Topics

Feed Line Noise


Mark Parker <mwtp2@...>
 

Hi Chris,

I have been doing some tests with my CCW active loop and a little concerned about household noise ingress via the LAN feed line on certain ham bands.
This noise appears worst mostly on 30m and 17m bands even when power is not applied to antenna. I have temporary setup with antenna about 30-40m from houses and 2 to 3 m in height. The feed line I am using is 50m unshielded heavy duty LAN cable from amazon, see link below. Is it normal to get some breakthrough using this feed method with no power, I have looked at the power source and even made a ugly air spaced balun in the feed line with no luck. Any ideas?
https://www.amazon.co.uk/gp/product/B00I461X6M/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

73s
Mark


david
 

Hi Mark,

I'm not Chris, but I'll step in with my own answer.
You need a 'real' Common Mode Choke. An air-cored coil will not solve this.

Have a look at the LZ1AQ site. He uses Cat5 cable to feed his active antennas. I won't copy his designs, here, but you can download a pdf of the solution he uses at this link:

http://active-antenna.eu/tech-docs/comm-filter-ftp-10.pdf

Make a version to suit the conductors for your CCW antenna. It works very well..
As for location, Leif Asbrink has produced a vast body of videos regarding the elimination of noise. His recommendation is to put the CM choke about 1 - 2m outside the buildings before the cable enters. This works for me. {I have a second CM Choke at the base of the mast, as well. Even better, although the 'house' choke does the lion's share of the noise reduction}.

Let us know how you get on.
Best Wishes
David, GM8XBZ

-----Original Message-----
From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Mark Parker via Groups.Io
Sent: 06 April 2019 12:12
To: CrossCountryWireless@groups.io
Subject: [CrossCountryWireless] Feed Line Noise

Hi Chris,

I have been doing some tests with my CCW active loop and a little concerned about household noise ingress via the LAN feed line on certain ham bands.
This noise appears worst mostly on 30m and 17m bands even when power is not applied to antenna. I have temporary setup with antenna about 30-40m from houses and 2 to 3 m in height. The feed line I am using is 50m unshielded heavy duty LAN cable from amazon, see link below. Is it normal to get some breakthrough using this feed method with no power, I have looked at the power source and even made a ugly air spaced balun in the feed line with no luck. Any ideas?
https://www.amazon.co.uk/gp/product/B00I461X6M/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&;psc=1

73s
Mark


leslie norton
 

I don't want to put a spanner in the works but it depends on what the noise is, i'll give you an example, I had a Wellbrook loop and could not null out the noise (mine is caused by VDSL) I decided to go for the CCW active loop in the hope the filtering might be better. It isn't, I still have the same issues so in a way ive wasted money. My CCW is outside and above the lines that cause issues although ive tried in in loads of positions. The dropper cables are attached to all the houses and i live in a square so 360 degrees, I have the CCW mounted on a Yeasu rotator. I have now come to terms with not operating (apart from digital) on affected bands.
VDSL is particularly troublesome to amateur radio.
I have tried all sorts of filters and nothing works for VDSL.


David Cutter
 

Leslie

 

That's very interesting, as is the LZ1AQ data.  Does your experience then tell us that the VDSL signals are in fact coupling directly to the antenna and it is then irrelevant what else is happening? 

 

Your only escape is to place the antenna remotely, ie long distance from VDSL sources. 

 

So much for notching which is only done on a site by site basis and only if you know the engineer to ask, etc.

 

David G3UNA

 

From: CrossCountryWireless@groups.io [mailto:CrossCountryWireless@groups.io] On Behalf Of leslie norton
Sent: 06 April 2019 15:47
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

I don't want to put a spanner in the works but it depends on what the noise is, i'll give you an example, I had a Wellbrook loop and could not null out the noise (mine is caused by VDSL) I decided to go for the CCW active loop in the hope the filtering might be better. It isn't, I still have the same issues so in a way ive wasted money. My CCW is outside and above the lines that cause issues although ive tried in in loads of positions. The dropper cables are attached to all the houses and i live in a square so 360 degrees, I have the CCW mounted on a Yeasu rotator. I have now come to terms with not operating (apart from digital) on affected bands.
VDSL is particularly troublesome to amateur radio.
I have tried all sorts of filters and nothing works for VDSL.


Virus-free. www.avast.com


Tom Crosbie G6PZZ
 

Perhaps I’m going off at a tangent here and talking through my ar$e but as CAT5e has become a bit of a standard for power and signal, would there be any merit in converting the signal to use a fibre optic cable to transfer the signal from antenna to receiver? Has anyone tried this? Feel free to tell me I’m way off here!

Tom G6PZZ

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of leslie norton
Sent: 06 April 2019 15:47
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

I don't want to put a spanner in the works but it depends on what the noise is, i'll give you an example, I had a Wellbrook loop and could not null out the noise (mine is caused by VDSL) I decided to go for the CCW active loop in the hope the filtering might be better. It isn't, I still have the same issues so in a way ive wasted money. My CCW is outside and above the lines that cause issues although ive tried in in loads of positions. The dropper cables are attached to all the houses and i live in a square so 360 degrees, I have the CCW mounted on a Yeasu rotator. I have now come to terms with not operating (apart from digital) on affected bands.
VDSL is particularly troublesome to amateur radio.
I have tried all sorts of filters and nothing works for VDSL.


Mark Parker <mwtp2@...>
 

Many thanks guys for the input, I really want the CCW to work after reading many good reviews especially on VHF bands. I also have two original Wellbrook ALA1530s, one of them on a rotator which needs repaired, probably water ingress after many years of Scottish winters!! 
The noise is not broadband in origin but suspect switch mode power related, will need to persevere and be patent, going down the elimination route etc.
On good news so far with the CCW after some comparisons with the ALA1530 the CCW knocks spots of the Wellbrook in LW and VLF department, was astonished by the amount of NDBs coming in, I thought for a second, could it be the old RG58 feeder to the Wellbook be at fault!!
I suppose that`s whats challenging with this hobby, there is always room for improvement...

73`s
Mark 


Chris Moulding
 

In normal use the ethernet cable may pick up some noise or external signals but the level should be so far down that it will be drowned out when power is applied and the amplifier in the head unit starts working.

If the external noise level is high I would recommend that you try one of the ethernet cable testers on your cable. If one of the wires in the cable is broken or open circuit at the connector then it will unbalance the twisted pair and may act as an antenna coupling noise into the other three pairs. When ethernet cable is correctly terminated in the correct impedance then the crosstalk specification between the pairs is better than 40 dB and is typically around a measured 55 dB with the outdoor cable we supply with the antenna. One of the first tests of the prototype HF Active Antenna was to attach the ethernet cable to my test mast as an inverted vee antenna to prove the cable isolation. Even in this severe test the external signals received by the cable were well down on those received by the active antenna.

I agree with the other comments about "ugly baluns". They only work at a spot frequency where the coil of cable acts as a resonant circuit. Otherwise its a waste of good cable!

interesting to read the LZ1AQ filter document. I see he's still making the same mistake!

Good to hear that you like the VLF and LF performance of the latest loop antenna. It does work rather well down there.

Regards,

Chris


leslie norton
 

Hi David, been trying to solve this for over 2 years and as ADSL now is common place the only cure i think is way in the future when we all have optical cable direct to the house and at 67 years old i do wonder if it will happen in my lifetime!
I have Common mode chokes on all my antennas inc long wires etc. I also have Common mode filters at my receiver and transciever.
I have a Timewave ANC-4 noise phase unit and a Timewave DSP-9+ digital filter.
I can reduce household noise to 0 but not VDSL.
I suspect the pick up is the antennas rather than the leads in.
I did do a rather interesting test last year, I built a loop on the ground - similar to a beverage but in a loop, this goes to a balun and then to a common mode choke then to the receiver via another common mode choke. half of the loop is buried about and inch due to the lanscape (paths) The noise inc VDSL went down quite a bit but the signal did too, however signal to noise was good enough to listen to weak signals previously drowned out by noise. A few amateurs near me now recieve on Hack green and tx on an antenna - remote is the only way sometimes. Tom Crosbie (G6PZZ) has an interesting point, if it were possible to convert Fibre optic for transfer.


Chris Moulding
 

Tom,

I did some work a few years back on a similar isolated active antenna to what you suggest. The idea was to use a fibre connection between the antenna and the ground with a solar panel and battery in the active antenna powering the amplifier.

It did work well but we thought that it would be too advanced for the market at that time. Using ethernet cable with attention to common mode filtering and correct cable termination gave results approaching the solar fibre antenna at a much reduced price so we went for that instead.

Regards,

Chris


david
 

Chris,

For interest's sake, what is the mistake?

73
David, GM8XBZ

-----Original Message-----
From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Chris Moulding
Sent: 06 April 2019 17:08
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

<snip>

interesting to read the LZ1AQ filter document. I see he's still making the same mistake!


Mark Parker <mwtp2@...>
 

Hi again Chris,

Thanks for the info.. I think you may be correct about the cable I am using, it is heavy duty and difficult to work with being so thick. I plan to get one of those 
LAN cable testers. The cable you supplied is perfect and quite flexible but not long enough, was wondering if you sell cable reels individually?
Thanks for the great support.

73s
Mark 


Tom Crosbie G6PZZ
 

David,

Could you please expand on “notching”. I have Previously built notch filters for 2m/70cms to insert in my neighbours TV downlead, so I’m familiar with the basics, just not how it applies to VDSL/ADSL.

Is this some magic device that would fit to the telephone line?

What are the magic words to say to an engineer to make a start on this process?

Kindest regards

Tom G6PZZ

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of David Cutter via Groups.Io
Sent: 06 April 2019 16:04
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

Leslie

 

That's very interesting, as is the LZ1AQ data.  Does your experience then tell us that the VDSL signals are in fact coupling directly to the antenna and it is then irrelevant what else is happening? 

 

Your only escape is to place the antenna remotely, ie long distance from VDSL sources. 

 

So much for notching which is only done on a site by site basis and only if you know the engineer to ask, etc.

 

David G3UNA

 

From: CrossCountryWireless@groups.io [mailto:CrossCountryWireless@groups.io] On Behalf Of leslie norton
Sent: 06 April 2019 15:47
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

I don't want to put a spanner in the works but it depends on what the noise is, i'll give you an example, I had a Wellbrook loop and could not null out the noise (mine is caused by VDSL) I decided to go for the CCW active loop in the hope the filtering might be better. It isn't, I still have the same issues so in a way ive wasted money. My CCW is outside and above the lines that cause issues although ive tried in in loads of positions. The dropper cables are attached to all the houses and i live in a square so 360 degrees, I have the CCW mounted on a Yeasu rotator. I have now come to terms with not operating (apart from digital) on affected bands.
VDSL is particularly troublesome to amateur radio.
I have tried all sorts of filters and nothing works for VDSL.

 

Virus-free. www.avast.com


Tom Crosbie G6PZZ
 

Chris,

Thanks for replying. Perhaps your R&D on that project would make an interesting subject for your blog

Would there have to be some sort of analogue to digital conversation involved?

I thought perhaps one way round the problem would be to install the preamp in the same case as say an SDR4, coupled directly to each other to avoid any pickup between antenna and SDR, with BIAS-T taking care of powering the amp.

There would be room in the case for a USB to Optical converter but I gave up on that when I found they were about $300 each!! And you would need a pair.

 

The only economical way around that would be a whole new product with the antenna preamp, SDR and optical converters built in to one board. I wonder, could it be done?

 

Anyone else? Especially if you know where I could get my hands on some cheap barebones optical converters!

 

Tom G6PZZ

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Chris Moulding
Sent: 06 April 2019 17:16
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

Tom,

I did some work a few years back on a similar isolated active antenna to what you suggest. The idea was to use a fibre connection between the antenna and the ground with a solar panel and battery in the active antenna powering the amplifier.

It did work well but we thought that it would be too advanced for the market at that time. Using ethernet cable with attention to common mode filtering and correct cable termination gave results approaching the solar fibre antenna at a much reduced price so we went for that instead.

Regards,

Chris


David Cutter
 

I'm not fully up to date but the last I heard was that the band of frequencies used for data distribution has the FACILITY  to notch out the amateur bands.  I recently heard that this is not always done and is done by the engineer in the street at the box, but is not part of their regular training so, might not/probably not done.  I don't have it to hand but there was an excellent article in RADCOM recently about this.

David G3UNA

 

From: CrossCountryWireless@groups.io [mailto:CrossCountryWireless@groups.io] On Behalf Of Tom Crosbie G6PZZ
Sent: 07 April 2019 14:04
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

David,

Could you please expand on “notching”. I have Previously built notch filters for 2m/70cms to insert in my neighbours TV downlead, so I’m familiar with the basics, just not how it applies to VDSL/ADSL.

Is this some magic device that would fit to the telephone line?

What are the magic words to say to an engineer to make a start on this process?

Kindest regards

Tom G6PZZ

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of David Cutter via Groups.Io
Sent: 06 April 2019 16:04
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

Leslie

 

That's very interesting, as is the LZ1AQ data.  Does your experience then tell us that the VDSL signals are in fact coupling directly to the antenna and it is then irrelevant what else is happening? 

 

Your only escape is to place the antenna remotely, ie long distance from VDSL sources. 

 

So much for notching which is only done on a site by site basis and only if you know the engineer to ask, etc.

 

David G3UNA

 

From: CrossCountryWireless@groups.io [mailto:CrossCountryWireless@groups.io] On Behalf Of leslie norton
Sent: 06 April 2019 15:47
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

I don't want to put a spanner in the works but it depends on what the noise is, i'll give you an example, I had a Wellbrook loop and could not null out the noise (mine is caused by VDSL) I decided to go for the CCW active loop in the hope the filtering might be better. It isn't, I still have the same issues so in a way ive wasted money. My CCW is outside and above the lines that cause issues although ive tried in in loads of positions. The dropper cables are attached to all the houses and i live in a square so 360 degrees, I have the CCW mounted on a Yeasu rotator. I have now come to terms with not operating (apart from digital) on affected bands.
VDSL is particularly troublesome to amateur radio.
I have tried all sorts of filters and nothing works for VDSL.

 

Virus-free. www.avast.com


Stewart G3YSX
 

They have other things on their mind at the moment but this is something we should be writing to our MPs about regularly.

However the thing to emphasis is not amateur radio, that is very low down on their list. The thing to push is high speed digital Britain being good for the economy, good for reducing pollution by travel reduction, good for the remote care of the elderly etc.

Those are vote winners, but amateur radio is not. However amateur radio will benefit in many ways from the introduction of universal FTTP.

- Stewart/G3YSX

On 06/04/2019 17:08, leslie norton wrote:
the only cure i think is way in the future when we all have optical cable direct to the house and at 67 years old i do wonder if it will happen in my lifetime!


David Cutter
 

I agree, don't mention amateur radio but you should mention not being able to receive BBC and commercial broadcasts particularly the new digital modes. If you are not within the normal footprint of a common radio station, then you can't complain about it.

David G3UNA

-----Original Message-----
From: CrossCountryWireless@groups.io [mailto:CrossCountryWireless@groups.io] On Behalf Of Stewart G3YSX
Sent: 07 April 2019 15:25
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

They have other things on their mind at the moment but this is something we should be writing to our MPs about regularly.

However the thing to emphasis is not amateur radio, that is very low down on their list. The thing to push is high speed digital Britain being good for the economy, good for reducing pollution by travel reduction, good for the remote care of the elderly etc.

Those are vote winners, but amateur radio is not. However amateur radio will benefit in many ways from the introduction of universal FTTP.

- Stewart/G3YSX

On 06/04/2019 17:08, leslie norton wrote:
the only cure i think is way in the future when we all have optical
cable direct to the house and at 67 years old i do wonder if it will
happen in my lifetime!


Tom Crosbie G6PZZ
 

Thanks David,

I’ll search that out. Although I maintain my callsign, I no longer transmit and RSGB membership was outside my limited budget following a massive stroke some years ago.

73’s

Tom G6PZZ

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of David Cutter via Groups.Io
Sent: 07 April 2019 14:56
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

I'm not fully up to date but the last I heard was that the band of frequencies used for data distribution has the FACILITY  to notch out the amateur bands.  I recently heard that this is not always done and is done by the engineer in the street at the box, but is not part of their regular training so, might not/probably not done.  I don't have it to hand but there was an excellent article in RADCOM recently about this.

David G3UNA

 

From: CrossCountryWireless@groups.io [mailto:CrossCountryWireless@groups.io] On Behalf Of Tom Crosbie G6PZZ
Sent: 07 April 2019 14:04
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

David,

Could you please expand on “notching”. I have Previously built notch filters for 2m/70cms to insert in my neighbours TV downlead, so I’m familiar with the basics, just not how it applies to VDSL/ADSL.

Is this some magic device that would fit to the telephone line?

What are the magic words to say to an engineer to make a start on this process?

Kindest regards

Tom G6PZZ

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of David Cutter via Groups.Io
Sent: 06 April 2019 16:04
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

Leslie

 

That's very interesting, as is the LZ1AQ data.  Does your experience then tell us that the VDSL signals are in fact coupling directly to the antenna and it is then irrelevant what else is happening? 

 

Your only escape is to place the antenna remotely, ie long distance from VDSL sources. 

 

So much for notching which is only done on a site by site basis and only if you know the engineer to ask, etc.

 

David G3UNA

 

From: CrossCountryWireless@groups.io [mailto:CrossCountryWireless@groups.io] On Behalf Of leslie norton
Sent: 06 April 2019 15:47
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

I don't want to put a spanner in the works but it depends on what the noise is, i'll give you an example, I had a Wellbrook loop and could not null out the noise (mine is caused by VDSL) I decided to go for the CCW active loop in the hope the filtering might be better. It isn't, I still have the same issues so in a way ive wasted money. My CCW is outside and above the lines that cause issues although ive tried in in loads of positions. The dropper cables are attached to all the houses and i live in a square so 360 degrees, I have the CCW mounted on a Yeasu rotator. I have now come to terms with not operating (apart from digital) on affected bands.
VDSL is particularly troublesome to amateur radio.
I have tried all sorts of filters and nothing works for VDSL.

 

Virus-free. www.avast.com


Chris Moulding
 

LZ1AQ make the assumption in his document that the reactive field close to the antenna drops by l/d squared.

This is an over-simplification of what actually happens.

With an electrically small antenna such as out HF Active Loop, HF Active Antenna and HF Active Vee antenna the reactive field drops rapidly by l/d squared from the antenna element to a radius of 0.1 wavelength. In the Fresnel zone between 0.1 and 2 wavelengths the fields reverse. The electric field antennas (HF Active and HF Active Vee antenna) have a higher response to the magnetic field and conversely the HF Active Loop has a higher response to the electric field.

From 2 wavelengths to infinity the far field response is then constant.

All antennas do this. There are differences in the size of the transition between near and far field especially in large antennas.

Unfortunately most of the amateur radio antenna handbooks give over-simplified descriptions of how antennas actually work so a lot of misconceptions abound.

Here is a link to a article copied by RF Cafe that gives the most thorough treatment of near to far field transition that I've ever read:
http://www.rfcafe.com/references/electrical/near-far-field.htm

An interesting image showing what happens with electrically small antennas appears at the end of the article:



From our antenna sales we note that only radio amateurs buy loop antennas and the HF Active and HF Active Vee antennas sell to professional customers.

Regards,

Chris


David Cutter
 

Leslie

I meant to add that remoting your rx antenna wouldn't have to be expensive particularly if you belong to a club (or form a club just for this) by using a remote sdr which can support several users simultaneously.  Something I have in mind for my club as most of my members suffer many noise sources.

David G3UNA

 

From: CrossCountryWireless@groups.io [mailto:CrossCountryWireless@groups.io] On Behalf Of leslie norton
Sent: 06 April 2019 17:09
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Feed Line Noise

 

Hi David, been trying to solve this for over 2 years and as ADSL now is common place the only cure i think is way in the future when we all have optical cable direct to the house and at 67 years old i do wonder if it will happen in my lifetime!
I have Common mode chokes on all my antennas inc long wires etc. I also have Common mode filters at my receiver and transciever.
I have a Timewave ANC-4 noise phase unit and a Timewave DSP-9+ digital filter.
I can reduce household noise to 0 but not VDSL.
I suspect the pick up is the antennas rather than the leads in.
I did do a rather interesting test last year, I built a loop on the ground - similar to a beverage but in a loop, this goes to a balun and then to a common mode choke then to the receiver via another common mode choke. half of the loop is buried about and inch due to the lanscape (paths) The noise inc VDSL went down quite a bit but the signal did too, however signal to noise was good enough to listen to weak signals previously drowned out by noise. A few amateurs near me now recieve on Hack green and tx on an antenna - remote is the only way sometimes. Tom Crosbie (G6PZZ) has an interesting point, if it were possible to convert Fibre optic for transfer.


Virus-free. www.avast.com