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Thanks for doing that.

I think the Apex is better than the loop, but in both cases you seem to be constrained by local interference.

I can hear and see noise from several switching supplies, possibly solar PV optimisers, plus what I think is a domestic Data over Mains Powerline adaptor.

The sensitivity of the Apex falls off below about 5MHz, which is what I observed with my clone, but it should still be adequate in most cases, as the noise floor naturally rises on the lower frequencies.

Have you checked your own home for sources of electrical noise ?

Regards,

Martin

Those are valid, and he has identified himself.

It's a member of the UDXF list logging ALE networks, which requires long periods of continuous monitoring to capture stations that may only sound once an hour.

I have given him passwords for my KiWi's so that he doesn't time out.

Regards,

Martin

There was a long thread about the Apexradio 303WA-2 some time ago on this forum.

https://forum.kiwisdr.com/index.php?p=/discussion/comment/17853

The height of the antenna above ground is likely to have a significant effect on its performance.

Generally speaking, the higher you can mount it, the better it will perform.

Can you state your KiWi URL so that I can take a listen ?

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

I recently did a bit more research into the various DC filter boards that can be bough cheaply from China.

I've previously mentioned the simple type with two separate inductors.

Simple DC Filter

But I wanted to compare it against some of the larger types with an additional common mode choke using a dual winding. All of these seem to use the same printed circuit board, but populated with different types of inductors.

Green rectangular core common mode choke, and black core inductors

With toroidal common mode choke and yellow / white core inductors (Type 26 Iron Powder)

Differential Mode attenuation - direct noise from the power rails

All the filters are pretty effective. The simple type is slightly worse, but I doubt you would notice much difference between them in "real life"

Common mode attenuation - conducted noise, usually via a ground path

The Green and White cored filters are much more effective. The White cored filter would be slightly better at reducing low frequency <1MHz switching noise from Switched Mode Power Supplies, but the Green cored version provides much better overall attenuation.

Note that the values of attenuation were measured in a 50 ohm system, and the actual amount of attenuation will depend on the circuit impedance. However, using 50 ohms does at least provide a standard reference for comparison purposes.

Regards,

Martin