BIAS TEE DC POWER INJECTOR

[iMONITOR]

I'm using an MFJ-1886 active receive only loop antenna. It came with a MFJ-4117 BIAS TEE POWER INJECTOR, HF, W/ON-OFF switch, 1-50VDC, 1A. Because I'm using this inside my home (office) I have the antenna mounted on a 9' adjustable light stand/tripod within my reach so I can turn it On/Off. The preamp is built-into the base of the antenna loop. This is followed by the BIAS TEE, followed by a PAR-BCST-HPF high pass AM broadcast filter, possibly soon to be followed by a CMC-0510-R RX Common Mode Filter Choke / Noise Suppressor / RF Isolator. Does it matter in what order these devices are daisy chained in the antenna line considering they're all after the preamp? For instance would the PAR-BCST-HPF filter block the voltage being sent to the preamp if is was mounted between the BIAS TEE and the preamp, etc.

Thanks,
Bill

 

[prcguy]

Ideally you want the AM broadcast hi pass in front of the preamp in the antenna, but that's not possible. I would place the common mode choke between the bias tee and the antenna, which will strip off RF gunge traveling up the power leads to the bias tee heading towards the antenna and also from the receiver side towards the antenna. The AM broadcast filter could go before or after the bias tee depending on if it will pass DC to the antenna from the bias tee.

I would expect the preamp in the antenna to succumb to AM BCB overload before many receivers will but if it survives it could then pass quite a large signal to the receiver, which your filter should knock way down.