Terminate un-used port?

[AK9R]

I have a radio capable of 2m and 222 MHz operation. I bought a Diamond CR320 mobile antenna and a Diamond MX324 triplexer.

The MX324 has a low-pass port for 1.6-150 MHz, a band-pass port for 220-225 MHz, a high pass port for 400-500, and then a combined port for all three bands. I will be connecting the low-pass port to the 2m output of the radio, the band-pass port to the 222 MHz output, and the combined port to the antenna. I have nothing to connect to the high-pass port.

Does that high-pass port need a 50 ohm termination? What might happen if I don't terminate it?

 

[zz0468]

I would terminate it. If not, you might not get rated isolation between the other ports you do use.

 

[LtDoc]

Or, do nothing. Covering it to keep the dirt out would be nice.
- 'Doc

 

[WouffHong]

termination thoughts

I have a radio capable of 2m and 222 MHz operation. I bought a Diamond CR320 mobile antenna and a Diamond MX324 triplexer.

The MX324 has a low-pass port for 1.6-150 MHz, a band-pass port for 220-225 MHz, a high pass port for 400-500, and then a combined port for all three bands. I will be connecting the low-pass port to the 2m output of the radio, the band-pass port to the 222 MHz output, and the combined port to the antenna. I have nothing to connect to the high-pass port.

Does that high-pass port need a 50 ohm termination? What might happen if I don't terminate it?

IMHO: It should have a 50 ohm termination even though there will be no intentional 450 MHz in the setups. Knowing the port-to-port isolation will determine the 50-ohm load rating, to be on the safe side as 450 MHz component represents the 3rd Harmonic of the 2-meter transmission.

Da Wouff