[ARC5] Bandwidth for IF Transformers

[Kenneth G. Gordon]

On 16 Mar 2016 at 22:42, Mike Feher wrote:

> Ken -
> 
> I have not looked at the manual, so do not know if they show a selectivity
> curve, but, from the table you listed I would expect that those numbers are the
> total bandwindth nad not half. 73 - Mike 

OK, Mike, perhaps you would care to interpret this quotation from the Navy 
AN/ARC-5 maintenance manual, AN 16-30ARC5-2, table 6.4 on page 47...

"   The SELECTIVITY, expressed in kilocycles, is defined as the 
displacement of the carrier frequency from the resonant frequency, 
required to produce standard output, when the radio frequency 
voltage input is twice (2X), ten times (10X), one hundred times 
(100X), and one thousand times (1000X) that required to produce 
standard output at resonance. Standard output for these 
measurements should be 1 volt across 300 ohms in order to keep the 
level low enough not to be affected by the AVC. The resonant 
sensitivity should be reduced to 50 microvolts by the manual RF 
sensitivity control in order to keep the output noise voltage low. The 
radio frequency voltage input to the receiver must be modulated 30% 
at 400 cycles for both the resonant and off-resonant measurements. 
The selectivity values shown below are those resulting from an 
average of the selectivity measurements made on either side of 
resonance."

Notice it says, "...EITHER side of resonance." and not, "...BOTH sides 
of resonance."

Over to you...

Oh. And by the way, the Army manual says substantially the same 
thing: that the measurement is from center to ONE SIDE of the IF 
passband, not both.

If you would like me to, I will also quote that one to you for you to 
interpret as you see fit.

Ken W7EKB
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