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saabguyspg

Antenna extension cable

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So I want to move my ant to the tail of my plane, is there any problem with doing this by extending a cable to the tail? I am not modifying the ant at all just adding a cable between the transmitter and the antenna.

I realise there will be some theoretical loss but really how much loss could there be?

I am not messing with the antenna tuning by doing this am I?

thank you!!

pics are attached, sorry about the poor quality but you can see the transmitter on the top of the wing with a cable to the ant. at the tip of the tail.

this is all because on channel 2-4 my HD video camera gets very unhappy (menues pop up etc) but if I get the ant. away from the camera it seems to go away. Channel one works fine but I alway have poor video transmision on channel one... of course.

post-3693-1225476971_thumb.jpg

Edited by saabguyspg

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Adding co-ax is a bad idea for the RX but the TX will not suffer so bad, as long as the cable and connectors are good then the loss will be small.

Terry

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What RF frequency are you using, which Tx antenna, and what is the length of the coax? Those details will matter.

I will warn you that I am not a fan of using coax feedline on a wireless A/V Tx or Rx. Except in rare cases, you will probably notice a difference in range.

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900mhz, tx is stock whip from future hobbies which is I belive lawmate trasmitter 500mw, 28inches of extensioncable, one receiver with patch.

I had a chance to test it and so far so good. I managed to fly much farther than on channel one and flew out of my visual range and waaaay out of my comfort range... at one point got very disorientated as to whicn way home was but never lost video signal.... Nice!!!

I have it all caught on HD (had the recorder on during "oh man I'm lost!"

I would have to remove the ant. to get an accurate measurement on the length.

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Coax losses at 900Mhz are manageable if you are careful and lengths are short. What coax type are you using? Did the SMA's come factory installed or did you install them?

The stock whip has a reputation for poor performance and it appears to promote unwanted RFI/EMI. It is probably responsible for some of the HD video camera issues. I suggest you upgrade to a dipole type ducky. With luck, doing that may eliminate the need for the coax.

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I am using the smaller coax (sorry can't remember the number.... RG64? darn i should know that..) anyway it is the thinner of the two.

I soldered the connections myself.... my crimpers only did the larger ones.

that is good infor about the ducky. I do have one but it is so large compared to my factory one... I will give it a shot and see. it's very easy to duplicate the problem. all I have to do is swipe the 900mhz tx ant. across or near the buttons and it's like I pressed them!! crazy.

I will swap ant. and do the test.

thanks again guys.

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Just keep in mind that at these frequencies the type of coax is critical and the installation of the SMA's needs to be textbook perfect. Otherwise, performance will suffer.

So, double check the specs to the coax and make sure that the SMA's are installed exactly as shown on the datasheet. Don't improvise; pay close attention to every little detail. When it comes to UHF and higher freq's, quality factory made cables that are rated for the intended RF band are the safest way to go.

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That looks like an EZ*...

With the camera in the front, I find I need a strip of lead around the tail to balance it anyway.

So why not make life easy for yourself, and extend your video/power lead to the transmitter i.e. put both transmitter AND aerial in the tail?

Extending your video cable isn't _nearly_ as critical as extending the RF cable. Over that distance you could probably get away with a servo extension lead...

Even if you're using a metal box Tx, rather than a micro "stamp" Tx, you may find it only needs a little extra weight in the nose to get the C of G back.

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