[Amps] AL-1500 pi-network capabilities

[Will Matney]

Rob.
Aluminum has several design features that aren't as good as copper for a 
tank coil. Copper has better conducting values and will not get hot near 
as quick. Plus, soldering to aluminum isn't as easy as copper thus 
connections aren't easily made. Aluminum also corrodes forming an 
aluminum oxide on its surface. The conductance, heat value, and 
corrosion all will vary the Q because of the skin effect.

If you recall, house trailers used aluminum wiring years ago. They 
stopped using it over the wire corroding and loosing contact in 
receptacles and switches. While under load, this caused some house 
fires. Now, the only aluminum wire used in homes is the large wire 
coming into the service entrance and some used to run electric heat, 
etc. Then, there is a grease type compound used at each connection to 
keep the wire from corroding in the joint.

Industry uses aluminum wire in large transformer secondaries for welding 
machines, and other types of equipment. All these connections are 
generally welded except where a connection has to be made with a bolt, 
lock washer, and nut. This is generally a strip of aluminum formed into 
a coil.

Antennas use aluminum pretty much as the main components material. This 
is due to the cost of aluminum being cheaper than copper. Plus, aluminum 
is stouter than copper in some respects, according to the type. Aluminum 
could be used in tank coils but it would require larger diameters than 
copper would. The connections to the load and tune capacitors, plus any 
taps, would be harder to make than using copper thus driving up the 
costs. In using an aluminum coil, it would need the ends flattened and 
drilled with holes to fit the studs on the capacitors. The taps would 
need to be made with clamps on the tubing made out of a solderable 
material like plated copper. Then you could run into more corrosion over 
using dis-similar metals. Generally, the studs on the capacitors are 
brass which is a copper alloy. This being said, copper to brass would 
not corrode as easily as aluminum to brass.

Aluminum has it uses but inside amplifiers, I dont think its that great 
as compared to copper.

Best & 73's

Will Matney


Hi Will,

thanks very much for these observations.  I apologize for not giving more 
information.  I naively thought the photos would be enough.  interesting 
what you said about the low frequency coil, as I have heard that having it 
wound on a solid cylinder form may be a problem (heat buildup?).
I wish I had one of the original h.v. transformers.  I would be glad to send 
it to you but I guess the shop kept it.  your comments about coil tube 
thickness and plating very interesting also.
Why don't these amp manufacturers just bite the bullet and make us an amp 
with the needed monster coils?  I don't care about having a compact amp.  I 
want an amp that works well.  If it is the size of a chest of drawers so be 
it.  Where did this mania for having everything smashed into a tiny cabinet 
come from anyway?  Some of these 1.5 kw amps being made today (i won't name 
names) are incredibly small for the p.e.p.  okay, end of rant.  The 
relationship between Q and tarnishing I did not know about.  I guess 
aluminum tube coils are not an option for some reason or surely they would 
be used.

73,
Rob/K5UJ