TOPIC:

Thinking about getting a 2.4GHz radio to save messing around with crystals and I am bewildered by the choice.
Requirements:
- Cheap
- 2 channel
- Sticks, not wheel
- Cheap

What does FHSS/DHSS/DSSS mean and which is best?
How much do receivers cost?
Will they work with vintage servos?

Oh, yeah - Did I mention it should be cheap?

Martin wrote:

Thinking about getting a 2.4GHz radio to save messing around with crystals and I am bewildered by the choice.
Requirements:
- Cheap
- 2 channel
- Sticks, not wheel
- Cheap

What does FHSS/DHSS/DSSS mean and which is best?
How much do receivers cost?
Will they work with vintage servos?

Oh, yeah - Did I mention it should be cheap?

It's been a while since I bought any radio gear, but these are the sets I've tried (none of these have model memories so having multiple RXs & swapping means binding & setting up each time)

Planet T5 (doesn't mention S's)
2 channels on each stick + on/off 5th channel so will need fiddling about with + gates for car use; nice quality feel; TX + RX c. 52 GBP, spare RX c 17 GBP.

Acoms Techniplus 2.4G (DSSS)
A little nicer than the Etronix IMO, but no longer available? were around 45 GBP

Radiolink T4EU (FHSS)
4 channel set so gates/fiddling again, didn't particularly like it compared to the T5 (especially not the random 3 out of 5 times full revs a few seconds after turning the radio on), no longer available.

Etronix Pulse (FHSS) (review on YB somewhere)
basic 2 channel set, feels a little cheap but nothing particularly wrong with it, TX/RX set 40 - 45 GBP, RX 25 GBP.

Overall, I like the Planet T5 the best by a long way, but probably best suited to slow scalers & not worth it unless you need the extra channels for shifting gears, lights, winch etc. Etronix Pulse (& equivalents) a little bit underwhelming & a bit steep (especially the RXs).

I did look at hobbyking, but once you add in the UK or euro warehouse filters the bewildering range drops to practically nothing. Given their very long shipping times & virtual guarantee of getting hit for import duty AND fees I wouldn't buy from their worldwide or US warehouses again.

I have no idea what all the S's mean in practical terms.

Servos - I haven't had a problem with any servo with a modern type plug on (1983 onwards?), but I know my cheapo light set refused to work on 2.4ghz sets.

I think you'd have more options if you could live with a steerwheel TX, but I know I just can't.

I'm sensing that low price is quite important to you ... can't really help you there, but it depends on what you mean by "cheap" ... 50 GBP per car isn;t to me - but I wouldn't mind paying 100 GBP+ for a stick TX with multiple model memory & 10 GBP RXs.

Martin wrote:

What does FHSS/DHSS/DSSS mean and which is best?

Wiki FHSS: Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver.


Cut/paste from a forum: "DHSS spreads the spectrum by modulating with a very high subcarrier frequency driven by a particular spreading code. That smears the data across about a 5Mhz band (generally referred to as a channel!!), and AFAIK all 2.4Ghz sets use this technology. The differences are that Spectrum uses twin transmitters on two 'channels', and Futaba uses all 'channels' sequentially. Most of the rest simply use a single channel, and rely on the different spreading codes, and digital codes in the data frames, to sort the tangle out .."

Wiki DSSS: In telecommunications, direct-sequence spread spectrum (DSSS) is a modulation technique. As with other spread spectrum technologies, the transmitted signal takes up more bandwidth than the information signal that modulates the carrier or broadcast frequency.

So now, it's clear what to choose, right

Jonny wrote:

I think you'd have more options if you could live with a steerwheel TX, but I know I just can't.

I'm sensing that low price is quite important to you ... can't really help you there, but it depends on what you mean by "cheap" ... 50 GBP per car isn;t to me - but I wouldn't mind paying 100 GBP+ for a stick TX with multiple model memory & 10 GBP RXs.

I've never tried a wheel Tx so I don't know if I could live with it or not. If they are cheap enough, maybe I could give it a try.

Seeing as part of the point was to have one transmitter for several cars (not that I have many that actually run at the moment ), I think model memory would be a must. I'm sorry, I thought all 2.4 gig sets had that
I agree, £50 per car is too much, but I wouldn't mind spending a bit up front if subsequent cars were very cheap. I probably have unrealistic expectations because I have stacks of 27 meg radios, none of which cost more than a tenner.

I had a HobbyKing HKGT3 pistol 3 channel 2.4GHz a little while back, I think it cost around 20-30 quid but came without servos, & yes standard servos worked with it.

I don't get on with pistols, so I had it to bits & built the guts into a stick case - that's when the fun started... turns out the servo rates are odd on that system & they're not adjustable (HK's other systems are adjustable by PC-link)

This makes interesting reading.

Seems I put this thread in the wrong place somehow . It should be in "Technical" - please could somebody move it?

Martin wrote:

Seems I put this thread in the wrong place somehow . It should be in "Technical" - please could somebody move it?

Done

I got about 3 lines in & lost interest - it doesn't need to be a complex as that.
Easiest conversion is buy a cheap 2.4GHz Tx & Rx (Pistol types being cheapest), then hack up an old stick case so the 2.4 board fits in it.
Only thing you have to watch is the values (Ohms, usually 5-kilohm) of the gimble pots match, ie the stick ones are the same value as the pistol ones, not only the 'whole' pot value, but the neutral value & 'swept' value, or you'll end up with odd stuff going on like under/over servo travel & sometimes shutdown as a result of a non-expected voltage input to the chip.
The fix for this is easy enough if they don't match - buy pots that DO match - the pots in stick cases are usually both standard-pattern ones, whereas the ones in pistols are usually mismatched (Throttle is different to steering) & are sometimes either 'special' or miniature versions.
Oh & you'll need to re-use the 2.4 stubby aerial, (Not a long shiny one) which might involve having to extend its coax connecting cable (Cable from an old wiFi board is ideal for this).

In case you might be interested, you can also convert some transmitters for more channels - eg Traxxas TQ3 (3 channel) can be converted to 4 channel, Acoms Techniplus Alpha can be converted to 3 or 4 channel, & I think I saw a Futaba one recently with the same possibilities (Attack?) - the trannies you're looking for are the ones with a chip looking after everything (Can't remember the chip number off the top of my head...) instead of all discrete components

Good tips there about moving 2.4 electronics into old stick radio.

I have a HK-310 pistol grip radio from HobbyKing.
It is great on features and can do proper mixing on 3rd channel.
It works with old and new servos, but precision is poor and steering is not smooth.
Something odd is going on, like the servo moves in small steps and it vibrates between them.
(Maybe "limited resolution" and "quantization error" come into play here.)
Unfortunately it sounds a bit jerkily regardless of servo,
but it works fine and is very nice for playing around with buggies.

Not sure about availability right now, but it is cheap, has 5k pots and looks hackable

I'll lay money the "jerkiness" of the servo movement will be poor quality pots (Most likely the method used for securing the "wiper" to the shaft, or possibly the type of lubricant used on the carbon track). It can also be the same problem(s) with the pots in the servos, particularly if their output shafts are worn/wiggly or they've been "puddled" at some point.
High speed servos are worst for it (Kyosho MiniZ steering pots are renowned for it)