Hi John mate,
I didn't use a transformer, Davy here did.
I can only presume he used a 230V mains isolation unit akin to the types used on building sites, (the blue type not the 110V yellow one), and maybe he can confirm.
These units are manufactured by many and do seem pricey for what they are with such examples linked below :-
https://www.carroll-meynell.com/product-category/standard-products/portable-isolation-transformers/
(Hint, about £120 or so from the likes of Screwfix.)
Davy certainly seems to have had luck with one but might be nice to see if you can try one and return it for a refund if you get no dice.
![Wink](https://2img.net/i/fa/i/smiles/icon_wink.gif)
My homebrew unit consisted of multiple T130-6 type toroidal transformers that I wound L, N & E coming in onto separate toroids. Additionally with a couple of common mode choke types on the L & N sides coupled with some class 'X' capacitors as well as some MOV's. (Metal Oxide Varistors.)
Really not a project for the feint of heart or unfamiliar with electrical safety practices.
(Don't play with the mains there kiddies if you don't know what you're doing!)
Hence why I made a link to the GM3SEK project that is well documented on the old internet.
(Google for 'whole shack mains filter'.)
I did however change my power supply from the Sharman SM-30 switch mode type to the Sharman PS-LM40 which is a linear type and although a blind gamble at the time of purchase it turned out to be just the ticket once hooked up. (Isolated ground connectivity etc.)
The usual trick for homebase setups is to run your rig from a battery and then the typical 'switch off the mains' scenario, but when switching off the mains the 'dirty' Earth is still always connected spewing crap around your home. My setup filters the mains including Earth and the shack is supplied from that. (Technically a 'spur', tut-tut.
![Wink](https://2img.net/i/fa/i/smiles/icon_wink.gif)
) You only have to hold an old AM/MW portable radio near mains cables, light switches etc. to hear the sort of hash the mains actually carries.
If supplying a typical external shack, (shed down the bottom of the garden, outbuilding etc.), via an isolation transformer or shack-filter then you too would be on a filtered 'spur' and hence away from any other rubbish usually found on the house mains supply.
Others, as inferred to later on in this posting may be running via a coiled extension lead and away from the house having a similar overall effect. Different setups may also include keeping everything away from the dirty mains and other electrically interfering devices by carefully placing antennas etc. as far away from your house (as well as neighbouring houses) as possible.
It certainly isn't always an easy task there John and I haven't even mentioned the abundance of additional ferrite material I had to place on my radios, laptop, monitors etc. to keep all the noise down!
Was all worth it though to finally get the low noise floor I now enjoy.
(If I wasn't in a deep-dark-hole-inland-valley I might grab a bit more DX! Best to work with what you've got that bemoan it.)
Apologies for the typical 'waffle' but trying to convey as many thoughts as possible in the chance it helps anyone.......running 'mobile' definitely seems to be the easiest solution to it all. (Freezing your butt off on a hill to catch winter solstice sporadic propagation is a bit of a young mans game though!
![Very Happy](https://2img.net/i/fa/i/smiles/icon_biggrin.png)
)
The things we get up to to enjoy this weird radio hobby....right?
All the best,
Victor