Recommendations for the 40m SAD

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f6irf's picture
Last seen: 12 years 3 months ago
Joined: 2008/04/18 - 12:24
Recommendations for the 40m SAD

Sorry for repeating the same things again and again, but it still looks necessary !
On 40m almost everybody will hear everybody, so a few precautions are required:

- 40m propagation, and characteristics are no that different from 30m (the band noise is just 4dB higher); except that signal at short distance are likely to be extremely strong. With a decent antenna, 5W allows to be heard worlwide. Unless you are in a very remote area, or have a poor antenna, please avoid higher power, especialy during daylight hours (less PWR is better).

- Get your PC-clock synchronized. A few "old generation" PC's are heavily drifting (I have seen up to 1s every 2 hours). The ideal is to get something like "dimension4" which will resync your PC-clock every 15mn or so. If you can't do it, watch the DT column; if you see a majority of station with 0.6 to 1.4 DT everything is fine. if you see a majority of stations with a negative DT, or with DT>+2, try to correct using the DT window below the date/time window (using the mouse) - for example if you see a negative value for a majority of stations set a positive DT in the window until you get a majority of stations in the range + 0.6 to +1.4

- Get your TRX-frequency calibrated (during the last 15mSAD a few stations were transmitting outside the band). On 40m an easy way is to set your VFO on 7037.5 USB for 2mn and watch the Russian Naval beacons - If your TRX-freq is well calibrated you should see a line at 1400, 1450, 1500 and 1550 Hz, like on this picture.
Correct your VFO freq until you get the beacons lined-up with the round freq indication (faster if you use a real time spectrum display like WSJT-Spec-JT, argos, spectran or Spectrum-lab). Note the VFO correction and make it the same on 7038.6

- Assuming your TRX-freq is well calibrated, try to use the full 200 Hz spectrum (you may just avoid the first and the last 10Hz). A large majority of stations use the center of the band... thus many collisions in this segment...

- Try to find a free frequency slot... listen for 10mn before going on transmit - it may not be that easy during a SAD, if the activity is high (hope it will be) but try...

- When the activity is high, only use 20% TX rate; higher TX rate just multiply the risks of collisions...

Sorry for being so boring and enjoy the SAD !