Insulation Versus Insulators - UK Vintage Radio Repair and Restoration Discussion Forum

HamishBoxer · 3rd Mar 2017, 11:01 am

Need to get my 160M aerial up and to get the 264 feet "V" dipole going it will go through the odd branch of trees.

Now as I don't climb ladders etc ,will the fact the wire used is insulated be good enough without too much of a loss? There will of course be pot insulators at the extreme ends.

Thank you

David

Herald1360 · 3rd Mar 2017, 11:19 am

The nearer the centre, the lower the voltage. PTFE or Polythene insulation might be better than PVC but I would think it'll be fine. Is top band still limited to 10/26 watts?

What about a long pole lopper to remove the problem?

Station X · 3rd Mar 2017, 12:01 pm

You might have problems feeding the wire through the branches, especially if they have leaves on them.

I have successfully hurled half bricks attached to string over the top of trees and then used the string to pull the wire over.

ISTR that to get a wire through branches I climbed the tree and pushed some sweep's rods through the branches, attached the wire to them, pulled it in and pushed it out the other side............

HamishBoxer · 3rd Mar 2017, 12:03 pm

Thank you for you thoughts.160M I believe is 400W SSB except the bit where I read the RSGB news and it is 10W 1.990Khz

Graham,I don't have a high enough point at the end of the garden to get over the trees that are in the way.Would saw them down (Apple) but they are nice in Summer and might give a bit of privacy as planning has gone through for 2 5 bedroom houses next to us.

G8BBZ · 3rd Mar 2017, 1:00 pm

Hi All,
I would second Herald1360 thought - provided the centre part of the dipole where the current is highest is in the clear, the effect of a few branches is probably acceptable. There will be a certain amount of power absorption, particularly in summer when the sap is up, and you may find that the antenna tuning will change slightly from summer to winter, particularly if there are branches close to the ends of the diploe where the impedance is highest.
PTFE or Polythene insulation would certainly be more durable than PVC - if you can find a suitable wire. As this is Top Band and a very long dipole, the weight of the wire may be significant. Obviously the wire has to be strong enough to withstand a bit of a battering where it passes through the trees, otherwiseyour choice would be the thinnest wire that would stand the tension. If you will use PVC, it is probably best to avoid black as this is often PVC coloured by loading it with Carbon black - which is conductive.
Lucky you to have a garden which will accomodate a full-size dipole on Top Band!
cheers
Peter G8BBZ

HamishBoxer · 3rd Mar 2017, 1:41 pm

Thanks Peter, yes the centre will be on the house gable in the clear. It won't be black as I have a roll of yellow multi stranded copper wire.

If I avoid the trees then it would be a "sloper" heading towards the ground also as it is a V then I won't get as much width at the far end.

Loppers sound a possible solution.

G6Tanuki · 3rd Mar 2017, 2:53 pm

Remember that insulation adds dead-weight - which can be enough to cause undesirable stretching of long antenna spans.

I was fortunate enough to obtain, some years back, some ex-Military kevlar-cored insulated antenna wire at a rather good price compared with what the taxpayer was originally charged by RACAL: this stuff is *tough* - like about 140Kg breaking-strain - and a 200-foot single span of it at my "stealth" location has survived without obvious damage for several years.

As to feeding it through/over trees - someone I know used a bow&arrow to fire a length of thin nylon monofilament fishing-line over a tree - they used this to haul aloft a thicker length of fishing-line which then pulled the actual antenna-wire up.

I guess these days a cheap "drone" would be an alternative?

Station X · 3rd Mar 2017, 2:57 pm

Quote:

Originally Posted by G6Tanuki

I was fortunate enough to obtain, some years back, some ex-Military kevlar-cored insulated antenna wire at a rather good price compared with what the taxpayer was originally charged by RACAL: this stuff is *tough* - like about 140Kg breaking-strain - and a 200-foot single span of it at my "stealth" location has survived without obvious damage for several years.

I too bought quite a lot of that Kevlar wire, new boxed and unopened. As you say it's very strong. One end of my aerial used to be supported by a tree which swayed in the wind. It was always the steel cored washing line running from the end insulator to the tree which broke. Never the Kevlar.

3rd Mar 2017, 4:06 pm

The core out of RG213? Or just give it a go with 'ordinary' wire, if the VSWR doesn't change that much dry to wet you are putting out a good signal. Also it's the current (as in amps) that radiate so a bit of high voltage (the ends) leakage isn't very detrimental.

Just stick some up, worst case you have a leader ready for posher wire!

I have most of a 500m (well it is big, 500m is a guess) reel of submarine grade wire, it is about 1/8th of an inch diameter. You are more than welcome to it, bloomin' heavy but I can't throw it out, much too useful (for someone). If you want it I can take it to work, weigh it and then you can send a pickup label. Drop me a PM.

3rd Mar 2017, 11:01 am	#1
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,931	Insulation Versus Insulators Need to get my 160M aerial up and to get the 264 feet "V" dipole going it will go through the odd branch of trees. Now as I don't climb ladders etc ,will the fact the wire used is insulated be good enough without too much of a loss? There will of course be pot insulators at the extreme ends. Thank you David __________________ G8JET BVWS Archivist and Member V.M.A.R.S

3rd Mar 2017, 11:19 am	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Insulation Versus Insulators The nearer the centre, the lower the voltage. PTFE or Polythene insulation might be better than PVC but I would think it'll be fine. Is top band still limited to 10/26 watts? What about a long pole lopper to remove the problem? __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

3rd Mar 2017, 12:01 pm	#3
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,286	Re: Insulation Versus Insulators You might have problems feeding the wire through the branches, especially if they have leaves on them. I have successfully hurled half bricks attached to string over the top of trees and then used the string to pull the wire over. ISTR that to get a wire through branches I climbed the tree and pushed some sweep's rods through the branches, attached the wire to them, pulled it in and pushed it out the other side............ __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

3rd Mar 2017, 12:03 pm	#4
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,931	Re: Insulation Versus Insulators Thank you for you thoughts.160M I believe is 400W SSB except the bit where I read the RSGB news and it is 10W 1.990Khz Graham,I don't have a high enough point at the end of the garden to get over the trees that are in the way.Would saw them down (Apple) but they are nice in Summer and might give a bit of privacy as planning has gone through for 2 5 bedroom houses next to us. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

3rd Mar 2017, 1:00 pm	#5
G8BBZ Pentode Join Date: Oct 2005 Location: Hebden Bridge, West Yorkshire, UK. Posts: 199	Re: Insulation Versus Insulators Hi All, I would second Herald1360 thought - provided the centre part of the dipole where the current is highest is in the clear, the effect of a few branches is probably acceptable. There will be a certain amount of power absorption, particularly in summer when the sap is up, and you may find that the antenna tuning will change slightly from summer to winter, particularly if there are branches close to the ends of the diploe where the impedance is highest. PTFE or Polythene insulation would certainly be more durable than PVC - if you can find a suitable wire. As this is Top Band and a very long dipole, the weight of the wire may be significant. Obviously the wire has to be strong enough to withstand a bit of a battering where it passes through the trees, otherwiseyour choice would be the thinnest wire that would stand the tension. If you will use PVC, it is probably best to avoid black as this is often PVC coloured by loading it with Carbon black - which is conductive. Lucky you to have a garden which will accomodate a full-size dipole on Top Band! cheers Peter G8BBZ __________________ Peter G8BBZ

3rd Mar 2017, 1:41 pm	#6
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,931	Re: Insulation Versus Insulators Thanks Peter, yes the centre will be on the house gable in the clear. It won't be black as I have a roll of yellow multi stranded copper wire. If I avoid the trees then it would be a "sloper" heading towards the ground also as it is a V then I won't get as much width at the far end. Loppers sound a possible solution. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

3rd Mar 2017, 2:53 pm	#7
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,995	Re: Insulation Versus Insulators Remember that insulation adds dead-weight - which can be enough to cause undesirable stretching of long antenna spans. I was fortunate enough to obtain, some years back, some ex-Military kevlar-cored insulated antenna wire at a rather good price compared with what the taxpayer was originally charged by RACAL: this stuff is tough - like about 140Kg breaking-strain - and a 200-foot single span of it at my "stealth" location has survived without obvious damage for several years. As to feeding it through/over trees - someone I know used a bow&arrow to fire a length of thin nylon monofilament fishing-line over a tree - they used this to haul aloft a thicker length of fishing-line which then pulled the actual antenna-wire up. I guess these days a cheap "drone" would be an alternative?

3rd Mar 2017, 4:06 pm	#9
Guest Guest Posts: n/a	Re: Insulation Versus Insulators The core out of RG213? Or just give it a go with 'ordinary' wire, if the VSWR doesn't change that much dry to wet you are putting out a good signal. Also it's the current (as in amps) that radiate so a bit of high voltage (the ends) leakage isn't very detrimental. Just stick some up, worst case you have a leader ready for posher wire! I have most of a 500m (well it is big, 500m is a guess) reel of submarine grade wire, it is about 1/8th of an inch diameter. You are more than welcome to it, bloomin' heavy but I can't throw it out, much too useful (for someone). If you want it I can take it to work, weigh it and then you can send a pickup label. Drop me a PM.