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Old Oct 03, 2012, 03:59 PM
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Amherst, VA
Joined Jun 2006
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No, the whole thing. Just mess around with its location and you will figure it out.

-Alex
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Old Oct 03, 2012, 06:02 PM
Air Crash Expert
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Louisiana
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Found my answer.
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Last edited by sawman; Oct 06, 2012 at 04:05 PM.
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Old Oct 08, 2012, 05:38 PM
Youtube Johnbrum26
Mckinney,TX
Joined Oct 2010
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OK got a question , I have the black cannon and the cloverleaf on my tracker. It wanted to stay on the cloverleaf the whole time on my duo. Why would that be? I would think that the black cannon would have better reception and would be chosen. I have the imrc 600 mw vtx. Also does it matter in which way the antenna is mounted. Cable up or down.

My next test will be to put a whip on the other side.
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Old Oct 09, 2012, 04:48 AM
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Quote:
Originally Posted by Killab View Post
OK got a question , I have the black cannon and the cloverleaf on my tracker. It wanted to stay on the cloverleaf the whole time on my duo. Why would that be? I would think that the black cannon would have better reception and would be chosen. I have the imrc 600 mw vtx. Also does it matter in which way the antenna is mounted. Cable up or down.

My next test will be to put a whip on the other side.
Since the CL's (or SPW for that matter) efficiency is better, the CL wins in closer proximity all times. The duo would switch to the helical if you fly beond the limits of the CL (or SPW).

Since you have a tracker, having a diversity receiver does not make much sense. Putting a 50 ohm termination onto the rx where you have the CL and exclusively use the helical is probably a safer aproach as it prevents the CL from takeing over in situations where it should not.

Markus
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Old Oct 09, 2012, 10:19 AM
Youtube Johnbrum26
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Quote:
Originally Posted by markus123456 View Post
Since the CL's (or SPW for that matter) efficiency is better, the CL wins in closer proximity all times. The duo would switch to the helical if you fly beond the limits of the CL (or SPW).

Since you have a tracker, having a diversity receiver does not make much sense. Putting a 50 ohm termination onto the rx where you have the CL and exclusively use the helical is probably a safer aproach as it prevents the CL from takeing over in situations where it should not.

Markus
Awesome make total sense, What is the 50 ohm termination? What if it just put a whip on instead of the CL?
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Old Oct 09, 2012, 11:18 AM
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What Markus is saying is that with a tracker there is no need for diversity. Why on Earth would you want an amni antenna when you have a high gain antenna pointed at your aircraft?

-Alex
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Old Oct 09, 2012, 11:45 AM
Youtube Johnbrum26
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Quote:
Originally Posted by IBCrazy View Post
What Markus is saying is that with a tracker there is no need for diversity. Why on Earth would you want an amni antenna when you have a high gain antenna pointed at your aircraft?

-Alex
Was just thinking that since i already have the tracker with a duo, I would need something hooked up to that rx line on the duo too. So a whip would be rarely be chosen. Don't want to burn it up not having something connected there. Or shoud i go another route here, That is why im asking. I had already ordered all the stuff before i found your posts about the tracker and diversity, SO i have the diversity so just want to see what i should put on it with the helical.
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Old Oct 09, 2012, 04:43 PM
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Poland
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Quote:
Originally Posted by dehicka View Post
IBCrazy
Alex
What's the piont of matching this antenna to 50 Оhm impedance?
I think that 90% people here will use it with the chinese 15ch 1.2Ghz recievers that have 75 Ohm impedance.
Quote:
Originally Posted by Hugeone View Post
The 75ohm impedance is on the video output side.

-Hugo
Quote:
Originally Posted by dehicka View Post
As long as they have standard comtech sat tuner clone modules inside with F-female input, they have 75Ohm RF input impedance and must be matched to your rx antenna for better performance.
http://www.comtech-tw.com.tw/pdf/bss479laidf.pdf
http://www.datasheetcatalog.org/data...rp/mXqwszx.pdf
In fact, 75 Ohm is a standart for CATV stuff.
I tried to read all these pages in this thread and did not find an answer.
So:

Does anybody know how to match the transformer to 75Ohm impedance?

By the way - I'm in the middle of building my own 5turns helical for 1160MHz - channel 6 on my chinese FOX800.
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Old Oct 10, 2012, 08:48 AM
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Quote:
Originally Posted by Killab View Post
Awesome make total sense, What is the 50 ohm termination? What if it just put a whip on instead of the CL?
It's basically a 50 ohm resistor across GND and ANT of the RF input. You kind of savely would HF wise "short cirquit" that input hence disable it all together. You thereby would trun your diversity rx into a single channel rx, which is best for use with a tracker.

Markus
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Old Oct 10, 2012, 10:55 AM
Youtube Johnbrum26
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Quote:
Originally Posted by markus123456 View Post
It's basically a 50 ohm resistor across GND and ANT of the RF input. You kind of savely would HF wise "short cirquit" that input hence disable it all together. You thereby would trun your diversity rx into a single channel rx, which is best for use with a tracker.

Markus
Thanks, ill give it a go.
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Old Oct 10, 2012, 01:14 PM
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Originally Posted by Killab View Post
Thanks, ill give it a go.
I may should add that you can buy them ready made, like this one here:

http://www.ebay.com/itm/EMC-M39030-3...item1e7329d965

Note, this one is a bit expensive, but it was the smallest one I found and it goes up to 18Ghz (probably the reason for the higher price). I only did one simple quick search on ebay. If you invest 10minutes I'm sure you would find a cheaper candidate of the same size. Not that the size really would matter though, nor the frequency range. Power also is not important as you would use it on the rx end of things, and even for the average tx we use in our application it should be ok as power levels we use are so low.

HTH

Markus
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Old Oct 10, 2012, 01:18 PM
Youtube Johnbrum26
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Quote:
Originally Posted by markus123456 View Post
I may should add that you can buy them ready made, like this one here:

http://www.ebay.com/itm/EMC-M39030-3...item1e7329d965

Note, this one is a bit expensive, but it was the smallest one I found and it goes up to 18Ghz (probably the reason for the higher price). I only did one simple quick search on ebay. If you invest 10minutes I'm sure you would find a cheaper candidate of the same size. Not that the size really would matter though, nor the frequency range. Power also is not important as you would use it on the rx end of things, and even for the average tx we use in our application it should be ok as power levels we use are so low.

HTH

Markus
Awesome man thanks alot. Wish i would have thought things through alittle more, could have saved a bit on the duo and gone with the uno.. Oh well wouldn't be the first time or last ive wasted some money on this hobby. lol
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Old Oct 11, 2012, 03:25 AM
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Quote:
Originally Posted by Killab View Post
Awesome man thanks alot. Wish i would have thought things through alittle more, could have saved a bit on the duo and gone with the uno.. Oh well wouldn't be the first time or last ive wasted some money on this hobby. lol
Well, there are probably times where you want to use a simpler setup, so you still could make use of the duo part of the duo :-). I.e. use two 3 turn helicals point apart like 60 degrees or such mounted to your goggles with the duo. Would be a nice "traveling" groundstation to take a small plane with you on a trip etc. etc. So getting such a SMA termination (dummy load) brings you the flexiblilty to use the rx both ways.

HTH

Markus
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Old Oct 11, 2012, 09:13 PM
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Louisiana
Joined Oct 2005
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Quote:
Originally Posted by Mieciu View Post
I tried to read all these pages in this thread and did not find an answer.
So:
Does anybody know how to match the transformer to 75Ohm impedance?
If you have an SWR meter, adjust the distance between the transformer and reflector/back plate to achieve lowest SWR. If you do not have SWR meter, put an ampmeter between power supply and transmitter and make same distance adjustment, but this time adjust for max current flow. Note: you must use transmitter to adjust antenna. It will then be matched to frequency and will be at resonance on receive or transmit .
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Old Oct 13, 2012, 10:48 PM
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India, Karnataka, Bengaluru
Joined May 2011
196 Posts
What should be the size of the reflector? I am building for 1280mhz with a 2.5inch pvc pipe
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