How to make a cardioid loop with a Loop Antenna Amplifier +

Chris Moulding

Recently I've been working on using a Loop Antenna Amplifier + to make a cardioid loop antenna.

I've already posted a few comments about it in one of the recent topics.

I've now written it up as a new web page with all the details, measured polar plot and detailed layout and how it works diagrams. You can click on the layout diagram to get a large size image ready for printing.

Is it worth making? Definitely yes, it's the best loop antenna I've made with a Loop Antenna Amplifier + and it has a far better signal to noise ratio than a conventional loop.

The best way to describe it is it's like using a HF Yagi on a tower but on LF and low HF!

The web page is:




Hi Chris..

How critical is the max height?

As in i want to raise to above house gutter..which will be circa 6m ..( to see if clears local noise.)

Also wondering ..radiation pattern suggests it will not null out my smpsu noise..( which is outside my premises.actually i think many 100m away..gets worse in rain..and on my quad active loop.. (see pic) below is critical to get correct direction to null..on a single loop its nigh on impossible..not enough null.)

So..another active loop..aiming at noise then a phaser seems to be an answer..??

About to go outside in the rain at 23.30 to add a vertical wire from my loop to gnd..though its rather short..just to see if makes any difference to existing setup..most likely will not due to arrangement of loops..( switchable 90 directions..)



This is a very interesting loop Chris.

In your opinion, will the results be similar with the VLF version of the Loop Antenna Amplifier + that I have?

Or should  the value of the resistor be adjusted for a better match?

What about the shape of the loop, will an equilateral triangular shape of 3 x 1 meter produce a similar pattern do you think?




Gerard PA3BCB


Chris, thank you so much for this great idea!
I have the CCW on the way to my home and meanwhile i will build this loop.
I have a copper wire of 1mm. Do you think it's suitable?
Again, i can build a loop of 80cm of diameter, should it work anyway?
Thank you very much

Chris Moulding

Hi Gerard,

The cardioid loop will work with the VLF version of the Loop Antenna Amplifier.

A triangular loop will be OK as long as the resistor is directly opposite the feed point.

The 110 ohm resistor will work fine with a triangular loop.



Chris Moulding

Hi Jakko,

1 mm copper wire will work OK. The prototype I built uses the 1 mm wire I supply with the LAA+.

A 80 cm loop will work well as a cardioid loop.



paul newland

As the performance offered by this cardioide loop design is so attractive, I am pretty keen to have a go at constructing one.
However, I have a couple of issues that are holding me back. Firstly, I am electronically "challenged" (know nothing) and have never, to my knowledge even seen  a resistor.
Never mind the hands full of thumbs, how would one actually connect the resistor(s) to the wire?
Would an electrical block connector work, or do they have to be soldered together and if so, how does one avoid putting the connection under stress?
Any guidance would be much appreciated.
Best Wishes


Ideally solder it on..but to try it out an electrical choc block thingy will do .( typically white or black small block with little screws in, used to join cables together in house wiring junction box etc..)

Re making the loop..Chris used am imaginative idea of a “hula hoop”. Just tape wire to it..(frame for loop needs to be non conductive.) so no good tapping wire and resistor to say an ali bike rim.


Oh i forgot to add..if buying resistors from ebay or wherever make sure they are NOT Wirewound type..

paul newland

Thanks for the input Simon
I'm one step nearer now.
My present iteration of the loop is an inverted delta, which works very well for me, is pretty sturdy and non-conductive, so may the way for me to go.
Best Wishes 


Hi Chris and everyone.

hope you are all well?

my initial evaluation of this loop gave me poor very little signal output..but I am not one to give up.I expect was hoping for a miracle antenna!! ( was only 1m dia single loop.)

After finding the original papers on this it suggests ( but gives no values.) of using inductance and not resistance in the loop ( directly above feed point.)

I ask please for more why 110r used? Does this value need to be altered if loop has higher or lower inductance/ size etc..( i wish to try to use my quad 1m square loop.( total area 4m)

why a resistor and not an inductor?( as per original paper)

I ask as still on a quest to make the best  rx loop array I can here..  ie possibly phasing cardioid loops ( if i can get them to work to my satisfaction..)

My delay line 2 quad loop array is working well, i can get a good f/b ratio, but still struggle to hear USA on 160m ssb.. looking for better!! ( though it trounces the single quad loop!) 

please excuse my questions..all my rf knowledge is home learnt.. (did mechanical and electrical at uni..) so always on a learning curve re rf..( though been 40 yrs now since passed rae!  Getting old...)

regards..stay well Simon g0zen 

Kev Haworth

Reading your reply, Simon, you mention NOT to use wirewound resistors on a cardioid loop,  I understand this is due to their self inductance and capacitance issues.

Open question, is there any merit in using a higher power rating (10 Watts upwards) for the resistors?




No i use 1/4 w ..but am changing to 2w carbon just to make a more sturdy connection that can be encased in heatshrink tubing..


Tom Crosbie G6PZZ

Can you get heatshrink in camo? :-)

-----Original Message-----
From: <> On Behalf Of Simon
Sent: 09 February 2021 23:02
Subject: Re: [CrossCountryWireless] How to make a cardioid loop with a Loop Antenna Amplifier +

No i use 1/4 w ..but am changing to 2w carbon just to make a more sturdy connection that can be encased in heatshrink tubing..