Some test with the internal LNA (P.AMP) of the IC-9700 and external LNA. What combinations will give the best SNR? Note that all tests are done without any type of professional equipment – only by looking at the waterfall and listening with my ears.
I have used my VHF and UHF yagis and external LNAs Mini-2 and Mini-70 mounted just below the antennas. I have aprox. 16 meters of high quality LMR-400 cables between the IC-9700 and antennas/LNAs.
VHF – beacon SK1VHF at 144.447 MHz
| Without internal P.AMP and external LNA | Not possible to hear beacon |
| With only internal P.AMP | Possible to hear beacon |
| With both internal P.AMP and external LNA | Better SNR but needed to reduce RFGain to get good SNR |
| With only external LNA | Best SNR! No need to reduce RFGain. |
Note on VHF: The difference between using both internal P.AMP + external LNA and only external LNA is not huge, but is clearly audible.
UHF – beacon SK1UHF at 432.405 MHz
| Without internal P.AMP and external LNA | Not possible to hear beacon |
| With only internal P.AMP | Possible to hear beacon |
| With both internal P.AMP and external LNA | Better SNR but needed to reduce RFGain to get good SNR |
| With only external LNA | Best SNR! No need to reduce RFGain. |
Note on UHF: Almost the same result as VHF, but the external LNA gives better result and SNR compared to VHF.
Summary:
If you do not have an external LNA it is mandatory to use the internal P.AMP on the IC-9700 for very weak signals.
If you have a good external LNA mounted close to the antenna it is best to turn off the internal P.AMP to get best SNR.