[ARC5] On Hacking

[mac]

ARC-5/SCR-274N equipment sure can be improved for HAM use.  First off,  
the power output of the transmitters on AM phone can be easily doubled  
(or more) from the 18 - 20W output level at which they were originally  
designed to run by upping the PA screen and plate voltage and adding a  
proper plate modulator.  A pair of P-P 6L6s for example or my  
favorite, a bias shifting Heising scheme see "The Reference Shift  
Modulator" see ER #9, Nov.96.  I would also lump in rewiring the  
heaters for 12 volts and adding an easily obtainable connector on the  
rear as improvements, again in the HAM context.  Another worthwhile  
improvement is a shaft extension and knob on the PA padder cap to  
allow the finals to be properly dipped under all conditions.  No  
problem with a coax connector on the front of the rig as long as a  
100pf  xmitting cap (for 75M, something less for 40 of course) is  
installed in series with the roller inductor behind it.  And, ground  
the other side of the cap and we now have an L network which works  
fine for loading directly into a half wave end fed wire.

Turning to the receivers the 12 volt rewiring and rear connector  
replacement again applies.  The selectivity of the 3 - 6 mc units can  
be usefully improved by juggling the spacers inside the IF cans and a  
neat  two-diode second detector modification adds a useful increase in  
audio output.  A BCB command receiver can also be used as a Q5er with  
the 3-6 units (and also with a BC-348 and an ARC-2).

Before anyone has a brain hemorrhage here let me hasten to say that  
have a nice collection of original, pristine units that I would not  
treat as above nor would I advocate that others do so.  Plenty of not- 
so-nice gear still floating around to play with as above which I have  
done (and had a lot of fun doing).

Dennis D.  W7QHO
Glendale, CA

***************

On Oct 17, 2012, at 8:56 AM, J. Forster wrote:

> Elequent in that, yet again, that the poster cannot provide proof,  
> hence
> resorts to further slurrs, hoping to muddy the issue.
>
> If you have proof, put it up. I don't think you can.
>
> -John
>
> ==================
>
>
>>
>>
>>>> On Tue, Oct 16, 2012 at 12:39 PM, J. Forster <jfor at quikus.com>  
>>>> wrote:
>>>>
>>>>> All right, you proponents of 'ham improvements' to ARC-5 gear
>>>>>
>>>>
>>>> I don't recall anyone ever making that argument.
>>>
>>> The claim has been made, repeatedly. And, IMO, is basically  
>>> nonsense.
>>>
>>> -John
>>>
>>
>> But by nobody credible that Im aware of.
>>
>>
>
>
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