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HelicopterRadio - Spektrum DSM › My experience with the DX7 spread spectrum radio
11-29-2006 08:42 PM  11 years agoPost 41
Augusto

rrElite Veteran

US

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The reason why the 40dB attenuation button is necessary is because the antenna being so short can't be collapsed or disconnected as in the regular 72MHz system.

To get an idea of what it means to do a 40dB attenuation you can use the free space path loss equation.

Path Loss = 32.45 + 20*log(f) + 20*log(d)
(f=frequency in GHz and d=Distance in meters)

So for instance if you're about 20 meters (about 21 yards) from the 2.4GHz radio your free space path loss is:
32.45 + 20*log(2.4) + 20*log(20)
32.5 + 7.60 + 26.02 = 66.12dB

When you click the button and add 40 dB is like you went 2000 meters away (2Km away) or 1.25 miles away.
32.45 + 20*log(2.4) + 20*log(2000)
32.5 + 7.60 + 66.02 = 106.12dB (40 db higher loss)

So in other words when you're at about 20 meters away and click the button the signal becomes equivalent to you going 2Km (1.25 miles) away and doing a range check.

Augusto.

Avant Aurora Ultimate

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11-29-2006 11:04 PM  11 years agoPost 42
Yug

rrMaster

UK. Herts

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Augusto - how do you rate the DX7 Tx in terms of it's stick feel and weight ?

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11-29-2006 11:04 PM  11 years agoPost 43
Barney

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Inverness Scotland

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JKos

I was thinking more of the spectrum Tx modules rather than the complete Tx which I'm sure will be available in the not to distant future. The one Ive seen has a short aerial on the Tx module itself.

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11-29-2006 11:59 PM  11 years agoPost 44
Augusto

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US

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Yug,

The sticks feels great. The release version comes with ball bearings. The weight was the only issue I posted about being that that the lack of a large antenna makes it a bit unbalanced for my taste but it's not really a big deal. I'm just too picky.
I did learn a trick from someone that told me he learned from Curtis about a piece of the hard side of a velcro at the bottom of the transmitter to make it stick to your t-shirt while you fly.

Barney,

There will be no transmitter module released for that new system.
The reason is that it's impossible to get the speed that the DX7 system has if you have to wait for the original transmiter to encode and put the info into a pulse train and then for the SS module to pick it up decode it, digitize it and re-encode, re-modulate it and spread it again into the spread spectrum signal. When they looked at the time it takes they dropped the idea of a module completely so don't wait for a module to come out.

Augusto.

Avant Aurora Ultimate

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11-30-2006 12:03 AM  11 years agoPost 45
trevorz

rrApprentice

Calgary, Alberta Canada

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Thanks Augusto for all the info.

If only it was an 8 channel I would buy it now, but alas the JR7000 gyro needs that extra channel.

I think the module being referred to above is the XPS one.

Regards,
Trevor.

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11-30-2006 12:16 AM  11 years agoPost 46
Yug

rrMaster

UK. Herts

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Thanks Augusto. Looks like it's just a case of waiting for the UK committes to wake up and give it the thumbs up.
One more question, being 2.4Ghz, I wonder how well it would work with a 2.4GHz video downlink mounted on the heli?

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11-30-2006 12:38 AM  11 years agoPost 47
greg

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Yorkville, IL

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I think modules adapted to any of the existing systems/brands would not be a good idea for the exact reasons stated by Augusto above.

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11-30-2006 12:48 AM  11 years agoPost 48
jab1969

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Fort Worth 76137, Texas , USA

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Hey Augusto, What about the moduels from extream power systems???? Are you saying that If I use one of their moduels in my 10X and their receiver it wont be faster?

Xtreme Power Systems, @Signs

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11-30-2006 05:33 AM  11 years agoPost 49
THX1138

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Camp Bondsteel, Kosovo

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We got the DX7's in today at the LHS I work at and I am pretty impressed. The RX is much smaller than I expected and this is a pleasant surprise. I think I will pick one up for plank use and maybe a T-rex 600. Looks good and it would seem that they are very functuional radios. Now we just need Paul to make some Spektrum modules for existing radios and life will be good.

Lou

Just give me five dudes and two flashbangs...

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11-30-2006 07:05 AM  11 years agoPost 50
OICU812

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Edson, Alberta, Canada

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thx....
There will be no transmitter module released for that new system.

...Once upon a time there were Nitros, flybars and frequency pins...

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11-30-2006 07:49 AM  11 years agoPost 51
COOKIEULT70

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CAMERON PARK, CA

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Are there any plans to release a 8 or 9 channel system? I have a plank that has 4 wing servos so I need at least 8 channels. Or does the battery not plug into one of the 7 channel ports on the receiver?

GAHH!!! Someone call 911!! My wallet is bleading heli parts!!

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11-30-2006 07:52 AM  11 years agoPost 52
Dood

rrProfessor

Wescanson

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My thoughts,

I figure that since I was considering a 9303, and if there was a possible trend going on, I would hold off until there was a DX9, or the 9303 DSM equivelant.

  ▲
▲ ▲

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11-30-2006 07:54 AM  11 years agoPost 53
Micro-Maniac

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Pasco,Washington Formerly: Captain Chaos

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Or does the battery not plug into one of the 7 channel ports on the receiver?
Notice how the battery is connected in a horizontally aligned slot below the 7 channel ones.
Separate battery connection aside from servo connections - So all 7 are free.

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11-30-2006 10:49 AM  11 years agoPost 54
hootowl

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Garnet Valley, Pa.

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The menu screens almost look Futaba 9C. Is this a coincidence?

Wolves don't lose sleep over the opinions of sheep

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11-30-2006 01:56 PM  11 years agoPost 55
THX1138

rrElite Veteran

Camp Bondsteel, Kosovo

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The DX7 and 7202 are identical(with the exception of spectrum) that is where the programing comes from.

Lou

Just give me five dudes and two flashbangs...

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11-30-2006 02:02 PM  11 years agoPost 56
JKos

rrProfessor

Redondo Beach, CA

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> The DX7 and 7202 are identical

Almost... The DX7 has a timer (up or down) whereas the 7202 does not.

- John

RR rules!

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11-30-2006 02:13 PM  11 years agoPost 57
Yug

rrMaster

UK. Herts

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JKos - I remember the latency on the 9C between channels 1 and 6 in PCM mode was about 120ms; what;s the latency in PPM mode ?
Just wondering what kind of benefit the 9C would get with using the XPS as it interfaces via PPM.

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11-30-2006 03:35 PM  11 years agoPost 58
JKos

rrProfessor

Redondo Beach, CA

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Yug,
In PPM mode, the 9C has a minimum latency of 50 ms and a maximum latency of 82.3 ms for eCCPM use (32 ms to 59.3 ms for a normal swash). So even if the XPS system added zero latency (obviously not possible), the DX7 would still whip its butt at 14 ms min to 40 ms max.

- John

RR rules!

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11-30-2006 03:38 PM  11 years agoPost 59
hootowl

rrProfessor

Garnet Valley, Pa.

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The DX7 and 7202 are identical
Are they made by the same company, Futaba?

Wolves don't lose sleep over the opinions of sheep

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11-30-2006 03:39 PM  11 years agoPost 60
Yug

rrMaster

UK. Herts

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thanks

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HelicopterRadio - Spektrum DSM › My experience with the DX7 spread spectrum radio
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