I have seen a few messages asking about small, cheap antennas to use for
portable SDRs, considering the RF bandwidths can span two decades. I
found an SMA female, 12 telescoping whip and made a video showing how to
remove the loading coil, along with the VSWR obtainable with an
appropriate counterpoise (i.e. B200 or bladeRF sized PCB). The OEM
antenna (Nagoya NA-773) is very inexpensive and easy to mod with basic
dremel and soldering skills. VSWR of 3:1 is obtainable from 200 MHz
through 6 GHz, with the exception of 1.8 - 2.2 GHz. Ill probably do a
follow-up experiment to see if tuning can be done by receiving via a
small, non-resnoant loop on the adjacent RX port.
Lou
KD4HSO