SIRIO 827 ... MODIFYING RADIALS

GOOD MORNING ALL

     Been thinking about replacing the radials with copper rods , available from eBay quite cheaply ,  in the correct diameter and length , I am at the stage of putting this into practical , thinking along the lines of removing the rods with there copper connectors and coating copper rods with clear  coat to stop them tarnishing , alloy conducts at around 60% where as coper conducts at about 99% theory should give good results may even look at replacing the whole antenna section by section for copper tubes , input ,advise ,  greatly received

 all the best

Hi, I'm not sure if you would see any benefits in doing so to be honest

I know, 60% difference seems big but...

To put this in perspective, the difference in resistance between copper, which is the most conductive metal used for antennas and stainless steel, the least conductive metal used for antennas is 0.0000006732 ohms (or 6.732 micro ohms) per meter squared.

Its a case of perspective, from one perspective, what is actually a very small difference in the real world is made to sound much bigger than its real world effects.  When it comes to metals, however, the reality is when you get past a certain point (such as five or six 0's in an exponent) even a large percentage difference in conductance/resistance really doesn't mean much.

Also, we are talking radials, which when set up properly don't actually radiate any significant amount...


The DB

The DB wrote:

Also, we are talking radials, which when set up properly don't actually radiate any significant amount...

M0MSN has just done a good video on Youtube demonstrating this with an EMF meter to demonstrate this with ground radials. It was only when running a couple of hundred watts, almost touching the radials and within a few metres of the antenna that he started to get any readings. 

https://youtu.be/_wJVo9vluFI

I can understand your thoughts on it. I had similar thoughts in the past. From my experiments I deduced no noticeable difference when changing the material used for the radiator or ground planes on a 1/4 ground plane antenna (I know not the same as yours but still a radiating element and ground planes). The only thing that did change going from steel, to ali to copper was the sizes.

I did choose copper to make a 1/4 radiating element earlier this year, but that was only because I got a nice new piece of tubing cheap and it's loft mounted, so no wind. Unless you find some very thick copper tubing I wouldn't try swapping out the whole antenna section because copper of the same thickness as your current tubing will bend in the wind and stay bent.

If you just want to make your antenna look a little different, then there's no harm swapping out those radials. It would just be a cosmetic choice though. Personably I like the copper look.. I named my 1/4 Ygritte (from game of Thrones) because of it's two legs and copper colouring. ..you probably didn't need to know that bit.

To be honest, you're basing the substitution 'gain' through differing VF's between materials badly.

Now where copper (pure copper or the equiv to 90%+ copper alloy used in power cabling) has a notably different VF and efficiency though distribution, it's far more significant in driven elements and feeder than in radial usage.

Now where you can make radials in a wide range of variations centered on a base of 0.4 of lambda (wavelength) and as such there will be some difference between 0.4 lambda in copper and 0.4 lambda in aluminium, any imbalance or change affects how the radial acts as a modifier to radiation pattern shape and firing angle, just as height. Similar, in earthing terms effectively to how height between a particular lambda multiple or division range can greatly impact the effective impact of impedance, effective resonance at centre freq and BW and also the firing angle and pattern at the basic core level.

So, as with anything, quantity of metal and the distribution in pattern of radials and whether they remain air-spaced from the pshysicai ground and if your radial array has an actual electrical bonding to true ground has far more impact in practice than the VF of radial material does to efficiency.

Now that's talking about the usual unbalanced (Marconi type) antennas.

Where you will stand to see difference that's tangible is when you are talking hertzian antennas aka balanced types.

This balance shift of 'radial' impact material wise is far more significant on balanced types. Because balanced types use the mirror partner of the driven element as a fixed balanced counterpoise (hence 'balanced' antenna, you'll find mismatched use of say two different constructions of balanced elements (be it types of metals, form differences, diameter and density) all have a much more distinct impact on the balance.

So just as adding extra arms to the offset/counterpoise side of a balanced antenna disturbs and disrupts many things and small disturbances become big in how they are part of a cascade of imperfections affecting the balance, adding the same to the driven half restores the balance more than effects efficiency overall (it's the imbalance that's significant where there's an offset in material deviation between the balance sections). Likewise, balanced antennas are typically more sensitive to installation height than unbalanced as unbalanced use the relationship to actual earth/group as their counterpoise but you can makeshift a vertical antenna in a near ground install and be operational where say a dipole's characteristics differ much more considerably when the physical ground/earth sits very close indeed near-field wise.

So whilst there's a theoretically sound reasoning to use higher VF and higher efficiency alloys on grounds and radials, it's mostly on actual grounding (I.e. physically bonded earth grounding) where you'll see significance to the theoretical thinking more than passive radials which are inductively coupled to the physical ground.

It's the manner in how the counterpoise (on vertically polarised) or the balanced pair as a whole on horizontal polarised use as installed and it's inductive relationship to ground that directly and significantly affects balanced antennas, which is why there's effectively a minimum suitable height (relative to lambda) where balanced antennas settle to their design characteristics and achieve their unity or better passive gain characteristics, but above a certain height over a multiple of lamba where you actually disturb and disrupt it's unity+ (unity or better depending on specific type).

So long wires are fairly resistant to ground proximity but benefit from some height, but it's the grade of it's physical bonding to earth that matters, just as verticals can have a wide range of distorted through low through high patterns of radiation pattern depending on their height, how they are physically bonded to the earth or not, amongst many variables but it's the nature of the distribution and it's reflective impact that mostly affects verticals beyond physical dimensions relative to lambda once you pass the minimum requirements for technical resonance.

I say technical resonance, because true resonance where there's a very notably S-parameter dip between how quickly it falls from poor resonance to distinct resonance that's as much to do with efficiency as anything. You'll find a technically deep dip resonance has a notable efficiency difference to a shallower technically wider spread example of technical resonance. Equally, the efficiency roll off as you leave the dip of a deep dip resonance becomes more notable quicker than the more marginal shallower example.

There's a world of difference between technical theoretically sound small but mathematically high proportional differences - which is part of why many model technically mathematically sound constructs in virtual modelling can actually be utter failures when you actually translate to metal and put in a real world context, where characteristics are probe to shifting when it's in a very analogue true physics defined world.

And whilst it's a bit off topic - that difference between accurate real world corrected refined use vs mathematically accurate known characteristics is why it's incredibly rare to get an off the shelf antenna and it just performs by the book to spec, since most characteristics claims are an amalgam of a choice of context distorted factors and technical characteristics based on the basic design.

Take note guy's.
A5H5ATAN1C knows everything

Blimey lol