On Sat, Nov 11, 2017 at 08:00 am, Ruben Navarro Huedo (EA5BZ) wrote:
Can we have 4.5v software switched Bias-Tee from HF+?
Tnx a lot.
The bias tee was not included in the HF+ and here's the reasoning behind it:
- You will never need a LNA on HF with the current MDS (-140 dBm @ 50 ohms at max gain)
- The MDS on VHF is also very low (-141 dBm @ 50 ohms at max gain) and sufficient for most real world use-cases
- Adding a bias-tee will cost a few dB's of MDS
- Even if you need lower MDS on VHF, to maintain the linearity of your system you will need a LNA that draw a lot of current, and probably operates at voltages greater than 4.5v
- It is not recommended to power such LNA from USB
Of course, the situation is different with mid-range SDR's, but we are not in that segment for the HF+.
Don't worry, it will just work :-)