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January 21, 2025. More Low Power Suggestions.

For starters, visit Todd's K7TFC website:

https://www.mostlydiyrf.com and load up on the really good stuff.

The reason I start with this is that Todd sent me two more suggestions for lowering the power draw of a rig and those involve switching over to JFET's for the lower-level stages and of course our favorite is the J310. The 2nd idea was to use the ADE-1L which is a 3dBm variant of the ADE-1. The "L" version is a 3dBm device.

When I designed the LBS transceiver we homebrewed the DBM's and I found the HB units needed more drive like maybe 10dBm. If you do the math 10dBm means you need 2 Volts PTP of drive whereas a 3dBm level is only 0.9 Volts PTP. That translates into eliminating a RF amp stage following a crystal BFO which means less current draw and less parts!


A SMD J310 for $0.57 at Digi-Key.

The exciting news for the J310 is the SMD version can operate at 10 Volts and 10Ma. That will certainly drop the receive current draw. I can see the P3ST using J310's for the Mic Amp, Audio Pre-Amp, IF Module, BFO, Super VXO and steerable Amp. The total count would be less than 10 (8 maybe) and thus less than $6 for those devices. A back of the envelope calculation suggests a receive current of perhaps around 100Ma.

A costly item is the Low Power version of the ADE-1L as that is $9 a pop. BUT if the goal is low power draw down and operating for long periods on Battery power then there is a strong performance versus cost determination.



The JFET's also require less hardware associated with biasing which is less parts to buy and install.

Get over it! Parts are shifting to SMD and less and less availability of through hole and when you can find legitimate through hole parts, they tend to cost a lot more than $0.57. 

I did a couple of more rig measurements yesterday and was a bit shocked. The KWM-4 draws 1 amp on Receive (good for about 10 hours just for receive on the LiFePO battery) and Gulp, 2 amps on Transmit. The Shirt Pocket Transceiver #1 needs 250Ma on Receive and 1 amp on Transmit. A 100ma draw on Receive with the JFET's would extend the "receive only" time to 100 hours. Big Difference!

BTW the LiFePO battery charger finally landed on my doorstep. The PSPS didn't happen but at least now I can charge my phone and laptop.

Them that know can make it go.

73's
Pete N6QW

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