Lmst

First (easy) test of the QB-150 Amps: Does the one with the top installed work? Answer: Yes! Measured 12.6 K Ohm on the power pin to GND. Applied 12.2VDC, measured ~120 mA current draw. Tested with NanoVNA-H4 with 40 dB pad on input side and found it has ~ +24.5 dB gain @ -50 dBm input level through the HF range (-3dB at ~ 446 MHz). Good to have a working sample to help with debug of the failed units. #HamRadio #RFAmplifier

Desktop photo showing NanoVNA-H4 connected to QB-150 RF amplifier through a 40 dB pad on the input side, measuring S21 gain of +24.5 dBm through HF up to 100 MHz. Amp has +12.2 VDC applied. It works!

Photo showing the stop frequency extended so as to measure the 3 dB gain point for the amp (~446 MHz). Amp was originally used as a HF antenna pre-amp up to about 30 MHz. Plenty of gain (and very flat) up to that point.

Photo of the working amp and summary of test notes. DC resistance on power pin to and was 12.6 K Ohm. Measured with a 40 dB pad. Indicated gain of -15.47 dB gain at ~ 30 MHz. Approx 120 mA at 12.2 DC test voltage. Overall amp has ~ 24.5 dB gain down in HF bands. 3 dB point is ~ 446 MHz.

Repair RF Amplifier Project: With some time off ahead, dug out the box of Q-Bit QB-150 RF amplifiers. Likely these are all toast, but will test and troubleshoot to confirm. (These were pulls from a field HF antenna system that occasionally had lightning strikes which zapped the input which then drew too much current and burned up the bias supply components. The board outside of a case is blackened and covered with soot. The others have burned bias parts.) #RFAmplifier

Photo of a hand drawn schematic, four modular RF amplifiers, and miscellaneous parts ready to replace failed parts on the boards. May be nonrecoverable, but will test and debug to evaluate before scrapping the boards (keeping the nice cases).

Found another ZFL-2000 amp in the lab stock - but this one is tagged as “BAD”. Will retest and if actually defective, will set aside for disassembly during next snow day. Curious to see if there is a part number / label on the back side of that 12-pin circular Mod-Amp case. #RFAmplifier #SmokeLetOut

Photo of a Mini-Circuits ZFL-2000 modular RF amplifier with a "BAD" label attached. Is it really bad (or just faking it)? Time will tell. If bad, will disassemble to see what RF amplifier module is used within.

What is inside a Mini-Circuits ZFL-2000 RF Amplifier? Had a few minutes to take a quick look inside one of these RF Amps. Didn’t learn much, and was surprised to see a fully-cased (pins) amplifier module inside. Would take a lot more effort to disassemble further…
#HamRadio #RFAmplifier #LookInside
https://www.minicircuits.com/pdfs/ZFL-2000+.pdf

Photo of a Mini-Circuits ZFL-2000 RF amplifier module with SMA female connectors on each side. Power and GND pins are on the side adjacent to the RF connectors.

Photo inside of the RF Amp, showing a small printed wiring board connecting the SMA jacks and power/GND pins to the module within. Disassembly would require removing the SMA jacks, unsoldering the center pins, removing the four screws and extracting the module/PWB from the case. Too much work just to see what module is used...

The input connector was removed and replaced with SMA connector, perfect for the amplifier cover.
RF Isolator and output connector removed and soon replaced by a small piece of coax and another connector. 👍
Which connector can i use on the PCB directly ? 🧐🤔
#qo100 #datv #AmateurTelevision #digital #pa #poweramplifier #rf #rfamplifier #palletamplifier #hamradio #AmateurRadio #radioamateur

Again today, i receive my new Eurorack 19 inch rackable 3U box for my DATV TX project Portsdown 4 with touchscreen and RF Amplifier, all in one and portable, I’m going to make it mobile powered with 12V, diy for the best !!!
#qo100 #datv #AmateurTelevision #portsdown #portsdown4 #touchscreen #digital #pa #poweramplifier #rf #rfamplifier #palletamplifier #hamradio #AmateurRadio #radioamateur