Splitter/Combiner Performance at HF
Small signal splitter/combiners are available surplus for very low prices, but there are a bewildering number of model variations. Many of these units are rated for fairly high minimum frequencies, particularly if you're interested in using them on HF.I've tested a handful of splitters and report their low frequency performance here. I used an HP 3585B spectrum analyzer with its built-in tracking generator for these measurements; the accuracy should be within .25 dB. In each case a 50 ohm load was on the unused port; generally, the isolation (output to output) goes to pieces if the input port is not terminated.
In each case, the insertion loss was 3.1 dB, plus or minus 0.2 dB, at either 100 kHz or 1 MHz. However, the port-to-port isolation varied greatly:
| Manufacturer/Model Number | Rated Min. Freq. | Isolation 100 kHz |
Isolation 1 MHz |
| MCL ZFSC2-1 | 5 MHz | 22.25 | 33.1 |
| MCL ZSC2-1B | 0.1 MHz | 24.3 | 40.9 |
| MCL ZFSC-2-2 | 10 MHz | 9.6 | 21.6 |
| MCL ZFSC-2-4 | 0.2 MHz | 15.7 | 24.8 |
| MCL ZFSC2-5-6 | 10 MHz | 12.75 | 21.9 |