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If you are using an unbalanced antenna, it needs something to provide the "missing" half, that would otherwise be present in a balanced antenna. All simple antennas are basically dipoles. It's just that sometimes you can't figure out where the missing bit is, but it's always there !

The trick with unbalanced antennas is to provide the "missing" half in a controlled manner, and not to let random conductors, which may be polluted with noise from other sources, provide it.

Use a separate "clean" earth at the base of the antenna, and choke off unwanted noise that may be present on the feedline, by means of strategically placed common mode chokes and maybe additional "clean" earth connections along the cable route, as this improves the rejection by working a bit like a potential divider network.

Burying the coax can also help, as this provides both additional shielding and a low impedance path to ground.

Balanced antennas with good common mode rejection are nearly always better performers, and low impedance balanced antennas, such as broadband loops, tend to have intrinsically good common mode rejection characteristics.

Regards,

Martin

Looking at the AliExpress pictures, it would seem to use a Qorvo TQP3M903 700 - 6000 MHz Ultra Low Noise, High Linearity Low Noise Amplifier

https://www.qorvo.com/products/p/TQP3M9037

Although many devices of this type can operate outside their specified parameters, it is difficult to tell how well this may work, without testing one in a specific application.

In this case, I suspect the IMD performance degrades outside the specified frequency range, and may not be adequate at short wave frequencies. I have used similar devices as the basis of an active antenna, but they easily overload if connected to anything other than a very small antenna element.

It's tricky to find a cheap commercial amplifier that has adequate performance to use ahead of the KiWi. I build my own design of RF distribution amplifier, and it was quite an undertaking to achieve decent IMD performance on the LF bands, whilst still having a good noise figure on the HF bands. In the end I used two separate amplifier chains, with diplexing filters to split the frequency ranges, but it is still barely adequate when connected to a decent antenna.

Regards,

Martin

Yes, I think 1 & 6 connected alone, should be loops A & B

I believe you have 4 & 6 transposed on S1 in your switch diagram

Regards,

Martin

Broadband loops don't have to be mounted that high above the ground. 2m is about the optimum, and my loops are actually ground mounted in among some bushes.

The key thing is to get them as far away as possible from potential noise sources. They don't significantly interact with nearby objects, which means that you can often locate them in spots that would not be suitable for other types of antenna.

In addition, you can rotate them so that local noise sources are nulled out, and moving them slightly can help ensure that the null does not fall in a desired direction.

Keep experimenting until you can't easily obtain further improvements.

Regards,

Martin

Hi,

Yes, for a single loop connected as "A" connect pins 3 & 6 together.

You don't need to use V1, V2 & Ground for a loop, those are only required if you wish to use a separate pair of dipole elements.

BTW The thing that catches many people out, is mentioned in the two notes highlighted at the beginning of the instructions.

IMPORTANT !

The Control board must be with removed jumpers J5, J6. Connect to J2 the mode control switches. Connect the PS output to J7. Be sure that the green LED is ON. That means that the polarity connection is right.

The Amplifier board should be with removed jumper J6. Connect the two boards with FTP cable crimped by the user. Be sure that the green LED on the amplifier board is ON. That means that the PS connection is right.

It is a very versatile amplifier with lots of options you can try, but as you have discovered, it can sometimes be tricky to ensure that you have selected the correct jumper configurations.

Good luck,

Martin

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Thanks,

Martin

Hi Frank,

That looks clean, and the distribution of noise looks to be correct.

The fun starts when you connect your antenna, mainly because of introducing other conducted paths for noise to ingress.

As a further test, connect just the ground from your antenna connection cable to the ground of the KiWi, and see what changes.

Then try and fix / resolve any additional noise you can see, before fully utilising the antenna.

Common mode chokes, galvanic isolation, and additional filtering of the power supply, network and GPS cable may all help.

Regards,

Martin

I'd be tempted to have a chat with your neighbour, mine have always been interested in finding out what could be causing such interference, but perhaps I'm lucky that many of them seem to be ex-engineers.

As previously mentioned, it's most likely a Chinese battery charger or similar, that hasn't got the mains filter components fitted.

Also, don't discount your own property, try and drop the main breaker if you can, whilst monitoring using batteries. It's surprising what can be overlooked.

Regards,

Martin

I tend to set the supply voltage at the DC connector, with the KiWi powered and running at 5.4v.

This gives 5v at the internal header due to various voltage drops.

As a result, I don't think 5.66v is likely to be outside the limits, but your issue may be more associated with the rise or ramp up time of the power supply itself, or the way it responds to a load being initially connected.

An old trick to reduce the voltage is to place a silicon power diode in series with the +ve DC supply. Depending on the diode, and the current being drawn, this could introduce anything from typically 0.6 to 1.2v voltage drop.

Regards,

Martin