copper that is moist and/or has other metals and ions (wiring and pipes in unventilated crawl spaces) might rot significantly in our lifetime.
We're talking decades, depending on the acidity of the water/environment. Also keep in mind, copper pipe (and 16oz copper roofing) is very thin stuff compared to 6 gauge copper wire. Of course, leaving the excess flux on when soldering copper can hasten the process, heh.

The lower units (aluminum) of unprotected outboards (or inboard/outboards) can be eaten away in just one season in the presence of stray electric currents (like from a trickle charger) in salt water. Especially if the hull is painted with a copper based anti-fouling paint.

You have to admit it's not bad for an antenna almost a half century old.
Yeah but, about 45 years of that were spent inside, heh. Its only been kept around because its small and of course it does still work (only about 10dbi) despite its looks.

Followed posts for awhile and now will try to build one. Since silver has a higher electrical conductivity than copper and the received signal is picked up on the surface of the elements, if I sweat lead free silver plumbers solder over the surface of the copper, would I gain any more signal? Copper oxide does not pass signals well and silver oxide seems to have no effect. I have noticed high priced military wire is silver or silver coated copper.

You could, but the difference after all that work would be in the hundredths of a db. The difference between silvers conductivity @ 63.01 × 10^6, and coppers conductivity @ 59.6 × 10^6, is much smaller than the difference between coppers and aluminums conductivity @ 37.8 × 10^6.
http://en.wikipedia.org/wiki/Electrical_conductivity

(I used to think gold was the best, but I guess not. Didnt want to use it anyway, heh)

I guess if you really wanted to, silver plating using various techniques and an old silver spoon would be cheaper, quicker, easier than spreading silver solder all over the elements. Of course, silver tarnishes pretty quickly and it wont have that shiny look for long, heh.

I seem to remember that the silver passed high frequencies better than copper , perhaps that was the point I was getting at, along with the silver tarnish was still conductive. Silver spoon Hmm...

The surface effect is at the surface of the conductor. As the copper forms a protective non-conducting oxide coat, the surface effect will move in a few microns. I don't think it's anything to worry about - at least, I don't recall ever hearing of anyone having issues.

Nah, it only changes the velocity factor a bit, so that would be shortening it, adding to the high end of the bandwidth spectrum a bit. As Martha Stewart would say, thats still a good thing, heh.

I seem to remember that the silver passed high frequencies better than copper
Hmm, based on that I ran some 4nec2 modeling tests on my bi-quad wifi antenna model at 2402mhz. The results: Copper - 10.3 dbi gain, 1.05 SWR. Silver - 10.3 dbi gain, 1.05 SWR.

I guess I have to rephrase my earlier statement, heh. The difference seems to be in the thousandths of a dbi.

Keep in mind, you can throw off an antenna build by at least a full dbi or two by poor workmanship, heh.

I’ve been reading through the “sometimes-lively” discussion here about conductivity of various metals and the benefits of some metals over others (usually favoring copper and aluminum). I’m still more than a little bit confused, so much so that I think my hair hurts.

I can understand the benefits of considering the best possible conductivity metals for the zig-zag elements, since that is where the signal is transferred electrically to your set. But what about the rod reflectors (which are only parasitic, with no direct electrical connection) ?

Previously, it seemed that many different metals and sizes were considered acceptable for the rear rod reflectors. Are we now saying that conductivity choices for those may be critical also?

But what about the rod reflectors (which are only parasitic, with no direct electrical connection) ?
Much less important than with the driven element, and a lot of times you use much more reflector material than element material. Because aluminum mesh is very expensive, painted steel and galvanized mesh are commonly used, even on commercial antennas. The large parabolic reflectors were generally aluminum due to weight issues, which becomes an important issue when a lot of steel is used. Even 1/4 inch steel rod is heavy and small steel tubing isnt that common. 1/2 inch steel EMT (7/8 inch OD) is cheap, but then you have the issue of wind resistance and some weight. Hard, straight, copper tubing in 1/4 and 3/8 inch sizes also isnt that common, and then you also have the issues of weight and cost to consider.

Much less important than with the driven element, and a lot of times you use much more reflector material than element material.

300ohm, thanks for your excellent, very detailed explanation. This supports my general understanding from reading earlier threads on this forum.

But, since the issue was raised in this thread, I have to ask the question: Can galvanized metal (steel) be used effectively as reflector rods, or will there be a performance penalty? From your cited examples, if galvanized mesh is commonly used on commercial antennas, by extension it would seem that galvanized steel (i.e. zinc-coated steel) would be acceptable. In other words, is there any downside?

My local Lowes sells pre-packaged 50 foot rolls of 9 gauge general purpose galvanized wire priced very reasonably (works out to be less than 18 cents per foot). Unexpectedly, when I measured the wire, the actual diameter turned out to be 9/64” (which is really closer to #7 AWG -- a bonus). Don’t know if that was an aberration with the roll I purchased. When straightened, this material could be a cost-effective source for reflector rods, since many of the other materials can be more-costly or are less-commonly available (as you correctly noted). However, of possible concern still might be any weathering or galvanic corrosion (dissimilar-metal) issues.

Are these assumptions reasonable?

Are these assumptions reasonable?

Yes, I think you have the right idea.
In other words, is there any downside?

The weight for the size.
Any performance penalty can generally be made up for with more metal on the reflector or directors, that seems to be their nature. Elements though, are a little different.

The weight for the size.
Any performance penalty can generally be made up for with more metal on the reflector or directors, that seems to be their nature. Elements though, are a little different.


Everything you have said makes perfect sense to me, and has helped my understanding tremendously.

Thanks for the clarification and the helpful guidelines. For the reflectors, I understand that material choices will always tend to be a tradeoff between reflector size vs. reflector weight (and certainly cost).

Are there any differences between soldering copper and soldering aluminum? I need to solder aluminum feed lines to aluminum driven elements. What is the appropriate solder to join aluminum?

Are there any differences between soldering copper and soldering aluminum? I need to solder aluminum feed lines to aluminum driven elements. What is the appropriate solder to join aluminum?

soldering is with copper

aluminum needs to be welded

easiest for home user is to mechanically fasten with nut and bolt

Theres this alumarod / Durafix aluminum soldering rod thats advertised on infomercials :
http://www.durafix.com/

Ive never used it, and the electrical conductivity is 24.9% of copper, so I dont know if it would be good for aluminum antenna elements. It looks like interesting stuff, but its pricey.
Edit: that puts it at just a little worse conductivity than brass (but better than stainless steel), so it may be OK for antenna use, if aluminum to aluminum contact is maintained (as in copper soldering).

I wouldn't recommend soldering alum but here (http://www.aws.org/wj/2004/02/046/) is some tips.



Various aluminum alloys have different solderability: 1xxx, 2xxx, 3xxx, 4xxx, and 7xxx are easier to solder than the 6xxx series alloys. Due to their magnesium content, 5xxx series alloys are the most difficult to solder.

Since most alum you can find at home stores and such are 6xxx series =/

Seems aluminum elements and feed lines is a bit of trouble, as opposed to copper. Consequently, shouldn't the recommendation for most appropriate metals for elements and feed lines for a DBGH be copper ?

Copper is what most use, for its better conductivity and workability (some types of aluminum are brittle and break when bent). But if you dont have to solder, aluminum also works fine. I used old Radio Shack aluminum grounding wire (no longer available) on my first GH build. And chromed aluminum 1 inch formica edging on my foldable SBGH. mlords builds are all aluminum. (but he also ran into the breakable type of aluminum)

Heh.. another forum member was over here the other night to look at the antenna setup, and I went to show him how brittle that T6 aluminium is.. except the scrap cutoff piece I chose then bent nicely without breaking!

Which means that, somewhere in my stock of 1/4" alum rod, is at least one bit of softer bendy aluminium. Dunno which one(s), though. :)