On the Air

[jerryk]

OK,

I got my (tr)uSDX working. Power could be a little more, I guess I need to play with the coils
a little. But it's adequate. From my QTH near San Francisco, I did a CW QSO on 20M with a station in Utah. And another one with San Diego. Got RST 589 for both of them. Not bad for 3.9 Watts!

Today, I put together a battery for it. 3 lithium-ion 18650 cells in series, spot-welded together with
nickel tabs, and a BMS. Voltage not quite as high as the wall wart I was using, so power out only 3.4W.
I had to order a baggie of those little tiny 3.5mm power connectors.

First impressions - got to do something about that squeal with the internal speaker. I read that it's
caused by mechanical feedback from the speaker back into the main board. There's also a bit of
electronic mods one can do. As a first step I propose to decouple the speaker from the circuit board.
I'll make the carrier a little shorter with my little metal lathe, and glue the carrier with speaker inside to the front panel. Leaving maybe 2mm clearance to the board. Make the speaker leads long enough so that the front panel can still be lifted off and set aside.

Right now, the carrier is fastened to the main board with a couple dots of superglue - the worst possible setup . Since I just used two dots, it should be easy to pop it off.

[jerryk]

Oh, and one more thing. During my Utah QSO, the transmitter froze 3 times. I had to unplug and plug
the power connector to keep transmitting. Embarrassing. No, my fist isn't THAT bad .

Since it's happening during transmit, I can think of two possible causes:
1. RF feedback into the CPU.
2. Power supply sagging under load.

If #1, maybe I could sneak in a Faraday shield between the two circuit boards? Just a piece of bare
copperclad, insulated with Kapton tape and connected to a ground somewhere?

for #2, maybe it'll work better with the battery.

[dl6sez]

Hello OM,

nice to hear it works for you.
I think you are right with a freezing due to RF returning into your trx.
A shielding is included in the pcb it is a "groundplane inside layer" so makes no sense to add one.
RF get's mostly inside on the coax outside because of bad antenna balancing to ground, eg. a common mode choke on the coax helps. The 5W produces such low electric and magnetic fields (in the near of an antenna not a real electromagnetic, because the wave is not really developped there in the near) are likely not enough to reset the cpu. Only when they can travel on the cable back as currents. Could also happen on your Mic or Key cable because it directly connects to cpu

73 de Chris

[jerryk]

Interesting. I have slipped a ferrite over the antenna lead, we'll see if it makes any difference. In general, my antenna system is pretty good; I routinely run a kilowatt on HF with no obvious RF in the shack. The antenna is a multiband vertical well up the hill from the house; the coax run is about 250 feet. The antenna has an Ufer ground - 80 feet of 8-gauge copper wire embedded in a 70 foot by 10 foot concrete slab. There is an MFJ kilowatt autotuner at the base of the antenna. The (tr)uSDX does not alas produce enough RF for the tuner to actually tune; it needs at least 15W to do that. But my indicated SWR is 1.38 to 1.

[jerryk]

I note that the CW paddle connections do not have bypass capacitors. Surely because they are shared with the ICSP connector.

[dl6sez]

Hello OM Jerry

yes because of the share... but you can add SMD Cs in the plug for example.
250 feet feedline lying on the ground should be good, but if its in the air partly.....
I have here also no problem with 800W sitting 6m from the G5RV tower only behind glass on most bands
but with 2x common mode chokes, one directly at ground level of the tower and the second one at the output of the tuner behind the ACOM 1000. Sometimes i have to cover my cw paddle with my hand, depends on frequency but this is normal behaviour with this reactive fields directly nearby.

73 de Chris