[ARC5] ARC-5 Alignment Question

[Kenneth G. Gordon]

On 20 Dec 2010 at 15:19, J. Forster wrote:

> The ARC-5s often use metal tubes. Are the inter-electrode capacitance
> variations of such tubes significantly better than glass tubes?

No. They are supposed to be identical, although there is, of course, some 
very minor variations between any two tubes. 

The main reason for metal vs glass tubes in those receivers (IMHO) is 
shielding. The metal tubes are shielded better. There MAY also be an issue 
with "delicate-ness" in that the metal tubes are (obviously) less likely to get 
broken.

However, I have had at least a couple of ostensibly NIB ARC-5 receivers 
which had at least one glass tube in them. Furthermore, I know that the top 
cover often has -G or -GT versions of some of the tubes painted on its 
surface as being suitable replacements.

> Are either metal or glass tube characteristics sufficiently well
> controlled so that a receiver could be fitted with off-the-shelf tubes
> and perform w/in specs without alignment, after initial alignment?

Absolutely, as long as you don't use some weirdo off-brand unknown POS. 

The Mil-spec tubes are all OK, IMHO.

Mike will correct me if I am off here. ;-)

I think you are worrying needlessly. Just put a set of good tubes in it, align to 
frequency, and use it.

Ken Gordon W7EKB