[MRCA] Navy MAK day two!

[B. Smith]

Be sure and check the grid dip meter on a near by receiver for the exact 
frequency while you are dipping. Why not just disconnect one of the caps 
and measure its value? Have you tried some crystals on a lower frequency 
below such as in the 3.5 , 3.6 range? That would confirm you theory.
Z

On 7/19/2019 9:00 AM, Ray Fantini wrote:
>
> Spent a little time playing with the MAK last night and developed a 
> new theory. Although the radio has a published specification of being 
> capable of operating from anywhere in the 2 to 4 MHz band the four 
> channels that were in the radio when I got it were all within 2.1 to 
> 3.0 MHz The output tank has six taps that can be selected in advance 
> for each channel depending on the frequency of that channel and that’s 
> how they match the PA for the band that the radio is using but the 
> oscillator only has a signal LC circuit for each of the four channels. 
> Using old school techniques learned from Mr. Smith brought out the 
> AN/PRM-10 grid dip meter and found that I can check the resonance of 
> the four oscillator tank coils and found that with the coil backed out 
> to the end of its range it only peaks at around 3.7 MHz, and that’s 
> with the slug backed all the way out of the coil. There are four 
> capacitors located just under the coils, one for each coil and I am 
> going to now speculate that maybe the reason the capacitors are so 
> easy to get at is because they were intended to be swapped out 
> depending on what section of the band the radio was on? And perhaps by 
> changing out to a lower value I will be able to get the oscillator to 
> osculate. Know for a certainty that until the LC tank for the 
> oscillator tunes to 3.885 the oscillator won’t work, just need to 
> figure out what capacitor I need. If I were smart I would know two 
> things. First, what’s the value of the existing capacitors? Take a 
> look at the picture. And second, what would the value of the new 
> capacitor be? Recall something about determining resonate frequency of 
> a tuned circuit and knowing the value of C can determine the value of 
> L and with that knowledge be able to determine what C would be at 3.9 
> MHz but just not that smart. If someone can tell me the value of the 
> capacitors, all four are the same then I will know where to smart with 
> smaller value capacitors and try to determine where the tuned circuit 
> is at that time.
>
> Think that they are 50 pf being green is 5 and red for a multiplier is 
> two zeros? Or would that be 500 pf?
>
> Ray F/KA3EKH
>
>
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