Tested 2 small porto antennas
1 Baofeng UV antenna left 2nd best signal on PI2NOS
2 eBay DIAMONDSRH805S wide band 144/432/1200 it works for its size as expected
3 piece of wire : best signal in the setup...
Unit under test at workbench.
It was stable 50mA at 5V few days, but sudden the current went up to 100mA
And i could no longer adjust it with the negative bias Voltage.
The - Voltage went to zero and the SPF input port became low Z.
This SPF5189z was broken no oscillations, no input overload just it broke while i was receiving the PI2NOS 430.125 using a small antenna at the workbench.
The specs of SPF5189z say it has an internal circuit regulating the bias current.
Replaced . again with an other of the 5 spare SPF i have.
The new one again could be adjusted at 50mA 5V
The current raises to 150mA when removing the negative gate voltage.
Where is that internal bias circuit ?
I suspect eBay …
Having relative poor signals on the local 70cm / 2m channels using this Diamond collinear 70/2 combi antenna at a height of 25m. I needed to investigate what could be wrong. Measuring the cable only 3W is left for the antenna of the 10W 435MHz output from a IC451E The cable is 30m type H100 Z50 10mm outside diameter it is semi air-spaced but has an impossible 4mm² solid CU inner conductor not much air left. I preferred the H43 Z75 cable having lower loss and mechanical better ratio in conductor size but it is no longer selling i think. This H43 3W should be enough for a comfortable noise free FM signal. But only 27km away at PA0A the signal is weak too weak something must be wrong? I made a simple reference dipole of 2x17cm CU wire. With this dipole the signals where totally worse. So the Diamond does work? I got curious to look inside. Maybe moisture penetration degraded the antenna. This antenna is rainwater close in its normal vertical mounting position. But take care if your mast can b…