Carbon poles & vertical antenna

Equipment Antennas
1

Hi,

I measured the impact of 2 carbon poles and 1 fiberglass pole on the resonance frequency of a vertical antenna. Impact of both carbon poles was significant, impact of the fiberglass pole was negligible.

Carbon poles:

  • Decathlon Caperlan Lakeside 5 travel, 6 m
  • Sotabeams Carbon 6, 6 m
    Fiberglass pole:
  • Decathlon Caperlan Lakeside 1 travel 600, 6 m

Antenna:

  • Endfed 5.05 m wire with a loading coil at 1.73 m from the top, which brings it to half wave resonance at about 14 MHz. Fed at the bottom at the high impedance end. This antenna is designed by Peter @OE5AUL. Antenna’s end fixed to the pole at about 5.5 m from bottom.

Setups:

  • Pole vertical, antenna hanging down, running directly along the pole.
  • Pole slightly tilted, antenna hanging down vertically, (projected) bottom point of the antenna 1.05 m from the foot of the pole.
  • Pole tilted like above and pole rotated twice, resulting in two antenna turns on the pole’s top.

Results, resonance frequencies in MHz (measured with nanovna):

                        vertical pole, tilted pole, tilted + 2 turns         
Lakeside 5 (carbon):    12.3(1)      , 13.95      , na
Carbon 6           :    12.9(1)      , 13.92(2)   , 13.0
Lakeside 1 (fiberg):    14.76        , 14.83      , 14.81

(1) small changes (centimeter) of antenna position resulted in big change of res. frequency
(2) additional 1 m distance of antennas bottom point from poles bottem point -> 13.97 MHz

Conclusions:
Carbon poles might have significant impact on the resonance frequency of a vertical antenna. You can/need deal with this by tuning the antenna, but question arises, if losses are increased by the carbon pole. Unfortunately, I don’t know. I feel uncertain, if I’ll use a carbon pole with a vertical antenna in the future. At least, I would tilt the pole. - I would like to try next, if a short piece of insulating cord between the top end of the antenna and the fixation at the pole reduces the influence. And I’ll like to find a way to measure the losses induced to the antenna - any ideas on how to do this? Measure the quality factor Q of the antenna?

73
Axel, DF1ET

7 Likes
2

Hi Axel,

For your info the Lakeside 1 Travel 600 is glasfibre and not carbon fiber.

Quote:
Material

  • Glasfaser

EDIT: Sorry I missed that you used it as reference.
I can confirm your observation.

But I have tested the 2m / 145MHz Wire J-Pole with the 4 m Lakeside- 5 (that is carbon fibre) and measured changes of resonance frequency by about 10 to 15 MHz if the antenna is fed along the pole.
A distance of at least 10-20 cm would be needed to avoid interference.

For dipoles or inverted-V setups it of course is not a problem.

73 Joe

2 Likes
3

Hi Joe,

You are right, first one is lakeside 5, not 1. I fixed this.

Thank you
Axel

4

Hi Axel,

interesting experiment; thanks for sharing; I will take it into account.
I use to deploy my HF antennas inverted vee, and so far all fine but in case of a vertical the carbon pole could affect.

Thanks again.
73 de Ignacio

5

Hi Ignacio,

thanks for comment!

73
Axel

6

I have found that some poles and tent tubes described as fibreglass clearly contain materials that affect the resonance of antennas I have taped onto them.

On 144 mhz, a wire dipole resonant on 144 dropped to 130 MHz or so, when taped to a spreader made from tent poles (the type that go into dome tents with metal connectors). The metal ends were beyond the dipole wire. The same dipole taped onto electrical conduit (grey) was close to the expected resonance based on a 5% end effect adjustment.

Another antenna (Coaxial dipole) which resonates on 146 MHz when taped to some poles dropped to around 127 MHz when taped to a pole purchased online from an Ali Express vendor. This pole was not labelled as containing carbon fibre, but a different pole that IS labelled as carbon fibre did not affect the resonant frequency of the antenna. Others labelled as carbon fibre may well affect resonance. I think this is a matter of inaccurate labelling or random manufacturing rather than something that can be taken as a general guide to materials.

A longer pole that had collapsed and broken was analysed for losses in a microwave oven. A small glass of water was included as a dummy load. No significant heating of the fibreglass material was observed.

There seems to be no common thread among my findings. I would recommend checking and assessing each pole material before assuming anything about it.

Before taping an HF vertical to a pole I would check for the pole’s effect on resonance before assuming anything about it, including resonance changes and losses. However I think it is safe to use a pole of any material to support a wire antenna that is well spaced from the pole.

73 Andrew VK1DA/VK2UH

2 Likes
7

Carbon fibre most definitely conducts electricity, You can prove this with your trusty Ohmmeter. Carbon film is one of the most common forms of electrical resistor. So the pole is not just a conductor it is actually a lossy resistor. The use of carbon is fine to support the central (neutral axis) of a vee or dipole. but to support a vertical or EFHW where the carbon element is coupled to the radiating element it is a source of RF loss and de-tuning. I also fit an end fed 1/2 Wave on the top of a carbon pole for 2m FM. The pole has no effect on resonance.

Some years, ago I tried installing a 1/4 Wave 40m vertical wire close to the trunk of a convenient fir-tree. The effect was a totally deaf rig. The tree was subsequently felled.

Regards
David
G0EVV

8

Hi

since last summer I have often used a 2 x 9,2m Up & Outer antenna on a 12m high fiberglass mast at my SOTA activations, because this antenna has achieved better reports in several comparative tests than my inverted-V-linked dipoles in 6-7 m height, which I have used for many years. However, the weight of the 12m fiberglass mast of 1,9 kg is somewhat annoying. So I looked for an alternative weight-saving alternative and bought a 12m long fishing rod made of carbon reinforced plastic on Ebay from China. This rod weighs only 850 grams.

For a first comparison test I built a second identical Up & Outer antenna and set up both antennas on a meadow with the fiberglass mast and the carbon mast side by side. At both masts I wrapped the vertical wire around the mast with a few strokes and stretched the horizontal wire diagonally above the ground. The comparison test was very clearly: the antenna on the carbon mast brought several S-steps lower RX signals, I didn’t even carry out a transmission test …

Then I did not wrap the vertical wire around the mast anymore, but led the wire downwards parallel to the mast with some distance to the carbon. I used two ATUs for this comparison and could quickly switch between the two antennas: When receiving and transmitting I could not find any difference between the antennas and my QSO partners also reported no difference. Therefore I use the Up & Outer with the carbon mast now. I tried out the antenna from 60m to 10m.
Some fotos showing the UP&Outer:

IMG_0575
IMG_05753888Ă—2592 1.54 MB

IMG_0574
IMG_05743888Ă—2592 3.47 MB

IMG_0576
IMG_05762592Ă—3888 1.22 MB

73 Lutz

5 Likes
9

Hi Lutz,
Very interesting, thank you for sharing!
Axel

10

HI,

Just for my information, what ATU do you use with this antenna and what bands can you work on ?

73 Patrick TK5EP

11

Hi Patrick,

I use a LDG Z100+ tuner and a homemade 1:4 hybridbalun described from ZS1AN. I built both things together in a plastic box for an easy use from 60m to 10m.
73 Lutz

12

Hello Lutz - when you write “2 x 9.2m Up & Outer” what do you mean? Does that mean 1 length of wire 9.2m long running vertically, and the 2nd length of 9.2m running horizontal to your operating position? From the one picture it appears as if the wire comes down the beside your mast, stopping some distance short of the ground - then running horizontal. So is one wire the radiator, and the other the counterpoise? And using the 4:1 balun between them? Thanks.

John VE7JBT

13

Hi,
You only need a few longitudinal fibres to make the pole very strong. There is not a lot of carbon in a typical mast/ pole.

They are well insulated in the resin so measuring resistance on an undamaged pole is not easy. The resistance of individual files is moderate. It’s different to the material used in resistors.

The combined dielectric constant of the composite will detune an antenna in close contact.

The fibres have a similar effect to thin metal wires in the mast. Not as large an effect as a metal tube but certainly enough to detune taped on aerials.

The losses in a section of mast in a microwave would be small as there is no closed circuit - exception if half a wave long at UW freq then high currents could be induced in them.

Similarly unless the mast sections are resonant lengths then the losses should be low. The apparent loss effects mentioned here are probably detuning effects.

Life is easier if you can keep your antenna away from the mast instead of taping it to the mast.

73
Ron
VK3AFW

1 Like
14

Hello John,

please search for: WB3GCK the “Up and Outer Antenna”
Here you will find a very good description.
I am currently on holiday in the netherland and have to write on my little phone…
73 Lutz

2 Likes
15

Thank Lutz - 73 de VE7JBT - John

16

Lutz,
Can you share the ebay seller for this 12m pole ?
73 Patrick

17

Hello Patrick,

I checked again, I didn’t bought the fishing rod on ebay but on amazon from the provider LZH Fishing. Please excuse my mistake.I ordered the 13m long rod and removed the thinnest upper element.

“LZH FISHING Carbon Angelruten 8 m-15 m Ultraharten Teleskop Spinn-Ruten Angeln Rod Freshwater Feederrute, 13m
Seller: TengFeiDongZi”

73 Lutz

18

Thanks Lutz,
I found something similar… Sellers are appearing and disappearing quite often… :grinning:
The folded pole looks quite long… a bit long for hiking.
I have a 10m DXwire pole which is 1.3 kg but only 67 cm, and … cheaper.
But 13m would definitely be better !

73 Patrick