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  #151  
Old 09-13-2015, 10:57 AM
Scrabo Scrabo is offline
 
Join Date: Dec 2008
Location: Phoenix, Arizona
Posts: 285
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Quote:
Originally Posted by emuyshondt View Post
The datasheet for the Skyguard antenna is at https://www.linxtechnologies.com/res...916-cw-hwr.pdf and says the antenna is recommended for 900 to 930 MHz. It has a pretty sharp VSWR curve that is at a minimum just below 916MHz. If tha antenna works well, the other one I posted should look even better. I haven't tried either, though, and Skyguard seems to get enough performance out of theirs.
Let me know your findings between the two antennas
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  #152  
Old 09-13-2015, 12:37 PM
emuyshondt emuyshondt is offline
 
Join Date: May 2009
Location: Leander, TX
Posts: 166
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I ordered the stub antenna. I may also try the Linx Technology (Skyguard) later on. I actually ordered it from Skyguard, but they refunded my money yesterday and told me to go get it from DigiKey. I'm traveling for a few weeks so it will have to wait until after I get back and try things with the stuff I already got. I don't have any measurement equipment to give detailed answers, though.

I thought maybe there are some RF gurus here that might know the answer without me having to buy a lot of hardware.

One thing I will try is running two receivers 978 and 1090MHz), with a splitter and a single antenna. I have the parts to do that waiting for me.
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  #153  
Old 09-13-2015, 02:52 PM
Scrabo Scrabo is offline
 
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Location: Phoenix, Arizona
Posts: 285
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Looking at this for some cooling relief

http://www.seeedstudio.com/depot/Ras...an-p-2132.html
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  #154  
Old 09-15-2015, 06:15 AM
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petehowell petehowell is offline
 
Join Date: Jan 2005
Location: MN
Posts: 2,269
Default More data....

While I would encourage others to experiment, I have been doing some test flights and am happy to report that science works and I am finding the best over all results with one antenna just under 3 in long feeding both SDR sticks.

This antenna consistently pulls in the same number of towers as the GDL sitting next to it on the dash, is compact, and seems to work pretty well on both bands.

I still get better reception on 978 with an extended antenna on my back porch, but I don't fly there very often, so I am gonna ask that people ignore my previous post (for those of you who don't ignore all of my posts already.....)


Quote:
Originally Posted by petehowell View Post
I took a quick and dirty sample of 978 UAT data tonight using the IFLY data rate dialog. One tower only from the comfort of my back porch. The data seems to support what I saw in the plane today - that a longer antenna with length of ~7.75-8.25 inches from transition of plastic base to metal antenna provides a better data transfer rate.

Methodology - Antenna length was set and then data taken at 10 sec intervals for 4 intervals.

I'll try it again later - not intuitive at all...happy to be proven wrong



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Amateur Plane - RV-9A N789PH - 2350+ Hrs
Amateur Radio - KD0CVN
Doggies Delivered - 25+
St. Paul, MN
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  #155  
Old 09-15-2015, 06:41 AM
RickG RickG is offline
 
Join Date: Nov 2013
Location: Durham, NC
Posts: 14
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Pete - which antenna are you using?
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  #156  
Old 09-15-2015, 07:21 AM
humptybump humptybump is offline
 
Join Date: Feb 2011
Location: USA
Posts: 3,179
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Quote:
Originally Posted by petehowell View Post
I am finding the best over all results with one antenna just under 3 in long feeding both SDR sticks.
Pete, if you don't mind, would you post a picture of your antenna? Also, when you say "feeding both SDRs" would you share what you did to share the antenna?

Thanks for your contributions!
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  #157  
Old 09-15-2015, 07:43 AM
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petehowell petehowell is offline
 
Join Date: Jan 2005
Location: MN
Posts: 2,269
Default Sure thing!

I'll try to grab it at lunch and post some pics. My daughter dubbed it the "killer bee".


Quote:
Originally Posted by humptybump View Post
Pete, if you don't mind, would you post a picture of your antenna? Also, when you say "feeding both SDRs" would you share what you did to share the antenna?

Thanks for your contributions!
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Pete

Amateur Plane - RV-9A N789PH - 2350+ Hrs
Amateur Radio - KD0CVN
Doggies Delivered - 25+
St. Paul, MN
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  #158  
Old 09-15-2015, 09:52 AM
humptybump humptybump is offline
 
Join Date: Feb 2011
Location: USA
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Quote:
Originally Posted by petehowell View Post
I'll try to grab it at lunch and post some pics. My daughter dubbed it the "killer bee".
Your daughter should be in marketing
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  #159  
Old 09-15-2015, 10:18 AM
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petehowell petehowell is offline
 
Join Date: Jan 2005
Location: MN
Posts: 2,269
Default Killer Bee.....

Quote:
Originally Posted by humptybump View Post
Your daughter should be in marketing
Here you go!



Lunch time cell phone greatness!



Printed case from a clever Reddit guy. 2x $1.43 usb extensions. Velcro strap from the bottom of my desk drawer. Yes - those are Legos as spacers........ The antenna is from the $12 SDR stick chopped to ~3" with 2 cables run into the base and soldered. Will probably incorp a small fan at some point. Antenna might get a bit shorter, but works pretty well. (5 Towers at 1000AGL just north of Minne. and good ES coverage of the big boys upstairs)

Clearly, this design is an acquired taste. Proceed with your giggling - I can handle it! My wife says it needs a sign that says "NOT A BOMB!"
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Pete

Amateur Plane - RV-9A N789PH - 2350+ Hrs
Amateur Radio - KD0CVN
Doggies Delivered - 25+
St. Paul, MN

Last edited by petehowell : 09-15-2015 at 01:30 PM.
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  #160  
Old 09-15-2015, 10:27 AM
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ChiefPilot ChiefPilot is offline
 
Join Date: Jan 2005
Location: Twin Cities, MN
Posts: 1,565
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Quote:
Originally Posted by petehowell View Post
My wife says it needs a sign that says "NOT A BOMB!"
LOL! When my boys saw mine, they asked if the Pi was a detonator and the battery pack was the explosive charge.

Definitely not going to put this thing in the carry-on luggage...
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