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AO-40 QRV report on orbit#251 from Japan.

Hello This is Yoshi.

  This is a report of my AO-40 QRV on orbit#251 during 13:25-21:50z
of 17th.May,2001. When the lats part of Xpond-on time (15:45-LOS),
EU was in the footprint with a good SQA.

1. Equipments

      S-Down : MAKI 29ele LOOP YAGI + LNA + 2way splitter
               FT-817 for Telemetry receiving.
               IC-821 for communication.
      U-Up   : IC-821 (5-20W) with 25deg. fixed elv. 6ele YAGI.

2. QRV Documents

 UTC__ MA_ Dist(km) Events__________
 13:25  38 37,230  Returned home and started S2-MB receiving. Could hear
                   with QSB.
 15:30  66 49,750  Pointed antenna at the direction of 1 hour later, then
                   went to bed with left AO40RCV running.
 - - - -
 17:33  94 56,750  (zzz..sleeping...) My PC hunged up!
 - - - -
 18:50 111 59,250  Woke up and found my freezed PC x-<. Restarted it.
 18:58 113 59,440  Restarted S2-MB receiving, then sleep in again.
 - - - -
 20:35 135 60,590  Woke up. Adjusted antenna direction.
 20:40 136 60,590  Did comparing of LNA effect (*) til 21:13
 21:07 142 60,520  PC Hunged up again! Gaaaa! x-O.
 21:13 144 60,480  Heard a strong foreign language (likes Italian?) voice
                   on 2401.348. Just only a few dB's weak than S2-MB but
                   had not warned by LEILA... From L uplink?? At this time
                   the U-Rx AGC was 13db!
 21:16 144 60,460  Loop test on 2401.430. RST = 419 so weak. Maybe somebody
                   is eating my signals somewhere...
 21:17 144 60,451  Heard "...Uno Alpha Oska Excele..." on 2401.348 as too
                   much strong voice. It might be "..1AOX.." in Italian
                   phonetic. Maybe he or his friend italian station heard
                   or worked with Ian ZL1AOX a few hours befor... No warning
                   of LEILA there was.
 21:18 145 60,440  Heard CW on 2401.356 sending "TEST VV...". But could not
                   get callsign.
 21:19 145 60,430  Heard SSB CQ from DC8TS Hardy on 2401.369. Then he worked
                   with JH1AOY.
 21:27 147 60,360  Called DB8TS on SSB, but my return signal was not enough
                   to reach him except "C", so I called him on CW then worked
                   on crossmode 53-559.
 21:29 147 60,340  Heard like as "PE..." at around 2401.370 SSB. Could not
                   copy well.
 21:31 148 60,320  Loop tested on 2401.380, RST 529. I called CQ on CW til
                   21:40 but no responce.
 21:40 150 60,200  QRT (06:40 local). I have to go to work...
 21:50 152 60,050  Stopped receiving S2-MB, then left home.

  Finally I got 1,164 CRCC OK blocks of total 1,717 (68%). At around
apogee, the rate was excellent 95%.
  And also I feel sad when I heard too much strong voice saying Ian's
callsign. If he love DX, he should not put so much strong power...

3. Compairing the effect of LNA.

  This morning, at around apogee, I tried to compare the receiving
ability (or effect of LNA) of my system for S2-MB. I kept my system
on same conditions except the preamp/att setting as below;

  case 1) Without LNA. Basic Modified Drake2880 only.
  case 2) With LNA of JI5MFZ's prototype ( 0.3dB NF / 15dB Gain )
  case 3) With LNA of MAKI electronics   ( 0.8dB NF / 20db Gain )
             + IF 10dB ATT
  case 4) Same as 3) without 10dB ATT

  I got 4 capture images of AO40RCV of each cases, then compared it.
All image captures were taken at the time of (perhaps) the end of E or N
block receiving (heard just like as 2 tone modulated signal).

Comparing Image.

  I could not find ant documentation on AO40RCV manual about how
much dB is per holizontal gage line. So I tried to measure it at my
case. I put my DMM (AC Voltage range) pararel at the cable between
FT-817 and PC, then adjust the AF volume of FT-817 to see the movement
of noise level graph without no signal receiving.
  My DMM said that there was about x3.1 voltage difference per line,
It is meaning **10dB per line**. Oh, it was bigger than I thought.

  So, if the line unit is 10dB, the S/(S+N) ratio of no-LNA is about
20dB, but with LNA is about 30dB. There can be seen no big difference
between 0.3dB LNA & 0.8dB LNA. Ofcouse I can not feel any difference
between these at hearing.
  And, please note that this capture image is almost not modulated
signal (same as a 2 tone modulated signal). When it had full-modulated
by telemetry data, maybe the peak signal will down about 10dB or less.
That is mean the S/(S+N) will be about 10dB smaller than the value
of above.

  So, finally, the S/(S+N) of S2-MB is 20dB with LNA, or 10dB without
LNA. It is totally close to the result of W3PM's excel sheet


  S2-MB is +8dB than S2-GB, and our communication signals have to
be smaller than it. Our signal levels should be 10dB less than S2-MB
level. This means that the S/(S+N) will be only 10dB with LNA, but
almost 0dB without LNA!
  How do you feel this result? if your equipemts are as same as mine,
you might feel "Wow how difficult itis to work on SSB".

# We should use a good LNA with our modified MMDS converter!

  By the way, at the case of enough gain LNA, there is no difference
between no IF ATT or 10dB IF ATT. If you see so much high S-meter
reading at your receiver, do not panic, it is just the noise floor
that had pulled up by your overgained converter.
  To keep the dinamic range of your receiver, you should put some
value of ATT pad at the IF stage of your system, to reduce your S-meter
reading to near zero. Or do not worry about the loss of IF cable,
maybe the cheepest long cable will be work fine!

  This was too very interesting result!

  Thank for reading.

Yoshihiro Imaishi JF6BCC/KH2GR
GL:PM53JV, ex KC6IY(T88IY),V63BP
mailto:jf6bcc@jarl.com or jf6bcc@jamsat.or.jp
<http://plaza16.mbn.or.jp/~palau/> Sorry, Japanese only now.
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