[OZAPRS] VK2HAB 25/05/16

Mark Jessop lenniethelemming at gmail.com
Mon May 30 12:09:05 AEST 2016


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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>>>>>>
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