[amsat-bb] BY70-1 Observations

John Papay john at papays.com
Wed Jan 4 06:39:50 UTC 2017


I had a chance to run some tests on BY70-1
this evening from my Arizona Station since there
was no one on the pass.  It was only a 15 degree pass
for me but the satellite did very well.

BY70-1 is much stronger than SO-50.  The morning passes
are around 500KM and the evening passes are only 250KM.
But the signal is quite strong on both.  If you are having
trouble hearing SO-50, try BY70-1.  You should hear it much
better.

At first I thought the sensitivity might not be very good, but
upon further testing it was possible to hold the satellite
at 1 watt provided that you were on the right polarity at
the moment.  I was changing between horizontal and vertical
frequently.  The wrong polarity produced noise, but a switch to
the opposite polarity yielded a full quieting signal consistently.

Many have experienced dropout when attempting to talk through the
satellite.  Sometimes it is due to the many signals present on
the input frequency including those that are not coming from
satellite users.  It's the same situation on SO-50.  But there
are also dropouts that occur when there is no one else on the
input.

It seems that if you are fairly wide in deviation, certain
speech will cause the satellite to stop transmitting.  This
may be a receiver bandwidth issue or perhaps the PL
decoder responding to voice frequencies etc.  At any rate
I think the dropouts are due to the PL decoder not decoding
the PL tone for the above reasons.

BY70-1 seems to be less sensitive to dropouts if you use narrow
band FM on the transmit.  I found very little difference in the
repeated audio level when using wide or narrow.  So there is
signal processing in play which keeps the audio output level
constant.  AO-85 audio levels do change quite a bit between
wideband and narrow.  So do use narrow FM on this bird for
best results.

The signal processing also apparently causes a significant
delay in the repeated audio.  It can cause some discomfort
but keep the rx level low so you are able to ignore the delay
and converse normally.  Audio quality is quite good.

Some have thought there is some sort of VOX on the bird
but a dead carrier seems to hold the transmitter keyed with
no audio present.  Again, the PL Decoder is likely responsible
for the dropouts.

Be sure to download the latest keps from Celestrak or apace-track.
The keps on the amsat site may not always be current.  The orbit is
changing daily so get the new keps every 24 hours.  The catalog
number is 41909. http://celestrak.com/NORAD/elements/tle-new.txt
The amsat nasa.all file can be edited with Wordpad and the new
keps can replace the ones in the file if different.  Set your PL
to 67Hz just like SO-50.

doppler.sqf:
BY70-1,436200,145920,FM,FM,NOR,0,0,FM Voice
BY70-1,436200,145920,FM,FMN,NOR,0,0,Narrow FM Voice
The coordinated frequencies seen to be close enough.

I have asked KX9X to facilitate adding BY70-1 to the list of
satellites in LOTW.

Don't be reluctant to try this satellite.  You will find
it much easier to access than SO-50 or AO-85.  It does have
a short window but you can hear it down low if you don't
have any obstructions.

73,
John K8YSE/7 


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