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Originally Posted by bobsgarage
Tripelo, thanks.
Here are the Ferrite cores ordered from Mouser:
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The graphs of ferrite impedance look OK for your application.
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Man, they are so very careful about the packaging. I guess they are very brittle.
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They are a form of ceramic, if they bang against each other they crack and separate.
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..Are you thinking I only need two Ferrite cores or, the more the merrier?
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Merry is a good state.
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At least one at the junction and at least one at the 1/4 wave length, 5.5" down?
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Looks like your UHF Fair-Rite's have somewhat more than about 400 Ohms impedance at 500 MHz. If you use four of them, that makes at least 1600 Ohms (from ferrite) to resist signal passage down the coax shield. Splitting locations, 2 at junction and two at 1/4 wave would likely increase the effective impedance to well above 1600 Ohms.
Four of them together at 1.126 inches length each would cover about 4.5 inches. Splitting for quarter wave leaves only a small space between.
The signal can divide some portion to pass through the interior of the coax at 75 Ohms impedance, some to pass through 1600+ Ohms (plus the inherent impedance down a coax shield outer conductor).
The point is, the higher the impedance, the less signal passes on the outer shield. Signal on the outside of the shield is for practical purposes 'lost'.
There are practical limits, cost, weight, difficulty handling and securing a ferrite laden cable.
In some cases, two or three is about all a connection at a junction can handle.
Diminishing returns, revisited.
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