Date   

Re: LLA+ gain control

Simon
 

Hi

Just listened to the kiwi..( must confess have no idea what sdr rx you are using..sorry if you said.)

Wow..one has to ask do you have local noise issues..?

I have same as your loop at 2m above gnd on test ( comparing against my large loop array.set it up to modify for cardioid loop)


I live in london..high noise floor..on ccw preamp with 1m loop my noise floor is s0 on 160m..hearing iu2bgh at time of writing this s2..(s9 on mag loop, but noise floor s5 ...s7 on large loop array s1 noise floor.)
You have s7 noise floor.( and no iu2bgh heard.( no idea which way your loop facing.)) .but same setup..

Very strange..led lighting next to loop?..thats a massive amount of noise for a ccw preamp and 1m loop..

00.20 hours..1848 khz..

Do you have any other antennas to compare with??

See pic of here in London..using high gain loop array and my high gain preamp...on said 1848khz ( just after Paulo signed off.)



I can not see a ccw preamp and 1 m loop overloading anything ( considering its atleast 10db down on my large loop array ( more like 20db with my higher gain loop amp, which the photo is of.)
I have never had overload issues with my ccw preamp..( even on mw.)

Sdr in use here is elad fdm duo via yaesu ftdx3000 rx port.

Simon g0zen


Re: LLA+ gain control

Chris Moulding
 

Hi Keith,

Good to hear that you like the LAA+.

I had a quick listen to your Kiwi SDR and your antenna is working well.

I'm not in the workshop so I don't have detailed figures to hand but I think that you will find it better to use the bias-tee and 12 V poser supply for use with the Kiwi SDR receiver.

The head unit has higher gain and dynamic range working at 12 V but as you say the bias-tee is not amplified.. You should be able to use it with your splitter without the extra attenuation.

The overall noise floor will reduce but you will have extra headroom for very strong signals.

BTW a Minicircuits four way splitter typically has 7 dB attenuation.

Regards,

Chris


LLA+ gain control

Keith
 
Edited

First off can I say the LAA+ is just a WOW little box of tricks and well worth the money, a big thumbs up to Chris ....
I have an LAA+ running with a 1m loop of 10mm copper tube and the supplied 5v USB Bias Tee board
running over about 7m of RG8 mini coax.
( If you want to test this setup via a Kiwi SDR then visit http://station.mynetgear.com:8073/ )
I note from the CCW webpage the following detail :-
"Gain (head and base units Loop Antenna Amplifier +): 26 dB at 14 MHz"
Now this setup was overloading the Kiwi SDR (and other SDR receivers) in this default configuration so I
have inserted a 6dB attenuator before a mini circuits 4 way splitter (which add about another 3dB attenuation I think)
on the receiver output of the Bias Tee to give around 9dB reduction which looks to have fixed the basic overload situation.
I do still notice the noise floor is a little on the high side however.
Now my question about gain and the other way of running the LAA+
What is the gain supplied in the head unit alone should it be used with the alternate Bias Tee board and the 12V RF quiet power supply (both on order)
which has no additional gain in the base unit ?
In this configuration after removing the 6dB attenuator but keeping the 3db from the 4 way splitter am I still going to have enough
gain to drive my SDR's and is this likely to drop the noise floor or indeed hurt the SNR I currently have ? 

Keith


Re: LOOP FOR LAA+

Simon
 

Actually thats not correct is it!! Opps..one would need to chop the loop and add a resistor..
Still make both and see..

Opps  ..Simon

On 12 Nov 2020, at 15:26, Jekko via groups.io <jekko123@...> wrote:

Thank you so much Paul,
I am waiting for my laa+ amplifier to arrive.
I think i will go with the "cardioid loop" of Chris.
happy listenings :)


Re: LOOP FOR LAA+

Simon
 

If were you i would build the 1m dia loop..no vertical wire..try it..then to make cardioid just add the wire..and compare..

Dont forget though deeper nulls with standard loop..( useful if have strong local noise from one direction.) however better forward “gain” with cardioid loop..

Simon


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

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.

Regards,

Chris


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

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.

Regards,

Chris


Re: LOOP FOR LAA+

Jekko
 

Thank you so much Paul,
I am waiting for my laa+ amplifier to arrive.
I think i will go with the "cardioid loop" of Chris.
happy listenings :)


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

Jekko
 

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


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

PA3BCB
 

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?

 

Regards,

 

Gerard PA3BCB


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

Simon
 

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..)



Simon


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:

http://www.crosscountrywireless.net/cardioid_loop_antenna.htm

Regards,

Chris


Re: LOOP FOR LAA+

paul newland
 
Edited

Hi Jekko
Sorry no-one's come "out of the woodwork" until now.
It depends what you want to do with it.
Personally, I have made and use an inverted "Delta Loop," using 2mm galvanised steel wire rope that works very well.
Aperture size in relation to frequency range coverage should be considered.
This is an extract from one of Chris's messages:"Usually I would recommend a loop of 1m or 3ft diameter so that it covers the full HF spectrum up to 30 MHz."
Also, although galvanised wire works for me, it may well be better to use copper (or aluminium).
Best Wishes
Paul


Re: Loop height above gnd and 2 loops

Chris Moulding
 

I should get the web page detailing the cardioid loop finished tomorrow evening UK time.

I'll confirm if a short counterpoise works tomorrow.

The improvement in signal to noise ratio over a conventional loop is very noticeable. Instead of having the two sharp nulls of a conventional loop there is a wide angle to the rear of the antenna pattern where noise or interfering signals are attenuated.

There is no noticeable pick up from nearby electrical equipment that I can measure.

Regards,

Chris


Re: Loop height above gnd and 2 loops

Simon
 

Sorry you say that possibly 1m of wire hanging down will do the job ( maybe.) do you mean just 1m of wire from loop?

Oh did you notice any increase in electrical pick up via the sense antenna?( compared to a standard loop?)


Thanks Simon..

On 10 Nov 2020, at 22:09, Simon <ohhellnotagain@gmail.com> wrote:

Hi Chris

Thanks for info..

If you get the time could you upload a rough hand drawing of your prototype cardioid loop..espically the sense wire..ie how long was yours and how was it terminated at gnd..( ie was it 6m of wire just hanging down and connected to a 6 inch gnd peg? Etc..)

On the hunt for some hula hoops..in lock down lol or will be making something..like to try tomorrow after work..

Thanks Simon..


Re: Loop height above gnd and 2 loops

Simon
 

Hi Chris

Thanks for info..

If you get the time could you upload a rough hand drawing of your prototype cardioid loop..espically the sense wire..ie how long was yours and how was it terminated at gnd..( ie was it 6m of wire just hanging down and connected to a 6 inch gnd peg? Etc..)

On the hunt for some hula hoops..in lock down lol or will be making something..like to try tomorrow after work..

Thanks Simon..


Re: Loop height above gnd and 2 loops

Chris Moulding
 

I hadn't spotted that that reply was going to the group.

Here's a tidier version of the cardioid loop polar diagram I measured today:

I'm working on a web page to show how to make a cardioid loop using a Loop Antenna Amplifier +.

Regards,

Chris


Re: Loop height above gnd and 2 loops

Chris Moulding
 

Hi Simon,

I plotted the antenna pattern today.

I used a strong medium wave station in ground wave range as a source and turned the antenna making signal measurements every 20 degrees.

Results on 160m will be similar only with slightly reduced levels in the nulls.

The unsymmetrical "lump" in the pattern was caused when the antenna was pointing directly at the reflection off the metal clad school building next door about 20m away.

The -3 dB beamwidth is 100 degrees.

On the attached chart the inner circle is the -20 dB ring.

In the design the resistor caused the loop to operate as it's own sense antenna but as the sense antenna works as a vertical it needs some form of earth or counterpoise. It doesn't need much as the earth rod I used was only pushed 6" into the soil so it's possible that say a 1 m length of wire hanging down will also act as a counterpoise. I'll test that tomorrow.

Regarding your comment on a Beverage antenna, I did some work on Beverage antennas a couple of years ago as I was commissioned to build antenna amplifiers for a major European contest group. I searched the internet for Beverage's original articles and found his original report to the A.I.R.E which details all his work after the patent was granted. A lot of the stuff written by amateurs about Beverage antennas is incorrect and they can be used at HF as long as the length is kept to a maximum of 2.5 wavelengths.

I did a demo at the Bolton Wireless Club where we ran 40m of wire out along the car park. It happened to be in direct line with Moscow and we spent the evening listening to radio amateurs on 80m around Moscow coming in like locals!

I've posted all the articles on a web page:

http://www.crosscountrywireless.net/beverage_antenna_amplifier.htm

Regards,

Chris


On 10/11/2020 18:11, Simon wrote:

[Edited Message Follows]

Hi Chris

did you have any time today to do measurements?

also..been thinking..( a bad thing maybe.)..if the directional  loop can not null out the smpsu noise here in the direction i want the antenna to face ( most of the time.) ie nw to usa, then a phasing unit with another standard loop picking up the noise..cancelling out.??? .though i can see this upsetting the radiation pattern abit..

also the earth on the new loop vertical sense wire..what type of earth? A rod in the gnd..or tied to existing radial system etc..
due to my location, the earth could be a long way from loop..( unless mounted on side of house.) even this if on side  I expect will cause issues..6 m vertical wire with 2 m horizontal at best..no way here of having the loop above gutter height and a direct gnd..
electical noise pickup from the earth..will it not make the loop “noisey”??

how about if vertical length at 6+2 is ok combining your neat recent isolated earth solution ( rad com.) 

is there a min or max length of sense wire?? Itching to try it..but to start with would be only 2-3m above gnd..( test.)

Sorry for the questions..simon

(of course all of above would be irrelevant if someone on here in the sticks would offer me use of their field to put up a beverage and use their wifi..happy to rent....lol.)
-- 
Chris Moulding
Cross Country Wireless
Unit 24562, PO Box 4336, Manchester, M61 0BW, UK
Cell/Workshop: +44(0)7752 391908
Fax:           +44(0)1204 410626
Email:         chrism@... (preferred contact method)                                     
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Re: Loop height above gnd and 2 loops

Simon
 
Edited

Hi Chris

did you have any time today to do measurements?

also..been thinking..( a bad thing maybe.)..if the directional  loop can not null out the smpsu noise here in the direction i want the antenna to face ( most of the time.) ie nw to usa, then a phasing unit with another standard loop picking up the noise..cancelling out.??? .though i can see this upsetting the radiation pattern abit..

also the earth on the new loop vertical sense wire..what type of earth? A rod in the gnd..or tied to existing radial system etc..
due to my location, the earth could be a long way from loop..( unless mounted on side of house.) even this if on side  I expect will cause issues..6 m vertical wire with 2 m horizontal at best..no way here of having the loop above gutter height and a direct gnd..
electical noise pickup from the earth..will it not make the loop “noisey”??

how about if vertical length at 6+2 is ok combining your neat recent isolated earth solution ( rad com.) 

is there a min or max length of sense wire?? Itching to try it..but to start with would be only 2-3m above gnd..( test.)

Sorry for the questions..simon

(of course all of above would be irrelevant if someone on here in the sticks would offer me use of their field to put up a beverage and use their wifi..happy to rent....lol.)


Re: Loop height above gnd and 2 loops

Simon
 

Hi

Thank you..

See below for really poor drawing of plan of house..end of terrace..
As you can see not much room..
160-80 loop and 40m loop are the tx mag loops.
The 10-40m dipole is inverted v at 8m apex..it is trx for 10-40m, but only 100w not full qro..

Currently the active loop is in corner of land next to house..small land, not actually ours..but owners happy..road runs next to front of house and this land..

So only options of a high( ish ) loop are at A B or C..shack is on gnd level.
Chimney is out of the question due to no way of getting to it without ££ spent ..

Option A and B both have mounts attached to house..point C would need me to make one..(easy.)

If it turns out your cardioid antenna has no significant nulls on side then I will not be able to null out local smpsu noise..so then would try 2 loops and phaser to try to get some more gain/ better snr..

But each loop soo close to each other..( max 7m.) would it work??

Noise appears to be n/s direction..

Could try a loop in loft..but that is bound to fail..

Note current active loop is not high..can not be in its location( hiding behind tall hedge.)
Loops on house would be circa 6m to base of loops

Simon




Photo below is old..but gives idea of where to place higher loops..


Ttfn Simon

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