Let me add here my experience with the SDR-ATU, further info you find in chapter on page 11 of the operating manual.pdf dated Mar. 31, 2005. v0.6:
- The SDR-ATU is not a coupler designed to match any chunk of wire like your home brew coupler might be able to do. It is more a "line-flattener". Therefore be extremely careful when attempting to match with the SDR-ATU other antennas than nearly resonant ones, or antenna systems pre-tuned with an external tuner. In my case I tried to match a 2x20m dipole with parallel wire feeder and 1:4 balun at the feeding point on the 17m band. The SDR-ATU cannot match such odd setups. Unfortunately I "succeeded" in blowing up parts of the SWR-bridge on the 100W PA (R8 and D1 and D2) when trying this. All in all I was rather lucky, replacing this components take less time than changing the final transistors :) So NEVER tune into an unknown/exotic antenna system. In tune mode with the ATU the SDR obviously delivers more power than selected in the setup. I use always default 10W tune power, but an external power meter shows between 30-50W depending on the tuning status of the ATU. Another unpleasant effect when tuning to "non matchable" antennas is that the console freezes and stays in transmitting mode. You can power off the console and close it on the screen, but the process is still in the task manager and cannot be killed. Only PC power off/on helps. Above effect may be caused by strayed RF jamming the USB adaptor even so my rig is grounded properly and the USB cable is fitted with an additional ferrite cube. Unfortunately there is no schematic available for the SDR-ATU, Gerald seems to be bound by a non discloser agreement with the OEM of the ATU so there is little chance to modify your ATU to your personal antenna conditions. Better you match your antenna parameters to the SDR-ATU ;-) - Tuning to a DRM station with beta 1.3.4 shows a strange behaviour on the panadapter display, reception on a specified frequency is not possible. - In SPEC mode the tuned signal is negative off the centre of the display. My setup: Beta 1.3.4, XP pro, SDR see above, USB adaptor, delta 44 setup according to the latest recommendations 0,98V/-10dBv, MP3+ for mic amp. 73 Werner, DL2JA
