The noise pulses at about 1 Hz and is worst on 20m.

It is also present on 80, 60, 30, 17, 15, 12, 6 (with a much longer period),

When it is present it is noticeable on all modes.

The attached file is an MP4 of my ExpertSDR2 app running on my W10 machine.

My antenna is an End Fed wire approximately 85 feet long. The SWR on 20 is less than 1:1.1 (no movement on the0 'reflected' at 100 W- Same on 40 where there's no pulsing).

Noise can be from any number of sources.
It is advisable to have a process of elimination.
Do you have the same problem with another HF radio?
Does the noise problem occur only with your SunSDR2dx radio?
Does your Internet use power line cabling?
Are you close to a defective transformer ?
Do you have wall warts near your radio?
Do you have LED light fixtures close by?
Does your neighbor have any gadgets that may be responsible?

There are also OVER THE HORIZON radar from military installations that can cause noise on specific frequencies.

Try disconnecting your antenna from the radio and connecting a dummy load to the Sun antenna port instead.
I bet the pulsing noise disappears!
If so, then the source of the noise is external to your radio and as Sam said you then have to try & identify it and hopefully eliminate it.
Are there any electric fences for stock (horses, sheep etc) nearby which can also produce a pulse or click ON/OFF at regular intervals
Please let us know how you get on.
73
Ray G3XLG

inov8tn wrote:
Solar Panel Chargers/controllers either at your location or neighbors, Cheap Chinese Wal warts- crappy power supplies, the list goes on and on! By the Way there wasn't a sound file attached, Attach a sound file and also a Video of the interface in a wide bandwidth, some of us may be able to help identify it possibly