[ARC5] What the heck is a "1/2 harmonic Q-5er?

[Kenneth G. Gordon]

On 10 May 2020 at 15:38, Al Klase wrote:

> Folks,
> 
> Don't try to confuse me.  That's my job!

Heh heh....or mine...

> I think the problem is that the subject should have read 
> "2nd-Harmonic Q-5'er."

Well, yes...sort of...

> 1. Assuming the BC-453 uses high-side local-oscillator 
> injection, if we tune that receiver to 415 KHz, the  LO will 
> be 415 + 85 = 500 KHz, and the LO second harmonic will 
> be 1000 KHz. 
> 
> 2. The IF of the BC-348 is 915 KHz. which is 85 KHz 
> below the BC-453 second harmonic.
> 
>  3. If we bypass the preselection in the BC-453, by feeding 
> the signal to the mixer grid, the receiver will have a 
> response at 915 KHz.
> 
> (So Jeep's dial was off by 8 KHz.)
> 
> Where did I go wrong?

Well, first of all the BC-453's IF doesn't even matter. It is completely unimportant for our 
present purposes.

You simply tune the BC-453 to the IF/2  (1/2 harmonic) of the BC-348, or 915/2 = 457.5 kc.

If Jeep really does have his BC-453 tuned to 407 kc, then his BC-453 calibration is off by 50 
kc. I find that absolutely impossible to believe. 

But I'm betting either he didn't mark his dial with the "5", or his photo isn't clear enough to 
show the "5". Furthermore, if his dial settinig IS exactly 457, then his BC-453 dial is off by 
0.5 kc, which is much more reasonable for a BC-453 in good condition.

MY BC-453s MIGHT be off as much as 1 dial-marking width....maybe. Calibration in a 
properly restored and aligned BC-453 is unusually good.

Ken W7EKB