[ARC5] Fw: Receiver current drain

[J. Forster]

Henry,

I'm not so sure lowering the cathode resistor is such a good idea.

The suggested change will roughly double the 12A6 plate current, and hence
increase the dissipation in the output transformer primary by 4X.

It also might saturate the transformer with excessive DC, since the radio
has a single ended output stage.

Best,

-John

==================>
> ----- Original Message -----
> From: "Henry Mei'l's" <meils at get2net.dk>
> To: "Mike Morrow" <kk5f at arrl.net>
> Sent: Thursday, January 06, 2011 7:32 PM
> Subject: Re: [ARC5] Receiver current drain
>
>
>>I also find that current drain varies from about 10-15 mA to 25-28 mA
>>depending on the B+ level.
>> Have also always found output sufficient for loudspeaker operation. Nice
>> to know I can get more
>> output by changing the 12A6 cathode resisistance, if I should ever need
>> increased audio.
>>
>> Henry. oz1uf - n2nr
>>
>>
>> ----- Original Message -----
>> From: "Mike Morrow" <kk5f at earthlink.net>
>> To: <ARC5 at mailman.qth.net>
>> Sent: Thursday, January 06, 2011 6:52 PM
>> Subject: Re: [ARC5] Receiver current drain
>>
>>
>>> >We must remember that in military service, this tube was driving
>>> >headphones
>>>>at the 100-200 mW level so there was no requirement to generate a large
>>>>amount
>>>>of audio.
>>>
>>> Is that really true?  WWII-era aircraft interphone systems
>>> (pre-AN/AIC-2)
>>> did NOT
>>> amplify the audio of ANY receiver connected to the system.  They simply
>>> routed
>>> receiver AF outputs to each station box.  Bomber installations of, say,
>>> the
>>> SCR-274-N could worst case have ten headphones connected in parallel to
>>> the AF
>>> output of the receivers. (Though most stations would be usually
>>> selected
>>> to the
>>> interphone amplifier's AF output, itself usually a simple one-tube
>>> amplifier that
>>> amplified *only* microphone audio.)
>>>
>>> Apparently the AF output of the command, liason, and DF receivers was
>>> enough to
>>> meet the demand.
>>>
>>>>...some owners have in the past reported adequate audio output into a
>>>>loudspeaker
>>>>even with the original value...
>>>
>>> In the 1960s, I often used a BC-453-B to monitor maritime Morse around
>>> 500 kHz.
>>> I got adequate drive for a speaker by using an appropriate
>>> impedance-matching
>>> transformer.  No receiver AF tag modifications were required.  (I used
>>> a
>>> 240 vdc
>>> HV supply.)
>>>
>>> Mike / KK5F
>>>
>
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