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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

You only need sufficient attenuation to take the strongest broadcast stations down by just enough to prevent ADC overloads from occurring. I generally try to keep all signals across the 0-30MHz spectrum below -30dB.

If you have an existing band stop filter, with too much attenuation, you can connect a 1K ohm variable resistor between the input and output of the filter, and then adjust the value until you have enough attenuation to prevent overload occurring at night, but still allow some signals to pass through at a usable level.

Even on a receive site where I had strong signals from local medium wave transmitters, I've not had to introduce more than 20dB of band reject filtering to fix the problem. In most cases, a simple 10dB slope frequency / amplitude equaliser provides a good compromise.

This and other techniques have been discussed in many previous threads, so it's worth searching for those.

Regards,

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

You can place attenuation ahead of an LNA to improve strong signal handling, but the amount of attenuation needs to be chosen carefully, to take into account the LNA gain and Noise Figure, in order to ensure that the overall system Noise Figure is not any worse than the basic receiver alone.

If you search though the forum you will find many posts on the subject of equalisers, filters and notches.

Here is one example

https://forum.kiwisdr.com/index.php?p=/discussion/comment/5723

For a more detailed analysis of how equalisation can be applied in order to reduce the noise contribution due to intermodulation effects without affecting the basic Signal to Noise performance, see if you can find a copy of this paper on-line.

https://digital-library.theiet.org/doi/10.1049/ree.1977.0028

Regards,

Martin

Personally, I think the internal attenuator is more trouble than it is worth.

An external attenuator controlled by the KiWi, as a separate accessory, may be a better option for those that need to handle day / night propagation changes.

However, in most cases, an amplitude / frequency slope equaliser and / or Broadcast band notch filters can fix most problems, without having to dynamically change the overall gain distribution once it has been initially set. Having a fixed system gain, makes it easier to observe changes in propagation and noise levels.

Regards,

Martin

You have pressed something by mistake.

Bring up the right click menu, and change the default setting back to zoom.

Regards,

Martin