Unexpected factory slug position

[brandon7861]

This Cobra 25LTD has been untouched. That slug sticking up is factory. Just sharing.

 

[Cable Guy]

I have seen that before, sometimes with a sleeve. I figure they are making do with what they have.

 

[Onelasttime]

I have seen that before too. Not in a long long time though.

 

[nomadradio]

The coil should have about the same inductance with the slug that same distance below the rim of the hole as it does above.

Never have had anyone explain why a factory finds this a better solution. Beats me.

73

 

[Cable Guy]

Hey Brandon, just found this in a uniden pc66a.

That's the sleeve I was referring to in my previous post.

 

[brandon7861]

Strange. Looks like someone added that sleeve. Maybe as time went on, they had a change in ferrite mix that led to these odd positions. Either that or they put less effort in finding the right number of turns. I guess it could be a variety of reasons. As long as it works and they peak, I guess....

 

[nomadradio]

It's not made by Toko, the most-typical type of 10mm slug-tuned "can". This one says "Mitsumi" on the top. Just a different design, looks like to me. The 2SC2075 final transistor was discontinued at least 40 years ago, plus or minus. This radio is an old specimen.

Even so, when the slug's top surface is even with the top surface of the can, this is almost guaranteed the max-inductance position of the slug. The protruding sleeve doesn't change that.

This also suggests another way to tell if the slug is "bottomed out" of adjustment range. There should be two peak positions of the tuning slug. One below the rim, another roughly the same distance above the rim of the hole. If you see this, the coil is indeed resonant at the peak. And if you see ONLY ONE peak, this means it's not really a resonant peak, just the slug's functional end of travel.

73