[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Orbit 250 apogee



At 18:33 16-05-2001, you wrote:

>Wayne replies:
>
>I was up for the orbit 250 apogee and made 5 contacts.  This was my first
>time to listen to AO40 near apogee.  I was impressed that the beacon was 3
>S-units above my noise level with relatively little fading.  That's with a
>21 dBi 60 cm TranSystem linear dish and AIDC3733 downconverter (stub cut,
>thermistor added).  I was disappointed that there weren't more stations on.

If it was the middle beacon you meant, stations are supposed to be 8 dB 
weaker than that. You say that you have the bcn 3 S-units above the 
noisefloor. Assuming max 6db per s-unit, that doesn't look like leaving 
much room for hearing any stations that are in compliance with the -8dB rule.
So, the stations were probably there, below your noise

>It was also my first experience with LEILA.  That thing is really picky.

It follows the standard that lets everybody get their fair share.
Do YOU, unless LEILA forces you!!!!

>Here are my observations about LEILA:

Best thing since bottled milk, lets the small stations get their share, at 
the expense of the deaf alligators!!

>1. With my (less than optimum) receiving setup

So, you admit where the problem is....?

>LEILA likes to make the siren
>tone just when I can start to hear my downlink well.

Which tells you what, Ali?

>  I can't run more than
>about 10W (after cable loss) into a 30 element CP yagi

Thank God!

>  without getting the
>attention of LEILA.

As you should!!!!

>2. For a few minutes before I shut down the radio I was doing other things
>while still tuned to the frequency of my last QSO.  There were no stations
>on that frequency, but the LEILA siren came on several times.  Did anybody
>else hear the LEILA siren on an empty channel?

Do you really believe it WAS empty....!

>3. It appears that people uplinking on 23cm can get MUCH stronger downlinks
>(than people uplinking on 70 cm) without triggering the LEILA siren tone.

It has been said that LEILA is not currently active on L-band.
Hopefully that will come soon.

>I'm not sure it's reasonable for LEILA to completely eliminate AGC on the
>70cm uplink because that doesn't permit decent downlink signal strength.

Are you quite sure you have grasped the concept of AGC?

>I don't know how much better I will hear when I finally get a 2155 MHz stub
>or ISM ceramic filter to eliminate noise from the 2155 MHz image in my
>TranSystem downconverter.

If you don't already have a preamp, get one. There is no getting around it.

>  I'm still disappointed in the downlink signal
>strength of AO40.  For me, the AO40 downlink is less readable than what I
>got from AO13 with much less RX antenna gain.

Go read some of G3RUH's articles, then you will understand how this scales 
with frequency.

>Part of my readability
>problem is that for AO13 I used a Timewave DSP-9+ noise reduction unit which
>greatly improved the readability of weak signals.  The DSP noise reduction
>in my FT-847 doesn't seem to improve readability at all.

DSP BS, there is no replacement for the strong, clear signal coming from 
the ant.

>I asked this question a week ago and didn't get an answer:  Will the "final"
>S-band downlink use more power and/or a higher-gain antenna?

As stations with a decent Ear will have told us by now, it's already fine.
Just need to improve your station.

73 de OZ1LRG

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home