Topics

Long wire puzzle


AllanIsaacs
 

I have a peculiar problem here.
For ages my long wire (about 250-300 feet long in dog legs etc) has worked fine with Radio 4 198KHz running at S9 +30dB.
Recently this has dropped to S8/S9 and also applies to Radio 1 Eire which is S5 ish. I put this down to the wire sagging so re-rerected it on Saturday only to find it was no different.
As the aerial has a U-shape the remote end was 50 feet away I added an extra 50 feet of wire and connected this to my receiver (so the aerial is now a large horizontal loop). So using the aerial back to front Radio 4 is now back to S9 +35dB and Radio 1 Eire over S9. Back to normal.
Switching back the connections resulted in S8 as before.
I checked continuity and saw 17 ohms so there isn't a break in the wire (my first thought).
What caused the aerial to suddenly stop working well and why does feeding it the other way round make it work as it used to?
I'm feeding the wire via a 9:1 unun (with a ground wire) but connecting it directly has exactly the same relative results.
Allan G3PIY


militaryoperator
 

I have a peculiar problem here.
For ages my long wire (about 250-300 feet long in dog legs etc) has worked fine with Radio 4 198KHz running at S9 +30dB.
Recently this has dropped to S8/S9 and also applies to Radio 1 Eire which is S5 ish. I put this down to the wire sagging so re-rerected it on Saturday only to find it was no different.
As the aerial has a U-shape the remote end was 50 feet away I added an extra 50 feet of wire and connected this to my receiver (so the aerial is now a large horizontal loop). So using the aerial back to front Radio 4 is now back to S9 +35dB and Radio 1 Eire over S9. Back to normal.
Switching back the connections resulted in S8 as before.
I checked continuity and saw 17 ohms so there isn't a break in the wire (my first thought).
What caused the aerial to suddenly stop working well and why does feeding it the other way round make it work as it used to?
I'm feeding the wire via a 9:1 unun (with a ground wire) but connecting it directly has exactly the same relative results.
Allan G3PIY



I had this years ago. Longwire ant, tuned ok all bands, one day, would not tune. 

Changed wire, all well again.  Maybe there's a hi z to rf near the original feed, feeding from the other end puts most of the wire back in cct. 

Ben
 
_


Alan_Riley_G6MXT
 

Hi Allan,

I would say that your wire is corroded and broken. You don't say what your wire is made of but assuming it is copper then 17 ohms seems like a lot for the length of your aerial. Something thin like 7/0.2 has a resistance of about 88 ohm per km. 17 ohms works out to be around 630 feet, you have about half that which would suggest a very thin wire. I'm thinking that the resistance that you are seeing is as a result of moisture and corrosion products in the insulation around a break.  

73
Alan G6MXT


Major Pain
 

Hello Allan,

I too listen to Radio 4 on 198 KHz using a 180ft long wire that has 150 ft of it horizontal at 50 ft AGL, the last 30ft or so comes down at an angle held off the building at 2ft with insulators feeds into a 64:1 UNUN then a 500 KHz 8 pole low pass filter, and in to the home made receive converter that has a SBL2 mixer and a 15 dB RF amplifier, 2 MHz IF to the R210. Ground being 4 x 6ft earth rods 6 feet from the feed point.

 

I suspect what you have seen is a movement in the path of the signal or signal polarisation due to something between you and the source having moved or being built, for example a large lattice crane. Adding wire alters polarisation also adding wire alters at what path the aerial is “seeing” the signal, so either theory could be the answer.

 

It’s perhaps also worth checking your ground resistance too.

 

Regards,

Keith.

 

 

I have a peculiar problem here.
For ages my long wire (about 250-300 feet long in dog legs etc) has worked fine with Radio 4 198KHz running at S9 +30dB.
Recently this has dropped to S8/S9 and also applies to Radio 1 Eire which is S5 ish. I put this down to the wire sagging so re-rerected it on Saturday only to find it was no different.
As the aerial has a U-shape the remote end was 50 feet away I added an extra 50 feet of wire and connected this to my receiver (so the aerial is now a large horizontal loop). So using the aerial back to front Radio 4 is now back to S9 +35dB and Radio 1 Eire over S9. Back to normal.
Switching back the connections resulted in S8 as before.
I checked continuity and saw 17 ohms so there isn't a break in the wire (my first thought).
What caused the aerial to suddenly stop working well and why does feeding it the other way round make it work as it used to?
I'm feeding the wire via a 9:1 unun (with a ground wire) but connecting it directly has exactly the same relative results.
Allan G3PIY

_._,_._,_


 


Pete_G4GJL
 

Alan, some random thoughts:

Have you developed an earth fault?
Inside set
Connector to set
In your mains wiring
At your mains earth stake.
Are you using a separate RF earth system?
Earth system dried out in ground?

What is the set you are using?
Are the relative strengths the same on another set?


Pete
G4GJL

On Mon, Sep 21, 2020 at 9:25 AM AllanIsaacs <allan@...> wrote:
I have a peculiar problem here.
For ages my long wire (about 250-300 feet long in dog legs etc) has worked fine with Radio 4 198KHz running at S9 +30dB.
Recently this has dropped to S8/S9 and also applies to Radio 1 Eire which is S5 ish. I put this down to the wire sagging so re-rerected it on Saturday only to find it was no different.
As the aerial has a U-shape the remote end was 50 feet away I added an extra 50 feet of wire and connected this to my receiver (so the aerial is now a large horizontal loop). So using the aerial back to front Radio 4 is now back to S9 +35dB and Radio 1 Eire over S9. Back to normal.
Switching back the connections resulted in S8 as before.
I checked continuity and saw 17 ohms so there isn't a break in the wire (my first thought).
What caused the aerial to suddenly stop working well and why does feeding it the other way round make it work as it used to?
I'm feeding the wire via a 9:1 unun (with a ground wire) but connecting it directly has exactly the same relative results.
Allan G3PIY


Henk_Parasetguy
 

Hi Allan

 

A sagging wire and an increase of resistance. My thought: the sagging made the wire a little longer (no problem) but also thinner. This might explain the relative high resistance. I once saw a big pigeon trying to find balance on my long wire. Did not succeed. Smaller birds do.

Another cause of signal loss can be more or less shorted isolators due to air pollution or bird droppings. Though this has nothing to do with the wire resistance.

 

 

Kind regards,

Henk - Parasetguy

 

Van: wireless-set-no19@groups.io <wireless-set-no19@groups.io> Namens militaryoperator via groups.io
Verzonden: maandag 21 september 2020 10:53
Aan: wireless-set-no19@groups.io
Onderwerp: Re: [wireless-set-no19] Long wire puzzle

 

I have a peculiar problem here.
For ages my long wire (about 250-300 feet long in dog legs etc) has worked fine with Radio 4 198KHz running at S9 +30dB.
Recently this has dropped to S8/S9 and also applies to Radio 1 Eire which is S5 ish. I put this down to the wire sagging so re-rerected it on Saturday only to find it was no different.
As the aerial has a U-shape the remote end was 50 feet away I added an extra 50 feet of wire and connected this to my receiver (so the aerial is now a large horizontal loop). So using the aerial back to front Radio 4 is now back to S9 +35dB and Radio 1 Eire over S9. Back to normal.
Switching back the connections resulted in S8 as before.
I checked continuity and saw 17 ohms so there isn't a break in the wire (my first thought).
What caused the aerial to suddenly stop working well and why does feeding it the other way round make it work as it used to?
I'm feeding the wire via a 9:1 unun (with a ground wire) but connecting it directly has exactly the same relative results.
Allan G3PIY

 

 

 

I had this years ago. Longwire ant, tuned ok all bands, one day, would not tune. 

 

Changed wire, all well again.  Maybe there's a hi z to rf near the original feed, feeding from the other end puts most of the wire back in cct. 

 

Ben
 

_


Pete_G4GJL
 

Wouldnt that be two lattice cranes?
 
  Bizarrely placed at the right point in the QTH to Eire path and separately in the QTH to Droitwich path.
 
 It seems unlikely that one crane would affect both signals in the same manner, at this frequency.
 
Pete
G4GJL

On Mon, Sep 21, 2020 at 11:27 AM Keith_Watt_RGN <keith@...> wrote:

Hello Allan,

I too listen to Radio 4 on 198 KHz using a 180ft long wire that has 150 ft of it horizontal at 50 ft AGL, the last 30ft or so comes down at an angle held off the building at 2ft with insulators feeds into a 64:1 UNUN then a 500 KHz 8 pole low pass filter, and in to the home made receive converter that has a SBL2 mixer and a 15 dB RF amplifier, 2 MHz IF to the R210. Ground being 4 x 6ft earth rods 6 feet from the feed point.

 

I suspect what you have seen is a movement in the path of the signal or signal polarisation due to something between you and the source having moved or being built, for example a large lattice crane. Adding wire alters polarisation also adding wire alters at what path the aerial is “seeing” the signal, so either theory could be the answer.

 

It’s perhaps also worth checking your ground resistance too.

 

Regards,

Keith.

 


Major Pain
 

It does not necessarily require two obstacles because it depends upon the signal path!

Something in the path is not to be so easily dismissed when we really have no idea what’s causing it.

 

I also mentioned ground faults, something more easily checked for, not just broken ground wire, but increased ground resistance.

 

Regards,

Keith.

 

 

Wouldnt that be two lattice cranes?

 

  Bizarrely placed at the right point in the QTH to Eire path and separately in the QTH to Droitwich path.

 

 It seems unlikely that one crane would affect both signals in the same manner, at this frequency.

 

Pete

G4GJL

 

On Mon, Sep 21, 2020 at 11:27 AM Keith_Watt_RGN <keith@...> wrote:

Hello Allan,

I too listen to Radio 4 on 198 KHz using a 180ft long wire that has 150 ft of it horizontal at 50 ft AGL, the last 30ft or so comes down at an angle held off the building at 2ft with insulators feeds into a 64:1 UNUN then a 500 KHz 8 pole low pass filter, and in to the home made receive converter that has a SBL2 mixer and a 15 dB RF amplifier, 2 MHz IF to the R210. Ground being 4 x 6ft earth rods 6 feet from the feed point.

 

I suspect what you have seen is a movement in the path of the signal or signal polarisation due to something between you and the source having moved or being built, for example a large lattice crane. Adding wire alters polarisation also adding wire alters at what path the aerial is “seeing” the signal, so either theory could be the answer.

 

It’s perhaps also worth checking your ground resistance too.

 

Regards,

Keith.

 

_._,_._,_



Michael O'Beirne
 

Alan and Allan
 
I suspect Alan (below) is correct.  Corrosion is a bit like non-Hodgkinson’s lymphoma .  You soldier on and then suddenly in the last few weeks your life collapses.
 
Long wires inevitably pick up a lot of noise.  For LW and MW reception you would do better with a good untuned amplified loop.  I have had the Wellbrook Loop, ALA 1530 for over 12 years.  It covers 50kHz to over 30MHz with a reasonably constant output at 50 ohm impedance.  The IP3 is about +43dBm.  The rx will intermodulate long before the loop!  And being a balanced design, the noise pick up is far less.  If the loop is mounted on a small rotator you can get up to 30dB attenuation of “off-beam” interfering signals as it has the usual figure-of-eight pattern.
 
The signal level is lower than with a long wire but the s/n ratio is better and most of the reviewers found reception was better.  You might like to read the review in RadCom January 2012 by Steve Nichols and the many comments on e.Ham.net. 
 
There was an issue over the potting compound protecting the amp having some air bubbles and allowing water to permeate in and corrode the pcb, but I think that has been resolved in the current product.
 
The drawback is the output socket – a BNC mounted horizontally on the enclosure.  I covered the BNC connection with a lot of the silvery gaffer tape and round the enclosure because it’s so difficult to protect a surface mounted socket.  I renew the covering every few years.  My loop has survived many winters and I’m about to renew the tape again before the wet weather returns.  Far better would have been to have a coax lead of a couple of feet sticking out of the enclosure via a proper waterproof gland facing downwards with a BNC female on the far end and then to cover that joint with appropriate heat shrink tubing plus tape.   Some professional aerials do that.
 
Also, take a look at the “repro” WellGood Loop described by George Smart M1GEO at his most interesting site at WWW.george-smart.co.uk.projects.  He repaired a few Wellbrook Loops that had been damaged by the owners’ accidental transmissions into them (not clever!) and reverse engineered the amplifier.  He also has an interesting paper on the construction of the PA0RDT MiniWhip, which is easier to make (no RF transformers to wind) but is not as good as the “Wellgood Loop”.
 
73s
Michael
G8MOB
 

From: Alan_Riley_G6MXT via groups.io
Sent: Monday, September 21, 2020 10:00 AM
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Long wire puzzle
 
Hi Allan,

I would say that your wire is corroded and broken. You don't say what your wire is made of but assuming it is copper then 17 ohms seems like a lot for the length of your aerial. Something thin like 7/0.2 has a resistance of about 88 ohm per km. 17 ohms works out to be around 630 feet, you have about half that which would suggest a very thin wire. I'm thinking that the resistance that you are seeing is as a result of moisture and corrosion products in the insulation around a break. 

73
Alan G6MXT
_._,_._,_


AllanIsaacs
 

I’ll try and respond to all suggestions.

The aerial now has three sections of wire, all stranded copper but the first section I noticed has tarnished strands even under the insulation.

That wire is the one I was feeding initially so I wonder if it has fractured strands resulting from being stressed so that continuity is via several highish resistance breaks. The other end is now fed with 50 feet of new shiny copper stranded wire (3rd section) joined onto the 2nd section which again has tarnished copper strands.

The ground wire is OK.

I guess I’ll have to replace the whole thing with wire having moisture-proof insulation.

I tried the wire on three receivers. My Andrus which works extremely well on VLF and an SDR Play and an RA17. All gave the same results.

Today feeding the wrong end of the wire 252 is S9+4dB, 234 is S9+4dB, 198 is S9+26dB

 

My active loop aerial is presently out of action waiting for corrosion to be sorted out.

 

Everything is now on hold however as a repair job just arrived. It’s a Trimod 16000UPS with 25 12-volt batteries… It must weigh double that RA17 rack mentioned by Chris…I really should retire!

Allan G3PIY

 


bty725381
 

Are you using Flexweave by any chance? This seems to be notorious for internal corrosion which turns all the strands black.
--
Keith - G3XGW
http://www.tibblestone.com/oldradios/milradio.htm


AllanIsaacs
 

I’m not aware of using Flexweave Keith.

I’ll have to look at the various reels in my collection of wire.

Most came from a skip where a local school was dumping a huge amount of stuff.

The strands are certainly very tarnished.. Maybe it’s working like Litz wire but with fractures and not very continuous…

Allan G3PIY

 


From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On Behalf Of bty725381 via groups.io
Sent: 21 September 2020 14:18
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Long wire puzzle

 

Are you using Flexweave by any chance? This seems to be notorious for internal corrosion which turns all the strands black.
--
Keith - G3XGW
http://www.tibblestone.com/oldradios/milradio.htm


AllanIsaacs
 

I forgot to erase the stuff…sorry

Allan G3PIY

 


From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On Behalf Of bty725381 via groups.io
Sent: 21 September 2020 14:18
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Long wire puzzle

 

Are you using Flexweave by any chance? This seems to be notorious for internal corrosion which turns all the strands black.
--
Keith - G3XGW
http://www.tibblestone.com/oldradios/milradio.htm

_._,_._,_

 


Michael O'Beirne
 

Keith
 
What is the best sort of wire to use?  In the military we used the normal 7 strand stuff on a big reel, but then most of our aerials were short term – a week tops.
 
I have used D10 but it’s not recommended for serious power.  I was never much sold on the open braid variety.
 
Is uninsulated solid copper better?  I seem to recall in an RSGB H/B it recommended that you tie one end to a doorknob and pull it hard slowly to strengthen it.
 
73s
Michael
G8MOB
 
 

From: bty725381 via groups.io
Sent: Monday, September 21, 2020 2:17 PM
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Long wire puzzle
 
Are you using Flexweave by any chance? This seems to be notorious for internal corrosion which turns all the strands black.
--
Keith - G3XGW
http://www.tibblestone.com/oldradios/milradio.htm
_._,_._,_


Alan_Riley_G6MXT
 

For what it's worth, I find that black PVC insulated 32/0.2 tinned copper makes quite good aerial wire. Moisture ingress doesn't turn the wire black due to the tinning and if it does get snapped in a storm you can just solder it at the break, slip some heat-shrink over the joint and put it back. Using bungee cord at the ends of the wire solves most of the winter storm issues.

73
Alan
G6MXT


Bob Burns
 

Hi Alan

Check any solder joints as they do degrade when exposed to the atmosphere over long periods of time. Also look for any cracks at the bends.

--
Regards

Bob

Bob F Burns
C Eng, FIET, MSE. G3OOU, @BobFBurns
Retired Electronics and Software Consultant
http://www.g3oou.co.uk/myexperience.html
Technical web site: https://www.qsl.net/g3oou/


DAVE SAUNDERS
 

MICHAEL  Any Idea if the Audiofools favourite would be better? Oxygen free copper is allegedly corrosion resistant, although the cable isnt hard drawn , I believe! It should result in hi fidelity DX!  M0"IIZ


Serious question though





Sent from my Xperia by Sony smartphone


Don_Vosper
 

Have you tried this with different receivers?
Don m5aky


AllanIsaacs
 

Two different SDRs and an RA17 Don. Same results. I had initially thought
the front end of the first SDR had failed.
I was wondering if I could do an electrical measurement on the long wire
(other than a simple resistance test) as I have access to both ends of the
wire.
For example, I have a directional coupler and a spectrum analyser/tracking
generator.
Or simply send a narrow pulse into the wire with one end terminated to 50
ohms to see if there's a reflection from a resistive point on the wire then
swap the ends over and see if the position makes sense.
Allan G3PIY

-----Original Message-----
From: wireless-set-no19@groups.io [mailto:wireless-set-no19@groups.io] On
Behalf Of Don_Vosper via groups.io
Sent: 21 September 2020 18:58
To: wireless-set-no19@groups.io
Subject: Re: [wireless-set-no19] Long wire puzzle

Have you tried this with different receivers?
Don m5aky


bty725381
 

Michael,

When I worked in Aerospace I was lucky enough to "acquire" a part roll of PTFE insulated wire (probably 7/.150 tinned copper). This has been up for at least 20 years and shows no sign of water ingress, hence no corrosion. Also it's grey which matches the colour of the sky most days! Occasionally this suff turns up a rallies (remember those!) but it's usually pink.

--
Keith - G3XGW
http://www.tibblestone.com/oldradios/milradio.htm