That makes complete sense. Thank you.
I re-read the original RCA article and the schematic.
Turns out I mis-remembered power: it is 150 watts output, not input, and RCA said it would provide 100 watts output plate-modulated 'phone, although they didn't give details.
There is also a 2V lamp in series with the crystal, and instructions include keeping the lamp "dim".
Keying is by screen, which requires a high-voltage (2500V) capable keylng relay, and instructions to never use a straight key in place of the relay. Duh!!
Anyway, I know of at least two examples of the transmitter being built and operated successfully, one by Walt Polete W7JIZ in Montana in about 1960, and the second one by W7QQQ only a couple of years ago.
I have photos of QQQ's rigs ( two versions) on my website at the link I provided earlier.
I have worked QQQ's rig on 40 meters. It sounds very good. No chirp or drift. I didn't hear any clicks either. It exhibits a kind of "bell-like: tone.
Ken W7EKB
Sent via the Samsung Galaxy S21 5G, an AT&T 5G smartphone
-------- Original message --------
Date: 8/7/24 07:21 (GMT-08:00)
Subject: Re: [Milsurplus] NOS ART-13
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
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 --------
Date: 8/6/24 17:31 (GMT-08:00)
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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