[OZAPRS] VK2HAB 25/05/16

Mark Jessop lenniethelemming at gmail.com
Mon May 30 18:41:31 AEST 2016


On the balloon we currently have a 1/4 wave monopole with ground radials.

On the ground (At least on matt's car) there is a crossed-dipole, mainly
for the hemispherical radiation pattern (no null directly overhead), but
the circular polarisation can help when the payload is tumbling (reduces
the depth of the nulls)

- Mark VK5QI

On Mon, May 30, 2016 at 11:46 AM, Norm McMillan <vk3xci at gmail.com> wrote:

> Mark Jessop said
>
> >* "Linear at one end and circular at the other is exactly how we do it
> right now."*
>
> I'm missing something here, maybe 'cause I've been on holiday and "lost
> the thread" hihi.
>
> What is the actual antenna on the balloon?
>
> What do you use for a receive antenna?
>
> Is there a HAB website?
>
>
> norm
>
> vk3xci
>
> On Mon, May 30, 2016 at 12:09 PM, Mark Jessop <lenniethelemming at gmail.com>
> wrote:
>
>> Linear at one end and circular at the other is exactly how we do it right
>> now. :-)
>>
>> - Mark VK5QI
>> On May 30, 2016 11:16 AM, "Norm McMillan" <vk3xci at gmail.com> wrote:
>>
>>> Mathew VK5ZM said
>>> >" No circular polarised antennas are not the solution"
>>> Boy, there's a can of worms right there, just waiting to be opened.
>>> Sherman, crank up the Way Back Machine!
>>>
>>> In the days of AO-10, 13 etc a LOT of work went into circular, v oblique
>>> v linear poz. Seems for satellite work, when the squint angle was
>>> constantly shifting, matched sense circular poz at each end provided the
>>> best compromise, about 3db loss max from true circular to oblique to
>>> linear.. Trouble is, the sense reversed as the bird went overhead, so
>>> switching poz sense was required at the ground station.
>>>
>>> Next best, circular to linear, 3db again and no need to switch sense.
>>> Unfortunately, the incoming sig was not always true circ. poz., often
>>> oblique, so 6db is a closer figure.
>>>
>>> Worst... linear to linear cross poz, around 20 to 30 db loss, and
>>> circular to circular crossed sense, 30 to 60 db loss.These are pretty much
>>> real world empirical figures... like I said... a LOT of work.
>>>
>>> Seems to me the best compromise would be linear at one end (balloon) and
>>> circular at the other. On the other hand if it aint broke, don't fix it :-)
>>>
>>> Radiation pattern is a different story.
>>>
>>> Maybe we need a new thread?
>>>
>>>
>>> norm
>>> vk3xci
>>>
>>> On Sun, May 29, 2016 at 11:27 PM, Matthew Cook <vk5zm at bistre.net> wrote:
>>>
>>>> I'd suggest you research polarisation of antennae a little more and
>>>> then think about that some more.  No circular polarised antennas are not
>>>> the solution.
>>>>
>>>> 73
>>>>
>>>> Matthew
>>>> VK5ZM
>>>>
>>>> On 29 May 2016 at 05:59, Andrew Rich <vk4tec at tech-software.net> wrote:
>>>>
>>>>> Hang a yagi looking back at earth
>>>>>
>>>>> -----------------------------
>>>>> Sent from my iPhone
>>>>> Andrew Rich
>>>>> vk4tec at tech-software.net
>>>>> www.tech-software.net
>>>>> 0419 738 223
>>>>>
>>>>> On 26 May 2016, at 11:08, Matthew Cook <vk5zm at bistre.net> wrote:
>>>>>
>>>>> Hi Norm,
>>>>>
>>>>> That sounds about right with respect to range, height is might !
>>>>>
>>>>> Also don't forget that if you've got local traffic on a digi that this
>>>>> will tromp on a balloon payload even at altitude.  It all comes down to
>>>>> sneaking through the gaps.  Even with altitude you still have free space
>>>>> path loss and the capture effect to contend with a the digi receiver.   It
>>>>> is always sensible to run open squelch with software DCD if your packet
>>>>> engine supports it.  That means weak signals don't have to crack the mute
>>>>> of the radio first or get truncated if it drops too low.
>>>>>
>>>>> Another quirk with balloons is the antenna pattern at altitiude can
>>>>> have severe nulls in it, so being directly under a balloon can make it very
>>>>> difficult to decode (from bitter experience) when people 50km or more can
>>>>> copy it fine.  YMMV.
>>>>>
>>>>> 73
>>>>>
>>>>> Matthew
>>>>> VK5ZM
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On 25 May 2016 at 17:44, Norm McMillan <vk3xci at gmail.com> wrote:
>>>>>
>>>>>> Thank you Mathew,
>>>>>>
>>>>>> 100,000 feet  is 30480meters, range 625km.
>>>>>>  VK3RBT to VK2HAB 510 km.
>>>>>>
>>>>>> Seems odd that VK3RBT picked it up but not VK3RBX, which is closer.
>>>>>> Better check the squelch/sensitivity on RBX I guess
>>>>>>
>>>>>> norm
>>>>>> vk3xci
>>>>>>
>>>>>> On Wed, May 25, 2016 at 4:55 PM, Matthew Cook <vk5zm at bistre.net>
>>>>>> wrote:
>>>>>>
>>>>>>> Norm,
>>>>>>>
>>>>>>> Yes 100,000ft for a HAB is not uncommon.  See if you can find an
>>>>>>> online radio horizon calculator and punch in 100,000ft. Take the position
>>>>>>> of the balloon when you received the posit and draw a circle around it from
>>>>>>> the horizon calculator.  I'm fairly certain you'll find Bambil tanks is
>>>>>>> within this circle.
>>>>>>>
>>>>>>> We regularly have VK3 stations receive our HAB telemetry with the
>>>>>>> balloon 25kms or more in to the stratosphere.  Height is might !
>>>>>>>
>>>>>>> 73
>>>>>>>
>>>>>>> Matthew
>>>>>>> VK5ZM
>>>>>>> AREG/Project Horus
>>>>>>>
>>>>>>> On 25 May 2016 at 16:12, Norm McMillan <vk3xci at gmail.com> wrote:
>>>>>>>
>>>>>>>> Copied a few (20 or so) packets from this event. the path is
>>>>>>>> interesting to say the least. Is there a digi not correctly identifying or
>>>>>>>> did VK3RBT at Bambil Tank REALLY receive the balloon direct.
>>>>>>>>
>>>>>>>>
>>>>>>>> 0:TNC->
>>>>>>>> VK2HAB-11>APT314,VK3RBT-1,VK2RBX-1,WIDE2*:!3349.O1S/14701.26E0161/003/A=100594/UpLift
>>>>>>>> Balloon Flights|$"!!!!|
>>>>>>>>
>>>>>>>> And did it really make it to 100594 feet?
>>>>>>>> And what does the   |$"!!!!|   at the end mean. I noticed the first
>>>>>>>> two characters change as the flight progressed
>>>>>>>>
>>>>>>>> Due to my inexperience with xastir I didn't log it, but I have a
>>>>>>>> screen shot!
>>>>>>>>
>>>>>>>>
>>>>>>>> norm
>>>>>>>> vk3xci
>>>>>>>>
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