HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Oct 07, 2011, 09:53 AM
Registered User
Russia
Joined Nov 2007
157 Posts
Alert
Spektrum DX8 range test issue + measurements

I did some range tests with my new DX8 and found that I can go 200-250 meters in the reduced power RT mode and still get solid link.
Then I measured DX8 output with a spectrum analyzer and found that output power attenuation in range test mode is only about 18-19db. For example, DX7 attenuation is more than 40db.
In terms of the range itself, assuming 6db loss per 2x range - DX8 in a range test is only 8-10 times less than full range! It's useless and dangerous, couse if you check for 30 meters as the manual says, then you could get into cut out at less than 300 meters!
Any comments?

UPD:
Why do I think it's a bad behavior?
Range test setup explanation and some more tests
dehicka is offline Find More Posts by dehicka
Last edited by dehicka; Oct 08, 2011 at 10:56 AM.
Reply With Quote
Sign up now
to remove ads between posts
Old Oct 07, 2011, 10:27 AM
Air, Ground & Water
freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
24,347 Posts
Quote:
Originally Posted by dehicka View Post
I did some range tests with my new DX8 and found that I can go 200-250 meters and still get solid link.
Is that in reduce power mode or full power? Because if its reduce then you have one super DX8 cause I get more then the recommended 30 but nowhere near what you are sugesting.
Quote:
Originally Posted by dehicka View Post
Then I measured DX8 output with a spectrum analyzer and found that output power attenuation in range test mode is only about 18-19db. For example, DX7 attenuation is more than 40db.
In terms of the range itself, assuming 6db loss per 2x range - DX8 in a range test is only 8-10 times less than full range! It's useless and dangerous, couse if you check for 30 meters as the manual says, then you could get into cut out at less than 300 meters! Any comments?
Too technical for me. I just had my brother drive off with the plane inside the car while I stood on the side of the road. I told him when the plane stop moving the control surfaces he should stop and take the plane out of the car to see if it would respond again.

This test prove satisfactory for me as when he pulled over and got out the plane responded to controls BUT yet I could not even see it.
freechip is online now Find More Posts by freechip
Reply With Quote
Old Oct 07, 2011, 10:59 AM
Registered User
Russia
Joined Nov 2007
157 Posts
Quote:
Originally Posted by freechip View Post
Is that in reduce power mode or full power? Because if its reduce then you have one super DX8 cause I get more then the recommended 30 but nowhere near what you are sugesting.
Reduced power mode for sure. I got 200m and still no FS.

Quote:
Originally Posted by freechip View Post
Too technical for me. I just had my brother drive off with the plane inside the car while I stood on the side of the road. I told him when the plane stop moving the control surfaces he should stop and take the plane out of the car to see if it would respond again.

This test prove satisfactory for me as when he pulled over and got out the plane responded to controls BUT yet I could not even see it.
Yes, I can do 300m test instead of 30m recommended. But I cannot see surfaces moving or not from that distance without help. And recommended minimal RT distance is 30m, not 300m in the manual or rage test menu.

If your model pass DX8 30m range test and fail at 35m then you got only 300-400m full range.
But if your model pass DX7 30m range test and fail at 35m then you got 1800-2000m full range.
dehicka is offline Find More Posts by dehicka
Reply With Quote
Old Oct 07, 2011, 12:16 PM
Air, Ground & Water
freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
24,347 Posts
Understand what you are saying but how do you explain HH/Spektrum Saying they are all calibrate to output the same.
freechip is online now Find More Posts by freechip
Reply With Quote
Old Oct 07, 2011, 12:40 PM
Registered User
Joined Oct 2011
15 Posts
Quote:
Originally Posted by freechip View Post
Understand what you are saying but how do you explain HH/Spektrum Saying they are all calibrate to output the same.
yah, every big business tell the truth 100% of the time!

Not saying it is or isn't but the manufacturer is typically going to tell you what you want to hear.
rational rc is offline Find More Posts by rational rc
Reply With Quote
Old Oct 07, 2011, 12:43 PM
Registered User
richard hanson's Avatar
United States, UT, Salt Lake City
Joined Oct 2007
7,174 Posts
Quote:
Originally Posted by rational rc View Post
yah, every big business tell the truth 100% of the time!

Not saying it is or isn't but the manufacturer is typically going to tell you what you want to hear.
Do you have info to indicate the suggested mfgr info is incorrect ?
richard hanson is online now Find More Posts by richard hanson
Reply With Quote
Old Oct 07, 2011, 12:57 PM
Air, Ground & Water
freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
24,347 Posts
Did you have issues with your DX8 and now are looking for a solution or just want to complain.

First off the 30m recommendation for range test does not translate into the radio is going to stop at 30m. All it is is that if it passes at 30m then you have enough signal strenght to have good flight.

You could pass range test but still have poor range or signal quality depending on how you arrange your antennas.

The fact that you claim 200-250m in range test seems not true to me for 2 reasons. #1 having done many range test with my DX8 and DX6i both for setting up plane and also to prove unrelated issue I was having I am certain your numbers are BOGUS. #2 the difference in the numbers you claim (200-250m) is quite big 50M is huge so which one is it 200 +- couple feet or meters or 250m +- couple feet or meters.

Your post just sounds like you had some sort of issue and now have a grudge.
If this is the case why not just say so so other can try to help you out.
freechip is online now Find More Posts by freechip
Reply With Quote
Old Oct 07, 2011, 01:02 PM
Air, Ground & Water
freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
24,347 Posts
Quote:
Originally Posted by rational rc View Post
yah, every big business tell the truth 100% of the time!
Who cares? If that's how they want to operate.
Quote:
Originally Posted by rational rc View Post
Not saying it is or isn't but the manufacturer is typically going to tell you what you want to hear.
If my car manufacturer tells me the max speed for it is 200 then this number maybe an optimistic number but what he's saying is that he drove is car up to 300-400.

Well first off which one is it? and Second why would the company benefit from saying it slower.

Spek say to range test up to 30m and if it passes your good to go. He said he gets 200-250meter. REALLY?

As for the DB value I have never check nore have the equipement to do so nore care to. I test my equipement the method that is recommended to me and it passes every time.

Never once had range issues so the method I use must work for me, right?
freechip is online now Find More Posts by freechip
Reply With Quote
Old Oct 07, 2011, 01:03 PM
Registered User
Halifax, NS
Joined Sep 2009
404 Posts
Quote:
Originally Posted by dehicka View Post
I did some range tests with my new DX8 and found that I can go 200-250 meters in the reduced power RT mode and still get solid link.
Then I measured DX8 output with a spectrum analyzer and found that output power attenuation in range test mode is only about 18-19db. For example, DX7 attenuation is more than 40db.
In terms of the range itself, assuming 6db loss per 2x range - DX8 in a range test is only 8-10 times less than full range! It's useless and dangerous, couse if you check for 30 meters as the manual says, then you could get into cut out at less than 300 meters!
Any comments?
I also noticed I could go way further than I ever would have expected when doing a range check. Last time, I stopped walking after about 150m. I agree that it is not very useful the way it is now. I will do some testing between the DX8 and DX6i to see how they compare during range test.
karlpenney is offline Find More Posts by karlpenney
Reply With Quote
Old Oct 07, 2011, 01:34 PM
Registered User
richard hanson's Avatar
United States, UT, Salt Lake City
Joined Oct 2007
7,174 Posts
we once used the washing machine as a signal attenuator
(w/o water)
or use the dryer (on fluff)
richard hanson is online now Find More Posts by richard hanson
Reply With Quote
Old Oct 07, 2011, 02:20 PM
Registered User
Romania, Dolj, Craiova
Joined Sep 2007
15,211 Posts
Guys in this thread that try to take it easy seems not understand what the real issue is... and how serious it is...
Any RF system manufacturer give that distance based on the fact that the output of the radio in range check more is VERY well known and exactly calibrated. Usually, the power in range check mode is 30dB less than the full operating power.
To say that for the same radio a guy reports 50m in range check mode, and other reports 250m does not mean the second is a fantastic radio with a stellar range. Conversely, is equivalent to say that the range check attenuator has a huge variation of attenuation factor, thus a very low quality check, and this radio must be sent for immediate service, because you can no more make any assumption of its real range !
renatoa is offline Find More Posts by renatoa
Reply With Quote
Old Oct 07, 2011, 02:30 PM
AndyKunz's Avatar
Illinois
Joined Sep 2001
24,784 Posts
The dB down in range test vs full-power modes is irrelevant.

The range test power is calibrated to one absolute level (within a tolerance, of course) for all radios. The full power is calibrated to another absolute level, but that standard varies depending upon region. Radios in US mode will have a greater output power difference than radios in EU mode.

Rather than basing a decision upon how many dB down range test is, one needs to verify it against a particular output level.

By the same token, one cannot use the test range in range test mode to determine range in full-power mode. Not only are environmental issues a HUGE factor in range testing (full power or low power), but because they are separately calibrated there is no simple multiplication you can do to determine what the full range distance will be based upon the test range. It just doesn't work that way.

Andy
AndyKunz is offline Find More Posts by AndyKunz
Site Sponsor
Reply With Quote
Old Oct 07, 2011, 03:04 PM
Registered User
Romania, Dolj, Craiova
Joined Sep 2007
15,211 Posts
So, based on your experience, what are the minimum and maximum range check distances reported by your tests or real users, that you consider normal, and not require an investigation of that radio ?
renatoa is offline Find More Posts by renatoa
Reply With Quote
Old Oct 07, 2011, 03:30 PM
AndyKunz's Avatar
Illinois
Joined Sep 2001
24,784 Posts
Minimum test distance 30m in test mode. We do not specify a maximum.

Andy
AndyKunz is offline Find More Posts by AndyKunz
Site Sponsor
Reply With Quote
Old Oct 07, 2011, 03:47 PM
Registered User
Russia
Joined Nov 2007
157 Posts
AndyKunz
I've got both DX7 and DX8 US versions (21.7dBm and 19.25dBm modules). So output levels are not the issue.
I did all RT with the same AR6100 reciever on the same simple setup - just reciever, battery and servo. Didn't change or move anything on the RX side betveen tests, just rebind.

To go further I can simulate harsh RF envirement around RX by the 2.4 noise gen up to the limit when DX8 RT mode will fail at around 30m. And then measure distance at full power.
dehicka is offline Find More Posts by dehicka
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Spektrum AR6200 range issue brians356 Radios 6 Sep 06, 2011 10:35 PM
Cool Flite Test - Spektrum DX8 - REVIEW - WATCH NOW! stonekap Radios 32 Nov 05, 2010 11:26 AM
Question A Question About the New Spektrum DX8 - Do you have one? Please do this test. Miami Mike Radios 0 Aug 16, 2010 02:17 PM