[Milsurplus] NOS ART-13

[Bob Camp]

Hi

The real limit is the dissipation / power in the crystal. Current is part of that. The resistance of the crystal is another part. 

Since P = I^2 x R, the math isn’t to crazy once you know R.

At 40 ma and 10 ohms, you would get 16 mw. 

10 ohms isn’t a bad random guess for “R” at ART-13 sort of frequencies.

1 mw is a pretty typical spec for a large package modern crystal. That of course *assumes* that they put a full sized blank in that HC-6 sort of sized package. Anything past 15 mw is getting into the "too much” range.

Yes, you can do this or that to bump things up a bit. Unless you are doing very fancy crystals, that’s not likely to happen. 

The large blank / open package FT-243’s (and their cousins) can handle more power. A typical drive number around 15 mw (vs the 1 mw on the modern part) is not out of the question on them. Still, they will have a limit. 

Bob

> On Aug 6, 2024, at 10:24 PM, Ken <kgordon2006 at frontier.com> wrote:
> 
> No.  Both of the two transmitters use FT-243s. In my experience, FT-243s start to chirp at currents around 40 mA. Neither of these transmitters chirp.
> 
> As I remember it, one of the builders measured crystal current and it was below 40 mA
> 
> 
> Ken W7EKB
> 
> 
> 
> Sent via the Samsung Galaxy S21 5G, an AT&T 5G smartphone
> 
> 
> -------- Original message --------
> From: Hubert Miller <Kargo_cult at msn.com>
> Date: 8/6/24 17:31 (GMT-08:00)
> To: milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] NOS ART-13
> 
> Re single tube 813 transmitter:
> 
> >A good friend of mine built and operated one of those. Walt Polete near Missoula,Montana. He loved it.
> 150 watts input.  Crystal controlled. I have the original RCA-published article on my web site as a PDF.
> Another ham built one of those recently and operates it, mostly on 40. It sounds good too.
> >Ken W7EKB
> 
> It doesn't eat crystals? 
> -Hue,  K7HUE 
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