[ARC5] ARC-5 TX output circuit modeling [long]

[Unserviceable but Repairable]

}
}Ian,
}
}Don't understand why/where on the 1500pf parallel cap.   In my experience, 30 
}- 50pf in series with the roller inductor alone works into 50 ohms just fine 
}with the BC-459 (100pf for the 75M BC-696).   Also, don't have figures at hand 
}but haven't experienced losses at the levels you're predicting.
}
}Dennis D. W7QHO
}Glendale, CA

Dennis I was coached to put a BCB variable in series w. output on anything
like a TCS, a BC-2/430, or a ARC-5-ish hf.  Make sure series inductor
rolled to 0 & start w. link @ half (45 deg.s).  Then tune BCB var. for 
max. load & this is where BCB var.'s Xc matches link Xl.  Then adjust
link for right output stage operating pt.

The tank / swinging link can be modeled as a variable tap autoformer 
(which it is in BC-2/430).   The feed R of an acft antenna is immaterial
& that's why variable link.  I think saying outa hand that all these
sets were designed for about R=4 ohms is fatuous.  The txs wud
work with a big range of R.

This R IS ofter 'way small since the acft. antenna's 'rise' may only be 
10 feet for a single 50' slanted wire.  (it's this 'rise' which makes 
dipole outa fuselage/hull acting as gnd. plane / counterpoise)

The design  of all these sets where such that the 'loading coil' was in 
the tx.  Almost any dang thing could be used for an antenna

And when the shipboard shacks were moved from behind stacks to below decks,
antennas went thru huge 'trunks*' that were sorta 4' square ducts
to allow continued use of tx's w. internal loading coils

Some theoretically xtra smart people behind all those radios.  Like Ian

And Ian,  I confess I've never measured efficiency of one of these
BCB variable things vs. roller pad 'trimmer' & vac. cap.  Efficiency 
choice being reason for that 50pf "RE2 cap." was a real revelation.

Hope I haven't muddied any water by giving this electro-plumber's
plain-language spin on the matter

  Marty 

 *tnx for bird's eye on Destroyer radio room a year back, D. S.  This
  put a lot together

  & I'd like a 'bulge bottom' & relay for my RE-2/ARC-5.  Think I've got
  an RF ammeter