[Boatanchors] Crystal Current

[Brian Carling]

Hang onto your incandescent lightbulbs! Some crooks will make them illegal soon. CF lamps will cost 10x the price and you can't monitor Xtal current with those or LEDs.

Best regards - Bry Carling



> On Apr 27, 2014, at 7:36 PM, Bill Stewart <cwopr at embarqmail.com> wrote:
> 
> 
> Tnx for the replies. 
> What brought this request on was an article in the Jun 1933 'Radio' mag. 
> They show a one tube osc/xmtr using a 2A5 tube. In the following month 
> they have a one tube amp for the osc, using a 210. My concern is the 
> xtal current. They, of course, were using the big round Bliley type xtals... 
> probably a bigger slab of quartz than our modern xtals. They suggest, in 
> other osc articles, the use of the fil. of a '99 tube as a fuse in line with the 
> xtal...the same as using a p. lamp now days. I think the '99 draws 60ma..... 
> so not too far from the p. lamp fuse. I have used a p.l. before and they 
> provide a good indication of the xtal current. I wanted to know if modern 
> xtals might safely work in this circuit. 
>   
> Tnx Mac, for the 40ma max recommendation. That might put the FT-243 
> types just in the danger zone. I think, in this circuit, that the grid leak across 
> the xtal (20-50K) can be adjusted for lowest xtal current along with keying 
> quality. Also, the B+ may also have some bearing. After these adjustments, 
> maybe ye ole FT-243 would work ok. Might be worth a try. 
>   
> As a side note, I am looking for a 1930s style 80m xtal...3530-3570kc or so. 
>   
> Tnx, 73 de Bill K4JYS 
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