Re: Adafruit booster cables and 5V powerbanks as ATS/MTR power sources

Joe Street

I put my contraption in a hammond die cast box with common mode chokes on the in and out wires.  I don't hear it in the RX but while I was testing it open on the bench I certainly did, but that was educational.  I know some designs run a fixed switching frequency but what I discovered with mine was that if a birdie came on the shoulder of my filter I could make it fly off by simply tweaking the pot for the output voltage of the switcher because in doing so the switching frequency would change.  This gave me the confidence to keep going and put it in a box.  The nice thing about it is the USB battery pack can stay in an inner pocket and stay warm and I can tune up at low voltage to save the finals and the change in DC supply voltage which sits outside or in my outer pocket at least, it also allows me to vary my output power by a full S unit. This makes it easy to see if they can still hear you when you QRPp.

On Mon, Mar 4, 2019 at 4:11 PM ajparent1/kb1gmx <kb1gmx@...> wrote:

The trick for switching converters is building them into a box with filter inputs and outputs.
Your not trying to keep the TX clean I'd be surprized if the other guy heard it.
However not have the converter whistling in your ears (your RX) or adding a large
chunk of wide band noise to try and hear over is critical.

My solution is if the radio runs on 9-12.6V well enough I use 3x 2800mAh Lipo 18650 cells
(4.2V full charge and 3.7 nominal discharge per cell) as it is small light and compact.  If
its fussy radio or wants more voltage its 4x LiFePO cells (3.65V max charge and 3.2V
nominal discharge cells).  They work well for me for my SB-1, 1W, QCX, KNQ7A, 
and ft817 ( for that I have a 4Px3S 11ah pack at 2.3 pounds and runs it for over
8 hours average use).

Less hardware and plastic and wires.  Less loss to conversion and no risk of converter
noise ( I test on 80M as it seem to be the band most impacted).


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