[Milsurplus] [ARC5] ARC5/SCR-274N question - L-52 - Correction

[C.Whitaker]

de WB2CPN
I thought the inside coil was a variable coupling to the
antenna loading coil.  Wasn't there a little knob that
adjusted the inside coil for the proper PA current?
73  Clete
++++++++++++++++++++++++++++++++++++

On 3/14/2013 4:32 PM, Mike Hanz wrote:
> Hi Mike!
>
> On 3/14/2013 12:28 AM, Mike Morrow wrote:
>> KC4TOS wrote of the T-15 L-52:
>>> Actually, it is an outer ceramic coil and an inner phenolic
>>> coil...similar to the TN-6 antenna tuner coil approach.
>> Mike, that description must apply **only** to L-52 (ARC-9271) for the
>> T-15/ARC-5.
>
> Yes, it does.
>
>> Even the T-16 L-52 is conventionally wound on ceramic.
>> I don't have a T-15 to look at.  Is the inner coil in series with
>> the roller coil inductance, such that the inner inductance is always
>> in the antenna circuit even when the roller is at zero?
>
> Correct.  It looks like they simply used an ARC-7992 coil with 60 
> turns and stuck this smaller 1.5"D coil inside the 2"OD ceramic form.  
> The output of the link coil T-54B feeds the roller as in all the 
> sets.  The right hand end of the outer coil (looking from the rear of 
> the transmitter) then feeds across internally to the left end of the 
> smaller coil that is suspended within the ceramic one. The right end 
> of that smaller coil then feeds the pickoff for the antenna relay.  
> So, you always have a small amount of inductance in the series 
> circuit, regardless of roller position. Given the frequency range and 
> aircraft antenna limitations, that was probably not a problem.  Sadly, 
> my 4342A appears to be suffering from oxidized contact disease, so I 
> couldn't get a reliable reading of the inductance of each section.  
> I'll have to pull out the Deoxit when I get a chance.
>
>> It makes a little sense, I guess, but it's still surprising.
>>
>> The AN/ARC-5 maintenance manual says that only a fraction of one watt
>> will reach the antenna when using the TN-6 and a short fixed antenna,
>> but it also says that the TN-6 allows use of short antennas from 1.0
>> to 2.1 MHz.  So even a TN-6 won't help a T-15 and a short antenna.
>
> Probably not, but I never say never. :-)
>
>> One wonders why the T-15 to T-17 exist. If they were to support actual
>> aircraft command communications, they were most likely on small aircraft
>> without trailing wire antennas, and radiating that fraction of a watt.
>> Larger aircraft could fire up the AN/ART-13 with O-16, and use the
>> trailing wire.  The documented intended use of these three "special 
>> purpose"
>> transmitters remain one of the more interesting mysteries.
>
> On the web page I provided in response to John Rose's query about the 
> insides of a TN-6, I mentioned the only story that made sense to me, 
> and that was actually corroborated by someone (now a SK) who flew in 
> the float plane scouts that battleships and large cruisers used to 
> carry.  Like you, I have never seen any documentation.
>
>            73,
>  - Mike  KC4TOS
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