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CX2SA > SATDIG 06.06.10 05:07l 903 Lines 31391 Bytes #999 (0) @ WW
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From: CX2SA@CX2SA.LAV.URY.SA
To : SATDIG@WW
Today's Topics:
1. WD9EWK - midday Saturday (Patrick STODDARD)
2. AO-27 schedule updated (George Henry)
3. Re: Re HELIX REFLECTOR? (John Belstner)
4. Re: Re HELIX REFLECTOR? (STeve Andre')
5. Falcon 9 video - moving early? (vk1pe.peter)
6. WD9EWK @ DM44xj/DM54aj now (Patrick STODDARD)
7. Re: HELIX REFLECTOR? (i8cvs)
8. Re: Falcon 9 video - moving early? (Andrew Glasbrenner)
9. Re: Falcon 9 video - moving early? (Joe)
10. Re: Falcon 9 video - moving early? (B J)
11. Re: Falcon 9 video - moving early? (B J)
12. Re: Re HELIX REFLECTOR? (John Belstner)
13. HELIX REFLECTOR (i8cvs)
14. Fw: WD9EWK @ DM44xj/DM54aj now (i8cvs)
15. Re HELIX REFLECTOR? (i8cvs)
16. Re: FIELD DAY SCORING (Gary "Joe" Mayfield)
----------------------------------------------------------------------
Message: 1
Date: Sat, 5 Jun 2010 12:05:18 -0700 (PDT)
From: Patrick STODDARD <amsat-bb@xxxxxx.xxx>
Subject: [amsat-bb] WD9EWK - midday Saturday
To: amsat-bb@xxxxx.xxx
Message-ID: <398303.56467.qm@xxxxxxxx.xxxx.xxx.xxxxx.xxx>
Content-Type: text/plain; charset=us-ascii
Hi!
This has been a good hamfest here in Show Low AZ. The morning started
with 12 QSOs on AO7 around 1400 UTC! More on VO52 and SO50 later.
Thanks to K8YSE and KD8CAO in Michigan for the QSOs, as well as N5AFV
operating as KK5W in Texas. I will be on SO50 @ 1913 UTC followed by
AO27 @ 1937 UTC to wrap up the hamfest demos.
Thanks to WA8SME, N5AFV as KK5W, and AA5CK for talking with a Boy Scout
that stopped by during the 1730 UTC SO50 pass! Several Scouts were able
to satisfy several requirements toward th Radio Merit Badge, including
the Scout who was on the mic.
My first pass from DM54 (or possibly the DM44/DM54 boundary) will
be a shallow AO7 pass at 2256 UTC. Hope to put more in the log then,
to go with 33 QSOs wlready logged at the hamfest with two passes
remaining.
73!
Patrick WD9EWK/VA7EWK - Show Low, Arizona
http://www.wd9ewk.net/
------------------------------
Message: 2
Date: Sat, 5 Jun 2010 14:26:30 -0500
From: "George Henry" <ka3hsw@xxx.xxx>
Subject: [amsat-bb] AO-27 schedule updated
To: "amsat bb" <amsat-bb@xxxxx.xxx>
Message-ID: <5284E4FBE1E74CD58D2C59AA4A4C332F@xxxxxxx>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
A new schedule was uploaded to the satellite on May 30th. All users of the
Java schedule lister should update your data files to be sure you have the
latest schedule.
George, KA3HSW
------------------------------
Message: 3
Date: Sat, 5 Jun 2010 14:07:15 -0700
From: John Belstner <jbelstner@xxxxx.xxx>
Subject: [amsat-bb] Re: Re HELIX REFLECTOR?
To: Clare Fowler <clarefowler@xxxxxx.xxx>
Cc: amsat-bb <amsat-bb@xxxxx.xxx>
Message-ID: <192F3222-C2A6-4CAB-8439-BE50F60F9BDB@xxxxx.xxx>
Content-Type: text/plain; charset=us-ascii
Just another $0.02 to add.
You will find that the size and shape of the reflector will not affect the
forward gain as much as it does the F/B ratio. It depends on what is
important to you and (of course) how high you are above the ground. Even
for satellite operation pointing up, large back lobes reflecting off the
ground can adversely affect the forward pattern when the antenna is mounted
only 6-8 feet above ground.
On Jun 4, 2010, at 10:13 PM, Clare Fowler wrote:
>
> To add to the discussion the July/Aug 2007 Amsat Journal has an article
> covering some gain comparisonmeasurements I made between four
> 13 turn (2.88 wavelengths) 13cm antennas with different square solid
> aluminum reflectors.
> The sizes were 0.56 wavelengths, 0.84 wavelengths, 1.0 wavelength and 1.4
> wavelengths.
> There was no difference between the 0.84, 1.0 and 1.4 wavelengths but the
> antenna with the0.56 wavelength reflector had 1.5 db less gain.
>
> However for my 70cm helix antennas I followed the Satellite Handbook
> minimum
> size of 0.6 wavelengthsor slightly over 16 inches. I used 1/2 inch hardware
> cloth
> mesh to keep the weight and windloading down.
> These antennas have performed well however it appears that they would be a
> bit better with a somewhat larger reflector.
>
> A brief description and picture of the 70 cm reflector is in the
> November/December 2005 Amsat Journal article on
> The Development of a Quarter Wave Match for helical antennas.
>
> Clare VE3NPC
>
>>> Hi All:
>>> I am rebuilding a 440 MHZ Helix that I built several years ago . It
>>> worked very well, but I would like to reduce the size of the reflector to
>>> a more manageable size than I had before. The only reference to reflector
>>> size I can find is, "minimum 20" ". I may be looking in the wrong places.
>>> I would appreciate it, if someone would steer me in the right direction.
>>> Thanks,
>>> Pete, K1HZU
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 4
Date: Sat, 5 Jun 2010 17:10:57 -0400
From: "STeve Andre'" <andres@xxx.xxx>
Subject: [amsat-bb] Re: Re HELIX REFLECTOR?
To: amsat-bb@xxxxx.xxx
Message-ID: <201006051710.57869.andres@xxx.xxx>
Content-Type: text/plain; charset="iso-8859-1"
john, whats a good rule for height of the antennas to avoid large
back lobes reflecting, ie how many wavelengths up should the
antennas be? Thanks...
--STeve Andre'
wb8wsf en82
On Saturday 05 June 2010 17:07:15 John Belstner wrote:
> Just another $0.02 to add.
>
> You will find that the size and shape of the reflector will not affect the
> forward gain as much as it does the F/B ratio. It depends on what is
> important to you and (of course) how high you are above the ground. Even
> for satellite operation pointing up, large back lobes reflecting off the
> ground can adversely affect the forward pattern when the antenna is mounted
> only 6-8 feet above ground.
>
> On Jun 4, 2010, at 10:13 PM, Clare Fowler wrote:
> > To add to the discussion the July/Aug 2007 Amsat Journal has an article
> > covering some gain comparisonmeasurements I made between four
> > 13 turn (2.88 wavelengths) 13cm antennas with different square solid
> > aluminum reflectors.
> > The sizes were 0.56 wavelengths, 0.84 wavelengths, 1.0 wavelength and 1.4
> > wavelengths.
> > There was no difference between the 0.84, 1.0 and 1.4 wavelengths but the
> > antenna with the0.56 wavelength reflector had 1.5 db less gain.
> >
> > However for my 70cm helix antennas I followed the Satellite Handbook
> > minimum
> > size of 0.6 wavelengthsor slightly over 16 inches. I used 1/2 inch
> > hardware cloth
> > mesh to keep the weight and windloading down.
> > These antennas have performed well however it appears that they would be
> > a bit better with a somewhat larger reflector.
> >
> > A brief description and picture of the 70 cm reflector is in the
> > November/December 2005 Amsat Journal article on
> > The Development of a Quarter Wave Match for helical antennas.
> >
> > Clare VE3NPC
> >
> >>> Hi All:
> >>> I am rebuilding a 440 MHZ Helix that I built several years ago . It
> >>> worked very well, but I would like to reduce the size of the reflector
> >>> to a more manageable size than I had before. The only reference to
> >>> reflector size I can find is, "minimum 20" ". I may be looking in the
> >>> wrong places. I would appreciate it, if someone would steer me in the
> >>> right direction. Thanks,
> >>> Pete, K1HZU
------------------------------
Message: 5
Date: Sun, 06 Jun 2010 06:59:47 +1000
From: "vk1pe.peter" <vk1pe.peter@xxxxx.xxx>
Subject: [amsat-bb] Falcon 9 video - moving early?
To: amsat-bb@xxxxx.xxx
Message-ID: <4C0ABAC3.6020103@xxxxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
I think that my eyes are not deceiving me.
See http://www.youtube.com/watch?v=sP5gykvTBpM or http://bit.ly/dx9Vot.
Falcon 9 appears to move at about T -3s. The count is still running
towards zero in the video, and the "call" seems to be between 4 and 3.
What do others think?
Also, were the umbilicals meant to "tear away" (as it moved) or "drop
away" (before it moved)?
Peter
VK1PE
------------------------------
Message: 6
Date: Sat, 5 Jun 2010 15:35:27 -0700 (PDT)
From: Patrick STODDARD <amsat-bb@xxxxxx.xxx>
Subject: [amsat-bb] WD9EWK @ DM44xj/DM54aj now
To: amsat-bb@xxxxx.xxx
Message-ID: <246321.60575.qm@xxxxxxxx.xxxx.xxx.xxxxx.xxx>
Content-Type: text/plain; charset=us-ascii
Hi!
I found a spot on the DM44/DM54 line for the passes starting with the
AO7 pass at 2256 UTC through at least the SO50 pass at 0206 UTC. Hope
to work you from here.
73!
Patrick WD9EWK/VA7EWK - north of Show Low, Arizona
http://www.wd9ewk.net/
------------------------------
Message: 7
Date: Sun, 6 Jun 2010 00:45:13 +0200
From: "i8cvs" <domenico.i8cvs@xxx.xx>
Subject: [amsat-bb] Re: HELIX REFLECTOR?
To: <k1hzu@xxxx.xxx>, "AMSAT-BB" <amsat-bb@xxxxx.xxx>
Message-ID: <001201cb0500$c3511180$0201a8c0@xxx.xx>
Content-Type: text/plain; charset="iso-8859-1"
----- Original Message -----
From: "Pete Norris, K1HZU" <k1hzu@xxxxx.xxx>
To: <amsat-bb@xxxxx.xxx>
Sent: Friday, June 04, 2010 2:51 AM
Subject: [amsat-bb] HELIX REFLECTOR?
> Hi All:
> I am rebuilding a 440 MHZ Helix that I built several years ago . It worked
very well, but I would like to reduce the size of the reflector to a more
manageable size than I had before. The only reference to reflector size I
can find is, "minimum 20" ". I may be looking in the wrong places. I would
appreciate it, if someone would steer me in the right direction.
> Thanks,
> Pete, K1HZU
>
Hi Pete, K1HZU
My 15 turns RHCP 70 cm Helix Antenna was built at first with a round
aluminum sheet perforated reflector with a diameter of 460 mm
( 0.67 wavelenght) and it worked very well but after enlarging the diameter
of reflector to 690 mm (about 1 wavelenght) overlapping to it a perforated
aluminum mesh I realized that the gain increases by about 2 dB and the front
to back ratio was much better than before.
The Helix is made with a non annealed wiredrawn aluminum rod 8 mm in
diameter and the boom is made with a very hard plastic pipe 42 mm outside
diameter and 31 mm inside diameter originally used for hight pressure oil
ducts.
Following "ANTENNAS" from John Kraus the lenght of a turn has been
made 1 wavelenght long into free space and the pitch angle between turns
is about 13.8 degrees while the calculated half-power beam width is about
28 degrees.
The matching system between the 150 ohm impedance at the feed point and
a 50 ohm coax cable is made using a 1/4 electrical wavelenght impedance
transformer with Zo = 86 ohm made with two coaxial tubing.
For better performance and not to distort the pattern the antenna is
fastened to the rear of reflector and the weight is balanced with a
counterweight made with few lead disks.
The picture of the above 15 turns helix antenna is visible at i8CVS in
QRZ.com
I have built two Helix Antennas the first one is a 10 turns with 0.67
wavelenght round reflector used beginning from OSCAR-7 to actually
FO-29 and HO-68 and it works very well.
The second one is a 15 turns helix with a 1 wavelenght in diameter round
reflector and it was used for the uplink from OSCAR-10 to AO40 as can
be seen at i8CVS in QRZ.com but unfortunately I cannot use it for LEO
satellites because the AZ/EL mount is slow because it was designed for
HEO satellites and this is why I pull for P3E !
If someone is interested to built the above antenna for 10 or 15 turns I can
send a zipped file with all the electrical and mechanical sized drawings of
it.
Best 73" de
i8CVS Domenico
------------------------------
Message: 8
Date: Sat, 5 Jun 2010 18:57:06 -0400 (EDT)
From: Andrew Glasbrenner <glasbrenner@xxxxxxxxxx.xxx>
Subject: [amsat-bb] Re: Falcon 9 video - moving early?
To: vk1pe.peter@xxxxx.xxxx amsat-bb@xxxxx.xxx
Message-ID:
<10984346.1275778627017.JavaMail.root@xxxxxxxxxxxxx.xxx.xx.xxxxxxxxx.xxx>
Content-Type: text/plain; charset=UTF-8
SpaceX starts all nine engines and makes sure they are operating to spec
before releasing the rocket from the pad. The shuttle does the same thing
with the three shuttle engines before they light the solids.
73, Drew KO4MA
-----Original Message-----
>From: "vk1pe.peter" <vk1pe.peter@xxxxx.xxx>
>Sent: Jun 5, 2010 4:59 PM
>To: amsat-bb@xxxxx.xxx
>Subject: [amsat-bb] Falcon 9 video - moving early?
>
>I think that my eyes are not deceiving me.
>
>See http://www.youtube.com/watch?v=sP5gykvTBpM or http://bit.ly/dx9Vot.
>Falcon 9 appears to move at about T -3s. The count is still running
>towards zero in the video, and the "call" seems to be between 4 and 3.
>What do others think?
>
>Also, were the umbilicals meant to "tear away" (as it moved) or "drop
>away" (before it moved)?
>
>Peter
>VK1PE
>_______________________________________________
>Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
>Not an AMSAT-NA member? Join now to support the amateur satellite program!
>Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 9
Date: Sat, 05 Jun 2010 18:27:06 -0500
From: Joe <nss@xxx.xxx>
Subject: [amsat-bb] Re: Falcon 9 video - moving early?
To: amsat-bb@xxxxx.xxx
Message-ID: <4C0ADD4A.7020701@xxx.xxx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
yES BUT IN THAT VIDEO BELOW IT IS CLEASRLY OFF THE PAD AND MOVING UP AT
T-3 SECONDS.
The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com
On 6/5/2010 5:57 PM, Andrew Glasbrenner wrote:
> SpaceX starts all nine engines and makes sure they are operating to spec
before releasing the rocket from the pad. The shuttle does the same thing
with the three shuttle engines before they light the solids.
>
> 73, Drew KO4MA
>
> -----Original Message-----
>
>> From: "vk1pe.peter"<vk1pe.peter@xxxxx.xxx>
>> Sent: Jun 5, 2010 4:59 PM
>> To: amsat-bb@xxxxx.xxx
>> Subject: [amsat-bb] Falcon 9 video - moving early?
>>
>> I think that my eyes are not deceiving me.
>>
>> See http://www.youtube.com/watch?v=sP5gykvTBpM or http://bit.ly/dx9Vot.
>> Falcon 9 appears to move at about T -3s. The count is still running
>> towards zero in the video, and the "call" seems to be between 4 and 3.
>> What do others think?
>>
>> Also, were the umbilicals meant to "tear away" (as it moved) or "drop
>> away" (before it moved)?
>>
>> Peter
>> VK1PE
>> _______________________________________________
>> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
>> Not an AMSAT-NA member? Join now to support the amateur satellite program!
>> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>>
>
>
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>
>
>
------------------------------
Message: 10
Date: Sat, 5 Jun 2010 17:10:05 -0700 (PDT)
From: B J <top_gun_canada@xxxxx.xxx>
Subject: [amsat-bb] Re: Falcon 9 video - moving early?
To: amsat-bb@xxxxx.xxx
Message-ID: <195690.12376.qm@xxxxxxxx.xxxx.xxx.xxxxx.xxx>
Content-Type: text/plain; charset=us-ascii
--- On Sat, 6/5/10, Andrew Glasbrenner <glasbrenner@xxxxxxxxxx.xxx> wrote:
> From: Andrew Glasbrenner <glasbrenner@xxxxxxxxxx.xxx>
> Subject: [amsat-bb] Re: Falcon 9 video - moving early?
> To: vk1pe.peter@xxxxx.xxxx amsat-bb@xxxxx.xxx
> Received: Saturday, June 5, 2010, 4:57 PM
> SpaceX starts all nine engines and
> makes sure they are operating to spec before releasing the
> rocket from the pad. The shuttle does the same thing with
> the three shuttle engines before they light the solids.
<snip>
That's been the case even earlier as well. Listen to any of the countdowns
for the Apollo lunar missions. The Saturn V's engines would ignite at about
T-9 and take a few seconds to produce full thrust before lift-off at T = 0.
If I'm not mistaken, in the very early days, T (or, as it was originally
called X) = 0 was when actual ignition occurred, so lift-off was 2 or 3
seconds later.
73s
Bernhard VA6BMJ @ DO33FL
------------------------------
Message: 11
Date: Sat, 5 Jun 2010 17:12:23 -0700 (PDT)
From: B J <top_gun_canada@xxxxx.xxx>
Subject: [amsat-bb] Re: Falcon 9 video - moving early?
To: Joe <nss@xxx.xxx>
Cc: amsat-bb@xxxxx.xxx
Message-ID: <851639.24016.qm@xxxxxxxx.xxxx.xxx.xxxxx.xxx>
Content-Type: text/plain; charset=us-ascii
--- On Sat, 6/5/10, Joe <nss@xxx.xxx> wrote:
> From: Joe <nss@xxx.xxx>
> Subject: [amsat-bb] Re: Falcon 9 video - moving early?
> To: amsat-bb@xxxxx.xxx
> Received: Saturday, June 5, 2010, 5:27 PM
> yES BUT IN THAT VIDEO BELOW IT IS
> CLEASRLY OFF THE PAD AND MOVING UP AT
> T-3 SECONDS.
I noticed that as well, but, since I was watching this via webcast, what I
saw might have been due to a lag between the video and audio feeds.
73s
Bernhard VA6BMJ @ DO33FL
------------------------------
Message: 12
Date: Sat, 5 Jun 2010 17:33:36 -0700
From: John Belstner <jbelstner@xxxxx.xxx>
Subject: [amsat-bb] Re: Re HELIX REFLECTOR?
To: "STeve Andre'" <andres@xxx.xxx>
Cc: amsat-bb <amsat-bb@xxxxx.xxx>
Message-ID: <D0A47149-93BB-4234-869A-6D8AC7E6D365@xxxxx.xxx>
Content-Type: text/plain; charset=us-ascii
Hi Steve,
To avoid giving you bad info, I went back and looked at some of the modeling
I did a few years ago to refresh my memory and realized that was done on
crossed yagis and not helixes. Recently I did some helix modeling and took
some field measurements on a terrestrial sectored antenna application and
found that I could not get the F/B any greater than 20 dB without a
backplane that was at least 1 wavelength in diameter and with a
forward-flared rim at the end (like the lip of a screw top).
Since you asked the question, however, I went back and looked at the model
again. Perhaps the word "adversely" was a bit of an exaggeration. In the
vertical orientation (at 437 MHz), the forward gain of the main lobe didn't
change much between 1 and 5 wavelengths above ground; what did change was
the depth of the off axis nulls. More pronounced (of course) is during the
transition from vertical to horizontal, the ground reflections raise the
pointing angle of the main lobe to as high as 15 degrees off axis at
horizontal when the antenna is as low as 1 wavelength above ground.
Bottom line, 1 wavelength I guess. But not so much because of a degradation
in forward gain but because the angle of the main lobe is off axis.
Hope this is helpful and not just a rambling.
John
On Jun 5, 2010, at 2:10 PM, STeve Andre' wrote:
> john, whats a good rule for height of the antennas to avoid large
> back lobes reflecting, ie how many wavelengths up should the
> antennas be? Thanks...
>
> --STeve Andre'
> wb8wsf en82
>
> On Saturday 05 June 2010 17:07:15 John Belstner wrote:
>> Just another $0.02 to add.
>>
>> You will find that the size and shape of the reflector will not affect the
>> forward gain as much as it does the F/B ratio. It depends on what is
>> important to you and (of course) how high you are above the ground. Even
>> for satellite operation pointing up, large back lobes reflecting off the
>> ground can adversely affect the forward pattern when the antenna is mounted
>> only 6-8 feet above ground.
>>
>> On Jun 4, 2010, at 10:13 PM, Clare Fowler wrote:
>>> To add to the discussion the July/Aug 2007 Amsat Journal has an article
>>> covering some gain comparisonmeasurements I made between four
>>> 13 turn (2.88 wavelengths) 13cm antennas with different square solid
>>> aluminum reflectors.
>>> The sizes were 0.56 wavelengths, 0.84 wavelengths, 1.0 wavelength and 1.4
>>> wavelengths.
>>> There was no difference between the 0.84, 1.0 and 1.4 wavelengths but the
>>> antenna with the0.56 wavelength reflector had 1.5 db less gain.
>>>
>>> However for my 70cm helix antennas I followed the Satellite Handbook
>>> minimum
>>> size of 0.6 wavelengthsor slightly over 16 inches. I used 1/2 inch
>>> hardware cloth
>>> mesh to keep the weight and windloading down.
>>> These antennas have performed well however it appears that they would be
>>> a bit better with a somewhat larger reflector.
>>>
>>> A brief description and picture of the 70 cm reflector is in the
>>> November/December 2005 Amsat Journal article on
>>> The Development of a Quarter Wave Match for helical antennas.
>>>
>>> Clare VE3NPC
>>>
>>>>> Hi All:
>>>>> I am rebuilding a 440 MHZ Helix that I built several years ago . It
>>>>> worked very well, but I would like to reduce the size of the reflector
>>>>> to a more manageable size than I had before. The only reference to
>>>>> reflector size I can find is, "minimum 20" ". I may be looking in the
>>>>> wrong places. I would appreciate it, if someone would steer me in the
>>>>> right direction. Thanks,
>>>>> Pete, K1HZU
> _______________________________________________
> Sent via AMSAT-BB@xxxxx.xxx. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 13
Date: Sun, 6 Jun 2010 02:36:38 +0200
From: "i8cvs" <domenico.i8cvs@xxx.xx>
Subject: [amsat-bb] HELIX REFLECTOR
To: <k1hzu@xxxx.xxx>, "AMSAT-BB" <amsat-bb@xxxxx.xxx>
Message-ID: <004301cb0510$53cf47e0$0201a8c0@xxx.xx>
Content-Type: text/plain; charset="iso-8859-1"
----- Original Message -----
From: "Pete Norris, K1HZU" <k1hzu@xxxxx.xxx>
To: <amsat-bb@xxxxx.xxx>
Sent: Friday, June 04, 2010 2:51 AM
Subject: [amsat-bb] HELIX REFLECTOR?
> Hi All:
> I am rebuilding a 440 MHZ Helix that I built several years ago . It worked
> very well, but I would like to reduce the size of the reflector to a more
> manageable size than I had before. The only reference to reflector size I
> can find is, "minimum 20" ". I may be looking in the wrong places. I would
> appreciate it, if someone would steer me in the right direction.
> Thanks,
> Pete, K1HZU
Hi Pete, K1HZU
My 15 turns RHCP 70 cm Helix Antenna was built at first with a round
aluminum sheet perforated reflector with a diameter of 460 mm
( 0.67 wavelenght) and it worked very well but after enlarging the diameter
of reflector to 690 mm (about 1 wavelenght) overlapping to it a perforated
aluminum mesh I realized that the gain increases by about 2 dB and the front
to back ratio was much better than before.
The Helix is made with a non annealed wiredrawn aluminum rod 8 mm in
diameter and the boom is made with a very hard plastic pipe 42 mm outside
diameter and 31 mm inside diameter originally used for hight pressure oil
ducts.
Following "ANTENNAS" from John Kraus the lenght of a turn has been
made 1 wavelenght long into free space and the pitch angle between turns
is about 13.8 degrees while the calculated half-power beam width is about
28 degrees.
The matching system between the 150 ohm impedance at the feed point and
a 50 ohm coax cable is made using a 1/4 electrical wavelenght impedance
transformer with Zo = 86 ohm made with two coaxial tubing.
For better performance and not to distort the pattern the antenna is
fastened to the rear of reflector and the weight is balanced with a
counterweight made with few lead disks.
The picture of the above 15 turns helix antenna is visible at i8CVS in
QRZ.com
I have built two Helix Antennas the first one is a 10 turns with 0.67
wavelenght round reflector used beginning from OSCAR-7 to actually
FO-29 and HO-68 and it works very well.
The second one is a 15 turns helix with a 1 wavelenght in diameter round
reflector and it was used for the uplink from OSCAR-10 to AO40 as can
be seen at i8CVS in QRZ.com but unfortunately I cannot use it for LEO
satellites because the AZ/EL mount is slow because it was designed for
HEO satellites and this is why I pull for P3E !
If someone is interested to built the above antenna for 10 or 15 turns I can
send a zipped file with all the electrical and mechanical sized drawings of
it.
Best 73" de
i8CVS Domenico
------------------------------
Message: 14
Date: Sun, 6 Jun 2010 02:41:42 +0200
From: "i8cvs" <domenico.i8cvs@xxx.xx>
Subject: [amsat-bb] Fw: WD9EWK @ DM44xj/DM54aj now
To: <amsat-bb@xxxxxx.xxx>, "AMSAT-BB" <amsat-bb@xxxxx.xxx>
Message-ID: <006701cb0511$08f44440$0201a8c0@xxx.xx>
Content-Type: text/plain; charset="iso-8859-1"
----- Original Message -----
From: "Patrick STODDARD" <amsat-bb@xxxxxx.xxx>
To: <amsat-bb@xxxxx.xxx>
Sent: Sunday, June 06, 2010 12:35 AM
Subject: [amsat-bb] WD9EWK @ DM44xj/DM54aj now
Hi!
I found a spot on the DM44/DM54 line for the passes starting with the
AO7 pass at 2256 UTC through at least the SO50 pass at 0206 UTC. Hope
to work you from here.
73!
Patrick WD9EWK/VA7EWK - north of Show Low, Arizona
http://www.wd9ewk.net/
------------------------------
Message: 15
Date: Sun, 6 Jun 2010 03:21:00 +0200
From: "i8cvs" <domenico.i8cvs@xxx.xx>
Subject: [amsat-bb] Re HELIX REFLECTOR?
To: "John Belstner" <jbelstner@xxxxx.xxx>, "Clare Fowler"
<clarefowler@xxxxxx.xxx>, "AMSAT-BB" <amsat-bb@xxxxx.xxx>
Message-ID: <00cb01cb0516$864cf180$0201a8c0@xxx.xx>
Content-Type: text/plain; charset="iso-8859-1"
Hi John,
I agree with you.
I have in my hands the book "RADIO ASTRONOMY" by John Kraus
ISBN 07-035392-1
This is the text of page-200
"An example of a partially steerable (meridian transit) array antenna is
presented in Fig.6-41
This antenna,built in 1952 at the Ohio State University radio observatory,
consists of an array of 96 helical-beam antennas, each of 11 turns, mounted
on a tiltable steel grounded ground plane 160 ft long (east-west) by 22 ft
wide. At a wavelenght of 1.2 meters the beam width measured 1 degree in
right ascension by 8 degrees in declination."
My comment:
As seen from the photograph 6.41 the tiltable steel ground plane seems to be
mounted at no more than 10 to 12 ft from the ground so that when the
reflector is very large it seems that the high of it from the ground is not
very important both for gain and front to back ratio.
In this array the tiltable steel ground plane is 160 ft long and 22 ft wide
with 24 helices in the longer side and 4 line of helices in the wide side
(24 x 4 = 96 helices) so that the total ground plane area is 160 x 22 = 3520
square foot and each helix reflector takes 3520 / 96 = 37 square foot or
about a square surface of 6 x 6 foot or a round area of 3.4 square meters
with a diameter of 2.08 meters.
Since the operating wavelenght of the radiotelescope is 1.2 meters the
reflector diameter for each helix antenna has been made large
2.08 / 1.2 = 1.73 wavelenght and probably this is why a tiltable steel
ground plane made so large can be mounted very close to the ground
surface without affecting gain, front to back ratio and without to take
too much noise at 290 kelvin from the ground.
73" de
i8CVS Domenico
----- Original Message -----
From: "John Belstner" <jbelstner@xxxxx.xxx>
To: "Clare Fowler" <clarefowler@xxxxxx.xxx>
Cc: "amsat-bb" <amsat-bb@xxxxx.xxx>
Sent: Saturday, June 05, 2010 11:07 PM
Subject: [amsat-bb] Re: Re HELIX REFLECTOR?
> Just another $0.02 to add.
>
> You will find that the size and shape of the reflector will not affect the
> forward gain as much as it does the F/B ratio. It depends on what is
> important to you and (of course) how high you are above the ground. Even
> for satellite operation pointing up, large back lobes reflecting off the
> ground can adversely affect the forward pattern when the antenna is
> mounted only 6-8 feet above ground.
>
> On Jun 4, 2010, at 10:13 PM, Clare Fowler wrote:
>
> >
> > To add to the discussion the July/Aug 2007 Amsat Journal has an article
> > covering some gain comparisonmeasurements I made between four
> > 13 turn (2.88 wavelengths) 13cm antennas with different square solid
> > aluminum reflectors.
> > The sizes were 0.56 wavelengths, 0.84 wavelengths, 1.0 wavelength and
>> 1.4 wavelengths.
> > There was no difference between the 0.84, 1.0 and 1.4 wavelengths but
> > the antenna with the0.56 wavelength reflector had 1.5 db less gain.
> >
> > However for my 70cm helix antennas I followed the Satellite Handbook
> > minimum size of 0.6 wavelengthsor slightly over 16 inches. I used 1/2
> > inch hardware cloth mesh to keep the weight and windloading down.
> > These antennas have performed well however it appears that they would be
> > a bit better with a somewhat larger reflector.
> >
> > A brief description and picture of the 70 cm reflector is in the
> > November/December 2005 Amsat Journal article on
> > The Development of a Quarter Wave Match for helical antennas.
> >
> > Clare VE3NPC
> >
>>> Hi All:
>>> I am rebuilding a 440 MHZ Helix that I built several years ago . It
>>> worked very well, but I would like to reduce the size of the reflector
>>> to a more manageable size than I had before. The only reference to
>>> reflector size I can find is, "minimum 20" ". I may be looking in the
>>>wrong places.
>>> I would appreciate it, if someone would steer me in the right direction.
>>> Thanks,
>>> Pete, K1HZU
------------------------------
Message: 16
Date: Sat, 5 Jun 2010 22:57:32 -0500
From: "Gary \"Joe\" Mayfield" <gary_mayfield@xxxxxxx.xxx>
Subject: [amsat-bb] Re: FIELD DAY SCORING
To: <amsat-bb@xxxxx.xxx>
Message-ID: <COL114-DS4CF8825A6431203D4C4FB8AD40@xxx.xxx>
Content-Type: text/plain; charset="us-ascii"
Pete & Bruce,
Good to know about the LINEAR birds. The rules are still different,
AMSAT will allow one V/U and one V/S contact on AO-51. The ARRL will only
allow one contact on AO-51.
73,
Joe kk0sd
-----Original Message-----
From: amsat-bb-bounces@xxxxx.xxx [mailto:amsat-bb-bounces@xxxxx.xxxx On
Behalf Of Bruce
Sent: Saturday, June 05, 2010 10:13 AM
To: Peter Portanova
Cc: amsat-bb@xxxxx.xxx
Subject: [amsat-bb] Re: FIELD DAY SCORING
That should make it much easier for everyone as you don't have to do one log
and then strip out the unwanted calls for the other. Thanks Pete. I am glad
that the two minds (ARRL and AMSAT) have become one.
73...bruce
________________________________
From: Peter Portanova <roic@xxxxxxxxx.xxx>
To: amsaT-BB@xxxxx.xxx
Sent: Sat, June 5, 2010 9:33:07 AM
Subject: [amsat-bb] FIELD DAY SCORING
Hello,
I was in contact with the ARRL, after I read 7.3.7. and 7.3.7.1. in the
Field Day Rules. I mentioned to the League that I would like them to point
out where in those rules it would prohibit scoring the same call on multiple
Linear Satellites. They listened to my point's and agreed that even though
the rules refer to satellite contacts as a separate "band" there is nothing
in those rules that prohibit the aforementioned scoring. In conclusion
Field Day and the AMSAT scoring are now in agreement, have fun.
73's Pete
WB2OQQ
www.massapequanyweather.com
------------------------------
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End of AMSAT-BB Digest, Vol 5, Issue 254
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