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eHam Forums => Mobile Ham => Topic started by: WA1SEY on March 09, 2011, 05:44:18 AM



Title: Stainless steel versus titaninum versus copper for whip
Post by: WA1SEY on March 09, 2011, 05:44:18 AM
Folks:

I am thinking of doing home brew for a whip with a center loading coil for bicycle mobile.

Doing research, it seems to me that copper has far lower permiability (metal resistance) than either stainless steel or titaninum, although stainless steel and titanium are stiffer and lighter.

Originally, I was thinking of using 1/4 inch titanium due to it's strength and lightness (yes, it's expensive, but I am willing to splurge if it's worth it).

Now I hear that titanium is not that great for conductivity and that the resistance for a 10 to 12 foot whip is neary 2 to 3 ohms due to what is called permiability.

It appears that I may have to resort to using copper wire affixed to fiberglass rods.

Is this a reasonable assumption?

What are your experiances with copper/stainless/titanium for antennas?

Thanks

Mark
WA1SEY
Portland, Oregon


Title: RE: Stainless steel versus titaninum versus copper for whip
Post by: KH6AQ on March 09, 2011, 07:00:21 AM
I have performed actual loss measurements at HF on stainless steel vs aluminum whips. The loss of the SS whip is measureable and is in the range you cite. But it is just a small part of the total system loss. Ground loss and loading coil loss dominate and I would use SS for low cost and strength.


Title: RE: Stainless steel versus titaninum versus copper for whip
Post by: K3GM on March 09, 2011, 11:04:09 AM
Wasn't this the premise for Larsen's KulRod whips?  It's a stainless whip that's overplated with copper, then nickel, and then a final layer of chrome.  I don't know how much of a difference it made, but I do know the plating lasted perhaps half of a winter here in the northeast, before the plating was all pitted from the salt spray.


Title: RE: Stainless steel versus titaninum versus copper for whip
Post by: WB6BYU on March 09, 2011, 11:48:01 AM
The fiberglass CB whips with a wire inside aren't a bad place to start for HF work,
depending on what sort of antenna you are planning to build.  The most important
portion (from the perspective of loss resistance) is that part below the loading
coil where the current is highest.  Above the loading coil the current tapers off
to almost zero at the top of the whip, so an adjustable stainless top whip isn't
too bad of an idea.  In the end you may very well end up with something like a
Hamstick, using copper wire wound on fiberglass for the bottom and an adjustable
whip on top - a larger diameter form for the loading coil would help increase the
efficiency, though.


Title: RE: Stainless steel versus titaninum versus copper for whip
Post by: K0BG on March 09, 2011, 01:17:07 PM
The truth is, the higher the frequency, the less loss in 17-7, but there is always some present.

I personally don't like fiberglass whips for several reasons. Down here in the desert SW, they weather really quickly, after which even a small tree limb smack will break one.


Title: RE: Stainless steel versus titaninum versus copper for whip
Post by: KD8DEY on March 09, 2011, 02:35:14 PM
No mention of which band......

I would just go with a commercial made whip such as a hamstick, Hustler , or whatever depending on band......

Dunno how you plan to mount but one of those old truck mirror mounts on a rear rack might be nice... could probably also maybe mount a small gell cell/battery box to one as well :)

Could always tie in one of those little light generators............ :)


Title: RE: Stainless steel versus titaninum versus copper for whip
Post by: KH6AQ on March 10, 2011, 05:43:38 AM
The truth is, the higher the frequency, the less loss in 17-7, but there is always some present.

I personally don't like fiberglass whips for several reasons. Down here in the desert SW, they weather really quickly, after which even a small tree limb smack will break one.

17-7 exhibits less loss with increasing frequency? The permeability must be decreasing with frequency. Can you give us some numbers or a reference?


Title: RE: Stainless steel versus titaninum versus copper for whip
Post by: K0BG on March 10, 2011, 07:34:50 AM
http://vk1od.net/antenna/conductors/loss.htm


Title: RE: Stainless steel versus titaninum versus copper for whip
Post by: KH6AQ on March 10, 2011, 11:45:21 AM
There is nothing there that says the loss of 17-7 decreases with increasing frequency. Just the opposite is what it says.


Title: RE: Stainless steel versus titaninum versus copper for whip
Post by: N1DVJ on March 11, 2011, 06:08:59 AM
Wasn't this the premise for Larsen's KulRod whips?  It's a stainless whip that's overplated with copper, then nickel, and then a final layer of chrome.  I don't know how much of a difference it made, but I do know the plating lasted perhaps half of a winter here in the northeast, before the plating was all pitted from the salt spray.
I got a couple of years from my KulRod before it went into the toilet.  Thing is, it still tuned, but would hardly move a field strength meter placed a short distance away.  Changing the whip pegged the meter.  (I tested first with a coat hanger cut to length and filed to fit.) 

Larson doesn't sell the SS whip anymore.  They used to have a selection of 'colored' whips with matching colored coils.  Now they are just black. 


Title: RE: Stainless steel versus titaninum versus copper for whip
Post by: KC2MMI on March 18, 2011, 06:07:27 PM
Seems like you could take a titanium rod and either insert it into a copper capillary tube, to stiffen the tube, or have it copper plated. Which should be cheap enough even for multiple plating.

If it's really that important to keep it vertical at high speeds...By all means, go for it.


Title: RE: Stainless steel versus titaninum versus copper for whip
Post by: KE3WD on March 19, 2011, 08:11:29 PM
Hell, the titanium would work.  Try it.