Does anyone have an LNA they have tested and like as well? I have one of the above units deployed but I need moar. Sure, I could buy and test several units but it seems like several folks have already done that here :-).
Also, I have two LNA4ALL’s but they have failed me. One I managed to mechanically break and after repairing it a second time it no longer seems to work right, just raises the noise floor without improving any signals. The second unit I have basically does the same thing so I’m not impressed so far.
Alfredo: Any further opinion pro or con for the SPF5189z LNA? How susceptible does it appear to be to overload from FM and Aviation band signals?
All: I’m also interested in finding a current good source for LNAs, preferably that can be powered from the RTL-SDR phantom power output. FM notch filtering would be great but I can use an RTL-SDR FM band filter if I have to. I’m currently testing an omni ground station and running an AMSAT-NA FoxInABox (FIAB) in parallel. Eventually, I’d like to locate 1 or 2 Satnog systems and the FIAB at/near an antenna and feed them from a common antenna via a LNA and splitter network.
I can borrow from my portable hamsat station an AMSAT-NA preamp (100-500 MHz) or an older Advanced Receiver Research preamp; I don’t want to permanently use the AMSAT preamp for this role and the ARR unit is good for 2M downlinks but may be too narrow for NOAA APT signals.
So, I ended up getting a couple of these brand new/old stock at an amazing price at hamvention:
They are commercially made so no surprise they work well. Only thing is they seem to need an FM broadcast notch filter as there’s some harmonics being picked up way up into the VHF band. I’m using it for a separate project not related to satnogs, but if I get another ground station running it will probably be using one of these guys.
I’m still interested in a replacement for the now defunct FM filter+LNA though if someone finds one. Thanks.
Filters: I recently ordered a 144MHz and 440MHz bandpass filteres from HobbyPCB. I was told that they have about a 1.4 dB insertion loss at 137 MHz (design freq is 146 MHz). I plan to try them as an alternative to an FM broadcast notch filter. They said they are aimed at filtering out FM broadcast and DVB TV signals, not really designed for blocking airband or pagers. They are rated to 20W, so I may also try them for portable 2-way use with the amateur satellites.
With this 40 dB LNA you have to be sure that the receiver won’t be saturated with amplified signals and it also might benefit from an additional Bandpass Filter.
I had been using a generic 5v SPF5189 LNA for the last few months, which provided ~15 dB gain, and have recentlly replaced this with a 12v INA02184 LNA which delivers ~30 dB gain… both behind a “2m” filter.
Both appear to deliver lower noise than the equivalent from the RTL-SDR’s software gain, but perhaps not by much.
