Mini teardown/overview of XTD's XDT-PA100X HF amplifier
Вставка
- Опубліковано 1 жов 2024
- This XDT-PA100X by XTD (that's what the silkscreen on the PCB says) is sold as a 100W HF (1.8-30MHz) amplifier. I opted for an IC705 interface, but, that was ignored and I got the generic (maybe Xiegu) interface cable.
I had planned to take it out portable tomorrow to use with the IC705, and decided to have a look inside first to check.
The amplifier transistors are IRF530N HEXFET PowerMOSFET parts. Not RF parts at all!
The little part near the input transformer that I couldn't read in the video turned out to be an 78L05, a 5V voltage regulator, which sets the biasing for the IRF530N transistors with a small variable resistor feeding the gates through a ferrite bead and the input transformer winding. The power input to the 78L05 bias regulator is cut when in receive, as expected.
An LM317 sets the fan speed with a thermistor floating near the IRF530N tabs. The thermistor doesn't feed into the biasing as I would have expected, as is common to prevent thermal runaway.
TX/RX switching is done with two transistors near the LM317.
Hope this helps someone!
73, George M1GEO!
Lies....absolute lies....and Aliexpress descriptions. ..
I too am an Aliexpress junkie that can spend hours looking for random rf products for sale, having myself just found this amp for sale I was intrigued to see it quoted a range of 1.8-30 Mhz which seemed unlikely as most start at 3.5 Mhz...that coupled with a switch on the front marked 20 and 40 raised even more suspicions the description was being economical with the truth. Hunting about I found your video so you have proven my suspicions. Having said that there are some incredibly high power fet amps running many hundreds of watts out on 48 volt supplies for sale. Another product I found for less than £300 is a 88-108 transmitter,200 watts out variable power, built in reflectometer, bluetooth linked, no obvious harmonic filtering on the output but will no doubt be soon installed on one or many high buildings in the cities of the UK...
Smoke test please 😂
I still don't understand the band switch. The manual says (21M, turn to middle).
Yup. One way puts in a 7 MHz LPF. The other way outs in a 14 MHz LPF. If you select neither, a default 30 MHz filter is selected.
Thank you George. That is helpful! It appears as though the the 40M position is used for 40-80m, the 20M position is used for 20m and the center (unidentified), for 10-17m. Guessing there are harmonic issues. The manual uses "M" as an abbreviation for meters & MHz. I wonder why some of the XDT-PA100X units don't have a switch at all! So far, I have gotten only 70 Watts out on CW with 10 Watts in. Appreciate your expertise!
Did it work with the 705?
No. It wasn't linear so no good for SSB. I have designed my own. 😂
@@m1geo bummer but cool that you built your own.