Fuba diplexer input K60 what was that for?

[ctc15]

Hi
l have a Fuba diplexer from Biggeswade it has 3 inputs LMKU l lll VHF input
K21 - 55 UHF and a K60 input what was that for?
Thanks Keith

[Graham G3ZVT]

It sounds like a passive splitter/combiner for Band I, Band III and UHF TV. Perhaps it should be called a triplexer rather than a diplexer.
It would be to use a common downlead for the three bands.

A photo would be good, I have no idea why the letter K, or letters LMKU are used (Long Medium Short-Ultra-Short-Wave would make sense, but not in this context).
Picture please!

[Synchrodyne]

“LMKU” just might make sense. As I recall, Fuba also made combination FM-AM aerials that used a vertical whip for AM and a common 75 R coaxial downlead for FM and AM. This would fit the “LMKU” input on the multiplexer at interest. Presumably then the Band I input was via a wide bandpass filter (with a corresponding bandstop in the LMKU path) rather than via a lowpass filter.

The K in K21-55 probably means Kanal = channel.

Some wild speculation in respect of the separate K61 input – perhaps this UHF channel was used for VCR RF outputs and the like, and was a quasi-standard channel number for this purpose in some parts of Europe? If so, then having it as a separate input would enable the inclusion of a channel-specific bandpass filter, which would help attenuate some of the RF 3MI often associated with low-cost modulators?


Cheers,

[Synchrodyne]

That should have been K60, not K61.

Based upon the above (not necessarily correct) analysis, that unit looks to have been oriented more to combining rather than splitting. At the splitting end, one might expect LMU (AM) and U (FM) to have been separate outputs. Although it could have been that Fuba intended that its separate AM-FM splitter unit be used for that separation, typically at the tuner/receiver input.



Cheers,

[kan_turk]

These diplexers were in quite common use in continental Europe where reception of an additional, usually remote, channel was required - in this case the local channels were in the Ch 21 - 55 range while the remote channel was on Ch 60 and could be amplified if required before being combined - these diplexers were widely available in various channel configurations

Rgds to all

[ctc15]

It looks like l now have the answer. Thank you for all you help.
l am going to see if l can feed my Hedghog band 1 ch1 standards converter into my UHF system without the harmonics.
Thanks
Keith

[Herald1360]

My guess would be that the LMKU-I-III input is a lo-pass filter covering Long, Medium and Short waves (Lang, Mittel, Kurz (welle)), VHF (Ultra (kurz welle)) and Band I and Band III VHF TV.

? ??

[Joe_Lorenz]

Kan Turk is right! Those diplexer (or triplexer ff. ...) were quite common. One might have separate antennae (aerials?) for AM and FM radio bands, for Band I, Band III and Band IV-V. Well known on the continent as "Antenna Switch" to feed all together.
Oh yeah, and maybe there was a very special TV station, much beloved, broadcasting from another direction on say channel 49 that one wanted to feed into the 75 Ohms coax cable, too. So you needed an extra high-db yagi antenna pointing there and such a "Switch" with an additional K49 input. In my case that was necessary to be able to receive "Bayern III TV" although I was pretty much out of range, theoretically at least.

Fuba was not the only manufacturer of these, I think Hirschmann and Kathrein also made these.

Regards, Joe

[SteveCG]

I agree that the lower input was just a low pass filter, the middle input was for general UHF whilst the upper input was for a specific UHF channel. I saw quite a few of these in TV shops in West Germany during the 1990s (with the specific channel in question depending on where you were in the country)