[MRCA] ARC-2A loading into 50 ohms

[Mark]

Hi Rob-

Thanks for the advice.  I had previously been trying around 100 - 200 pf.  Thought that would be enough.

I tried 400 pf in shunt and started to get more out.  At 700 pf in shunt I was loaded to 135 ma ;  at 1000 pf in shunt I got 180 ma.  Curiously I did not see any increase in power output in going from 135 ma to 180 ma plate current....I get about 25 watts or so, which is the rated value according to the manual.  I'm a bit puzzled by this.  Perhaps I'm being fooled by the wattmeter somehow.

It sure is a neat set.  A beautiful piece of engineering.

73 Mark ABØCW


  ----- Original Message ----- 
  From: Rob Flory 
  To: Mark 
  Cc: mrca 
  Sent: Saturday, June 08, 2013 1:50 PM
  Subject: Re: [MRCA] ARC-2A loading into 50 ohms


  Hi Mark,


  Try 400pF as your capacitance.


  You can lower the resistive component by putting 2 lengths of 50 ohm line in parallel with each other between the antenna and the series capacitor.


  RF


  On Sat, Jun 8, 2013 at 2:31 PM, Mark <mbdittmar at comcast.net> wrote:

    Hi-

    I recently fired up an ARC-2A transceiver I have here,  and just can't seem to load up to full power ( 180 ma at 500 VDC ) with it on 80 meters...best I can do is about 100-110 ma.  The tubes are good and my PS is more than capable of suppplying the current.  I know they were designed to run into a reactive load and a lower resistance, so I've tried adding series capacitance in series with the antenna,  then tried some shunt capacitance, but still peak out at about the same value of plate current.

    Anybody use one of these with a 50 ohm antenna ?  What if anything did you use to obtain more amp loading ?

    My antenna is an inverted L, fed at the base with an autotuner...so should generally look like 50 ohms at the shack end of the coax.

    Thanks and 73

    Mark ABØCW

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