FDM-S3 Power Supply

[jfurness]

Hi All...

I'm fortunate enough to be picking up an FDM-S3 later today but, as a non-ham with little or no electronics experience I really need some advice as to which power supply to purchase to get up and running.

I'll only need it for the S3 for the forseeable future so it can be fixed voltage and I've been advised to get a regulated rather than switching unit.

My preference would be one that has as small a form-factor as possible but the most important thing for me is that it won't fry the S3 if I set something up wrong, i.e. as little human error adjustment potential as possible!!

Thanks in advance for any help you can give me.

James

[Max]

Hi All...

I'm fortunate enough to be picking up an FDM-S3 later today but, as a non-ham with little or no electronics experience I really need some advice as to which power supply to purchase to get up and running.

James

I guess recommendations for item/supplier will depend partly on where (which country) you are based?

Spec says 12v at 1.1A is required (for the OCXO version). There are plenty of 12 volt "wall wart" plug-in supplies that give 12 volts at, say, 2A. Linear are still available (probably very few these days) but most are switched mode. I would not rule those out because some, if they have been designed well with all the correct and necessary filtering, can be very "RF quiet". The problem comes with cheap supplies (many) where they have not bothered fitting the filter components just to save a few pennies per unit.

Max

[KA1GJU]

If you want to listen to birdies across the HF spectrum (usually in the lower bands of 160-75m) then get a cheap switching power supply that lacks proper filtering as Max cautions you above. A linear power supply is RF quiet, heavier due to a transformer operating at 60/50hz vs a switcher that operates in the tens of kHz range. Looking at images on the web, you'll need Anderson Powerpoles, the standard connector for amateur radio operators. Having cleaned out an estate of ham gear, DO NOT BUY them from Amazon! They are cheap, Asian knock offs that are terrible to work with, fall apart, and don't even lock together properly. Do yourself a favor and get genuine Anderson Powerpoles. Be ready with a stack of FT241-31 ferrite cores, because you will soon find out that the Ethernet cable feeding your computer where the SDR is attached is radiating RF, as well as numerous other SPS's (Switching Power Supplies) in the house, or your neighbors. I even found a failing SPS in a PC being used as a server was QRMing my SDRC Servers at 2/10 mile away!

Here's a good example of a knock off of an Apple SPS charger, and how poorly it's constructed:
https://www.righto.com/2014/05/a-look-i ... ricey.html

The heavy, linear 12Vdc wall warts are getting harder to find, but Jameco has some:
https://www.jameco.com/z/DFU120200RU007 ... 18003.html

I have a large bin of wall warts in basement, because you never know when you might need one! lol

[jfurness]

Thanks Max and Kriss...

First off I'm in the UK which probably changes the list of suppliers that I can consider.
Secondly I'm intending to use the S3 for FM broadcast reception only, does this make things any easier?
Thirdly, and I apologise for my ignorance (I'm very much used to plug and play!) if I could get away with a 12V wall wart would I simply have to snip the plug at the end of the cable and attach each of the wires to the supplied power cable (which has bare wire at one end and Anderson power poles at the other - these connect into the S3)?
Fourthly - would it just be better for me to buy a linear bench-top power supply?

I've bought the TCXO version which only draws 0.7A so I plainly don't need anything "clever"!

Thanks,
James

[Max]

I could get away with a 12V wall wart would I simply have to snip the plug at the end of the cable and attach each of the wires to the supplied power cable (which has bare wire at one end and Anderson power poles at the other - these connect into the S3)?
Fourthly - would it just be better for me to buy a linear bench-top power supply?

I've bought the TCXO version which only draws 0.7A so I plainly don't need anything "clever"!

Thanks,
James

I would try not to over-think it. I actually had a look online and I was pretty shocked at the lack of any linear power supplies these days other than specialist units for audiophile applications and such like, and of course these come with correspondingly high price.

If it would me I'd just pick a switched mode wall wart from a reliable brand on somewhere like CPC Farnell. In case you don't know CPC is the more consumer friendly part of the massive supplier Farnell so in general they won't sell any products that don't come with the required conformity certifications. They sell an absolute load of wall wart supplies. I'd get one that is well over specified, so ideally a 2A unit (they also call this a 24W unit). Some manufacturers that should be OK are Power Pax and Meanwell. There's no guarantee these will be totally RF quiet but there's a good chance they will be perfectly adequate, especially if you are feeding the receiver with a matched outdoor antenna of some sort. Using an indoor antenna is not a great idea. For a start your whole house will be totally littered with noisy SM PSUs for just about every device int he house..... DVD machines, set-top boxes, modems, LAN switches, USB hubs, you name it. The PSU you buy to supply the FDM will most likely be the least of your problems.

Anyway, as your main interest is VHF FM then again, the SM supply you buy for the FDM will not be likely to be the source of any issues. RFI issues are usually far more critical at LF/MF/HF where just about any SM supply will radiate some sort of RFI at those frequencies.

Just to add, if you buy a cheap wall-wart supply on eBay or Amazon then this is asking for trouble. They are mostly the cheapest of the cheap Chinese imports and are by far more likely to radiate than anything you buy on CPC because they routinely leave out any filtering components to save every last penny. Avoid. It's not actually worth it anyway, because CPC have loads of suitable supplies at less than £10 (GBP):

You could probably do worse than something like this. I see Canford Audio is also a supplier of the Power Pax brand so I would guess they are a pretty safe bet:

https://cpc.farnell.com/powerpax/sw4298 ... dp/pw03079

On the other hand if you want more of a station supply to add other bits of 12 volt kit at a later stage then you could probably look at something like these, but at a far higher price of course. For what you've described most likely a massive overkill:

https://www.radioworld.co.uk/sharman-sm ... wer-supply
https://www.hamradio.co.uk/jetfon-pc-35 ... nuous-30-a
https://www.hamradiostore.co.uk/alinco-dm330fxe

Good luck

Max

[jfurness]

Hi Max....

Thank you so much for elaborating and giving me some examples.

I believe you're right, I'm overthinking it, and will probably try the wall-wart option to start with. Can I literally cut the circular plug off and attach the wires to the cable supplied by Elad?

How do I identify which is +ve and which is -ve?

Thanks!
James

[Max]

Can I literally cut the circular plug off and attach the wires to the cable supplied by Elad?

How do I identify which is +ve and which is -ve?

Hi James. Yes, you can do this no problem. I've got a few here where I've done just that. In my experience the thin twin black cable is always marked with a faint white stripe on one of the conductors. My experience is that this is always the +ve conductor?

However, do you have a multimeter that you could check it with before you connect to an expensive bit of kit? If you don't have one I suggest you get one as it's always useful anyway. Ideally get an auto-ranging one which are about £25 on eBay (I have a Proster VC97) but for little more than a fiver this would do just for polarity checking and basic measurements so long as you are careful with setting the range:

https://www.ebay.co.uk/itm/146052188463

Max

[jfurness]

Hi Max,

Great stuff... I think I'm armed with enough info to make a confident decision - you've probably saved me about 50 quid

I'll order one of the better wall-warts and a multimeter today.

Really appreciate you taking the time to help.

73
James

[KA1GJU]

FYI
A 12Vdc linear wall wart (heavy transformer type) may show higher Vdc on your DMM when not connected to anything, i.e. unloaded. The switching type usually show what the published rating is.

[jfurness]

Thanks Kriss, I'll bear that in mind.

73
James