[Ground-station] G/T

[KENT BRITAIN]

 For this bird you would still be transponder noise floor limited.The G/T would be a very very minor noise contribution.
Actually only half of the antenna pattern sees 290K, the other half iscloser to 4K.    We used 180K for antennas that see 1/2 earth, 1/2 sky.
Oh, if we only had such issues!!!!    I did work PA1EW thru Oscar 100 two weeks ago.
Certainly a different way to operate.   Kent




    On Thursday, May 2, 2019, 2:43:31 PM CDT, Howie DeFelice <howied231 at hotmail.com> wrote:  
 
 Agreed, at elevations above 10 degrees, but at zero degrees you see allot of that big 290K noise source along the path. 🙂

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From: KENT BRITAIN <wa5vjb at flash.net>
Sent: Thursday, May 2, 2019 3:14:26 PM
To: Howie DeFelice; Wally Ritchie
Cc: Dan White; KC9SGV; Michelle Thompson via Ground-Station
Subject: G/T Not much of an issue with Oscar 100.
With even a 18" dish you see the transponder noise floor.So that's your weak signal limiting factor.  

Kent WA5VJB/G8EMY    

On Thursday, May 2, 2019, 10:57:02 AM CDT, Wally Ritchie <wally.ritchie at gmail.com> wrote:

Might be an interesting exercise. Some thoughts just for fun:
The G/T on the ground might be better than expected if the site directly overlooks the ocean, especially a few hours before dawn.My understanding is that the Antenna is a global beam without shaping. It is likely slightly larger than the globe as the edges are dark and do not contribute to uplink noise. There is likely only a 3/4dB loss at the edge. Probably need to rotate an offset antenna 180 degrees so the arm is at the top. (We do this for tropo when aiming a couple of degrees above the horizon). While it doesn't make much difference in normal satellite operation, there is bending near the horizon. We even see this on ISS contacts that start earlier and last longer than predicted due this effect. There will definitely be some troposcatter. So even if the main beam cannot be picked up, there will be forward scatter paths that follow a Rayleigh fading model. It is possible to use two antennas spaced about 100 wavelengths apart and realize space diversity gain and overcome the separate fading of the two paths. Of course to take advantage of this some non-trivial processing of the receive signal would be required. There is always the possibility of tropo ducting and it may even be somewhat predictable.It might be useful to have some kind of very narrow psk31 beacon. There is a possibility of reflections from the numerous airliners in the path (a major transatlantic route). However, these are typically short.Note that ducting and/or aircraft reflections can result in sudden signal jumps of 50dB. 
Too bad it wasn't 15 degrees closer. 
WU1Y (Wally)




On Thu, May 2, 2019 at 10:52 AM Howie DeFelice via Ground-Station <ground-station at lists.openresearch.institute> wrote:

I don't know about Nova Scotia. Even if the global pattern of the satellite antenna illuminated to the edge of the beam you would still need some beam bending to get over the earth. The G/T will be horrible no matter how good your LNA is and the downlink is not all that hot to begin with. It would be fun to try though. If you're going to do a DXpedition to Nova Scotia now is the time to do it. Been there in the winter and that ain't no fun.
Howie AB2S
From: Ground-Station <ground-station-bounces at lists.openresearch.institute> on behalf of KENT BRITAIN via Ground-Station <ground-station at lists.openresearch.institute>
Sent: Wednesday, May 1, 2019 9:30 AM
To: Dan White; KC9SGV
Cc: Michelle Thompson via Ground-Station
Subject: Re: [Ground-station] Operation 1.2m Dish Pickup: Dayton Hamvention 2019! I made a QSO thru OSCAR 100 2 weeks ago.   But wasn't in North America
It is said that a QSO is possible from Nova Scotia,  But no one there to give it a try.
I've got CP Patch feeds that I used.    Kent WA5VJB

On Wednesday, May 1, 2019, 8:27:03 AM CDT, KC9SGV via Ground-Station <ground-station at lists.openresearch.institute> wrote:

I will take one in Chicago !Still think we can hit QO-100 with CW at least, at 0 deg elevation out over Lake Michigan.Read somewhere that 10 Watts at the feed point will give ~2.5 KW ERP out of a 1 m dish...Depending on the specs.Diffraction, refraction and tropo scatter.Remember the GEO sat sits at 36000 Km above Africa.Weird, about 75 deg magnetic az and -25 deg el from Chicago.Worth a test shot.But, we really need/want our own all mode GEO sat or commercial solution transponder above the Americas !
Bernard,KC9SGV

Sent from my iPad
On Apr 30, 2019, at 12:00 PM, Dan White via Ground-Station <ground-station at lists.openresearch.institute> wrote:


Michelle,
I'll be at Hamvention and can pickup a dish there.
Also, I'm willing to haul a few more back to the Chicago area (60min drive from Midway) for others to pickup that won't be in Dayton.  Conditioned on them fitting in my '12 CRV  :)
--Dan AD0CQ

On Fri, Apr 26, 2019 at 2:22 PM Michelle Thompson via Ground-Station <ground-station at lists.openresearch.institute> wrote:

Operation 1.2m Dish Pickup: Dayton Hamvention 2019!

Doug Phelps will be at Dayton with transportation. He can take 10-15 of the free 1.2m dishes to Dayton for pickup.

I will send out a separate email directly to everyone that said they want one for potential coordination. 

If you are driving to Dayton, and are interested in a nice Andrews 1.2m offset feed dish, and missed out on this the first time around, then here is your chance! Forming the "Dayton List" now. 

-Michelle W5NYV





  
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