votes
Is a balun really necessary for a small loop antenna?
You may be overlooking that the feedline is itself an antenna.
If signals came only from the loop, then sure, there would be no need for a balun. But the feedline is also effectively a big vertical ...
- 50.8k
3
votes
Accepted
Loop Antenna Construction
When I connect the probe from my oscilloscope, does the probe also act as an antenna?
As it appears in your photo, yes. In some applications this may not matter, but in your case it sounds like your ...
- 50.8k
3
votes
Is it necessary to have a "loop" antenna to make the primary antenna work?
The loop antenna is a different antenna than the primary antenna. Because the primary antenna and the loop antenna work differently, sometimes one antenna can be used to make contact with another ...
- 8,982
2
votes
Rules of thumb for large ("somewhat" full wavelength) loop antennas?
Rules of Thumb
ah... I can answer that
higher is better for DX (more lower angle lobes)
lower is better for NVIS (more higher angle lobes)
longer is better than shorter, but much longer than a full ...
- 2,107
2
votes
Is it possible to determine if I'm adjusting gamma match in correct direction with an SWR meter and if yes, how?
Well, I'm a little out of my depth, but this does seem to have all the usual parts of a gamma match: the matching section hanging off the main loop is a balanced transmission line, and the part ...
- 50.8k
2
votes
Why are variable capacitor plates made from aluminium?
I'm not familiar with the practical design of such antennas (so consider this answer a placeholder until someone more knowledgeable comes along), but here are some speculations:
The current density ...
- 23.7k
2
votes
Can a Loop Antenna send and receive 10,000 miles away
The short answer is rarely, if at all on SSB.
STLs are notoriously lossy, since their radiation resistance is in the milliohm range. The best ones are made from large copper tubing, vacuum variable ...
- 7,605
2
votes
Why are there differences in antennas that depend on electrical component and magnetic component of a radio wave?
RE: It's an oversimplification to say that antennas respond to E or H fields. Antennas respond to the electromagnetic wave. Loop antennas are just as "electric" as dipoles.
Following is some ...
- 2,912
2
votes
Loop antenna layout and radiation?
The space I have pretty much requires the loop to enclose the house [...] How will the steel roof (about 5x20 meters) affect the radiation of an 80m loop?
Although such antenna may work, personally I ...
2
votes
Accepted
cubical quad reflector tuning stub design
Using this Cubical Quad Antenna Calculator, it appears that the length of your driven element targets 95MHz operation. As you surmise in your comment, wire insulation and PVC housing will reduce the ...
- 7,743
2
votes
Loop antenna layout and radiation?
As other answers have established, the presence of the roof doesn't affect the loop pattern too much. However, the proximity to ground does make the antenna quite inefficient, and radiation is mostly ...
- 50.8k
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