KO 2.4 RX with no range

[Northy]

Anyone seen this before?

Had a 408S RX that sudden;y had no range - about 10 foot. Aerial looked broken so i got a new one from Demon (but it's very short). Have fitted it and it's made no difference.

any ideas?

g

[pugs]

not seen it before G, but have you tested from the end of the wire to the board with a meter? both cables ( its a bit like a coax cable on spektrum )? might be worth checking incase the connector isn't doing its job properly...

[Cardnim]

Hey Graham,

DOnt know for sure whats up with the KO, but couple of questions that spring to mind (apologies for teaching Gran to suck eggs!)

- are the batteries in the TX over 10.5v?
- is the RX powered from the ESC or seperate batt pack?
- is there a power cap fitted?

If a power cap or ESC is fitted then measure the voltage going INTO the RX. You might find that it is intermittant and/or low.

- Has all your testing been int he same location? (thinking here that 2.4Ghz is a very busy freq. and other things may be colliding with your signal

Interesting that you say about the new aerial being shorter than the previous one.
That worries me as the RX will be tuned to the wavelength coming from the original aerial and if that has now changed, then performance will change too.
(I know 2.4Ghz doesnt need a big aerial, but its all about what signal spec the RX was originally designed to expect)

- Was the aerial connection a little gold plug? Was the new part a like for like fit?

Hope some of that helps mate.
Keep us posted!

[Northy]

Tested in same car, with same speedo and lipo as 2 others last night that work fine.
Car sat at the bottom of the garden and me stood at kitchen door. Proper scientific! lol

New aerial was from Demon and yes had the little gold plug fitted, was this one:
http://demonpowerproducts.co.uk/prod...a-sanwa-p-6473

G

[Cardnim]

Arse, was hoping it was either dodgy voltage or dodgy co-axial wiring.
Neither seem likely after your own tests.

Problem is, that the new aerial is shorter (I wouldnt be happy about this) but thats probably not the problem you're having.
You said the RX range went crap BEFORE replacing the aerial, so must be something else.
However, the new short aerial may give us the same lower range issue - so you wouldnt know if you've fixed the original problem or not.

My advice -, go back to the original aerial, fix the problem with that one, then replace for your new one and hopefulyl all should be well.

Sorry cant give more help mate, not up to speed on the internals of RX's just yet

[Northy]

The reduction in range first coincided with a friend driving my car into a brick wall (thanks EBP) and when I checked the aerial it looked like it was broken all the way through about an inch away from the case, so not sure that would be any good to try and repair and try.

I'll try removing an aerial from a good working RX and put it on the dodgy range one and see what happens

One thing I did notice though was that there looks like there's a pad on the PCB for the non co-ax aerial version - the version that just uses a piece of normal wire - I had thought about just soldering a length of wire onto that!

[Cardnim]

Worth a try, but I wonder if that is jsut a legacy connection from the old 40Mhz boards?

Cant see how a 2.4ghz signal could be picke dup along a random length of simple wire without some crazy attenuation occuring.

But hey, I know you love your science (!) so worth a try.

I reckon (without knowing for sure, so its just my thoughts) that the length of your 2.4Ghz aerial (the co-axial one) is critical. I cant see how any other length could work correctly. Your RX is jsut going to be tuned to a certain impedence and thats linked to the length.
Like I said though, thats based on nothing more than some reading and thinking

[Northy]

Well the 2.4 407s rx has a bit of wire for an aerial, the 408 and 409 have the co-ax aerial. You are right though the pcb components could be different.

[Cardnim]

Originally Posted by Northy

Well the 2.4 407s rx has a bit of wire for an aerial

Really? Thats bonkers!
I cant understand that.

Are you sure it doesnt have the co-axial end piece before it plugs in the circuit board?

Well, there goes the tiny bit of knowledge I thought Id learnt!!
Cheers Graham!!!

[Col]

Originally Posted by Cardnim

...the length of your 2.4Ghz aerial (the co-axial one) is critical. I cant see how any other length could work correctly...

I always believed the same thing, until I bought a second spektrum receiver and it came with about 70cm of ariel attached to it! Worked fine at that length and works fine now I've chopped most of it off

[Cardnim]

And they say the laws of physics cant change!?

Good to know though - cheers guys.

@Graham - let us know if you get the RX any further along as to the cause/solution. Good luck.

[Northy]

I just got a couple of the cheaper 210 rxs for vintage cars and they just have a bit of wire too :-)

[blue_pinky]

On 2.4Ghz radios the aerial length that is critical is only the 30ish mm of exposed wire at the end...that is the tuned length...based on some simple maths to do with 1/4 wavelength...the rest of the aerial could be any length essentially as it's shielded up to that point.

My brother (who works with electronics and has access to the right tools for stripping the wire nicely!) has done some testing with this and has cut a spektrum aerial wire right down...and re-stripped the end to the right length...worked perfectly!

Sounds to me like the impact the car had might have done some damage to the receiver itself maybe???