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

[Dennis Monticelli]

You have it exactly right, Al, along with the new name that isn't a
misnomer.

Dennis AE6C

On Sun, May 10, 2020 at 12:38 PM Al Klase <ark at ar88.net> wrote:

> Folks,
>
> Don't try to confuse me.  That's my job!
>
> I think the problem is that the subject should have read "2nd-Harmonic
> Q-5'er."
>
> 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-248 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?
>
> VY 73,
> Al
>
> On 5/10/2020 8:47 AM, Doran Platt wrote:
>
> OK... herewith positively confirm that the BC-453 was tuned to 407 kHz.  Fortunately, I have some high res photos of my ARC-8 setup.  Looking at the dial, and a placard I made up, its clearly 407 kHz.  BTW, there was no hacking of the BC-348.  A small insulated pickup loop was positioned at the base of the last IF.  The connectorized RG-174 coax is routed to the grid cap of the BC-453 mixer via a tacked on 10pf dipped mica. The reason for going to the mixer was to bypass the front end of the BC-453 which would attenuate the 457.5 kHz signal from the BC-348. That was the setup and it works marvelously well.
> Jeep K3HVG
>
>
>
>
> On May 9, 2020 at 7:53 PM Hubert Miller <Kargo_cult at msn.com> <Kargo_cult at msn.com> wrote:
>
>
> So maybe I finally understand this, maybe not.
> In the video, the guy's BC-453 is tuned to 420 kHz. That means osc = 420 + 85 = ~505.
> Harmonic = 1010.
> Harmonic - 915 kHz BC-348 IF = 95 kHz. Maybe one or the other is not aligned quite right ?
> Should be 85 kHz.
>
> There should be another point, I think, on the 453 dial where this would work.
> BC-453 dial = 330 kHz. Osc = 330 + 85 = 415.
> 415 x 2 = 830;  915 - 830 = 85 kHz.
>
> For the ARC-2, the challenge is, the IF continuously varies with the main tuning. What fun
> that is. I think, IF the above stuff is correct:
> 3885 kHz = ARC-2 IF  @ 1295 kHz.
> 1295 kHz - 85 kHz = 1210 kHz.
> If BC-453 is set to 520 kHz, osc is at 520 + 85 = 605 and second harmonic is 1210 kHz.
>
> Of course, I may have gone of the rails at point A.
> -Hue
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> --
> Al Klase – N3FRQ
> Jersey City, NJhttp://www.skywaves.ar88.net/
>
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