[ARC5] Transmiitters: Parameters?

[Dennis Monticelli]

Ken,

Data from a T-22 measured in 2001.  All measurements key down.

Vp = 468V
Ip = 106mA
Screen = 245V
Osc - 210V regulated via VR tubes
Grid bias = -52V across 16K (measured the R)
Grid current = 3.25mA
Coupling control at max
Pin = 49.5W
Pout = 27W  (54% efficiency)

I have since boosted the raw DC and added regulation to the plate, running
it at 500V. The screen is now regulated at 262V and I made some minor
changes to the tank for better loading to 50 ohms.  This has resulted in an
operating point of Ip of 100mA which equates to 50W input.  Pout improved
to 30W yielding a plate efficiency of 60%.  I did not remeasure the grid
bias or drive but inasmuch as the osc remained regulated I did not expect a
significant change.

With all the voltage regulation the chirp is quite minor and I consider the
60 percent efficiency pretty darn good given the modest plate voltage and
modest drive.  I think it really helps to have those two 1625's in parallel.

Good luck with your research.

Dennis AE6C


On Mon, Mar 21, 2016 at 7:46 PM, Kenneth G. Gordon <kgordon2006 at frontier.com
> wrote:

> For those of you who are actively using your ARC-5 transmitters on the
> air, I
> am very curious about what operating parameters you are coming up with:
> plate voltage and current, grid voltage and current, screen voltage (and
> maybe current), power input, power output, etc.
>
> I am especially interested in what you are seeing for grid voltage and
> current.
>
> I'd also like to know what value of screen-voltage dropping resistor you
> are
> using (if any), what source of voltage for the screens you are using, and
> what
> the measured screen voltage turns out to be.
>
> I would love to get one of my junkers in operation here, mainly just to see
> what it is going to sound like on the air.
>
> FYI, according to the RCA Transmitting Tube manual, in Class C as an
> amplifier, with 600 VDC on the plate, the grid voltage SHOULD be -45 at 4.0
> mA. This is with an 11.2 kOhm grid resistor, but the grid-resistor in the
> ARC-5 transmitters is 15K, which at 4 mA would give a grid voltage of -60,
> which would then require more drive.
>
> I am thinking that the grid-current is low in the ARC-5, possibly well
> below 4
> mA, since the driver is the 1626 and the grid resistor is high. This would
> make for a pretty inefficient amp and in addition, could contribute to
> chirp.
>
> Ken W7EKB
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20160321/e164d492/attachment-0001.html>