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Author Topic: Omni's - Eggbeater and Texas Potato Masher  (Read 3886 times)
VK5DO
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Posts: 82




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« on: April 06, 2010, 11:31:03 PM »

Hi All,

I'm thinking of dipping my toes into the world of satellites.  

Are omni antennas like the Texas Potato Masher, the eggbeater or a turnstile with reflector any good at all for LEO satellites or am I just wasting my time completely?

At this stage I'm hoping to use an omni before I decide if I want to go further with it and get into tracking systems etc.

Radio will be an IC7000.

Yours,
Dene VK5DO
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XE1VE3OQC
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Posts: 20




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« Reply #1 on: April 07, 2010, 05:48:45 PM »

Hi Dene,
First of all you need to hear your downlink signal on these birds such as AO-52, FO-29 etc. Using the 7000 you are transmitting but not receiving your downlink (correct me if I´m wrong about this radio) the 7000 is not full duplex.
Using two 817´s, or separate 70cm and 2 meter rigs will work.
As for the eggbeaters, I have heard other people use them with good results. You will get the signal from about 30 degrees before your zenith to about 30 degrees to end.

Glenn, XE1/VE3OQC
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K6LCS
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« Reply #2 on: April 08, 2010, 09:18:50 PM »

>> ... Texas Potato Masher, the eggbeater or a turnstile ...

Polarization really hasn't been an issue for me with the FM birds - so a full-blown TX Masher might be overkill for that aspect of working the satellites.

I take my M2 Eggbeater with ground radials to shows and demos - but more for a conversation starter than anything else. Again, I am just working the FM birds. For receive, it's OK. For transmit, it just "scatters" and makes you use so much more power than you need to use.

Then again, I am working several sats with 2W or less and a handheld beam or Yagi.

A turnstile may be great mounted on a satellite - but I really think you'll appreciate the performance of a simple beam or Yagi more.

Clint Bradford, K6LCS
http://www.work-sat.com
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Clint Bradford, K6LCS
http://www.k6lcs.com
VK5DO
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Posts: 82




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« Reply #3 on: April 08, 2010, 10:34:08 PM »

Hi Glenn,

If you mean will the IC7000 do split band operation, ie: receive on 70cm then when you button-on TX on 2m or vise-versa, then yes it will do that in any mode.

Yours

Dene VK5DO
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K4KRW
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Posts: 98




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« Reply #4 on: April 13, 2010, 02:47:41 PM »

Dene,

Glenn is talking about full duplex.  The split mode you describe is not the same.  

Full duplex means you can hear the downlink frequency (ex: on the 2 meter band) at the same time you are transmitting on the uplink frequency (ex: on the 70 centimeter band).  

Your radio can transmit on 70 centimeters and after you un-key listen on 2 meters.  It can't transmit on 70 centimeters while you are listening to 2 meters.

There are not many all mode transceivers that do this.  The Icom IC-910 was one.  The Yaesu FT-847 was another.

73,

Richard
K4KRW
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KA1DBE
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Posts: 121




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« Reply #5 on: April 23, 2010, 08:30:37 AM »

Dene,

Omnis will work but as stated, you will appreciate the gain of a beam.  The downlink will be very weak with an omni.  BUT, don't let that deter you.  I have made satellite contacts using my 1/4 on the car for the uplink and a CJU hand held antenna (Google this, very simple to build and will give you some gain!).

You don't need a full duplex radio to work satellites.  I would suggest starting out on the FM sats (AO51, SO50, AO27 etc) as they are very easy to work.  If you venture into the SSB/CW birds then you will need to be thinking full duplex or separate transmitter and receiver.

I started out by building a "Cheap Yagi" (Again, Google this) for 70 centimeters and just listened to the birds until I got comfortable with the doppler shift and the protocol. 

Good luck and enjoy.

73's,
Jeff, KA1DBE
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