> >No, it has air insulation.
>
> The coil-form has air insulation? Did you mean to say ceramic insulation?
Air.
> > >The Oren Elliot Products roller was never used at Ameritron.
>
> Where did the Delrin roller inductor come from that reportedly melted down
> twice in the ARRL lab? thanks > cheers, Tom
Don't know. Ameritron never used the Oren Elliot Products roller.
But I can tell you this, the Q difference between ceramic and
Delron when only the roller material is changed is minimal. The Q
of the OEP roller measures about 110 at 3 MHz, the same size
ceramic core inductor measures 132 both at full inductance.
The actual problem is the wire gauge and resistivity, and the fact
there is little air circulated across the roller winding, which heats
primarily from I^2 R losses. As little as 50 watts of heat can ruin an
OEP roller. Replace it with a ceramic core roller, and the same
dissipation rises to over 125 watts.
WA1OXT is using two ceramic form rollers in a tuner designed by
you, and it has severe heating problems on 160 meters.
Fortunately ceramic melts at very high temperature.
To cure the problem, he needs to switch to a large gauge
conductor in the rollers.
>
73, Tom W8JI
w8ji@contesting.com
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