km1h@juno.com wrote:
> The Ameritron uses the same basic switch in many of their amps....the
> only difference is the 60 degree indexing which sure improves the
> potential for arc-over. Other than that there is no difference. Same
> sources...period.
That's not completely accurate.
The Ameritron switch has 30 degree indexing, but it has
different contact layout that increases voltage breakdown considerably
over the Heathkit switch (and Dentron switches).
Contact design and layout are critical to voltage breakdown. Two
switches of the same physical size and basic type can have greatly
different voltage ratings when used in a practical circuit with very
subtle changes in contact design.
> High quality amps such as ALL Alphas, the Amp Supply LK 800, and others
> opted for the Centralab JV series of switches. Other manufacturers went a
The JV-9000 is a higher current switch, but the contact to contact air
gap is almost identical since it is a 20 degree indexed switch. The
voltage increase is only slightly better than a optimal design smaller
30 degree wafer, unless the contact arrangement is specially considered
in this switch also. It is certainly not worth the effort to install one
in a SB-220.
A properly designed and installed identical family (30 degree) switch
wafer will push the 220's switch breakdown above the rating of the
tuning capacitor. That is all that is necessary to insure long switch
life, since the bulk of failures are due to voltage breakdown, not
current rating deficiencies.
> Final line...I am the owner of Radiokit; a supplier of QRO components.
> Tom, W8JI, is the chief "consulting engineer" to MFJ, Vectronics and
> Ameritron which are all 100% owned and controlled by MFJ.
> My involvement in QRO is open and evident....I dont hide it. I wish Tom
> was as open since his recent discourse to this group was superb. I
> prefer playing on a level field.
I prefer a full deck.
73 Tom
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