Low noise would be like .5dB. 3dB NF is lousy. And CATV drop amps are not designed for use with an antenna, they are intended for a known range of frequencies at nearly equal levels in a closed cable system. An active antenna multicoupler is designed for use with an antenna. There is a big reason why drop amps are cheap and multicouplers are not.
No way is 3dB lousy. It is about as high of a noise figure that you will want for very good performance with general receiver applications such as scanner radios, and up to 5dB is acceptable for general receiver applications, unless HF which can have much higher noise figures. 1.5dB NF or less is excellent. I have used a 6dB NF antenna amp in the past and it worked just fine for scanner reception. The amp must be near the antenna, otherwise it may add more noise than signal. The application is to distribute signal and overcome feedline losses. Not try to improve the signal at the antenna connection, although signal gain can be realized especially with very low noise figure amps. Drop amps are an affordable option for antenna distribution amps. There is no technical reason they cannot be used to deliver signal from a single antenna to several receivers, unless you are trying to receive outside their passband of 54 to 1002 MHz. Sure that was not their intended application, but no reason not to use them that way.
I have used the Electroline drop amps for several years and the proof is in the performance I get. Their noise figure is 3dB. For the cost, I have not needed better. Reception is improved with any antenna I have used with them. They overcome feed line losses allowing me to use less expensive more flexible feed lines, and I do get overall signal gain.
Comparing reception from any of my antennas on a short feed line without these drop amps, I get better signal using these drop amps over a long RG58 drop to the scanner. Often 25 ft or more from the amp. Amp to antenna is usually 5 feet.
I take one of these drop amps and a homemade broadband multi-element dipole antenna with me on vacation feeding 3 to 4 scanners, and enjoy excellent reception of MilAir on 137-144 Mhz, 148-151 Mhz and 225-400 Mhz. 162-174 Mhz Federal LMR including P25. Also VHF marine and VHF/UHF USCG LMR sometimes in the clear. Reception of local 700/800 Mhz also works well, but typically unecessary as the antenna on the SDS100 is all that is needed.
I have a deployable kit for vacation that includes an Electroline EDA2400 4 port CATV drop amp with power supply and power inserter. Multiple lengths of RG58 cables for connection of antenna to amp and amp to radios. I have 3 foot lengths of RG174 with female BNC for feeding through door and window cracks. Wideband dipole antenna mounted to PVC pipe. Nite Ize Gear ties to mount the antenna to a balcony railing or other structure.
The Florida Keys are target rich for MilAir, Marine, USCG and civil aviation. When down there I receive quite a bit of MilAir in the Tarpon Range area. Sometimes very interesting.
