[Boatanchors] WE 407 and 408 tubes

[Norman Hairston]

Bill:

They were used by AT&T Long Lines in the 60'S in their Single Frequency 
singling units on long distance circuits and perhaps other applications. 
They were thought to be more rugged than other tubes with similar 
characteristics. I assume that Bell labs or Western Electric ran tests 
to make that  determination. I know they were desired by amateurs but I 
don't recall how used. The frequency of the SF units was at audio level 
so no use in higher frequencies by AT&T to my knowledge.

I know one fellow Ham and fellow AT&T retiree who will know. I will 
contact him and report if any more info.

Norman (Harold)


On 06/11/16 21:28, Bill Cromwell wrote:
> Hi,
>
> I found a 407A and a 408A vacuum tube (also known as valves) lurking 
> in my stash. These tubes seem to have some special or magical 
> characteristics. Can somebody tell me about their special virtues? 
> They seem to focus on VHF. I get nosebleeds starting at 21 mc so VHF 
> tubes are not so special to me (even though I have others that work at 
> VHF).
>
> If it turns out that I don't need them and no audiophile offers a 
> fortune (WE ye know) Do any of you need them to get your radio back on 
> the air? I have one of each.
>
> 73,
>
> Bill  KU8H
>