Hi, 

Sorry for the newbie question but on the LAA++ is the null area the hole in the middle of the "doughnut" ?

So just to check my understanding the antenna is picking up broadside.. is it a 360 pattern and the null is the hole through the middle? 

Anyone have a visual of this?

Thanks

it is - if you view it as a wheel, then the nulls are along the axles...

Martin (G8FXC)

Like at the side? Trying to get an idea myself and I don't have a clue.

Hi

It works like this..will try to explain

Mount vertical. Just like a bike wheel is..

Forget horizontal for now..( that typically needs HEIGHT to work..vertical will be fine with bottom of loop 1m above ground.

Ideal shape of loop is a circle..can be square, triangle etc..

Assuming a circle then aim for 1m diameter..BUT lets assume you just want to try it..
Make a cross, like what jesus ( if belive) was nailed to..cable tie, clip etc the wire loop in a diamond shape 💠 with wire ends at bottom.connect to loop amp..
Really easy to do..2m and 1m bit of say 50mm by 50mm wood..couldn’t be easier..but try to keep 1m across the diamond shape..

Now nulls..

Again imagine a bike wheel on a bike..you are sitting on bike..lets just assume has only one wheel ( don’t worry you won’t fall off as imaginary!)
The max signal is inline with wheel. The NULLS ARE AT 90 degrees to wheel. You will hear stuff say at 45 degrees to wheel, but not as strong as inline with wheel.

So the idea is.. say directly North of you ( or south) you have horrible nasty noise..you point wheel 90 degrees away from. Ie west or east..then the noise is in null..hopefully gone!

It was explained rather well in previous post.. imagine a wheel on an axle ( bike wheel,) the axle is in same direction as null and max signal is inline with wheel.

There is so so much on google about this..google “magnetic loop polar pattern”

Regarding will it stand up to Canada winter..well that is up to you to figure out..use thicker wire? Use tubing ( water pipe) etc..the wire included in ccw amp is just to get you started..

Have gun Simon

I think I get it. Just researching the thickness of the wire, does a thicker wire bring in the signals better?

"does a thicker wire bring in the signals better?"

No, a good antenna for the frequency of use brings in signals better, and "good" is subjective, and relative.

Thicker wire provides greater bandwidth and power handling for transmitting, and changes the dimensions of an antenna, from inches, to feet depending on the material, thickness, and operating frequency.

The "k-factor", a long forgotten step in the antenna calculation process determines length based on diameter, which alters inductance, and capacitance. Other common things to take into consideration are magnetic properties, and skin affect/velocity factor (based on even more calculations) of the material used.

Skipping all of these is why, in the case of dipoles (and all other antennas), 468/f doesn't work, that was only one of several steps, and not even a step near the beginning...

Kurt

Okay great, I understand now. 

Thank you 

Hi

I feel last message was unhelpful, also not really correct, atleast in the fact we talking small mag loop rx antennas and not dipoles.
Yes a thicker wire/ better still tubing for the loop WILL make the preamp work better ( as long as a decent loop amplifier.) as lower loop inductance..

But this is irrelevant.. you need to do some reading on magnetic loop antennas.. plenty reading out there.
If you don’t know how it works so be it.. you don’t need to..but making one is silly easy..the physics behind it, well to use it you don’t need to know..

Max signal = <—————-> = max sig.

^ ( null)
|
——————-
|
V ( null)

Rotate loop so noise you don’t want is pointed at null..

Easy.

There are slightly different requirements for transmit and receive loops.

With broadband active loop antennas used for receive purposes, using thicker wire or tube reduces the loop inductance for a given size, which improves the loop sensitivity.

It also increases the self resonant frequency, which is desirable, as Ideally for a use on the short wave bands, you need this to occur on a frequency greater than 30MHz (or whatever upper frequency limit you desire).

Some notes on the subject can be found here.

https://www.g8jnj.net/loop-inductance

Regards,

Martin

I don't get it. My nulls are north and south, but when I browse the FM broadcast band, I'm getting all the stations from the north perfectly. If I look at the loop, it's pointing directly at the house (east/west) and I should change that, since that's where the electrical lines are.

I don't get it. My nulls are north and south, but when I browse the FM broadcast band, I'm getting all the stations from the north perfectly. If I look at the loop, it's pointing directly at the house (east/west) and I should change that, since that's where the electrical lines are.

_._,_._,_

---

 

The directional pattern of "null off the face of the loop" only applies when the loop is very small relative to the wavelength being received; i.e. around a tenth wave-length or less circumference.   At FM broadcast frequencies (88-108 MHz) the wavelength is around 3 meters, meaning a 1 meter length loop now is about 1/3rd wavelength; i.e.no longer "small".   

If you want the classic "small loop" directivity off the edges at FM broadcast freqs, you would have to cut the wire length down to around 1/3 meter (about 1 foot) circumference.

---

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I'm guessing that is why the reception of 88 - 108 MHz is so amazing?  But for the lower bands, HF, MW, and LF,  does the direction of the loop really matter? Technically if I want to get anything in Europe or in VK land, the edges of the loop should be pointing east/west, correct? I guess I should have the nulls of the loop (front/back) aiming east/west to cancel out the RFI but wouldn't that only give me South America? Trying to figure out which way I should have it.