Questions tagged [magnetic-loop]
The magnetic-loop tag has no usage guidance.
30
questions
0
votes
0
answers
60
views
Measuring impedance and baluns for magnetic loop antenna
I’ve been using the magnetic loop antenna dimension calculator here:
https://www.66pacific.com/calculators/small-transmitting-loop-antenna-calculator.aspx
And have built an antenna of ~2m ...
- 101
2
votes
4
answers
118
views
What's the methodology of MDF magnetic field antenna?
I get a MDF 9400 magnetic field antenna from school.
I am not able to disassemble this flat antenna to take a picture.
I am not sure if this antenna detect only magnetic field.
I am not sure if ...
- 600
1
vote
0
answers
106
views
What is the differece between a large loop antenna and a small loop antenna in terms of their response to an electromagnetic wave?
There is something that I don't get. I read that a small loop antenna (also called magnetic loop) responds more to the magnetic field than a large loop antenna does. I was wondering why this is the ...
- 71
6
votes
0
answers
81
views
How does Large Loop Antenna work physically?
I am learning about loop antennas at the moment. I read that the respone of a small loop Antenna is propotional to the rate of change of magnetic flux through the loop which causes a uniform current ...
- 71
1
vote
1
answer
213
views
Is a MagLoop antenna better than my 50ft end fed di-pole for 20-80 meters?
I'm restricted to putting antennas in my attic which is 50 feet long and peaks at about 8 feet. I'm currently using the Nelson UJM-150-50 end-fed dipole 80-10 meter antenna. The attic is about 25 feet ...
- 11
4
votes
1
answer
632
views
Debugging SM0VPO's spiral loop antenna build
I had built SM0VPO's spiral loop antenna. And here it is.
Recently I got myself a NanoVNA to see how finnicky it is to be tuned with that poor man's tuning cap. I brought it from 12 MHz into the 14 ...
- 395
4
votes
3
answers
281
views
High-Z RF amplifier for magloop RX vs Q-factor
I've noticed that increasing load on magloop reduces it's Q-factor, it becomes less selective.
Traditional way to approach this is reducing size of pickup loop, or alternatively, using transformer.
...
1
vote
2
answers
384
views
Loop Antenna Construction
I have a loop antenna.
When I connect the probe from my oscilloscope, does the probe also act as an antenna? If so, how should I fix that? I read about feeding technique, but I still do not ...
- 129
3
votes
5
answers
2k
views
Is a magnetic loop antenna a good option for those in an apartment?
Are magnetic loops a good choice for those living in apartments or condos where a permanent installation is often not an option and the operator still wants access to the HF bands? Why or Why not?
...
- 147
2
votes
2
answers
198
views
Magnetic loop antenna: Which side of conductor is the current due to skin effect?
Contemplating a big magnetic loop antenna.
Would a wide copper strip be better than a tube with the same conducting surface?
Where will all the current be due to the skin effect?
Would a flat ring be ...
- 66
1
vote
2
answers
234
views
How many turns of wire inside 60 cm shielded loop antenna (9kHz - 30 MHz). How can I find this number without destroying the antenna?
Lots of information about shielded loop antennas is available on the internet. However, antenna manufacturers do not indicate the number of turns. How can I find the number of turns of a manufactured ...
- 25
2
votes
2
answers
2k
views
Is a balun really necessary for a small loop antenna?
I am in the process of designing a small receiving loop antenna for the lower HF bands. By small I mean a circumference of less than $0.2\lambda$. Thus, a uniform current distribution can rightly be ...
- 121
3
votes
3
answers
528
views
Magnetic loop antenna : loops vs selectivity
I've built 2-turn magnetic loop RX antenna using 5 meters of 6.5mm copper tube. I was able to tune it with a variable air-spaced capacitor in the range of 1.8-10Mhz, but I noticed that as tuning ...
2
votes
5
answers
3k
views
Magnetic loop antenna: vertical vs horizontal
I have a magnetic loop antenna for T/R with remote tuning. I would like to mount this in the attic horizontally. Will I loose much performance between mounting it horizontally verses vertical?
- 21
10
votes
4
answers
5k
views
Real world performance of magnetic loop antennas?
I was investigating about magnetic loop antennas. In a paper about them I found some bold claims:
and
This almost sounds too good to be true, considering a lot of us hams are surronded by city noise ...
- 1,179
9
votes
4
answers
889
views
Why are there differences in antennas that depend on electrical component and magnetic component of a radio wave?
I understand the idea that when we are targeting the electrical component of the radio waves we need to have some form of a linear conductor that receives the electrical component, this creates a ...
- 169
3
votes
2
answers
843
views
Magnetic Loop Antenna with RFI Choke
Because of space limitations, am purchasing a magnetic loop antenna. Because of needing to move the antenna around, do i need a RFI choke in the feed line?
- 31
6
votes
1
answer
1k
views
Do short waves pass through or reflect off concrete buildings?
I live in Moscow, Russia and use DIY indoor magnetic loop antennas to listen amateur radio. Recently I received quite strong signals from Italy (20m, IV3UTV) and Slovenia (40m, S51CK), both operators ...
3
votes
2
answers
204
views
Running mag loop feedline INSIDE the loop tube
We are building a 4 ft diameter mag loop using 1" copper tube. The coupling loop will be at the top of the loop (we are using a large vacuum cap in a weatherproof box and it is too heavy to be ...
- 31
1
vote
3
answers
2k
views
How to attach a magnetic loop antenna to the 50Ω coax of an RTL SDR?
I'm planning to make a magnetic loop antenna mainly for receiving LW, MW, and SW radio broadcasting bands, as well as perhaps the 2.2km band and 630m band.
(Not all of them with the same antenna, I'mm ...
- 257
3
votes
3
answers
1k
views
How do active loop vs. passive loop differ in terms of noise rejection?
As a urban ham (Harvard Square, Cambridge MA), I'm on the hunt for RFI rejecting antenna configurations. After hours of research, I've come across many strong recommendations for loop antennas, since ...
- 185
3
votes
4
answers
3k
views
Optimising a small magnetic loop with 1:1 SWR but little radiation
I'm trying to build a small magnetic loop for 5W on at least 40m - 20m following ideas of G4ILO's wonder loop. For this, I'm using coax with a ~2mm copper core and ~1mm spacing to the braid (see 1st ...
user885
2
votes
2
answers
802
views
Loop Antenna - configuration?
Due to space limitations, I'm looking at loop antenna designs. I'm starting with receive only, but hope to eventually transmit.
I've seen magnetic loops (single turn with a coupled loop) and I'm ...
- 246
10
votes
3
answers
937
views
Stealth HF station setup advice
I need some advice on setting up my first HF station in a somewhat restricted townhouse community. If I had a detached house with a backyard I’d probably already have everything setup. But with this ...
- 123
5
votes
1
answer
819
views
Using a loop antenna on a harmonic of the intended antenna frequency
I bought a MFJ 1786 Magnetic Loop Antenna, which is made for 10 thru 30 MHz. It is not meant for use on 40 meters. The antenna has its own built in tuner. I have a Yaesu FT-890AT with built in antenna ...
- 161
4
votes
4
answers
863
views
Why does an "electrically small" antenna have narrow bandwidth?
Reading this interesting piece on magnetic loop antennas, the author explains that a magnetic loop has great efficiency even at small size, but the the price you pay is very narrow bandwidth. Why is ...
- 255
3
votes
1
answer
272
views
Are the voltage ratings on Vacuum Variable Capacitors RMS or Peak
I'm building a magnetic loop antenna and was wondering if the voltage ratings on the vaccuum variable capacitors I have are:
RMS
Peak to Peak
Peak
other?
I have been looking at this wonderful ...
- 329
2
votes
1
answer
3k
views
How to estimate or measure the max voltage of an air variable capacitor
I have a big box of air-variable capacitors I inherited and want to see if I can use one of them for a low power magnetic-loop antenna for 30m digital.
How can I figure out if any of them have a high ...
- 329
8
votes
1
answer
4k
views
What's an appropriate core material for a loopstick antenna?
A loopstick antenna, if you don't know, is a coil of many turns around a high permeability core. They are frequently encountered in AM receivers and look like this:
This particular example is ...
- 50.8k
3
votes
1
answer
857
views
Why are loop antennas placed horizontally in HF
I am thinking of a large (circumference $\approx \lambda$) loop antenna at low (HF) frequencies. At higher frequencies the loops are used as quad antennas that have relatively high gain towards the ...
- 960