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Re: Loop antenna amplifier - new version

Chris Moulding
 

The main difference is that it now covers the full frequency range covered by the previous VLF/HF and HF/VHF versions.

The latest VLF/HF version you have Mat has all the latest changes apart from the change of ferrite material.

Regards,

Chris


Re: Loop antenna amplifier - new version

info
 

Hi Chris

Is this any better than the one I bought last week ?

I,d of waited if I had known a better one was just about to come out

I dont need the vhf spectrum

Regards

Mat Hallows 



Sent from my Samsung Galaxy smartphone.


-------- Original message --------
From: Chris Moulding <chrism@...>
Date: 25/03/2020 19:33 (GMT+00:00)
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Loop antenna amplifier - new version

There are quite a few minor differences to the new version but the biggest change to get the wide frequency range is a change of ferrite material and supplier used in the toroid cores.

The ferrite material used in the toroid cores has a wider frequency range and noticeably lower loss compared to the Amidon toroids previously used.

Compared to the original the frequency range is wider, the loop input is better balanced and the common mode choke in the head unit gives higher isolation to common mode noise on the feeder.

Regards,

Chris


Re: Loop antenna amplifier - new version

Chris Moulding
 

There are quite a few minor differences to the new version but the biggest change to get the wide frequency range is a change of ferrite material and supplier used in the toroid cores.

The ferrite material used in the toroid cores has a wider frequency range and noticeably lower loss compared to the Amidon toroids previously used.

Compared to the original the frequency range is wider, the loop input is better balanced and the common mode choke in the head unit gives higher isolation to common mode noise on the feeder.

Regards,

Chris


Re: Loop antenna amplifier - new version

Paul Gulliver
 

I've lost track a bit, what are the differences between this version and the original, assuming all the various mods were made to the original.

I might give this new version a go

Paul


On 25/03/2020 at 18:23, Chris Moulding <chrism@...> wrote:
Some weeks back I mentioned that I was working on a new version of the Loop Antenna Amplifier.

It's now available for sale.

The frequency range is now 20 kHz to 150 MHz.

More details on the web page:

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

Regards,

Chris


Loop antenna amplifier - new version

Chris Moulding
 

Some weeks back I mentioned that I was working on a new version of the Loop Antenna Amplifier.

It's now available for sale.

The frequency range is now 20 kHz to 150 MHz.

More details on the web page:

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

Regards,

Chris


Re: Loop Antenna Amplifier - Service Bulletin 4 - HF performance improvement

Martin - G8JNJ
 

OK.

I'd suggest making a 1/4 wave notch stub from a short length of twin mains cable.

The open end is to be connected across the loop where it connects to the loop head amplifier.




Make it longer than 1/4 wave to start with and very gradually (approx 5mm at a time) cut it down to the required length as you watch the level of the 106MHz unwanted signal decreases.

The actual length will depend on the velocity factor of the cable you are using, but 0.58m from the loop terminal to the open end of the twin wire is a good starting point.

Once you see the signals start to increase again you have cut it too short. So use the piece you have just cut to make a second one that is slightly longer and use that instead. Alternatively if you can find a constant signal that is just a bit higher in frequency than 106MHz and cut to that, it should then be getting close to the desired length on the lower frequency. Having something like a Nano VNA makes this very easy, but it's still possible to do it with just a receiver and a lot of patience.

I hope this helps.

Regards,

Martin



Re: Loop Antenna Amplifier - Service Bulletin 4 - HF performance improvement

@sdoros
 

Hi,

101.8 and 106.5.
The first one with 20kw, the other one should be 3kw. Should be a third one but I could not figure out the frequency.


Re: Loop Antenna Amplifier - Service Bulletin 4 - HF performance improvement

Martin - G8JNJ
 

Hi,

Yes I realise that there is likely to be more than one transmitter.

I was trying to figure out if there was a simple way of reducing the signals at your location.

In order to do this I'd like to identify the frequency and power level of the transmissions relative to your receive location, then we can figure out if there is anything we can do to improve the situation.

For example it would be a lot harder to fix if they were all very high power and spread across the FM broadcast band. However if they are all relatively low power and very close together in terms of frequency, then it's a lot easier.

Regards,

Martin


Re: Loop Antenna Amplifier - Service Bulletin 4 - HF performance improvement

@sdoros
 
Edited

There are 2-3 different stations / frequencies not just one, the thing is that Loop Antenna Amplifier interfere at other antennas/tuners.
The picture above was from a 1.2ghz antenna connected at another SDR.


Re: Loop Antenna Amplifier - Service Bulletin 4 - HF performance improvement

Martin - G8JNJ
 

Which transmitter site is it ?

Do you know the frequencies and radiated powers used at the site  ?

Regards,

Martin


Re: Loop Antenna Amplifier - Service Bulletin 4 - HF performance improvement

@sdoros
 

FM trasmiters are about 15km away, if I tune to the noise I can hear the FM stations.


Re: Loop Antenna Amplifier - Service Bulletin 4 - HF performance improvement

Martin - G8JNJ
 

It looks like IMD produced by FM broadcast band stations.

Have you got any transmitters located nearby ?

If you tune to the noise and use WBFM can you hear the modulation ?

Regards,

Martin




Re: Loop Antenna Amplifier - Service Bulletin 4 - HF performance improvement

@sdoros
 

In did the tests you mentioned, I even switched off the power from the building and run the SDR from laptop and from a PC with UPS. Seems to me that the noise is coming from the loop amlifier. It also affects other two antennas I have close.
I moved the amplifier to my balcony using different coaxial cable and the antennas on the roof affected less.
As I said I tried different power supllies for feeding the amplifier and tried also to feed it via SDRDuo bias tee. 
Same results like the picture below on all close antennas.


Re: Multicoupler Question

Daryl Hooke <dghooke@...>
 

Hi Chris,

THANKS for the comprehensive and prompt reply. I will place an order for the HF/VHF/UHF version.

Cheers

Daryl Hooke
Paradise Beach
Vic AUSTRALIA
VK3AWA




On Tue, 24 Mar 2020 at 09:24, Chris Moulding <chrism@...> wrote:
The difference between the Multicouplers is that the VHF/UHF version has a high pass filter on the input to filter out HF signals.

The VHF/UHF version is usually sold to customers at or near airports to monitor airband traffic 24/7. They may have a HF radio on site that they need to filter out of the VHF system.

The HF/VHF/UHF version is a favourite of radio amateurs and airband listeners. It allows them to use it with different antennas and a wide range of receivers for whatever project they are experimenting with.

There is no difference in performance between the two versions other than the HF filtering.

As we are about to build a large batch of Multicouplers for stock during the coronavirus outbreak we will probably only make the HF/VHF/UHF version rather than try and stock multiple options.

Regards,

Chris


Re: Multicoupler Question

Chris Moulding
 

The difference between the Multicouplers is that the VHF/UHF version has a high pass filter on the input to filter out HF signals.

The VHF/UHF version is usually sold to customers at or near airports to monitor airband traffic 24/7. They may have a HF radio on site that they need to filter out of the VHF system.

The HF/VHF/UHF version is a favourite of radio amateurs and airband listeners. It allows them to use it with different antennas and a wide range of receivers for whatever project they are experimenting with.

There is no difference in performance between the two versions other than the HF filtering.

As we are about to build a large batch of Multicouplers for stock during the coronavirus outbreak we will probably only make the HF/VHF/UHF version rather than try and stock multiple options.

Regards,

Chris


Multicoupler Question

Daryl Hooke <dghooke@...>
 

Hi,

Why are there two available multicouplers in the VHF/UHF range? One includes HF.  Would it not be more practical to produce just one unit covering HF/VHF/UHF.
I note there is no price difference between the two.

I am looking at ordering one predominantly for VHF airband and ADSB 1090 reception. However, as a ham I’m thinking adding the HF option may come in useful. 

Is there any advantage/disadvantage between the two multicouplers.

THANKS

DARYL de VK3AWA 
--
Sent from my Ipad


Re: HF LOOP

Paul Newland
 

Thanks Martin
I should have guessed that there wouldn't be a simple answer.
Thanks for the explanation, I'll carry on somewhat better informed and leave you in peace.
Best Wishes
Paul



On Wed, 18 Mar 2020 at 20:27, Martin - G8JNJ via Groups.Io <martin_ehrenfried=yahoo.com@groups.io> wrote:
On Wed, Mar 18, 2020 at 03:00 PM, Paul Newland wrote:
when one has two (in this case loop antennas) closely located, at the same elevation and orientation, is it nevertheless possible for them to receive signals form different paths
Hi Paul,

Yes and no :-)

If everything is identical and the spacing between loops is minimal then they should receive the same signals at the same strengths.

However in practice there are always slight differences, it could be spacing between loops being a fraction of a wavelength so you get space diversity, or it could be coupling into the antenna from differently routed feeder cables of different lengths connected to different items of equipment with different 'earth' paths etc. So it's actually quite difficult to produce 'identical' antenna systems.

Regards,

Martin


Re: HF LOOP

Martin - G8JNJ
 

On Wed, Mar 18, 2020 at 03:00 PM, Paul Newland wrote:
when one has two (in this case loop antennas) closely located, at the same elevation and orientation, is it nevertheless possible for them to receive signals form different paths
Hi Paul,

Yes and no :-)

If everything is identical and the spacing between loops is minimal then they should receive the same signals at the same strengths.

However in practice there are always slight differences, it could be spacing between loops being a fraction of a wavelength so you get space diversity, or it could be coupling into the antenna from differently routed feeder cables of different lengths connected to different items of equipment with different 'earth' paths etc. So it's actually quite difficult to produce 'identical' antenna systems.

Regards,

Martin


Re: HF LOOP

Paul Newland
 

Thank you for that useful guidance Martin.
I promise no to badger you any further, other than to ask one question, which is; when one has two (in this case loop antennas) closely located, at the same elevation and orientation, is it nevertheless possible for them to receive signals form different paths.
By the way, in the past II have taken advantage of your Kiwi SDR, admired that fantastic antenna that you, I believe, received an award for (perhaps there are more than one of those though) and read your findings on the various different aerials that you have investigated.
So thank you for all that also.
Best Wishes
Paul
Best Wishes
Paul



On Wed, 18 Mar 2020 at 13:20, Martin - G8JNJ via Groups.Io <martin_ehrenfried=yahoo.com@groups.io> wrote:
Hi Paul,

I don't disagree with anything your say.

When comparing waterfalls or spectrum displays it's sometimes useful to set the noise floor on the display so that they are all equal, regardless of the antenna or RF gain, then set the amplitude scales so that they all show the same number of dB per division. That way you can more easily compare the different S./N ratios.

More objective methods are to compare digital modes such as PSK, WSPR and FT which provide a S/N value for each signal received. as long as you compare the same callsign in the same time slot against each other, you should be able to obtain sensible values.

Regards,

Martin


Re: HF LOOP

Martin - G8JNJ
 

Hi Paul,

I don't disagree with anything your say.

When comparing waterfalls or spectrum displays it's sometimes useful to set the noise floor on the display so that they are all equal, regardless of the antenna or RF gain, then set the amplitude scales so that they all show the same number of dB per division. That way you can more easily compare the different S./N ratios.

More objective methods are to compare digital modes such as PSK, WSPR and FT which provide a S/N value for each signal received. as long as you compare the same callsign in the same time slot against each other, you should be able to obtain sensible values.

Regards,

Martin

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