Questions tagged [magnetic-loop]

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1answer
77 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 ...
4
votes
1answer
162 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 ...
4
votes
3answers
100 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
2answers
168 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 ...
3
votes
5answers
497 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? ...
2
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2answers
116 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 ...
1
vote
2answers
111 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 ...
2
votes
2answers
435 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 ...
2
votes
2answers
291 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
5answers
1k 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?
8
votes
4answers
3k 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 ...
8
votes
4answers
435 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 ...
3
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2answers
493 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?
5
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1answer
703 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
2answers
141 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 ...
1
vote
3answers
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 ...
3
votes
3answers
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 ...
3
votes
4answers
2k 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 ...
2
votes
2answers
601 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 ...
10
votes
3answers
814 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 ...
5
votes
1answer
577 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 ...
4
votes
4answers
725 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 ...
3
votes
1answer
214 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 ...
2
votes
1answer
2k 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 ...
8
votes
1answer
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 ...
3
votes
1answer
731 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 ...