[ARC5] VFO dial alignment

[AKLDGUY .]

I said:
"That is, set the slug so that the error is now 6 KHz low (2994 KHz)."

What that means is, set the slug so that the dial must be turned to 3006
KHz to obtain zero beat with the 3.0 MHz signal source. In other words, if
the zero beat initially gave a high dial reading (3004 KHz), increase the
inductance so that setting the dial to 3.0 would result in a signal of 2994
KHz.

Essentially the method used by the manual uses offsetting of the dial to
judge the error. Today it would be much simpler to do and describe with a
frequency counter.

73 de Neil ZL1ANM

On Tue, Aug 23, 2016 at 1:04 PM, AKLDGUY . <neilb0627 at gmail.com> wrote:

> J McVey wrote:
> *when I said 4khz end to end I meant that if I tune the dial at the top
> end (4 MHZ) to be dead on(zero beat) , then go all the way down to the low
> end (3mhz), I will find 3 mhz reading more like 3004 khz on the dial.
> Obviously, the error progressively gets worse as I tune down the dial until
> it culminates in the 4khz error at the bottom end.*
>
> *This what I mean by dial tracking. It is said to "track" when the dial
> frequency and the actual frequency match exactly.*
>
> *Bottom line; There is only one combination of L and the variable C where
> the frequency will correspond with all the tick marks on the dial.*
> *I was wondering what is the best way to proceed in finding that perfect
> combo.*
>
> The manual is clear about how to get the VFO to track the dial markings.
>
> Section V
> Maintenance
> p. 43
>
> Paraphrased:
> Remove the top cover.
> Set the dial to the highest calibration mark (4.0 MHz in this case). Tune
> the transmitter for maximum power on VOICE  into dummy load.
>
> Adjust the trimmer mounted on the VFO capacitor for zero beat against a
> (4.0 MHz) signal source of very good accuracy. If zero beat cannot be
> obtained, set the trimmer midway between its end stops, loosen the lock on
> the VFO capacitor, and obtain zero beat by adjusting the VFO capacitor.
> Then lock the capacitor shaft again.
>
> Now set the dial to the lowest marked frequency (3.0 MHz) and check for
> zero beat against a very accurate signal source. If there is an error, note
> the amount (you reported 4 KHz). This error must be corrected by a proper
> adjustment of both inductance and capacitance. ie. the coil inductance is
> in error but the error cannot be corrected by adjusting it alone.
>
> Adjust the slug in the VFO coil until the error is about 1.5 times the
> former error, but in the opposite direction. That is, set the slug so that
> the error is now 6 KHz low (2994 KHz). Now reset the dial to the 3.0 MHz
> calibration mark and adjust the VFO trimmer capacitor for zero beat.
>
> Check the high dial setting (4.0 MHz) again, and if not in agreement,
> repeat the above steps. Check several frequencies in the band for accuracy
> better than 0.04 per cent (1.4 KHz at 3.5 MHz).
>
> It is desirable after this process that the VFO trimmer capacitor
> should be near its mid-travel position, so as to allow minor trims during
> service life without having to disturb the lock on the VFO tuning capacitor.
> ------
>
> The process will be very easy with the aid of a frequency counter, and
> won't need to involve resetting of the dial for the 3.0 MHz measurements.
>
> 73 de Neil ZL1ANM
>
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