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Registered Member #1637
Joined: Sat Aug 16 2008, 04:47AM
Location: Kiev, Ukraine
Posts: 83
Im sending on/off control signals. There is no tradeoff between speed and error rate because tr24a operates at fixed speed of 1Mbps. The tradeoff is between distance and error rate. My tr24a works with no errors in radius of "10meters+2walls". Error rate quikly achieves 100% when I move transmitter 2 meters further away from receiver.
I modified tr24a a bit - i placed 100nH coil from antenna to GND. The coil acts like hi-pass filter. Also, I had to place receiver into "faraday cage" to make it work. "faraday cage" acts like hi-pass filter too.
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
> Richie Burnett once told me that his SSTC would only interfere with analog TV if his kitchen foil topload wasn't making good contact.
Yeah, I remember doing some tests regarding this...
CW SSTC's using MOSFETs can be pretty noisey in the frequency range from low MHz up to around 150MHz. They radiate supprisingly little at the actual operating frequency (typically 200kHz or so) because the electrical length of any component carrying significant current is too short to make an efficient antenna. At these low frequencies you're more likely to get conducted interference leaking through the line filter.
Likewise there's little energy generated above 150-200MHz because the slew rates of the signals generated by the MOSFETs are typically many tens of nanoseconds at the fastest. So, even though the wiring would radiate UHF and microwave singals efficiently, power MOSFETs simply don't switch fast enough to produce much energy in this frequency range.
As Steve said, what I found to really produce a lot of UHF noise was allowing sparks to break down tiny air gaps between metal. Hanging lots of small conductive objects in a line that were almost touching each other, and then letting the TC arc to them, caused horrendous broadband emissions well up into the GHz range.
I'm guessing that tiny air gaps can probably be broken down in processes that cause pico-second rise-times. The resulting rapid charging and discharging of small conductors produces an efficient source of UHF EMI. The conventional RQ-TCBOR static spark gap would seem to be about as bad as it gets in this regard!
Registered Member #74
Joined: Thu Feb 09 2006, 09:17AM
Location: Nottingham UK
Posts: 99
Joan, now has a Blue SMIRF Bluetooth RS232 adapter which works extremely well, sending data and control bidirectionally at 115.2Kbd.
The unit is fairly well shielded in an aluminium covered pipe apart from the arial to prevent RFI and the usable range is well over 10M with little or no interferance when the coil is running.
I have appied the same mod to my NOAH brick DRSSTC and I'm awaiting an opportunity to fire up a proper sized coil with this adapter.
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bluetooth to control the external mod
