[NSRCA-discussion] 2.4 Ghz

[Dean Pappas]

Thanks for the info, Jim.
 

Dean Pappas 
Sr. Design Engineer 
Kodeos Communications 
111 Corporate Blvd. 
South Plainfield, N.J. 07080 
(908) 222-7817 phone 
(908) 222-2392 fax 
d.pappas at kodeos.com 

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of J.Oddino
Sent: Sunday, December 17, 2006 5:52 PM
To: NSRCA Mailing List
Subject: [NSRCA-discussion] 2.4 Ghz


I flew the Dx7 on Thursday and it felt pretty good.  It was in a Dog House Extreme with marginal servos but still had a very nice feel.  I took it way up and out so we could barely see it and had no problems.
 
Today I ran a few tests.  Following are some results and my comments:
 
1) The update rate, that is, the rate at which the servos get new information was about 45 Hz or every 22 milleseconds.  This is a little slower than most modern day systems.
 
2) The resolution less the servo, that is, the minimum change in the pulse width to the servo, was 1.0 microsecond.  This is better than any system I have measured. When I connected one of my elevators with a good JR digital servo it was extremely accurate and neutralized perfectly as far as I could see.  This was confirmed by measuring the pulse width on a scope scaled to one microsecond per cm.  This also says the mechanics of the transmitter gimbal are not creating an error in commanding neutral.
 
3) The change in pulse width per click of the digital trim was 3 to 4 microseconds which is not good.  The basic system is a 1024, 1024 steps from lock to lock, but you can only trim it as if it were a 256.  To me it is setting the trim that requires the best resolution.  We could fly with a 256 system as long as we could trim to 1 in 1024. 
 
4) An interesting thing was the dither on the pulse width of .4 to .8 microseconds.  I assume this was done on purpose because there should be no pulse jitter in a digital system.  I'm wondering if this can contribute to the good feel when flying.  Any opinions out there?
 
This system looks like a very good value and the big boys better get a spread spectrum system out if they want to sell systems in this price range.
 
Jim O
 
 

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