RF Power Protector

1st Official Post

    Hi All,


    Does anyone know sources where I can purchase the SSB RF Power Protector (http://www.ssb.de/download/EN-3020_RF-POWER-PROTECTOR.pdf), or are there any alternative products to this?


    Reason for this is to protect the LNB against accidental transmission especially those with IF frequency of 432 MHz when used with a standard amateur transceiver such as the IC-910H that is capable of transmitting at 432 MHz.


    I have tried searching around but unfortunately cant find anyone who carries this. It was a famous protector back in the AO-40 days and connected inline between the UEK-3000 LNC and a 144 MHz IF transceiver to protect the UEK-3000 against accidental TX.


    Any pointers would be greatly appreciated. Thank you.


    73, Sion, 9M2CQC

    Well, the power protector is not supposed to and neither is it designed to handle long accidental transmission into the LNB path. Its there just to prevent accidental brief key ups from damaging the LNB just like how it was used to protect the SSB UEK-3000 receive only converter during the AO-40 days.


    The whole idea of using the IC-910 transceiver is that I can receive on the main band (top portion, on 432 MHz) while transmitting on the sub band (bottom portion, on 144 MHz into a upconverter) in satellite mode that allows automatic tracking of the uplink and downlink frequencies across the transponder.


    Yes, I have looked into the idea of a pull-up tx-inhibit too but it does not seem to help because I still need to transmit on the sub band while receiving on the main band. However, I need some extra measure in case the top and bottom band is accidentally swapped, thus causing me to accidentally transmit into the LNB.


    Thank you very much for the reply and hope that the above explanation clarifies my original question.

    Maybe you can use a coaxial relay and a dummy load, where the relay is energized when the transmitter is keyed? Or you could connect the other port to your antenna and use the relay to switch between local QSO and LNB reception, the relay would be energized only on receive via the LNB (using a switch and a circuit to connect it to the TX line).

    Thanks for the reply. The thing is I need full duplex operation, so the relay should only be energised (N.O. to dummy load) when the accidental transmission into 432 MHz band takes place. When transmitting on 144 MHz (the upconverter's IF), the relay should not be energised (still in N.C.) so that I can continue listening from the LNB.


    And yes, this can be done with a transceiver like the FT-847 that has PTT lines for individual bands. Unfortunately the IC-910 only have one PTT line irrespective of bands and therefore cant work with this solution. Guess I will just swap transceivers to mitigate this problem :)


    Thank you for all the hints once again :)


    73, Sion, 9M2CQC

    Quote from DH2VA

    not ANY TX power... only up to its directivity if inserted the correct way around. I would guess maybe 20dB (?) in reverse direction. If you add another 20dB as plain attenuator (which a LNB with its huge gain might easily compensate) you have 40dB of protection for the LNB again accidental TX.

    Great and thank you for the pointers. I will look into this alternative too.


    73, Sion, 9M2CQC