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CX2SA > SATDIG 13.05.13 20:42l 214 Lines 8527 Bytes #999 (0) @ WW
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Sent: 130513/1926Z @:CX2SA.SAL.URY.SA #:6183 [Salto] FBB7.00e $:AMSATBB8155
From: CX2SA@CX2SA.SAL.URY.SA
To : SATDIG@WW
Today's Topics:
1. Re: J-Pole Antenna (Robert Bruninga)
2. Re: J-Pole Antenna (Werner, HB9BNK)
3. Re: J-Pole Antenna (Matt Patterson)
----------------------------------------------------------------------
Message: 1
Date: Mon, 13 May 2013 13:12:46 -0400
From: Robert Bruninga <bruninga@xxxx.xxx>
To: "Werner, HB9BNK" <hb9bnk@xxxx.xx>, amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: J-Pole Antenna
Message-ID: <ecd259d580f193ef0a3946dbf1742749@xxxx.xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1
> The antenna, that I want to build, is described in a paper (probably 20
years old)
> by Dick, WD4FAB, titled 'Antennas for microsat ground stations', and the
paper
> describes the large time, a LEO remains at low elevations - about 76 %
below 20 degrees -
> and then concludes, that this is fine for a J-Pole.
Absolutely true with respect to the*antenna pattern* but the current batch
of LEO satelltes even though they are in the main beam of the omni antenna
at the horizon, are -too-far-away- to be heard with only 2.1 dB of omni
dipole antenna gain.
So yes, those are good "satellite antennas" for omni coverage, but they
wont hear anything that low because the satellites are 3000km away and the
current crop of satliltes mostly operate in the 1/2 watt or less area.
The only thing you will hear down to the horizon with these antetnnas is
the ISS that is operating at 10 watts or more.
You are better off simply giving up on the horizon (for an omni) and
increasing your gain higher up. And a 1/4 wave whip over a ground screen
will give you 5.1 dBi instead of 2.1 dBi. And then you may begin to hear
things above about 15 degrees or so (and 3 dB better than you would hear
on any antenna optimized for the horizon..
And it is even better to go to a 3/4 wave vertical over a ground screen
and then you get almost 7 dBi gain starting around 30 degrees. You wont
hear the low satellites (you can't anyway on an omni) but you will hear
them much better when they do get above about 25 degrees... (but notice,
this is less than 1/4th of all passes).
------------------------------
Message: 2
Date: Mon, 13 May 2013 20:02:14 +0200
From: "Werner, HB9BNK" <hb9bnk@xxxx.xx>
To: Robert Bruninga <bruninga@xxxx.xxx>
Cc: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: J-Pole Antenna
Message-ID: <51912AA6.8000205@xxxx.xx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Thank you for your advice - very much appreciated.
The beauty of the J-Pole, I have in mind, is, that it contains
both 2m and 70cm Systems on one mast - so I could simply attach
the two cables going to the IC910 directly .... hi
The little yagi, I used, has a gain of 5.5 dBd for 2 meters and 8
dBd for 70 cm. So, I guess, you say, investing time for the
defunct rotor is better spent than trying omni.
Yes, I must find a solution for this.
Am 13.05.2013 19:12, schrieb Robert Bruninga:
>> The antenna, that I want to build, is described in a paper (probably 20
> years old)
>> by Dick, WD4FAB, titled 'Antennas for microsat ground stations', and the
> paper
>> describes the large time, a LEO remains at low elevations - about 76 %
> below 20 degrees -
>> and then concludes, that this is fine for a J-Pole.
>
> Absolutely true with respect to the*antenna pattern* but the current batch
> of LEO satelltes even though they are in the main beam of the omni antenna
> at the horizon, are -too-far-away- to be heard with only 2.1 dB of omni
> dipole antenna gain.
>
> So yes, those are good "satellite antennas" for omni coverage, but they
> wont hear anything that low because the satellites are 3000km away and the
> current crop of satliltes mostly operate in the 1/2 watt or less area.
> The only thing you will hear down to the horizon with these antetnnas is
> the ISS that is operating at 10 watts or more.
>
> You are better off simply giving up on the horizon (for an omni) and
> increasing your gain higher up. And a 1/4 wave whip over a ground screen
> will give you 5.1 dBi instead of 2.1 dBi. And then you may begin to hear
> things above about 15 degrees or so (and 3 dB better than you would hear
> on any antenna optimized for the horizon..
>
> And it is even better to go to a 3/4 wave vertical over a ground screen
> and then you get almost 7 dBi gain starting around 30 degrees. You wont
> hear the low satellites (you can't anyway on an omni) but you will hear
> them much better when they do get above about 25 degrees... (but notice,
> this is less than 1/4th of all passes).
>
------------------------------
Message: 3
Date: Mon, 13 May 2013 13:57:41 -0500
From: Matt Patterson <mattpatt@xxxxxxxx.xxx>
To: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: J-Pole Antenna
Message-ID: <519137A5.50101@xxxxxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Back when I was on the FM sats I used a small yagi for 2m and another
one for 70cm. I built a mast out of some 2" PVC that came out to a T
and had 45 degree elbows on it. I then mounted the antennas on the
elbows so that they were pointed roughly 45 degree up. The whole thing
was mounted to a cheap radio shack rotator. The rotator was mounted to
a metal fence post (t-post). The antennas were maybe 7' off the ground
at the highest point. I could work just about all passes with this
setup. Using one radio for RX and another radio for TX. Only passes I
couldn't work were either real low or I would loose signal for a few
minutes when I had overhead pass. Do a google on my callsign and you'll
find several recordings I made of suitesat with this setup that I have
uploaded to Soundcloud.
73 Matt
W5LL
On 5/13/2013 1:02 PM, Werner, HB9BNK wrote:
> Thank you for your advice - very much appreciated.
>
> The beauty of the J-Pole, I have in mind, is, that it contains both 2m
> and 70cm Systems on one mast - so I could simply attach the two cables
> going to the IC910 directly .... hi
>
> The little yagi, I used, has a gain of 5.5 dBd for 2 meters and 8 dBd
> for 70 cm. So, I guess, you say, investing time for the defunct rotor
> is better spent than trying omni.
>
> Yes, I must find a solution for this.
>
>
>
>
> Am 13.05.2013 19:12, schrieb Robert Bruninga:
>>> The antenna, that I want to build, is described in a paper (probably 20
>> years old)
>>> by Dick, WD4FAB, titled 'Antennas for microsat ground stations', and
>>> the
>> paper
>>> describes the large time, a LEO remains at low elevations - about 76 %
>> below 20 degrees -
>>> and then concludes, that this is fine for a J-Pole.
>>
>> Absolutely true with respect to the*antenna pattern* but the current
>> batch
>> of LEO satelltes even though they are in the main beam of the omni
>> antenna
>> at the horizon, are -too-far-away- to be heard with only 2.1 dB of omni
>> dipole antenna gain.
>>
>> So yes, those are good "satellite antennas" for omni coverage, but they
>> wont hear anything that low because the satellites are 3000km away
>> and the
>> current crop of satliltes mostly operate in the 1/2 watt or less area.
>> The only thing you will hear down to the horizon with these antetnnas is
>> the ISS that is operating at 10 watts or more.
>>
>> You are better off simply giving up on the horizon (for an omni) and
>> increasing your gain higher up. And a 1/4 wave whip over a ground
>> screen
>> will give you 5.1 dBi instead of 2.1 dBi. And then you may begin to
>> hear
>> things above about 15 degrees or so (and 3 dB better than you would hear
>> on any antenna optimized for the horizon..
>>
>> And it is even better to go to a 3/4 wave vertical over a ground screen
>> and then you get almost 7 dBi gain starting around 30 degrees. You wont
>> hear the low satellites (you can't anyway on an omni) but you will hear
>> them much better when they do get above about 25 degrees... (but notice,
>> this is less than 1/4th of all passes).
>>
> _______________________________________________
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>
------------------------------
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End of AMSAT-BB Digest, Vol 8, Issue 155
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