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HomeRC & Power✈️Aircraft🚁HelicopterRadio - Spektrum DSM › Range check and antenna orientation
08-03-2007 07:30 PM  13 years ago
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BrunoBL

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Pomerode, SC, Brazil -26.71, -49.17

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Range check and antenna orientation
Hi All,

New DX7 user here.
After a long wait, my MA Spectra-G gasser heli finally has its own radio.

My installation has the main Rx sitting on top of the battery on the radio tray, with the satellite Rx attached to the fuel tank under the tray. The short connection harness won't allow a lot of possibilities with regard to receiver location.

Inspecting the resulting installation, I suspected that my worse orientation would be with the transmitter at the 5 o'clock position to the helicopter, as both receivers would be blocked from view by the heli CF frame in this position.

Here is what I found during range check with low power on the TX (range test button pressed):

- In "normal" transmitter positions, I could walk all day and not have any Rx glitch, even from the 5 o´clock sector described above. I gave up from increasing the distance at about 60m, or twice the prescribed range check minimum safe distance.

- If I purposely pointed the Tx antenna directly at the heli (admittedly the worse radiating direction), one of two things happened: If inside the 5 o´clock Rx shadow zone, the range decreased dramatically to about 20m. Outside the shadow sector, range remained well above the 30m minimum, even pointing the Tx antenna at the heli.

During the range test blackouts described above, simply changing the antenna orientation from "zeroed in the heli" to a more natural position regained signal instantly.

From the above, I would think that in order to avoid pointing the antenna directly at the heli, it is best not to use it streched out straight. If it's bent about 45 degrees at its pivot and rotated slightly so it is never pointing the same way as the radio's centerline (skewed right or left), the chances of pointing the antenna directly at the heli are remote, minimizing possible glitches.

Thoughts?
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08-03-2007 10:47 PM  13 years ago
Four Stroker

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Atlanta

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I always face the helicopter when I fly. Some airplane guys land over their shoulder - very bad. Why don't you point the antenna down about 45 degrees ? This is going to be very popular when the Futaba modules come out since they won't point up because of the handle !

There are longer satellite extensions available up to 36". Why don't you get some ? If I had a Spektrum I would use the 9000 RX and two satellite RX's in a heli - one on each side, both vertical. Failing that I would put the one satellite in the back with a long extension - 12 to 18 inches.

It's hard to fly and avoid your shadow zone.
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08-04-2007 12:09 PM  13 years ago
BrunoBL

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Pomerode, SC, Brazil -26.71, -49.17

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Why don't you point the antenna down about 45 degrees ?
Unfortunately, the DX7 antenna only bends up not down. Also, it doesn't swivel freely (which would make it possible to point it down if rotated upside down). Its rotating movement is limited to a 180 arc, sort of like a servo.

The longer extension with the satellite in the back would be great with a nitro heli, but I wouldn't want to route the long extension past/near the gasser ignition system (my spark plug faces back).

I like your double-satellite idea. It may just be the ticket.

Thanks for your ideas.
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08-04-2007 06:33 PM  13 years ago
midwestpilot

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Crystal Lake, IL

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You dont need to route one to the tail...
that is over the top...you can get a slightly longer ext. and place it out as far as you can out in the front of the canopy. My buddy has a jetcopter with the satalites still under the canopy and no issues(he has that logger thingy and has great numbers)
In life there is no spacebar!

Rich Erikson AMA 6175
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08-04-2007 10:56 PM  13 years ago
Garry s

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Brighton, England

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Did a range check before maidening my new Joker yesterday. Have the Rx on a plastic tray coming out of the back of the battery tray, aerial as far away from the carbon frame as I could get it, and the satellite on a plate fixed to one of the boom supports.

We had the heli on the ground, in a little dip so it wasn't quite line of sight to the Tx, and I walked a good 50 paces away. With the heli's nose pointed towards me, so maximum amount of heli frame blocking the signal, range check button depressed and aerial pointing right at the heli - worked perfectly. Remarkable.
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