Re: Dirty Transmitters

Bob McGraw - K4TAX

Yes, the small footprint, the lower physical weight,  the lack of transformer humm, the excellent regulation, the low noise.   

I have 3 of these supplies.  In each case I do not find them to generate any RFI on any band including 160M - 2M.  There are a couple of points I will stress and that is to check the individual supply to find the following:

(a) open the supply and make sure the AC 3rd pin ground green wire is electrically connected to the chassis.  I have found instances where the nice paint job actually insulates the connection.   Scrape away the paint and re-attach the wire.

(b) the outer shell is sometimes insulated from the bottom pan by paint.   I removed the screws and sanded the area around the screw holes and the mating areas on the shell, then put the screws back in place. 

(c) I also added a ground terminal to the back of the supply.  Again making sure the terminal is connected and not being insulated by the paint.  This is my common point ground for the entire station.  Each piece of equipment uses a dedicated jumper to this terminal.

As to switching supplies and their reputation, I think this comes from hams recovering supplies from various sources with out regard for any filtering.  In many cases, the EMI filtering is done outside of the supply and is not removed when the supply is removed {as in computer suplies} .  And some supplies are just pure crap.   I purchased a 12V 20A switching supply off of Amazon.  It is intended to supply voltage to LED illumination strips.  It is very noisy in terms of EMI and RFI.  If a ham gets and uses one of these then they will likely brand all switching supplies as noisy.    All switching supplies are NOT created equal.


Bob, K4TAX

On 11/6/2019 9:52 AM, Edward McCann wrote:


 I no longer use a linear supply with my station as I find my Astron SS-30M to be superior

could you be a bit more specific on what features make it “superior”?

And could you comment on the notion that the linear Astron version might be quieter in spurious emissions claims traditionally linked to SS supplies?

Would be helpful, as I was about to buy one.


Ed McCann

On Nov 6, 2019, at 7:45 AM, Bob McGraw - K4TAX <rmcgraw@...> wrote:

My Astron 30 amp linear supply on the bench will adjust to about 16 volts and maintain good regulation, no load to 20 amps.  On the other hand, I no longer use a linear supply with my station as I find my Astron SS-30M to be superior.


Bob, K4TAX

On 11/6/2019 9:40 AM, HB via Groups.Io wrote:
What is the upper limit of say an Astron Linear 35 or 50 amp supply?

On Nov 6, 2019, at 10:21 AM, Rob Sherwood <rob@...> wrote:

 I think Wayne said as high as 15.5 volts, which approaches the upper end of spec. In spec is within spec, which would be 15.87 volts.  The low side spec would be below 12 volts, which would not be ideal. Rob, NC0B

On Nov 6, 2019, at 5:28 AM, Steve <99sunset@...> wrote:

I remember a comment from Elecraft saying that the K3 will transmit a cleaner signal with voltage around 13.8 to 14 volts.   I don't remember the exact comment.

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