Great story Roy!
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Neil: I think Roy's mishap was a bit of a fluke. If you refrain
from working on the device with batteries plugged in, you should
be fairly safe. Roy's loopstick lead must have fallen on a power
trace, briefly shorting the supply and building up a lot of
current in the inductance. Then, when the lead bounced away and
the circuit opened, the collapsing magnetic field caused a big,
high-energy voltage spike and arc. ESD discharges have large
voltages and even peak currents, but the total energy is small.
It's a good idea to use any normally-closed switch in the antenna
jack to provide additional protection. I don't think a short
circuit on AMI will damage the chip in any way. It is AC-coupled
and can't provide huge currents anyway.
--- In ultralightdx@..., "Roy" <roy.dyball@...> wrote:
Scott I remember when I about 12 using an old automobiles ignition coil
sparking madly and powered by an old valve radios HT transformer with a
wire antenna to send mores code to my friend next door. The trouble was
it radiated just about over the whole band and the neighbourhood and I
was soon found out and received the proverbial kick in the rear end.
It would be a silly man who says not to worry about static discharge but
in the thousands of operations on circuit boards I haven't damaged
many chips. Maybe because I wear a lot of cotton cloths and I am aware
of static when the need arises.
It is very difficult to ground AMI on the chip as it is on the lower
circuit board. I think all you can do is tack a ground on the trace that
the active antenna lead is going to be soldered to. I don't put the
damage I caused down to static and no one else in the group has damaged
their chip attaching loopstick wires. You may be able to utilise the
break contact on most 3.5mm jacks to ground the antenna input lead when
it is not plugged in. but after reading the detailed explanation of the
Si4734 tuning process of feeding a signal onto that lead it may not be a
good idea to use the radio with the with the antenna lead grounded.
Maybe Scott can say if this is safe.
If you have any questions or need any help with the USB mod I will
--- In ultralightdx@..., "sdwillingham" <sdwillingham@>
It was truly amazing the arc that the 660 Litz wire coil produced on
7.5" rod and with freshly charged 2650MA NiMH batteries providingSounds like you were duplicating some old-old-school radio
current into less than an ohm. It looked and sounded like RF.
You accidently built a spark-gap transmitter! . . . briefly :(