[ARC5] Plate impedance...

[Roy Morgan]

On Dec 14, 2008, at 10:02 PM, Kenneth G. Gordon wrote:

> Anyone know what the plate impedance is of a pair of 1625
> at, say, 7.0 Mhz, a plate voltage of 550 VDC, and a plate
> current of about 150 mA?

Ken,

Nope, not readily.  There was an RCA Ham Tips about values of PI  
networks for common tubes of the day that.  I interpolate the numbers  
given for other plate I an V values and I get about 1500  ohms.  The  
RCA HB-3 pages for the 1625 or 807 aren't much help with this.

New topic:  Has anyone used a piece of coax for the series capacitor  
to feed a normal 50 ohm load on these transmitters?  That is, a short  
piece of coax, with the center conductor as one terminal and the braid  
as the other terminal.  One table I found lists RG-213 at about 30 pf  
per foot.  So a couple of feet of the stuff gets you close to the 70  
pf that some have mentioned. Seems like such a capacitor would not be  
subject to heating.

Roy



Roy Morgan
k1lky at earthlink.net
529 Cobb St.
Groton NY, 13073