[ARC5] BC-AS-230 Transmitter, part 1 - tube adapters, general clean-up, quest for a dummy load

[J Mcvey via ARC5]

The 'phantom antenna is the best thing to use on an unmodified transmitter
After all, they were designed to work with short, capacitive aircraft antennas. 
If you want to match 50 ohms, I think you might need a 100 pf transmit cap in series to a 4:1 balun or some other such impedance transformation. 

     On Monday, December 22, 2014 5:42 PM, Mike Hanz <aaf-radio-1 at aafradio.org> wrote:
   

 On 12/22/2014 5:23 PM, Ben Hall wrote:
> Sigh...I looked thru at least four of the ones I've got here and 
> didn't see that paragraph...

It likes to hide.  One of Murphy's Corollaries, I believe.

> Back to my Mouser / Digikey searching...  :)

Well, as Robert mentioned, your choice will depend on whether you want a 
phantom antenna, or a (non-inductive) dummy load that Brian assumed you 
were seeking.  The phantom antenna merely has to roughly replicate the 
complex impedance seen looking into the input of the typical WWII 
aircraft antenna, and that is overwhelmingly capacitive, even though the 
antenna itself possesses both inductance as well as capacitance.  It's a 
more realistic load for tuneup, frankly, at least if you have an 
aircraft antenna you want to eventually mate up with.

73,
Mike  KC4TOS

> On 12/22/2014 6:52 AM, Mike Hanz wrote:
>>
>> Most of the SCR-183 manuals contain this excerpt:
>>
>> (a) Antenna A-55. This is a small phantom
>> antenna having a capacity of 100 mmfd. with a
>> resistance of 5 ohms. If the unit is not available
>> a substitute may be used, for approximate measurements,
>> consisting of a small mica condenser
>> and a wire resistance, connected in series between
>> the Transmitter antenna and ground binding
>> posts. The condenser should be of standard
>> make, rated capacity 100 mmfd. and the resistor
>> should have a d-c resistance of 3.5 to 4 ohms.
>> Antenna A-55 is suitable for bench testing
>> throughout the range 4000-7700 kc. The capacity
>> of 100 mmfd. is too small for use throughout
>> the entire range of 2500 to 4000 kc, and if tests
>> are desired in these bands a substitute unit
>> should be used having a higher capacity: A unit
>> having a capacity of 200 mmfd. with a resistance
>> of 5 ohms is suitable for testing throughout the
>> whole of this lower frequency range.
>>
>> 73,
>> Mike  KC4TOS
>>
>
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