I did some improvements to my CG-3000 ATU. All the caps in the output part of the PI network was changed to western branded 6kV low loss ceramics from Vishay etc. See pics.
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Mod of low cost XY table with roller bearings
CG-3000 antenna tuner. High resolution schematic diagram
The CG-3000 is a clone of a SCG tuner. It uses a PI network for tuning. There are many schematic diagrams on the Internet. However 95% of those have so low resolution that they are not readable when you zoom in. I finally found a schematic with enough resolution to show the component values. It is the output circuit that receives the highest voltages when matching a high impedance antenna and those are the most likely to be damaged. To be proactive I changed mine to 6KV types low loss Vishay Cera Mite and TDK CC45SL3 types. Below you can find the schematic, should you need to repair your tuner.
If you need to change components in the output circuit and want quick info, all the capacitors are either 100pF or 50pF ceramic. There are series and combinations of from right to left 4x100pF par, 2x100pF par, 2 x 50pF par, 2 x 100pF ser, 2 x 50pF ser. This gives the values 400pF, 200pF, 100pF, 50pF and 25pF. The relays can then switch in several combinations from 25pF to 775pF. Note that the schematic does not show that the 100pF cap is two 50pF in parallel, that the 50pF is two 100pF in series, that the 25pF is two 50pF in series. I may have an older or newer hw version than the schematic.
Turner plus three microphone schematic
I found a schematic of the Turner +3 mic online. It is more advanced than you should think as Turner already implemented compression in the late seventies. They called the compression technique “modu-guard”. It is a rectifier circuit that rectifies the audio and sends a DC attenuation signal back to Q3 in the source of the FET amplifier.
CG 3000 remote antenna tuner, control box (CTU) schematic
To use the CG 3000 antenna tuner for remote operation there is a control box (CTU) that could be purchased from the manufacturer. Some people want to make such a control box themselves. Here is the schematic info.
Thanks to https://sp5kab.pl/pl/sterownik-cg-3000-cg-antenna-tuner-control-unit for doing the work with determining the schematic
SGC antenna tuner info (including antenna examples and schematics)
SGC has made an automatic antenna tuner that has several smart ideas implemented. It uses a phase detector to be able to know if the load is capacitive or inductive. The design uses a RF mixer and several clever multifilar transformers. SGC also included several practical antenna antenna ideas in their manuals. I have uploaded the information here. Credit: SGC
Manual 1 PDF1
Manual 2 PDF2
Manual 3 PDF3
Icom AH-4 remote interfacing info
K9EQ made a good description of the Icom AH-4 antenna tuner including the signalling interface from the radio to the tuner and from the tuner and back to the radio. I did take the liberty to post the pdf here. Credit: K9EQ
AH-4_Design_and_OperationBandpass filters for HF RX
DJ0IP has collected a few interesting HF RX BPF designs. These are fairly narrowband. With todays EMI problems (that NRRL and the other radio amateur organizations seem to care little about), using filters such as these can have an improving effect. Not only for noise emanating inside the amateur radio bands but specifically noise outside the bands. Why?: broadband noise from LED switchers, SMPS, Solar arrays etc often cover a wide HF spectrum, also outside the amateur radio bands. If the input of a HF receiver lets in noise energy also from those frequency ranges outside this will often be altered in slight non linearity in the input stages of the receiver and turn into noise inside the amateur radio bands. I have seen this with comparing switching noise in the 40, 20, and 10m bands and just outside the bands. My FT2000 transceiver switches out the preselector filter when the RX is just outside the amateur radio bands. This results in quite significant noise increase from LED switchers, SMPS etc. while it is fairlig quiet inside the amateur radio band, indicating that the preselector filter indeed has a good effect. For radios that doesnt have this built in, these filters can be of interest.
Download the PDFs from the links below –>
Teardown and review of an ultrasonic cleaner from Vevor (China)
I purchased a cheap china made ultrasonic cleaner. Here is a teardown and review video where I also touch the electrical safety aspcect. The safety grounding was ok so as long as you use a receptacle with a ground connection and a protective fuse (with earth fault detection and isolation) it should be ok. I wouldn’t recommend spilling fluid inside the ventilation holes though so use care.
Cable locating with signal generator and AM radio
Sometimes there is a need to locate a cable in buildings or in ground. It could be because there are many cables running in paralell without marking or that you dont know if a cable is going at all to a location you “think” it is going to. It may also be buried cables that you dont know where to dig for. In this video I show how you can use a signal generator, an AM receiver of the cheap generic type and a counter weight radial to inject a 650 KHz on a cable and later locate it.