2.4 conversion - range problem

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Nick M
Posts: 77
Joined: 19 Dec 2018, 20:39
Location: Camberwell london

2.4 conversion - range problem

Post by Nick M »

Can anyone kindly advise?

I 'retroed' an old 2.4 gh Radiolink (10+ yrs?) to make it work like a reeds set and put it in an ali box (Thanks Martin for the advice replacing pots with resistors)

I'm now having serious range issues - 4ft

The case is bent aluminium with 3 d printed sides

The new layout runs the antenna cable near the other electrics (reed switches) - not near power supply though

I unsoldered the antenna from the board to run it through a hole in the casing

Because it was close to the pots I shrouded the antenna wire inside the tx using a bit of coaxial cable shroud and enclosed that in heat shrink tubing - keep it neat(ish) and avoid possible grounding

I'm pretty sure the solder join is good.

I didn't run tx without an aerial

Got to the slope with it in the Zeitgeist - and obviously didn't fly

Any genius thoughts?

Thanks

Nick
Pchristy
Posts: 332
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: 2.4 conversion - range problem

Post by Pchristy »

I unsoldered the antenna from the board to run it through a hole in the casing
I suspect this is the heart of your problems! Soldering at these sort of frequencies is a bit of a black art - especially with such thin wires!

The ground (outer) sheath is just as important as the inner - which carries the signal. It is very easy to leave a whisker of wire or solder bridging the lands. The exposed portion of the inner needs to be as short as possible. Even a blob of excess solder on one of the joints can be detrimental.

Personally, I will only unsolder and resolder leads at these frequencies when there is no other alternative, and will move heaven and earth to find an alternative!

It will be difficult to diagnose without some fairly sophisticated test equipment . Ideally you need an RF power meter that you can connect in place of the aerial to see what is actually arriving at the aerial. I use one of these: https://www.hobbyrc.co.uk/immersionrc-rf-power-meter-v2

Beware of cheap ones from the bay of evil! They may not provide the correct 50 ohm termination at UHF frequencies! I've run in to this problem even at 459MHz, where a 50 ohm termination was anything but at that frequency!

A spectrum analyzer is also very useful, but ones that operate at this sort of frequency are very expensive - even old second-hand ones!

Best of luck!

--
Pete
Tobe
Posts: 517
Joined: 16 Feb 2018, 06:19
Location: Varberg or Stockholm, Sweden

Re: 2.4 conversion - range problem

Post by Tobe »

What 2,4 GHz module are you running?
As Pete mention proper wiring is a must and wiring can include twisted wires, ferrites, low ESR caps, inductors, shielding, positioning etc. I know by experience that many of the processor we use in our conversions i.e. ATmel Mega 328P/168PA are quite sensitive for RF interference which often shows in extreme low range if any.
Any pictures?
Martin
Posts: 661
Joined: 16 Feb 2018, 14:11
Location: Warwickshire

Re: 2.4 conversion - range problem

Post by Martin »

I also suspect a soldering problem where the co-ax antenna cable attaches to the PCB. I've repaired quite a few receivers for club members who have managed to pull the whisker antennas off - either in a crash or with careless handling: it's always a nightmare and I always insist on them doing extensive range checks before flying again, even though I do the soldering as carefully as possible, using a tiny soldering tip, good lighting and magnification.
Nick M
Posts: 77
Joined: 19 Dec 2018, 20:39
Location: Camberwell london

Re: 2.4 conversion - range problem

Post by Nick M »

Thanks all

Will invent time machine to avoid having unsoldered antenna...

I unsoldered initially to route through hole in case - could actually have left intact with a bit of thought

This the Tx - which has worked well for years = 'vintage' of a sort
adiolink tx.png
I have lots of receivers for this tx - hence the interest


I haven't actually soldered the coax to the PCB... just fairly tight shroud round almost all of the cable inside the tx (pulled tight to be close around cable, heatshrink around it to prevent and contact with case, etc


Perhaps unsoldering and having cabling outside tx and see what range is a sensible next step

Cable inside tx is fairly long - didn't want to shorten in case had to rearrange components as thought proximity to reed switches might be a problem


I'll remove shroud, put cable outside tx and see what happens

I'll check soldering

Thanks all

I have another radiolink 4 ch tx (more primitive, no lcd) if all else fails will tray that

Best

Nick
bluejets
Posts: 261
Joined: 19 Jun 2019, 04:09

Re: 2.4 conversion - range problem

Post by bluejets »

By "pictures" pretty sure Tobe was referring to the new layout internals etc.
Tobe
Posts: 517
Joined: 16 Feb 2018, 06:19
Location: Varberg or Stockholm, Sweden

Re: 2.4 conversion - range problem

Post by Tobe »

Yupp!
Nick M
Posts: 77
Joined: 19 Dec 2018, 20:39
Location: Camberwell london

Re: 2.4 conversion - range problem

Post by Nick M »

Many thanks for all your help

I have had some time and got back to the project

My fault (not a surprise)

The aerial required very careful soldering and I had assumed it needed to be soldered to a larger area than turned out to be the case

I re soldered and range certainly good for 50 yards at least - and will do a proper range check before committing aviation

Going to be used in Zeitgeist and with W of Oz with a non lifting tailplane

It'll be up Cook Peak and single channel too demanding for me but reeds will be ok hopefully - most slopes are spine backed
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