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My experience with the new loop amplifier so far


chipbutty
 
Edited

I've been testing my VLF/HF loop antenna amplifier for a few days now and comparing it to my MLA-30. I don't have any means of creating a loop with the coax so I've been using the supplied coax in a diamond formation with a brace across the middle. Both loops have been tested in the same spot near a window with the MLA-30 using its stock thin wire loop. On LW and MW the CCW loop is far superior. No contest. I don't know why the MLA-30 is advertised as functioning at those frequencies. Mine doesn't very well at all.

Above 6 MHz however things change dramatically in the MLA-30's favour. Signal strength is consistently higher than the CCW loop to the point where the CCW loop hears nothing but the MLA-30 is pulling in a weaker station very well. On my Sangean ATS-909X typically this shows as no bars on the signal strength meter and 3 or 4 bars on the 909X. It's the same story all the way up the shortwave bands. For shortwave listening I find myself not using the CCW loop.

Is this typical behaviour of this loop? I must admit I'm a bit disappointed in its shortwave performance compared to the MLA-30. It does seem to perform well on MW and LW however. So is this the compromise made in its design to ensure good MW/LW performance? Is there anything I can do to improve its shortwave performance? Maybe my diamond shape isn't optimal?

I shall keep experimenting.

Thanks,

Rob


Paul Gulliver
 

Hi Rob,

I have already been in direct contact with Chris over my findings, but basically as far as the normal HF bands are concerned I agree with your results.

My interest lies in 5MHz and above and I have a 1m loop made from 8mm dia copper tube, I done some tests using the FT8 mode on 14074KHz using an RSP1A receiver with SDR Console, I consistently found th MLA-30 out-performed both versions of the CCW amplifier - I used the CCW bias tee in all my tests.

I also done some tests using a "bike rim" loop (approx 26" dia) but had similar results so I don't think loop size has any connection

Like you, I was also disappointed with the results, the MLA-30 seems to have had some bad press with some "experts" claiming it was only suitable for beginners so I was expecting better results with the CCW units - for now the CCW units are left to one side and I'm using the MLA-30 for day to day use.

I haven't done any tests on the MF/LF bands


Paul



On 17/12/2019 at 10:44, chipbutty via Groups.Io <stellablade72@...> wrote:

[Edited Message Follows]

I've been testing my VLF/HF loop antenna amplifier for a few days now and comparing it to my MLA-30. I don't have any means of creating a loop with the coax so I've been using the supplied coax in a diamond formation with a brace across the middle. Both loops have been tested in the same spot near a window with the MLA-30 using its stock thin wire loop. On LW and MW the CCW loop is far superior. No contest. I don't know why the MLA-30 is advertised as functioning at those frequencies. Mine doesn't very well at all.

Above 6 MHz however things change dramatically in the MLA-30's favour. Signal strength is consistently higher than the CCW loop to the point where the CCW loop hears nothing but the MLA-30 is pulling in a weaker station very well. On my Sangean ATS-909X typically this shows as no bars on the signal strength meter and 3 or 4 bars on the 909X. It's the same story all the way up the shortwave bands. For shortwave listening I find myself not using the CCW loop.

Is this typical behaviour of this loop? I must admit I'm a bit disappointed in its shortwave performance compared to the MLA-30. It does seem to perform well on MW and LW however. So is this the compromise made in its design to ensure good MW/LW performance? Is there anything I can do to improve its shortwave performance? Maybe my diamond shape isn't optimal?

I shall keep experimenting.

Thanks,

Rob


Chris Moulding
 

The VLF/HF version of the Loop Antenna Amplifier is designed to have a very low input impedance so that it will work with a small loop down to VLF frequencies. As you have found it works well at long and medium wave frequencies with a wire loop.

With the wire we supply for your first loop it will have inductance that rises significantly above 6 MHz.

For good HF performance you need to reduce the inductance of the loop. The best way to do this is to use a thicker conductor in the loop. This is why in the video on the web page for the Loop Antenna Amplifier I show it working on HF using an alloy bicycle wheel rim. Other users also use thick 1/2" coax or copper pipe.

Following feedback we now also produce a HF/VHF version of the Loop Antenna Amplifier. This has a higher impedance input amplifier that can work with inductive loops at HF and VHF but doesn't work below 500 kHz.

Regards,

Chris


chipbutty
 

Thanks for the reply Paul. Interesting that your results concur with my findings. It would seem it's inherent to this loops design then. I must say the MLA-30 is unfairly maligned in my opinion. It performs very well on shortwave compared to antennas I've used previously. Though there are plenty of others very happy with it and Youtube videos showing why.


Chris Moulding
 

Paul and Rob,

Here's an offer for you.

Ship the VLF/HF Loop Amplifiers back and I'll replace them with HF/VHF Loop Antenna Amplifiers. They would significantly improve your HF performance with the antenna loops you have.

I will be interested to hear your reviews of the HF/VHF version.

Regards,

Chris


chipbutty
 

Thanks Chris. I have some RG58 cable. Would that be worth trying or maybe something thicker? I'm not sure how I would attach it to the posts.

I would try the bike rim as you suggest but Paul has tried that and seen no improvement on shortwave. I'm a mountain biker so I've probably got an old aluminium rim knocking around in the shed.


chipbutty
 

Thanks for the offer Chris. Sounds like a good idea. I shall see if I can get it back to you this week for an exchange.


Paul Gulliver
 

Chris,

You have already sent me a second version of the amplifier, you marked it "HF" in pen - in the email you sent you said

It's possible to rewire the PCB in the head unit to change the amplifier
so that it has a higher input impedance to match the loop better at HF
frequencies.

is this the HF/VHF version you are referring to, if not I'll send the original back to you for a swap.

Paul


On 17/12/2019 at 11:22, Chris Moulding <chrism@...> wrote:
Paul and Rob,

Here's an offer for you.

Ship the VLF/HF Loop Amplifiers back and I'll replace them with HF/VHF Loop Antenna Amplifiers. They would significantly improve your HF performance with the antenna loops you have.

I will be interested to hear your reviews of the HF/VHF version.

Regards,

Chris


Chris Moulding
 

Paul,

I'm not sure which version I sent you so it's probably best to send the original back and I'll send you the latest version back for comparison.

Regards,

Chris


Brent Mcl
 
Edited

If you have  sdr console i have two airspy hf + on line one with highest noise level is on the CCW Loop and the one on my Wellbrock loop is lowest noise floor the ccw loop is not always on

Server is Blauchlin


Chris Moulding
 

Brent,

Have you added an attenuator on the input of the Airspy HF+ as I recommended in Service Bulletin 2?

This will help correctly match the antenna (or any other HF antenna) to the Airspy receiver as they don't have a good 50 ohm match on HF.

Regards,

Chris


Brent Mcl
 

Yes i gave it a try never noticed any different s on  any of my SDR's i have a few


Paul Newland
 

Still “building” my ccw low-cost loop setup. I was an early customer, have a Wellbrook loop connected to a SDRplay RSP duo HiZ inputSnd the ccw loop to the tuner 2 50 ohm port (using usb power). The ccw is on an “elderly” run of RG58 whilst the Wellbrook is a “mature” setup.  So there is no meaningful comparison. However, so far the ccw is considerably better at VLF, whilst it is poor on LW (mainly judged against NDB’s, somewhat worse on HF up to around 8Mhz above which it becomes a bit of a “toss/up.” If it’s at all helpful I ‘ll do a bit of a “write-up” when I think that I have gone as far as I can. However, thanks for the tool to experiment with - learning on my feet and much appreciated.

On Wed, 18 Dec 2019 at 22:40, Chris Moulding <chrism@...> wrote:
Brent,

Have you added an attenuator on the input of the Airspy HF+ as I recommended in Service Bulletin 2?

This will help correctly match the antenna (or any other HF antenna) to the Airspy receiver as they don't have a good 50 ohm match on HF.

Regards,

Chris

--
Best Wishes
Paul


Brent Mcl
 

The CCW is now on my Perseus sdr


Paul Gulliver
 

Hi Brent

Just logged onto to it using SDR Console, difficult to judge because of our distance apart (I'm in the UK) but with your receiver I'm getting very little on the 14MHz band (14.074 MHz FT8 mode) whereas here (on my antenna)  it's quite busy.

What version of the amplifier are you using - the LF/HF or the HF/VHF and what type of loop is being used.

I tried logging on to your HF+ receivers about an hour ago but although I appeared to connect I couldn't get any form of signal


Paul


On 19/12/2019 at 15:39, Brent Mcl <blauchlin@...> wrote:
The CCW is now on my Perseus sdr


Paul Newland
 

PS: to my last - Antenna still 1M x 15mm copper pipe square

On Wed, 18 Dec 2019 at 22:40, Chris Moulding <chrism@...> wrote:
Brent,

Have you added an attenuator on the input of the Airspy HF+ as I recommended in Service Bulletin 2?

This will help correctly match the antenna (or any other HF antenna) to the Airspy receiver as they don't have a good 50 ohm match on HF.

Regards,

Chris

--
Best Wishes
Paul