Topics

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

Paul Schreier
 

Given the abundance of inexpensive powerbanks for mobile phones, I was looking for a way to use one of them as a power source for my ATS and MTR rigs. I ran across two very inexpensive booster cables from Adafruit that convert the powerbank 5V to 9V and 12V, respectively. I was warned there might be some spurious emissions from the dc/dc converter, but after examining the setup with a spectrum analyzer, everything looks great. And the power budget is within that specified for the Adafruit booster cables.

You can read a detailed report, including photos and spectrum analyzer screen shots, on the SOTA reflector at
http://reflector.sota.org.uk/t/cable-for-usb-power-banks-with-kd1jv-rigs-ats-mtr-models/19509

There are also links to the Adafruit Model 2777 and 2778 booster cables. Seems like quite a viable option! I've tried the cables in several SOTA activations, and got plenty of contacts and no complaints about the quality of my signal. Can't ask for more!

de Paul, HB9DST / AA1MI

Joe Street
 

One thing I didn't like with these boost converters is the efficiency really drops as the difference between Vin and Vout gets larger than a few volts.  They are always sold with a quoted efficiency which is tested in a best case scenario.  On the SOTA page you linked Ji1kbf commented that he used a boost converter based on the XL6009 chip which was what I also used but to get around the efficiency issue I mentioned previously, I put two of these cheap and widely available boost converters in series.  I removed the onboard multiturn potentiometers from each board and instead connected the two boards to a single dual stage pot with some external limiting resistors so that each of the boost converters only has to do half the job and efficiency stays high. 

On Mon, Mar 4, 2019 at 11:17 AM Paul Schreier <aa1mi@...> wrote:
Given the abundance of inexpensive powerbanks for mobile phones, I was looking for a way to use one of them as a power source for my ATS and MTR rigs. I ran across two very inexpensive booster cables from Adafruit that convert the powerbank 5V to 9V and 12V, respectively. I was warned there might be some spurious emissions from the dc/dc converter, but after examining the setup with a spectrum analyzer, everything looks great. And the power budget is within that specified for the Adafruit booster cables.

You can read a detailed report, including photos and spectrum analyzer screen shots, on the SOTA reflector at
http://reflector.sota.org.uk/t/cable-for-usb-power-banks-with-kd1jv-rigs-ats-mtr-models/19509

There are also links to the Adafruit Model 2777 and 2778 booster cables. Seems like quite a viable option! I've tried the cables in several SOTA activations, and got plenty of contacts and no complaints about the quality of my signal. Can't ask for more!

de Paul, HB9DST / AA1MI

ajparent1/kb1gmx
 

Paul,

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).

Allison

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:
Paul,

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).

Allison