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Re: Tips to improve LAA+ Performance?

David Cutter
 

Hello Simon

Sturdy looking loops and it looks like you've put a lot of effort in to them.  

I was wondering how these would compare to Chris's idea of bicycle rims.  

David G3UNA

On 03 December 2020 at 16:46 Simon <ohhellnotagain@...> wrote:


The amp likes low inductance..

So bigger dia tubing the better (there is a point of low return though..ie dont be silly and use 3 inch tubing.)

To improve more then use 2 or 3 loops in parallel, spaced say 6inches apart.



Or even better use 4 crossed parallel loops..



To improve hf over lf use smaller dia loops..above pic shows loops of 80cm ( circa) squares..i have the preamp switchable directions, hence why 8 loops in pic.

Above works well from dc to 20mhz..

Simon g0zen




Re: Tips to improve LAA+ Performance?

Simon
 

The amp likes low inductance..

So bigger dia tubing the better (there is a point of low return though..ie dont be silly and use 3 inch tubing.)

To improve more then use 2 or 3 loops in parallel, spaced say 6inches apart.



Or even better use 4 crossed parallel loops..



To improve hf over lf use smaller dia loops..above pic shows loops of 80cm ( circa) squares..i have the preamp switchable directions, hence why 8 loops in pic.

Above works well from dc to 20mhz..

Simon g0zen


Re: Tips to improve LAA+ Performance?

leslie norton
 

Hi Eric

I can give you my experience with the LAA+ as initially i was disappointed.
Initially i used the wire that came with the LAA+ and quite near the house, supplied with bog standard RG58, then i used some screened sky type shotgun cable which is 75ohm.
performance improved, then i decided as i had bought a drum of the cable, to move it well away from the house by 70ft and put it on the shed, again an improvement (less noise)
The loop is only 2m up from the ground.

I then put my Airwave loop on that i was using with my Wellbrook ALA-100, a big improvement.

Now here is an interesting development, i used my SDRplay to supply 5v from its own supply and that worked but then i swapped that for the LAA+ own biasT with the DC socket on and supplied it with 13.8v that i supply my FTDX3000 transceiver with. I can now say that the set up i have equals my Wellbrook.

Note the shotgun cable i bought was a decent type and of course you have to split it, advantage is you now have double the length!!

Hope this helps.

I now use the LAA+ set up plugged into my Rx port on my FTDX3000 and if noise is high I Tx on my Halfwave end fed and Rx on my loop.

Les
G4JNW




On 3 Dec 2020, at 04:00, Eric Inloes <compaq963@...> wrote:

[Edited Message Follows]

So, I've had my LAA+ for awhile but initially HF performance above say 5 Mhz was pretty disappointing. Below that I was quite happy with it's performance.

With that said I'm back to the drawing board to try and improve it's performance. I've sense upgraded the loop form 10 feet of 1/4 inch copper pipe to 10 feet of 5/8 inch copper pipe bent into around a 1m loop to reduce the inductance. 

I was also using RG-6 75 Ohm coax and currently awaiting on some Amphenol RG-58 to switch to 50 Ohm and to try again. Figured RG-8X and LMR-240 isn't worth the cost for this. 

Any other ideas? :) 

Thanks


Re: Tips to improve LAA+ Performance?

Paul Newland
 

Hi Eric
From what experience that I've had, the LAA+ is a serious performer.
I have only used it with the associated base unit, which I'm sure works better than the Bias-T of my SDRplay RSPs and of course takes good care of frequencies below 500Khz.
I previously used athe forerunner of the LAA+, the HF/VHF version and the one before that.
I attached the HF/VHF version to a !M aperture loop,constructed of 15mm copper tubing and it worked well powered by a RSP BiasT above 500Khz and am still using it indoors attached to an aluminium bicycle wheel loop (handy at times).
Performance is AT LEAST comparable to my Wellbrook antenna and although I have now optimised my antenna for lower frequencies, it is also an excellent performer on the VHF airband ( although the loop is however centered only just over !M above ground level).
This experience has persuaded me that using the associated base unit is advantageous.
Best Wishes
Paul



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On Thu, 3 Dec 2020 at 03:10, Eric Inloes <compaq963@...> wrote:

[Edited Message Follows]

So, I've had my LAA+ for awhile but initially HF performance above say 5 Mhz was pretty disappointing. Below that I was quite happy with it's performance.

With that said I'm back to the drawing board to try and improve it's performance. I've sense upgraded the loop form 10 feet of 1/4 inch copper pipe to 10 feet of 5/8 inch copper pipe bent into around a 1m loop to reduce the inductance. 

I was also using RG-6 75 Ohm coax and currently awaiting on some Amphenol RG-58 to switch to 50 Ohm and to try again. Figured RG-8X and LMR-240 isn't worth the cost for this. 

Also I need to use the Bias-T for stuff below 500 KHz as the Bias-T with the SDRplay stuff will cut off anything below it. For that I decided to upgrade the PSU to one of these https://www.amazon.com/gp/product/B00B8860R0/ to avoid switching noise there. 

Any other ideas? :) 

Also, Sorry for all the edits!

Thanks


Tips to improve LAA+ Performance?

Eric Inloes
 
Edited

So, I've had my LAA+ for awhile but initially HF performance above say 5 Mhz was pretty disappointing. Below that I was quite happy with it's performance.

With that said I'm back to the drawing board to try and improve it's performance. I've sense upgraded the loop form 10 feet of 1/4 inch copper pipe to 10 feet of 5/8 inch copper pipe bent into around a 1m loop to reduce the inductance. 

I was also using RG-6 75 Ohm coax and currently awaiting on some Amphenol RG-58 to switch to 50 Ohm and to try again. Figured RG-8X and LMR-240 isn't worth the cost for this. 

Also I need to use the Bias-T for stuff below 500 KHz as the Bias-T with the SDRplay stuff will cut off anything below it. For that I decided to upgrade the PSU to one of these https://www.amazon.com/gp/product/B00B8860R0/ to avoid switching noise there. 

Any other ideas? :) 

Also, Sorry for all the edits!

Thanks


Re: Looking for UK source of low noise 5V DC supply

obrianboru@...
 

I have a clean 30 Amp 12 v shack psu but found that even short leads from it to bias tees, etc, were picking up rfi from nasty switch-mode PSUs in the house and shack.

I soldered small Belling-Lee filters at the point these leads enter the bias tees, amps, and other rf sensitive equipment and rfi has been cleaned up enormously.

Photo on my QRZ blog here: https://forums.qrz.com/index.php?threads/which-side-of-a-current-choke-needs-grounding-to-help-prevent-common-mode-or-rfi.700474/page-2

How they would cope with much stronger rfi on the power leads from a dodgy 5 v switch mode PSU, I don't know..... but it's worth a try.
73 Jeff


Re: Looking for UK source of low noise 5V DC supply

Keith
 

Thanks for the info Chris, that sounds just like what I am looking for and I will give it a try.
It will be much better than my current arrangement and at those prices you can't go wrong.

Keith


Re: Looking for UK source of low noise 5V DC supply

Chris Moulding
 

Due to EU regs for energy saving it is no longer possible to buy or sell a 5 V USB power supply.

There are some manufacturers who can still build a high quality switch mode power supply with good RF filtering.

For my own use to power antenna amplifiers and to replace all the cheap tat passed off as phone and tablet USB chargersI I've replaced them all with TT Electronics SW4479B 5 V 2.1 A USB chargers. This is designed for UK use with the 3 pin plug. It was originally designed to meet the high reliability (MTBF of 50000 hours) specification so it's a well made quality item. It appears to be RF quiet with no noticeable conducted RF on the mains supply or USB cable. If you put a receiver and antenna up against the charger there is some RF noise very close in within a few inches.

I bought mine from Rapid Electronics part number 85-2892, the current price is £6-89 + VAT.

TT Electronics probably make versions for other electrical supply sockets but I've not checked yet.

Regards,

Chris


Re: Looking for UK source of low noise 5V DC supply

David Cutter
 

I would be tempted to use a discrete regulator off your 12V supply, with suitable heatsink

David G3UNA

On 02 December 2020 at 11:12 Keith <groups.c6545e@...> wrote:

Hi, I know CCW do a low noise 12V power supply (which I have) but I am looking for a UK supplied 5V
version to run the USB port of the CCW LAA+ base amplified PCB.
Linear 5V supplies appear to be difficult to find at present in the UK.
Would also consider a variable voltage bench supply if that would work, but which one at a reasonable cost.
Anyone have any recommendations for this and where to get one from ?

Keith


Looking for UK source of low noise 5V DC supply

Keith
 

Hi, I know CCW do a low noise 12V power supply (which I have) but I am looking for a UK supplied 5V
version to run the USB port of the CCW LAA+ base amplified PCB.
Linear 5V supplies appear to be difficult to find at present in the UK.
Would also consider a variable voltage bench supply if that would work, but which one at a reasonable cost.
Anyone have any recommendations for this and where to get one from ?

Keith


Re: Loop height above gnd and 2 loops

Martin - G8JNJ
 

Hi Simon,

As you have effectively already got two identical loops mounted at 90 degees relative to each other, I think you should be able to steer the pattern simply by summing the two feeds and varying the amplitude between the loops. You may also need to provide a 0/180 degree phase flip to cover the full 360 degrees.

This has traditionally been done by feeding a Goniometer with the two signals, but I think you could just use two pots to do pretty much he same thing.

https://en.wikipedia.org/wiki/Bellini%E2%80%93Tosi_direction_finder

I originally thought that the Goniometer provides a phase variation as well as amplitude, but apart from a 0/180 degree phase flip when the moving and fixed coils cross their axis, this doesn't happen.

It simply relies upon the fact that the antennas are already in quadrature, so any angle or bearing can be synthesised by simply varying the amplitudes of the two signals relative to each other.

If you do wish to try varying both the amplitude and phase of the signals, then the simple circuit at the beginning of this document is a good start.

https://groups.io/g/loopantennas/files/WA1ION%20Phaser-everett-techcol%20dxm%20NHP.pdf

More notes on this page.

https://www.g8jnj.net/rfnoisecancellation.htm

Regards,

Martin


Re: Loop above gnd.height vs take off angle

Simon
 

Hi Chris

Interesting..not concerned about hf..have fan dipoles for them and the existing loops.

Ok will give this a go tomorrow..( bigger loop on cardioid.)though it may well end up being square in shape as easier to make.

If you fancy sending me crt dia for the phaser please do..
I will keep it to myself..that I promise..if you dont fancy sending it I fully understand..

Currently building phaser using differential capacitor..thus eliminating the resistive lossy phase control..should also give full 360 degrees..The wa1ion ( might have got that wrong.) I recently built is too lossy, also relies on potentiometers which even though brand new are becoming tiresome..though it does work well better than the one i had before..( much better.)

Simon


Re: Loop above gnd.height vs take off angle

Chris Moulding
 

On 160m even with the smaller output from the cardioid loop the Loop Antenna Amplifier + will have enough gain. You could try increasing the loop size to 2m but you would loose performance at higher frequencies.

It would be a waste to use copper pipe for the cardioid loop, with the resistor wire works fine.

With a phasing unit if two loops are facing in the same direction (towards the USA in your case) they don't need to be inline or broadside as you can adjust the phasing between them for maximum gain. If they are not inline or broadside it may give a skewed pattern of nulls but this may be an advantage as you will be able to steer the nulls with the phasing unit at the expense of a dB or so of forward gain.

The original C and S Antennas cardioid loop array used four cardioid loops to give a very sharp forward pattern using separate coax phasing harnesses for inline or broadside operation.

I made a prototype phasing unit about two years ago and it was excellent at phasing two antennas especially nulling out noise or interference. We decided not to go ahead with it as it needed a lot of workshop assembly. I did get a lot of practice and experience of phasing antennas with it.

Regards,

Chris


Re: To earth/ground the CCW Loop Antenna Amplifier+ #chat

Paul Newland
 

Thanks Chris 
Working well is quite an understatement,
But the cardioid design seems pretty attractive and a tempting way to go...
Best Wishes
Paul



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On Sat, 28 Nov 2020 at 19:27, Chris Moulding <chrism@...> wrote:
Hi Paul,

A simple loop antenna should not be earthed or grounded and using a non-metallic pole will avoid distortion of the antenna pattern.

You are correct with your installation of the Wellbrook and a simple loop antenna with the Loop Antenna Amplifier +.

The cardioid loop was an example of a different type of loop antenna based on an original design of C and S Antennas back in 1974. This adds a resistor at the top of the loop and grounds one side of the loop to give a cardioid pattern with low angle properties. Another advantage of the cardioid loop is that the antenna element is earthed or grounded so it will help with lightning protection on exposed sites.

By the way it's good to hear that the Loop Antenna Amplifier + is working well for you.

Regards,

Chris


Re: Loop above gnd.height vs take off angle

Simon
 

Thank you Chris.much appreciated..

Ok then..160m only.

So my parallel crossed loop has to go or better be used for the noise antenna..shame..stunningly good for Europe..( or switched for Europe only.)

Cardioid loop..
How to make it have more output to drive the preamp.?
Is there any point in making loop from copper tubing? I suspect not due to the 110r resistor..

Is there any gain from making loop bigger dia? Say 2m? Maybe..

Is there any gain to using a different type preamp? Maybe..

And how to combine more than one loop? Making a new phaser to try just this..only issue I an facing is loops will not be inline to the direction i want, but broadside..not helpful..

Wondering if my parallel crossed loop could be converted to cardioid..maybe an experiment for tomorrow here..

Fun and games..all to be a bigger mouse on the 160m stage...

Simon


Re: To earth/ground the CCW Loop Antenna Amplifier+ #chat

Chris Moulding
 

Hi Paul,

A simple loop antenna should not be earthed or grounded and using a non-metallic pole will avoid distortion of the antenna pattern.

You are correct with your installation of the Wellbrook and a simple loop antenna with the Loop Antenna Amplifier +.

The cardioid loop was an example of a different type of loop antenna based on an original design of C and S Antennas back in 1974. This adds a resistor at the top of the loop and grounds one side of the loop to give a cardioid pattern with low angle properties. Another advantage of the cardioid loop is that the antenna element is earthed or grounded so it will help with lightning protection on exposed sites.

By the way it's good to hear that the Loop Antenna Amplifier + is working well for you.

Regards,

Chris


To earth/ground the CCW Loop Antenna Amplifier+ #chat

paul newland
 
Edited

I find it quite embarrassing to ask this basic question, but here goes (with explanation).
I have noted that on the design/schematic for the cardioid loop an earth is used.
My simple question is whether or not my current Loop Antenna Amplifier+ should be earthed.
My first loop antenna that I still own/use is Wellbrook ALA15330LN, which has given sterling service and as I understood from it's original installation instructions should be mounted on a non-conductive mast and that it should not be grounded/earthed.
I had assumed same that same would apply to the CCW  Loop Antenna Amplifier series and have mounted them on  non-conductive masts and not earthed them.
This applies to my current "+"  version, which has been and is giving excellent service.
Regards
Paul


Re: Loop above gnd.height vs take off angle

Chris Moulding
 

OK I've run some simulations using a 1m diameter loop at 0.1, 0.5 and 5m above average ground.

The loop at these low heights in terms of wavelength is a high angle radiator with the peak of the pattern vertically upwards.

Mounted 0.1m above ground the pattern at a vertical angle of 10 degrees suitable for DX working is 13 dB below the maximum. The mounting heights of 0.5 and 5m are even worse with the pattern at 10 degrees 15 dB below the peak.

The conventional small loop antenna is not really a good DX antenna on 160m as it will pick up a lot of high angle interference and noise. It's main purpose is the reduction in local RF noise in many situations.

I ran a simulation of the cardioid loop antenna mounted at 0.5m above ground.  This gave the peak in the pattern at 30 degrees. The pattern at 10 degrees is only 3 dB below the peak at 30 degrees. It also had good directivity so noise and interference off the back and sides of the antenna will be much reduced. The pattern is similar to a short Beverage antenna.

The cardioid loop antenna is relatively inefficient on 160m so it will give a lower level output to the antenna amplifier but with the high levels of natural background noise on 160m it is still very effective and will be far better for 160m DX than a simple loop antenna.


Re: Loop above gnd.height vs take off angle

Simon
 

Kool

Thank you

Simon


Re: Loop above gnd.height vs take off angle

Chris Moulding
 

Give me an hour or so and I'll fire up the antenna modelling program and give you an answer.

Regards,

Chris

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