Holland HPNA splitters go down to 4 MHz. here:
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www.hollandelectronics.c ··· Splitterand spec sheet here:
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www.hollandelectronics.c ··· ters.pdfHolland model SBD (Sub-Band/CATV Separator/joiner) has a range of 1 - 42 MHz. & 54 - 1000MHz. here:
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www.hollandelectronics.c ··· r-Joinerand the spec sheet is here:
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www.hollandelectronics.c ··· iner.pdfInterestingly; the label on the SBD (Sub-Band/CATV Separator/joiner) has the sub band range at 5 - 40 MHz. and the spec sheet pdf document lists the range as 1 - 42 MHz.These types of devices are extremely cheap and likely have poor repeatable quality, with a very shallow slope at the band limits. This allows them to function reasonably well outside the limits posted on the label.
Good filters for lab work will cost in the $100.00 and up range and usually have a steep slope and a repeatable spec from one device to another.
Rick.