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Member postings for Brian Parker

Here is a list of all the postings Brian Parker has made in our forums. Click on a thread name to jump to the thread.

Thread: High voltage low current.
30/12/2010 16:30:21
Heat is the enemy.
 Ohms law is dependent on constant temperature. The Current flowing is proportional to the source/applied voltage and inversely proportional to resistance.
 Resistance changes with temperature. Under load the battery, motor, ESC and wiring will all be at varying temperatures.
 Maximum power transfer (efficiency) will only occur when the load resistance is equal to the source (battery) resistance. Source resistance limits the total current and will drop the voltage at the battery terminals.
 Load voltage across battery terminals = Source voltage - Current drawn x source resistance.
Thread: Spektrum? Futaba? Hitec? JR? or XXXXX for 63
19/12/2010 13:36:35
GFSK is ‘Blue tooth’ (Gaussian filtered Frequency Shift Keying) modulation, it is performed after the frequency hop.
Thread: Futaba T6EXAP
12/12/2010 11:46:30
Absolutely Peter, it’s in the harmonics. I was attempting to keep my posting non-technical.
 The 455Khz and 10.7Mhz IF frequencies are pretty much standard, also a 17.xxMhz crystal is far more robust than one oscillating at a higher frequency and it is easier to keep it ‘ringing’.
 I’ve never had any problems using various makes of receivers with either JR or Futaba transmitters and generic RX crystals.
10/12/2010 04:47:14
Boots, 
I was under the impression that you were using a Futaba TX crystal.
 If the TX crystal is not a genuine Futaba crystal then that could be your problem.
 As you have discovered, the TX crystal oscillates at the frequency required by the RF exciter stage to produce the required output frequency. That’s why TX crystals are not usually interchangeable between manufacturers.
 RX crystals are interchangeable in single conversion PPM receivers regardless of manufacturer. Dual conversion receivers have two crystals, one internal and the one we change to achieve the required channel.
 Hope you get it sorted.
08/12/2010 19:37:09
Paul, Agreed, a modulation fault (see my posting above).
 
Boots,
 If you’ve reset the transmitter to de-fault settings, are using the correct compatable transmitter and receiver crystals, the correct mode and the field strength meter is detecting a carrier then it is a modulation fault.
 Wasn’t impressed (compared to JR) when I opened the back of mine, that’s why it’s still under the bench.

Edited By Brian Parker on 08/12/2010 19:37:46

Edited By Brian Parker on 08/12/2010 19:38:03

Thread: Nimh Mythbusters test
08/12/2010 08:31:14
Just use Sanyo Eneloops and charge every other full moon.
Seriously, It might prove informative if you could include a budget supermarket ‘4 pack’ for comparison.
Thread: Storing LiPos
07/12/2010 20:56:11
I have to admit that I take no special care of mine other than to double check when charging.
07/12/2010 19:53:54
The internal resistance of a battery is immaterial when the battery is not under load, it is just a series resister in an open circuit.
Thread: Futaba T6EXAP
07/12/2010 11:56:29
Boots, 
It should function straight from ‘switch on’ provided you have the correct modulation (PPM or PCM).
 Try clearing the model memory using the Data reset option (RCST) then setting the modulation using the ‘PULS’ option( It probably defaults to PPM).
 I have a T6EXAP.
 It lasted until the guarantee ran out then the RF decided to cease modulating-it’s still under the bench gathering dust, never got round to fixing it-useless.
Went back to my ancient JR Apex.
 Now on 2.4Ghz (non-Futaba of course).

Edited By Brian Parker on 07/12/2010 11:57:25

Thread: Testing the Orange DSM2 receiver when shielded
06/12/2010 14:37:41
Yes amazing -  I wonder what’s the absolute range of the AR500?
 From the top of the Orme its probably Dublin.
06/12/2010 10:53:54
The Spektrum AR500 receiver.
  Comparison with previous Screening tests (and slightly off thread).
 
The test was conducted with the Spektrum AR500 receiver in the screening box as per previous tests.
The receiver passed  full range tests with the transmitter antenna at both horizontal and  vertical  on all but one occasion when it failed at 24 paces (with the transmitter antenna horizontal).
The Long screened antenna was curled and in physical contact with the inside of the box, so the testing was repeated with the antenna padded and away from the sides of the box..it still (as anticipated) passed the range tests.
Conclusion, either this is a very robust receiver or the screening box is useless as a screen.  I suspect the former.
05/12/2010 22:52:08
I'll put an  AR500 receiver in the screening box and compare its 'range test'  to the others tested.
Thread: Why not a slow speed retract servo?
05/12/2010 22:43:58
Small Stepper motor?
Thread: Testing the Orange DSM2 receiver when shielded
05/12/2010 21:07:44
Chris,
 
My tests were all conducted outdoors and repeated several times (because results were not as expected).
 The only one to vary (and then by only a small amount) was the Orange receiver (screened and without the remote).
 The box is of Die-cast Alloy previously successfully screening a VHF module, not sure of its UHF/micro wave properties and at 6X3X2inches antenna installation just about OK, the antenna wires themselves were not individually supported. Testing was with the box 'earthed' to 0volts and also tried 'un-earthed'.
 I initially expected to have a very weak signal or even no signal at all into the box.
 It seems to me the system very robust and reinforces the view that the majority of failures are due to poor installation or pilot error rather than to system weakness.
 Also the Orange receiver is a good buy.
05/12/2010 19:47:02

I’m aware of what Spektrum state but my test indicated an increased gain with the remote connected and equally screened.
 How else to explain the difference in range observed when only the main receiver was connected and screened.
05/12/2010 17:09:58
Tim,
Yes, I was surprised at the performance of the Orange Receiver.
A test with an Orange remote (when they come down in price) as opposed to the Spektrum Remote on both main receivers might produce further unexpected results.

More test results
This time with the main receiver only in the screening box.
 The Orange range test was almost the same as its previous test failing at 8-9 paces but the AR6200’s range was reduced to 9 paces.
 The remote RF/antenna on the AR6200 must be increasing the gain of the main receiver/antenna ie. they must be working together (matched?) whilst the Orange receiver is looking at the each antenna separately and using the strongest (switching or locking? more testing needed).
Results of the tests were not fully as expected but confirms that the remote receiver is RF active and will give added security to both main receivers. Also the Spectrum receiver combination performed better overall than the Orange receiver in combination with the Spektrum remote.
 Performance under screened conditions was much better than anticipated throughout the testing.
05/12/2010 12:08:51
  

 

Some unexpected results.

Equipment..        Spektrum AR6200 Receiver.

                                Spektrum Remote Receiver.

                                Orange 6 channel Receiver.

                                Multiplex Tiny-s Servo.

                                4 cell NiMH Battery.

                                Sealed High EMC screening Box

                                Spektrum DX6i Transmitter.

Results..

a)      With Orange receiver + remote + battery all in box with servo outside box with only 2mm cable exposed. (Antenna closer to each other than recommended.)

Transmitter at ‘Range Check’

Range test failed at 9 paces.

b)      With Remote receiver outside the box.

Range test failed at 16 paces.

c)       With AR6200 +remote + battery in box and servo outside

Range test failed at 14 paces.

d)      With remote receiver outside box.

Range test failed at 16 paces.

Range testing (normal). Both receivers (18inches above ground) gave the Orange receiver a slight edge over the AR6200.

Range testing both receivers with the remote receiver connected gave the AR6200 slight edge.

A vertical antenna gave slightly better results than when horizontal. (But remember this was with the receivers close to the ground). Range test failed (as Expected) when the antenna was pointed directly at the receiver.

 

Tim,
Regarding Park Fly receivers. It’s a bit like Performance Cars. You have to do a lot(and spend more) to gain that little extra. With receivers the problem is ‘noise’, selectivity and overloading of  the front end. From what I’ve heard Park Fly2.4Ghz receivers seem to have more than ‘Park Fly’ range.

 

Edited By Brian Parker on 05/12/2010 12:09:34

05/12/2010 09:13:59
 
 The signal is in all probability penetrating the screening.
 To be fully effective the screen should be grounded. ie connected to the negative 0volt line.
 The power feed cables are always a possible source of ‘noise’ at lower frequencies, but for a 2.4Ghz signal to reach the RF stages through the power cables and at the same time maintaining full integrity is extremely doubtful.
 Intrigued by the results with the remote Spektrum receiver.
 May try some tests to compare results. If OK with you Tim.
Note. The remote will not have quite range of the main receiver.
04/12/2010 18:48:18
 

Tim,

Did you re-establish contact with the main receiver before testing the remote receiver in your final test?

Thread: Move over Wildthing the Fusion has landed
01/12/2010 15:40:16
 
Agreed, elevator trim it is.
My CoG is tad over 4”(105mm) with an AUW of 2lbs.
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