How many recievers can be connected to a LNA?

[hruskacha]

I have 4 SDRs that i want to use on one antenna for 800MHz trunking. How can i properly figure out how many sdr dongles i can have connected to it before signal gets too low. Im getting a Nooelec LNA that has +20 Db of gain.

 

[prcguy]

A 4-way divider will have 6 to 7dB of loss leaving about 13dB of gain from a 20dB gain amplifier. I won't bore you with my thoughts of the piece of junk Nooelec LNA and how it can make reception worse if you use it on an efficient antenna and you are in a congested RF environment and that it has too much gain and too little IP1 and IP3 ratings, etc.

If your just trying to make up for divider loss then choose an amplifier with enough gain to make up for the loss and no more than 1 or 2dB more gain. Ideally an LNA goes at the antenna where it makes up for feedline loss and does the most good. However you need to match important LNA specs with your antenna and environment otherwise reception can suffer.

I have 4 SDRs that i want to use on one antenna for 800MHz trunking. How can i properly figure out how many sdr dongles i can have connected to it before signal gets too low. Im getting a Nooelec LNA that has +20 Db of gain.

 

[Ubbe]

Im getting a Nooelec LNA that has +20 Db of gain.

I looked at the specs and it seems to have good P1 and noise figure. Use a CATV splitter, that has F connectors, and get pigtails or adaptors to connect each SDR to its own output. The CATV splitter will isolate the SDR receiver from each other to reduce interference. Try and install the LNA at the antenna and you must have an additional 10dB attenuator between the LNA and the splitter or you will probably overload the SDR's.

Sometimes CATV splitters will have only one port that has power pass to feed the LNA with power, but it shouldn't matter anyhow if all SDR's have their LNA power feed enabled.

/Ubbe

 

[AB5ID]

I have 4 SDRs that i want to use on one antenna for 800MHz trunking. How can i properly figure out how many sdr dongles i can have connected to it before signal gets too low. Im getting a Nooelec LNA that has +20 Db of gain.

Hook it up first and see if you're system gives you enough signal to work with using a passive splitter.

 

[W4EMS]

I use 4 port Striesburg with no problems. Have no equipment to measure port output but signal on distant frequency is close enough to same my ear cannot discern a difference. Using 4 port splitter alone had a definite loss but YMMV.