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Re: L band Uplink



I looked into this myself before even running antenna simulations, and 
attached is a collection of messages from earlier this year on the topic.
I wanted to try to calculate this myself, but i can't run the Excel
spreadsheets on PowerPC LINUX and couldn't find anything about how to
calculate these things manually.  Collected estimates of needed EIRP 
varied from 400W to 8KW, depend on various factors, especially squint
angle.

So i picked the 1KW SSB figure and tried to get 20dBi gain on the uplink,
in order to run QRP.  I may be falling somewhat short of that, due to
linear vs. circular polarization mismatch.  But so far, i'm not hearing 
myself at all on the downlink, but the squint angle wasn't great, i'm not 
sure how much power i'm using or factors like SWR (both to be determined on 
Friday), and i'm not certain that the homebrew antenna design is working
properly.  I can comfortably copy anyone vaguely likely to interest LEILA 
on the 2.4G side of the dual-band feed, without any noticable de-sense from
the 1.2G side to the beacon or SSB QSO's.  I think i'm under-illuminating 
my dish, so there may be room for some improvement.  I'm not 100% certain
about the frequency calculations, either (other than avoiding the MB).

I'll report back later this week. Meanwhile, anyone else have any clues?

			         -- KD6PAG

Attachments: Messages from AMSAT-BB, first quarter 2002 (edited slightly
	     to remove quotations and unrelated details).
-------------------------------------------------------------------------------
From: "Rick Vidmar - K9KK" <k9kk@earthlink.net>
To: <amsat-bb@AMSAT.Org>
Subject: Fw: [amsat-bb] Recommended ERPs ?
Date: Sat, 5 Jan 2002 15:25:35 -0600

20 watts at a true 18.4 dbi linear antenna on 23 cm will do it at squints
below 10 degrees


Gang

Has anyone yet defined just how much power (ERP) it takes for satisfactory
comms via AO 40 yet ?  Both on 70cm (until LEILA takes an interest) and on
23cm (to achieve a signal 10db below the strength of the beacon).

-------------------------------------------------------------------------------
Date: Sat, 5 Jan 2002 20:34:31 +0000
From: Reinhard Richter <dj1km@dj1km.de>
To: Richard@g3rwl.demon.co.uk ((Richard W L Limebear))
CC: amsat-bb@AMSAT.Org
Subject: Re: [amsat-bb] Recommended ERPs ?

Hallo Richard,

Saturday, January 05, 2002, 3:48:03 PM, you wrote:
[...]

I think it's not defined, but when talking with people I learned that with
2 kW ERP on mode L you're on the safe side, while on U-uplink 500 W ERP is
more than sufficient. I think, that Domenico, I8CVS will know that much
better.

73,
 Reinhard
 DJ1KM                            

-------------------------------------------------------------------------------
From: "i8cvs" <domenico.i8cvs@tin.it>
To: "Reinhard Richter" <dj1km@AMSAT.Org>,
   "(Richard W L Limebear)" <Richard@g3rwl.demon.co.uk>
Cc: "AMSAT-BB" <amsat-bb@AMSAT.Org>
Subject: R: [amsat-bb] Recommended ERPs ?
Date: Sun, 6 Jan 2002 13:43:00 +0100

Hallo Richard,

Following a report  received from  Rene', DJ1KM using his panoramic receiver
on day December 12/01 with AO40 at very low squint angle for me about
3 to 4 degrees,i was 3 dB above the beacon using my 23 cm uplink.

My power was about 40 W in to a 4 x 23 elements yagi horizontally polarized
array.

Since the gain of this array is about 23 dBi = 200 time in power,my EIRP
at that time was 40 x 200 = 8000 W

If i liked to stay 10 dB belove the beacon at that time i had to reduce my
power by 13 dB or  20 time and so 40/20= 2 W

2 W in to my 23 dBi gain antenna make 2 x 200 = 400 W EIRP and this power
match very well with the nominal EIRP required for the L/S operation.

If the squint angle is very high like it is now days around 25 degrees or
more for me,the above 8000 W EIRP has not the capability to override the
beacon level by 3 dB but my signal is more than 10 dB belove the beacon
level.

Unfortunately,using 23 cm uplink it is very easy to override the beacon
because LEILA do not operate with the same level for uplink signals as in
the U band 435 MHz

In conclusion,the necessary EIRP using 23 cm uplink  changes from 400 W EIRP
...........and up depending on satellite Squint angle and Range

About the necessary EIRP using 70 cm uplink my antennas are 2 x 21 elements
yagi horizontally polarized and the gain is about 20 dBi or 100 time in
power.

When the Squint angle is very low,in the same order of 2 to 3 degrees,my
power must be 50  W or less at the antennas in order do not disturbe LEILA

In any case,when the Squint angle is around 25 to 30 degrees like it is at
some MA now days,i must use 300 W at the antennas or 3000 W EIRP to
be barely audible in to the S passband with a very havy QSB

Even in this conditions it is possible to get LEILA using 70 cm because the
uplink signal is very strong in to the U band satellite receiver input but
it is very weak in to the S dowlink receiver on the ground because of the
AO40 very high off-point.

I hope this help.

73 de i8CVS Domenico

-------------------------------------------------------------------------------
From: "Rick Fletcher" <rfletcher@plumdragon.com>
To: <simon@creoch.freeserve.co.uk>, <amsat-bb@AMSAT.Org>
References: <20020116145150.MPNS18169.fep06-svc.ttyl.com@localhost>
Subject: Re: Re: [amsat-bb] Another Uplink Antenna Inquiry
Date: Wed, 16 Jan 2002 14:08:57 -0800

I just recently put one of of Wimo's 23cm helix antennas (the 20-turn, 4 ft.
version) on my AZ/EL boom and finally worked AO-40 yesterday (in combination
with a 2' x 3' bbq grill/Transystem AIDC 3733 downconverter).  Distance was
> 24K miles, elevation was approx. 37 degrees and squint was about 22.  I
was driving the helix with a Kenwood TS-2000X which puts out 10 watts on
23cm.  There's 65 ft. of 9913 low loss feedline in between as well!

This morning, I decided to see if I could hit the bird when it was > 37000
miles away, elevation was just under 11 degrees and squint was over 54.
While the signal would be tiring to struggle with on a real voice QSO, it
was still there and recognizable.  Satellite "QRP"!

73 de KG6IAL

-------------------------------------------------------------------------------
From: "L Clare Fowler" <lcfowler@magma.ca>
To: "amsat-bb" <amsat-bb@AMSAT.Org>
Subject: Re: [amsat-bb] fiberglass boom
Date: Sun, 10 Feb 2002 19:48:40 -0500

I have two az/el rotor systems both using booms of 10 foot lengths of 
1 1/4 inch ID PVC electrical conduit pipe reinforced with an 8 ft piece 
of hardwood dowel.

One has been up there for over 10 years and the other  about 4.
They have been used to support a variety of home built helix and quagi 
ants that have given me thousands of satellite QSO's. My experience 
does not indicate any detrimental effects due to losses in the boom.
It currently supports and runs through the middle of my 23 cm 4 X 27 turn
helix array.  More than one third of my AO-40 QSO's have
lately been made with 10 watts in the shack with this array.

[...]

Clare VE3NPC
-------------------------------------------------------------------------------
From: "Howard Long" <howard@howardlong.com>
To: "Scott Elliott" <scott@pieh0.co.uk>, <amsat-bb@AMSAT.Org>
Subject: RE: [amsat-bb] s band converters, is the rsgb one any good?
Date: Mon, 4 Mar 2002 07:40:28 -0000

Hello Scott

> also, what sort of power is required to get on p3d on 23cms at apogee?

For a good signal, under good conditions at apogee, for SSB you need about
1kW EIRPc. I may get flamed for suggesting such high power, but I can only
go from my own experiences of the L band uplink. That's 10W into a 20dB gain
antenna.

[...]

73 Howard G6LVB
http://www.g6lvb.com

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