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You are kinda wrong..

Low band (30-50 MHz) repeaters are still in use.
Mostly in the logging industry, (in the pacific northwest) and other
highly forested areas used for communications.
Usually in the form of a community repeater where multiple logging
companies share a repeater with multiple PL tones.

Power companies especially in rural communities almost always used low
band base stations/repeaters. But that technology is mostly gone now.
They have moved to high band or even 800 mhz.

The splits are usually quite wide, so a duplexer can be used.

For some reason, the amateur coordinating bodies sometimes seem to be
technically naive as to the fact that a larger split on 6 meters is a
better solution.
Sometimes, there is not enough spectrum in some countries to not
accommodate a wide split.

Most duplexers are made my commercial companies that specialize in RF
filtering of all types and frequencies between 30 and 1.2 GHz.
For example Sinclair, DB Products, Cellwave, TX-RX Systems, Bird
Technologies, EMR Corporation etc.
Some of the above names have been changed in the above list, but a
search engine search of the above names, will net you a huge amount of
reading material on RF filtering in general.


73, Jim W7RY

On 4/8/2024 4:26 AM, Brian via groups.io wrote:

I’m just guessing this, someone correct me if there’s a better answer.
I have spent some time reading about duplexers and the many variations
of filter cavities and very seldom see them produced by amateur radio
manufacturers. There are a few hobby radio companies that have
contributed, they seem to be early models mostly. Im sure there are
some I’m unaware of too. Commercial radio use generally operates in
UHF or VHF, 800 mHz portion of the band, with exceptions of course.
The 6 meter portion of the HF band reserved almost exclusively for
amateur use, amateur radio using commercial grade duplexers almost
exclusively with few alternatives seems to have created a vacuum of
sorts for HF duplexers. This is my guess. I may be wrong.

On Apr 8, 2024, at 12:34 AM,
pu5aom.t_at_gmail.com_korabelleblue95@... wrote:

?
Hello Ric, Here in Brazil, repeaters in the 6 meter band have an
offset of [500 kHz], almost the same for 2 meters, which is [600
kHz]. I would like to know why it is so difficult to find a

Hello Ric,

Here in Brazil, repeaters in the 6 meter band have an offset of [500
kHz], almost the same for 2 meters, which is [600 kHz]. I would like
to know why it is so difficult to find a duplexer for this band,
while for 2 meters it is much easier? Do you have a link to the
website of this group in Dallas that builds 6 meter duplexers?

--
Thanks and 73, Jim W7RY