Hi Eric,
The steel cases are not an impediment to the magnetic field, at least not
enough to make retuning impossible. Microwave type circulators are built in a
similar fashion, just smaller, and the technique is well known among those of
us who play in the microwave region. Just to give an idea of the magnitude of
change that's possible, 1.8 GHz circulators can be moved up to 2304, and I have
moved 11.7 GHz circulators down to 10368 MHz.
I haven't specifically attempted to move 870 MHz circulators up to 928, but I
see no reason why this couldn't at least be attempted if someone was so
inclined.
If someone wants to attempt it, you can either dissect an unwanted circulator,
or maybe better yet, use some of those extremely powerful rare earth magnets. I
buy 'em by the handful at the county fairs for cheap, just to have them around
for such purpose.
The network analyzer makes it seem stupidly simple, but a SA/TG would work
nearly as well. Just remember to check it both ways before you apply the glue.
Mel - WA6JBD
> Mel,
>
> I have heard that done, and if it works, great.
> However, the
> remanufacturing of typical VHF and UHF circulators almost
> always involves
> machining or replacement of the ferrite components.
> Since the Celwave
> circulators that started this thread have steel cases, I
> wonder how an
> external magnet can affect the internal magnetic
> field. I certainly agree
> that a network analyzer is best suited for circulator
> tuning.
>
> 73, Eric Lemmon WB6FLY
>
