On Tue, Dec 7, 2021 at 08:53 PM, n4buq wrote:
By the way, I wonder if someone could clarify one of the steps in Chapter 6.
Paragraph 4.c. states:
"Adjust L18 (Fig. 6-7) midway between the two signal maximum amplitude points."
Does that mean that as the slug is moved through the coil, one should see two
maximums and then set the the slug midway between those positions? I ask
because I don't see two maximum values and, instead, the waveform changes
somewhat as I move the slug but that's a bit erratic and not a smooth
transition between two waveforms with maximums at both points.
I don't like to put my 184 at risk to try this. As to the theory I can only think that the two peaks appear because the filter L18/L19 is double-tuned (as are all those filters between stages); I might be totally wrong. Suppose L19 is tune below the 10 MHz crystal frequency. Then I expect peaks when (very roughly) L18 is tuned to the crystal frequency and when L18 is tuned to the same frequency as L19. Perhaps the idea now is to tune L18 midway and then tune L19 (and C108?) again as prescribed. Repeated until the results are satisfactory.
W.r.t. crystal temperature, in my 184 the crystal housing temperature stabilizes at about 38 C (measured with IR meter) while Tamb is 11 C.
The crystal frequency goes up (light on) and down (light off) with 1.2 ppm between the limits. If the (average) oven temperature equals the crystal design temperature then I would expect a maximum frequency or a minimum frequency midway in each on and off traject (or at least a stationary point midway, not simply monotone increase or decrease). Of course the oven temperature can have drifted away due to aging of the bimetal (?) contacts.
Albert
