[Amps] 'good engineering'

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Sat, 27 Mar 2010 08:26:52 -0700, "Jim Thomson" <Jim.thom at telus.net>
wrote:

>&&  Nice amp Bill.  Are you sure it only runs the legal limit ?  How many
>8877's  are inside?   If that  4:1 balun on your X-7 ever gives you trbl,
>Jay at Array solutions has the real deal  for  4:1 baluns.  5/10/20 rated.
>They also work good on the old KLM yagi's.

REPLY:

Thanks for the kind words. 

One 8877. No doubt it would go over the legal limit a little, but the
plate meter runs out at 1 amp so tune up might be problematical. I
hold it to 830 mA at 2900 VDC under load. The Palstar meter says
exactly 1500 watts out that way, confirmed with a Bird 43.

Thanks for the info on the X-7 balun too. Before I put the antenna up
I put it on sawhorses a few feet off the ground and ran 1500 watts
RTTY into it for five minutes on each of the three bands, while
monitoring the temp of the balun toroid with a non-contact
thermometer. I left the cover on to trap the max amount of heat, and
removed it quickly to take the measurement. The max temp rise was less
than ten degrees, just barely warm to the touch. So far so good, but
thanks for the tip on a replacement if it ever becomes necessary. 

73, Bill W6WRT