[Central-Electronics] CE 600L First Power up results

[Jim candela]

	Hi All,

  Last fall I came across a 600L Linear amplifier, and on an impulse I
bought it. I had two problems though. One is I made the decision without
consulting my XYL, and the other was that I was about to move. Collecting a
boat anchor prior to moving is not always a good idea. So I had it shipped
to my business address, where it sat tucked under my desk until yesterday.
Now that I have moved, I am starting to set up the shack. So far the XYL
hasn't mentioned anything about, "what's that over there, I don't remember
that". My lips are sealed.

   Anyway the 600L sure seems to be a marvelous engineering achievement. I
quickly discovered that my shack selection at the opposite end of a ranch
style house from where the AC mains power comes in is a problem. I have 120
volts AC until I turn the dang thing on, then 118 vac. Idle, 117 vac, and at
300 watts output, I get 112 vac. Sigh! Looks like I need to beef up my home
wiring to the shack.

	I have a few issues with this 600L however. Since it has an internal
blocking bias, why does CE suggest that you use the bias from the exciter? I
must be missing something. Jumper terminals 3-4, and that is solved, and
then close 1-2 from the exciter when transmitting. What's wrong with that?

	The gain of this thing is phenomenal. I see the following on 75 meters:

.8 watts in = 100 watts out
2  watts in = 200 watts out
3  watts in = 300 watts out
4  watts in = 300 watts out (saturated)


	So how the hell can you drive this with a 100 v / 200v with a 100 watt
rating, and not over drive the linear? a 13 db pad would take 100 watts to 5
watts...If the gain is the same on 10 meters, I bet a CB'er or two has used
these on 11 meters. Come to think of it I have a "President Lincoln" all
mode 10 meter rig capable of about 15 watts pep. Hmmm.

Driving this with my QRO 20a (50 watts pep capable) is way over kill with
drive. That said on AM I can run 300 watts (DC on meter) with 100 watts RF
output with headroom for 100% AM modulation. It looks beautiful on the
scope. The 813 though is dumping about 200 watts heat (kind-a-red).

The RF output waveform on 75 meter CW is perfectly sinusoidal. This is true
even at the overload point. This suggests that those broadband couplers are
resonant with low Q.

There is a little bit of AC power line ripple on the carrier. I didn't look
to see if it is 60 or 120 hertz ripple. I later noticed that the bias
rectifier is half wave rectified, so if the ripple is 60 hz, it's probably
the bias supply causing low level grid modulation. I might need to replace
those two 20 uf / 450 vdc electrolytics.

All in all a neat amp, and a fun smoke test!

Jim
WD5JKO


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