![]() Orange trace = PA0RDT with simulated 20pF input load and using standard 0.1uF coupling capacitors The plots shown below were taken with 10mH choke inductors. I used a FASTRON part number 77A-103M-00 10mH Inductance, 14.4 Ohms DC resistance and 300mA current rating, which is stocked by CPC. Ensure that any chokes used for this purpose have a low value of resistance and a high enough current rating. Need to be increased in value from 470uH to 10mH. ![]() Injection / RF blocking choke in the antenna circuit and Bias Tee also That in order to achieve the reception of such low frequencies, the DC Reception of frequencies below 50KHz with these antennas. Similar result with the PA0RDT design if you are interested in the ![]() To decrease the lowest operating frequency. With changing the value of the 0.1uFcoupling capacitors to 10uF in order In the case of the PA0NHC antenna I also experimented Graph below shows the measured gain frequency relationship of the two PA0RDT design, which would further contribute to an improvement in The gain of the PA0NHC antenna seems to be about 4dB less than the The influence on it's performance by the length of feed cable and otherįactors associated with its installation. Measured the IMD performance of this design (without input protectionĭiodes) to be OIP2 = +75dBm & OIP3 = +32dBmĭuffy has performed a detailed analysis of this antenna. Junction connected to the amplifier input. That they are reverse biased between ground and +ve supply rail with the If you do want to add diodes connect them in series so The amplifier input of these high impedance designs (as shown in the That it's not a good idea to add back to back protection diodes across ![]() Without degrading performance at the LF end of the operating range but ![]() Modifying the shape of the antennaĮlement to increase its self-capacitance improves the HF performance The upper frequency limit seems to be constrained by the Adding the choke lifts the response at 30MHz byĪpprox. I may need to experiment and build a balanced version toįrequency response of the version without the 10uH series chokeĬonnected between the antenna and the amplifier is very flat +/-0.5dBįrom 50KHz to 30MHz. It picks up a lot of noiseĪll E probe antenas it is very prone to common mode noise. This is veryĭifficult to choke off the feed line due to the high input impedance of Higher off the ground than the current 1.5m. Working in the garden about 5m away from the house, but needs elevating ![]()
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