Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Antenna Wire - Stranded or Solid - Which is best?  (Read 7419 times)
KE7CIE
Member

Posts: 5




Ignore
« on: March 21, 2005, 08:09:11 AM »

I am a new ham and am getting conflicting advice on antenna wire.  I use an ICOM AH-4 and currently stranded 12 gage copper wire.  I have one ham friend that states stranded copper wire is the best because of the more surface area for radiation with the bundled wires.  Another ham friend states that RF "like" smooth surfaces for radiation like copperweld solid wire.  I have just stated the gist of both arguments, but both seem to make sense.  They are both very polar about their arguments and the problems with the other type of wire. I work primary hf in the 40 meter range and primary cw.  I would appreciated the communities advice and experiences.  Does it really make a difference?
Logged
K5QBX
Member

Posts: 1




Ignore
« Reply #1 on: March 21, 2005, 08:20:06 AM »

Why argue the point...build the same exact antenna out of both materials and experiment.  That's the nature of this hobby.  If that's more than you want to do, like the guys at the drag strip say...run what you brung!  In other words, use what's on hand...or cheaper.  I don't believe you'll see a noticeable difference at the frequency you are using.  As a side note, stranded is usually easier to work with...both types are readily available from your local electric supply house.  You normally don't need to be a contractor to buy in bulk, just go to the "will call" desk and make your request.  I bought 500 feet of 14 gauge stranded, insulated wire for about $20 bucks recently and it seems to work just fine.  Enjoy your new hobby...

            Fred
Logged
K0RFD
Member

Posts: 1368




Ignore
« Reply #2 on: March 21, 2005, 08:32:06 AM »

ditto.
Logged
AA4PB
Member

Posts: 13032




Ignore
« Reply #3 on: March 21, 2005, 08:32:21 AM »

Basically they are both wrong. The added surface area of stranded wire won't make a detectable difference on the HF bands. The difference in the "smoothness" of the surface of solid wire won't make any detectable difference either.

Personally I prefer solid copperweld to stranded copperweld because when the tension is removed it tends to lay relatively flat instead of coiling up into a bundle like the stranded copperweld. That makes it easier to work with. Electrically there is no difference.
Logged
AA4PB
Member

Posts: 13032




Ignore
« Reply #4 on: March 21, 2005, 08:36:37 AM »

The problem with copper wire purchased from the electrical suppliers is that it is "soft draw" and will stretch when you suspend it in the air. That may or may not make any difference, depending on the particular antenna. I prefer copperweld because the steel core makes it stronger and it won't stretch.
Logged
WB2WIK
Member

Posts: 20666




Ignore
« Reply #5 on: March 21, 2005, 08:55:43 AM »

Solid wire (not stranded) actually has lower surface impedance (inductance) than stranded wire of the same gauge; so, when dealing with very small desired values such as a ground wire, where "zero" impedance would be desirable, solid works better.

However, in an antenna where usually the radiation resistance is about 50 Ohms or higher, it really doesn't make any difference.  To make a measurable difference you need to not just change from stranded to solid but make a quantum leap in radiator diameter, also: Like going from #20 gauge wire to 1/2" diameter tubing.  A lesser change is too insignificant to measure.

Copperweld is strong, cheap and very available; however it is "springy," whether solid or stranded, and I'm not a big fan of copperweld only for that reason.  I prefer to use multistrand, insulated copper wire.  The more strands it has, the more flexible it is, and the easier to work with.  To help keep strands from fraying/breaking as birds land on it and such, I go for the stuff with a strong insulating jacket, which protects the wire but still provides excellent flexibility.

I have spools of #12 gauge insulated, stranded with about 100 strands or so.  I can coil it up so small that I can literally stuff a 40 meter dipole into my pocket, climb the tower, grab one end of the roll, and let the rest drop to the ground -- and it will uncoil itself gently and straight, dropping straight down without any attempt to hold its coiled up form.  That, for me, is a huge advantage in doing antenna work.

I might go to copperweld for a 160 meter dipole, because it's so long and great strength is required to keep it taut.  But for the "higher" bands (80m on up), the soft, stranded stuff works great for me.

WB2WIK/6
Logged
K0IZ
Member

Posts: 742




Ignore
« Reply #6 on: March 21, 2005, 10:17:42 AM »

First the theory:  Propagation on a stranded wire is slower than solid because the RF (which flows on the surface of each strand)actually has to travel farther than on a smooth (solid) wire.  This effect can be best seen with high grade coax with stranded center conductor vs that with solid.  All of the super-low loss coax uses solid for that reason.

Now for the practical:  For a wire antenna, it makes no difference.  Use whichever you have, or prefer.  Continuing with the practical, stranded hard-drawn copper (14ga) is my preference since it is much easier to work with compared with copperweld (very springy, don't let that spool get away from you!).  Radio Works and other places sell a nice 7-strand 14ga hard drawn wire at reasonable cost (about $.09 or $.10 per foot).  For 12ga wire (longer antenna spans), I haven't found an equivalent, but have used the Flex-Weave (many, many strands, very flexible, almost like small rope, you can even tie a knot in it).  There is also a 14ga version.  However Flex Weave is more expensive and thus not my first choice.

House electrical wire (stranded THHN) sold by Home Depot, etc is quite cheap.  However it is insulated (and thus the resonant frequency will be a little different from bare of same length).  Also the insulation makes it heavier (more droop, sag), and as pointed out above, is soft copper, and will over time stretch (wind and ice will accelerate this process).  So THHN is best used for shorter antenna legs and places where you might want some insulation (tossing a wire directly over a tree limb, for example).

John.
Logged
AA4PB
Member

Posts: 13032




Ignore
« Reply #7 on: March 21, 2005, 11:07:07 AM »

I wonder how the skin effect plays out when the strands are not insulated from one another. Does the current follow the surface of each strand or does it flow from strand to strand since they are in contact?
Logged
N6AJR
Member

Posts: 9927




Ignore
« Reply #8 on: March 21, 2005, 11:52:38 AM »

any antenna is better than no antenna at all.

I use what ever is cheep.  current I have several rolls of 22 g teflon insulated stranded wire, I bought on ebay for $5 plus $4 shipping for 1000 feet each.  so this week that is the best wire made for antennas.


its is really 6 of one , half dozen of the other.

its a hobby, if the wire is cheep enough, long enough and strong enough, use it.

I have used 18 and 20 g painted magnet wire for antennas ( almost invisible)

here is a nice antenna for flat top, inverted v or sloper

http://www.hamuniverse.com/multidipole.html
Logged
K0IZ
Member

Posts: 742




Ignore
« Reply #9 on: March 21, 2005, 12:10:54 PM »

Re AA4PB's question, there is a difference between strands insulated and touching.  Litz wire has strands individually insulated.  Ordinary stranded copper antenna wire is of course not insulated strand-to-strand.  Thus the flow of RF on the surface is actually a hill-and-dale, with a spiral direction.  Visualize water seeping along the wire, taking longer to go a distance vs a nice, smooth pipe.  

But again to the practical, makes no difference in HF wire antennas.

John
Logged
WA6BFH
Member

Posts: 646


WWW

Ignore
« Reply #10 on: March 21, 2005, 12:12:05 PM »

Some pretty good commentary all the way around -- for the HF bands and lower.

If ever you have similar concerns about the VHF and particularly UP frequencies, consider these points again more carefully. All that was said for whatever range of RF is true; it just makes a greater apparent difference at higher octaves of frequency!

You will see the evidences of this in some military UHF antennas. Smooth large surface area antennas of conical geometric shapes. One that has long intrigued me is a sort of dipole (conical) that looks like two smooth very modern looking salt shakers mounted end to end. It will cover a frequency spectrum range of 400 MHz to about 2000 MHz with virtually no loss!
Logged
K5LXP
Member

Posts: 4535


WWW

Ignore
« Reply #11 on: March 21, 2005, 02:17:21 PM »

I use Flexweave wire as found at an advertiser here at eHam, Davis RF.  It has high stretch resistance but is very flexible.  It can be purchased with or without a very UV and abrasion resistant coating.  From an RF standpoint the actual wire used makes little difference, but keeping it up in the air is more of a challenge than you might first imagine.  The Flexweave costs more, but I don't like to rebuild my dipoles very often.


Mark K5LXP
Albuquerque, NM
Logged
K1CJS
Member

Posts: 6061




Ignore
« Reply #12 on: March 22, 2005, 10:57:49 AM »

On HF frequencies, it makes no difference.  Solid wire is not prone to bunching up in a knot like some stranded wire will.  On the other hand, stranded wire may be easier to work with and may give where solid wire could break.  There are advantages and disadvantages to both.  Your best bet is to use what you feel comfortable using whether it be because of ease of use, availability, or cost.
Logged
WB6BYU
Member

Posts: 13567




Ignore
« Reply #13 on: March 22, 2005, 12:18:35 PM »

Basically, for HF wire antennas, the choice of wire is
based far more on MECHANICAL considerations than ELECTRICAL
ones.  In most cases you won't notice any performance
difference with different wire types, as long as the
antenna stays up.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!