[ARC5] BC-230 first run

[J Mcvey]

If the coil box is that difficult to deal with,I'd assume that it was meant to be "calibrate and forget" ( maybe there is a proceedure for this in the manual?)item. The challenge is to present an external load that makes the box happy. Once you know it's happy place, perhaps by trying more resistance up to 10 ohms, endeavor  to have the load look like that.For instance, running a 50 ohm antenna may require a 9:1 balun in series with the external antenna cap.
I'm not sure if Dave is saying that he is loading a 50 ohm antenna with 50pf or a low resistance one.  The ARCs in their natural state like real short antennas, not good for dx...If you have an antenna analyzer, it will show you what the exact antenna impedance is at a given frequency, so you know what kind of transformation is required to make the TX load properly.
 

    On Wednesday, March 30, 2016 5:50 PM, AKLDGUY . <neilb0627 at gmail.com> wrote:
 

 J Mcvey wrote:

> Those bc 230s are MOPA like the ARC5s but I have never seen one
> in one piece, let alone working!

Yes, MOPA means the VFO changes freq with loading and final tuning.
That's what I reported and it was not unexpected. It was nice that the
VFO always came back on frequency after dipping the PA plate current.

> I was wondering if there is a tunable roller inductor in there or do they
> use the antenna series cap to increase/decrease the inductance
> presented to the antenna?

The roller inductor is not externally movable. It's easiest to pull out the
coil box and shift it. It's almost possible, and very tricky, to slide two small
screwdrivers in from the side to lift the bar and shift the roller contact. I'm
working on the technique. The series antenna cap is Dave Stinson's
method of matching the antenna (it's not part of the set).

> Did you try the external variable at half mesh? Better or worse?

The ARC-5 cap? Definitely worse. Seemed most effective at full mesh.

> The SCR274 and ARC5 types have a sweet spot antenna reactance
> range where the roller inductor is effective. Too much or too little
> reactance and I have difficulty getting it to load.
>
> The ARCs will load into a pure 5-10 ohm resistance if the inductor is at
> zero. Not sure if that would work on the BC230, though.

Interesting. Seems to be borne out by my finding that the roller contact
position is non-critical (at least for my dummy load); different settings
require a PA plate tank re-dip and when that's done, the RF ammeter
is back to 0.7A.

> Loading them into  REAL antennas gets even more interesting!

Oh yeah, I'm really looking forward to pulling out the coil box another
500 times.

73 de Neil ZL1ANM


  
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