Can silver coloured covering affect radio signal?

[Ian Jones]

I'm referring to heat shrink covering and trim so that's solarfilm, solartrim, profilm etc.

One roll I have in particluar has a metallic effect, where does that come from?

Since I am about to cover the underside of delta in the stuff this is a serious question because if does shield the signal it will be in a big way!

I would expect this to effect (or not effect) all frequencies but in this case I am talking about 2.4 and so the intention is (was) for internal antennas.

Anyone know?

 

Edited By Ian Jones on 11/01/2013 15:18:57

[Steve Hargreaves - Moderator]

I certainly don't know Ian but intuitively if the metallic effect in the covering does come from metallic particles then I would indeed expect it to mask the RF slightly. Whether this effect will be noticeable or cause a problem is the real question.

There are lots of models out there covered with silver Solarfilm.....I suspect if it was a problem it would be well known by now....Personally I have a small silver covered model with a 2.4GHz Rx inside & it has been fine.....

Personally I think you'll be fine.....

[Martyn K]

Hi Ian,

I wouldn't have thought so, An easy check would be test the resistivity of the adhesive surface, but I would imagine that the colours are simply pigments. There is a possibility that the film may be aluminised, but this will be very thin film and I would imagine that at Radio Frequencies it will be transparent

If you have any doubts, I can do some basic range testing using a Spectrum Analyser and we can check what the attenuation of the film is.

Best wishes

 

Martyn

Edited By Martyn K on 11/01/2013 15:32:20

[Myron Beaumont]

Ian

You could test it by putting a sheet of the stuff between the Tx & Rx . I have had no problems with 2.4 with a caravan aluminium side in the way as an ultimate test ! Unbelieveable really with any signal .Of couse it is possible that the signal could have "bounced" off something so it might not mean much.I'm sure that a forumite could clarify that.

[001]

Ian, I looked into this several years ago, I sent in a complaint to Oracover in Germany about a small fault in some silver Oracover, they sent me ten metres of the stuff, so I was covering nearly everything I built in silver for several months. (P47, Cessna Skymaster, O/D sportster)

I had the same concerns (about 35 mhz then) and did some research (don't remember where). The conclusion seemed to be that the pigment does not have any effect. It certainly does not (Oracover and Solarfilm) conduct electricity. I expect someone more learned will come up with a technical explanation soon.

[Kevin Fairgrieve]

Fully on 2.4GHz and have a Flair Legionarre covered in silver Solatex.

To date I have had no issues. The Rx is a Spektrum AR6200. Not a special carbon job, just a bog standards DSM2.

The RX is located just aft of the firewall, close to the aluminium cowl.

Kev

[Bob Cotsford]

I had a Gladiator covered in silver tex, and that definitely affected the range with FrSky 2.4GHz gear. Not a total loss of signal but certainly a reduction in range that could be detected on a range test. I popped one aerial out of the top of the cockpit and the other out of the bottom and that got me back to full range. It may in part have been the rigging wires and metal struts that were to blame but I wouldn't rule out the tex having some effect.

[Ian Jones]

Well the question was niggling away at me and as we tell newcomers - if you want to know something then just ask.

Thanks everyone for your replies, I'm now convinced there's no problem

Ian

P.S. as I typed the above Bob Cotsford added his reply so I suppose a little caution wouldn't do any harm.

 

 

Edited By Ian Jones on 11/01/2013 17:14:56

[John Cole]

It would if it formed a Faraday Cage. Wikipedia describes this as follows:

A Faraday cage or Faraday shield is an enclosure formed by conducting material or by a mesh of such material.

Your covering is NOT a conductor so NO.

[ken anderson.]

hello ian...when i made this pushycat in november-i was told by the lad in the LMS...to make sure the rx ariel was outside the fuz as the signal wouldn't get through the covering...also i've read on the profilm website about the covering containing a thin foil layer in it...

ken anderson....ne..1....tin foil layer dept

[GrahamC]

It's interesting that we assume that silver might be the problem.

I was just thinking about this and, well rambling on....

If silver might [or might not] be a problem then what about other colours?

What about, for instance white? The most common pigment for white plastics and paints is titanium dioxide which is a semiconductor and is very effective at reflecting UV etc [which is why it is such a white white] Might it also be an effective reflector of RF frequencies too?

[Ian Jones]

Ken, did actually say metal foil? I can't find it on their (Oracover) wbsite.

Hmm good point Graham. Conversley can we conclude form that, that as white doesn't present a problem then other colours won't either?

Water's getting muddy isn't it .

[ken anderson.]

i've scanned the bit on the profilm/oracover instructions about the danger of shielding the signal when using the silver(chrome) coverings.....its a PDF file which i dont know how to display on the forum here---i've PM'd I Jones...if he wants a copy and he may know how to post it for all to see.......

ken anderson ne..1 ..... profilm chrome dept....

[Ian Jones]

Thanks Ken, we'll sort something out.

Pushycat looks nice by the way.

Hang on Ken, think I've managed to find it here, the relevent part being;

"ORACOVER SCALE and CHROME have an aluminium layer of only nanometres' thickness on the backside of the covering film. This layer is designed to maximize colour density and quality. To minimize the RF shielding effect of the covering on a ® fuselage covered with ORACOVER SCALE or CHROME we strongly recommend leading the Rx aerial out of the fuselage by the shortest route and running it out to the leading edge of the fin, or use a whip aerial. The same applies to wings covered with ® ORACOVER SCALE or CHROME: Do not run the Rx aerial along the wing as this too may cause a loss of signal. Always make sure that the Rx aerial has an open destination field. We recommend you follow the same procedure with models constructed from carbon fibre."

Orastick is the self adhesive version of oracover and the same advice is repeated for that.

Okay so what about Oracover in Silver? It appears that is okay... erm I think?

Ian

Edited By Ian Jones on 13/01/2013 11:59:34

[Plummet]

I would expect that any interference would depend upon wavelength. I know that they use glorified tinsel as chaff to disrupt radar. If the conductive particles are comparable in size with the wavelength of the radiation then there will be disruption.

wavelength = velocity/frequency

= 3 x 10^8/2.4 x 10^9 = 0.125m

So the wavelength is 12.5 cm. The metal particles in the film, as long as they are isolated from each other, are probably so much smaller that this that they will have little or no effect. You may have to be more concerned about bits of metal, struts, pushrods, joiners etc. which are in the 3 to 12 cm size range.

Plummet

[ken anderson.]

well done - young ian...that is the one....the pushycat --is the MK 3....... i love the deasign and would recommend it to anyone...........

 

ken anderson ne..1 ....that is the one dept.

Edited By ken anderson. on 13/01/2013 14:26:37

[Ian Jones]

Thanks Ken.

This is all very interesting and relevant because I still have my twin scorpion to finish some maintenance on. In the process I will change it from 35 mhz to 2.4 and it's covering is silver. I was also going to use silver underneath my EF2000 slope conversion and I probably still will do but I think for it's maiden flight I'll leave it off. Might make it easier to work out what went wrong .

Ian

Edited By Ian Jones on 13/01/2013 17:35:19

[ken anderson.]

ian....i'll put a photo on of my install in the pushycat -its top secret......but....since i know you etc.....

ken anderson ...ne...1.... top secret dept...

[ken anderson.]

as promised ......here is the install on my P/Cat....flown now about 6 times.....no problems etc....

no showing anyone else...... ....

ken anderson....ne...1 ....test dept...

[Mark Agate]

A friend of a friend was once flying a thermal soarer covered in the stuff at Richmond Park. He was tapped on the shoulder by a police officer, who said "Heathrow radar report an unidentified object at 1000ft. Please get that thing down."

[Ian Jones]

Posted by ken anderson. on 15/01/2013 10:45:59:

as promised ......here is the install on my P/Cat....flown now about 6 times.....no problems etc....

[Images removed for security purposes]

no showing anyone else...... ....

ken anderson....ne...1 ....test dept...

Ah the Hitec BODA antenna, an excellent device.

I would have thought that the covering on the wing would still make a pretty good shield though.

Posted by Mark Agate on 15/01/2013 11:01:11:

A friend of a friend was once flying a thermal soarer covered in the stuff at Richmond Park. He was tapped on the shoulder by a police officer, who said "Heathrow radar report an unidentified object at 1000ft. Please get that thing down."

At 1000 ft and still visible from the ground it couldn't have been very small.... so would it show up on radar anyway?

Ian

[John Olsen 1]

The shiny metallised covering will certainly shield a radio, it is conductive. You should be able to detect this with a multimeter, although only on one side. Oldies might remember the Echo Satellite, a balloon made from metallised mylar which was used to experiment with bouncing radio signals across the Atlantic. This sort of material is also what "window" or "Chaff", as used for confusing radar systems, is made from. So it is quite probable that a model covered with it would show up well on radar.

I don't know how much the matt silver coating would affect radio, the colouring there will be fine particles of aluminium or similar suspended in a binding agent. The particles are small and will not be in good contact so probably don't absorb all that well, however a test could be a good idea...just wrap a receiver, battery and servo up well in some offcuts and do a range check...see what sort of distance you can get to before an observer cannot hear the servo working any more.

The titanium dioxide pigment in the white (and possibly other) colours will not be a problem, titanium dioxide is a ceramic and these tend to be pretty good low loss dielectrics. Most pigments are going to be Ok in fact.

There is a way of checking if something is a good low loss dielectric...toss a sample into a microwave oven and zap it for a few minutes. If it comes out unharmed it is a pretty good dielectric. If it turns into a gooey mess it was not.

John

[Shaun K]

To add my 10 cents worth, I re-covered a long-faithful trainer and used silver solarfilm on the fuselage.

First flight out saw lost signal a number of times (with 2.4Ghz and internal antennas). At any further than about 80-100m away it was pot luck and required a very hasty return to the ground, which thankfully resulted in a wheels-first arrival.

After relocating the receiver and placing the antenna ends outside the fuselage, all is well again.

Hope this helps your decision, but I won't ever put my rx antenna inside silver film again.

Shaun.

[John Cole]

Posted by John Olsen 1 on 16/01/2013 08:11:10:

The shiny metallised covering will certainly shield a radio, it is conductive. You should be able to detect this with a multimeter, although only on one side.

There is a way of checking if something is a good low loss dielectric...toss a sample into a microwave oven and zap it for a few minutes. If it comes out unharmed it is a pretty good dielectric. If it turns into a gooey mess it was not.

John

1. Not if it has an insulating layer on BOTH sides.

2. I seem to remember reading that operating a microwave oven with nothing in it to absorb the microwaves (such as a glass of water) was likely to destroy the magnetron.

[John Olsen 1]

1. True, although they are unlikely to have made a sandwich, so you can probably scratch through the glue to the conducting layer if it is on the inside.

2. There is no rule against putting a cup of water in there along with the dielectric under test.