Hello, today I concluded my "5w HF PA Kit". I'm using the RD06HVF01 mosfet transistor; I know that it's total output power limit is 6 watts. I intend to use it from 21mhz to 50mhz only.
Everything works fine, and I'm using the "raised cosine envelope shaping". The PA is connected by thin coax (RF in and out) from/to US3 running version 3.12 firmware; the "Shapping ms/DAC" config is "05/115". The regulated power supply is at 12v.
*** I still did not do the "4.22 A recommended modification" about putting a 10 ohm resistor ate gate of Q7, should I do it for this case of transistor ?
As I don't know particularities about the RD06HVF1 transistor and it's bias setting and it's heat limit before toasting, I want to ask somebody to help about setting it's bias.
The U3S board with one BS170 has the bias is around 2.20v and it don't get hot. The current was about 97 mA at zero PA Bias, the initial adjustment point.
(I tried first the DAC with a wire from R26 to W4 adjustment, and it produced about 500 mW output, should I mantain it, accepting this 1/2 watt limit ?)
Step by Step:
a) I adjusted the PA Bias by moving the PA potentiometer from zero, and the current in power supply increased very slowly. Current started increasing at +- 160 mA while transmitting, having a PA Bias of 1.60v. At this time, the Wattmeter showed RF out of 200 mW, and the heatsink does not get warm.
b) Increasing the PA Bias to 2.00v, the current consumption was 333 mA and RF out about 400mW. The heatsink still does not get warm.
c) Continued to increase PA Bias to 3.38v, and current consumption was 520 mA, and RF out was about 800 mW. Now the heatsink stared to get little warm.
d) Continued to increase PA Bias to 4.08v, current consumption was 660 mA, and RF out was 1 watt. The heatsing got much warmer, almost hot. The PA potentiometer is now in it's 3/4 right turn.
I don't know if I can get more output from RD06HVF1, if is better to stay in (C) Bias adjust, or try more power., maybe 13,8v in supply...
e) I'm scared of putting more power (max potentiometer Bias) or 13.8 PSU and burn the mosfet.
For those who are experienced, can you help me to choose the best alternative ?
Roney Monte PY1ZB