[ARC5] Fw: Receiver current drain

[Henry Mei'l's]

----- 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
>>