Paintball Radio project [need help!]

[wookie]

Hi everyone,

I am working on a college project to design and build a 27MHz half-duplex walkie talkie for a paintballer and his teammates.

The circuit I would like to use is the one below:

I have some questions however:

-Can I use a whip antenna, and how long should it be?
-Can you buy the variable transformer off the shelf?
-Would having long leads from the microphone to the circuit (15cm+) be a major issue?

Thank you in advance!

 

[Nigel Goodwin]

As has already been explained in the other thread, it's a completely useless circuit, and will only work poorly (if at all?).

But to answer your questions:

1) Yes, about 4 metres long for correct operation (quarter wave whip) - the 22uH coil feeding it is probably an effort to make better use of a much shorter whip.

2) No.

3) No, as long as you use a suitable screened lead.

 

[wookie]

Hi Nigel,

I read the other thread (infact I revived it) but didnt see any claims that the circuit would be useless.
4 metres is a hell of a whip. I was hoping for much less than that.

Yes I believe that the 22uH is a loading coil to make use of an electrically short whip.

I used this calc and found that I can use a 27cm whip with 1mm wire with only 12uH loading coil. Would this work better?

 

[Nigel Goodwin]

The thing to do is try different whips and see which works best - but it's an appalling poor circuit, and an appalling poor choice of frequency.

 

[wookie]

Okay great, I can conduct some field testing and add it to my report- good idea

What improvements could be made to the circuit to optimize it? Can't be all bad surely?

 

[Nigel Goodwin]

What improvements could be made to the circuit to optimize it? Can't be all bad surely?

Pretty well, it's only 'redeeming feature' is it's very low component count.

I'll be interested to hear how you get on, and what sort of performance you get.

 

[JimB]

As you appear to be in the UK, can I also add that the use of this equipment is illegal.

Yeh, yeh, I know all the excuses/apologies/justifications, but strictly speaking it is illegal.

And I agree with Nigel, this is a bad circuit, for many reasons.

JimB

 

[Tony Stewart]

I think this is flawed due to lack of specs.

Why not Define the link? The worst design is one with few specs.

What latency is needed? How many channels? Transponder time? Voice and data channels.
Collision avoidance? Std Code burst communication for watch your back etc jammers hehe


http://www.paintballwarriortactics.com/tactical-blog/communication-critical-part-1-2

Come back with a 1 page detailed list of requirements.

 

[audioguru]

In the other thread I said the "receiver" is a Mickey Mouse super-regen. Mickey Mouse circuits are too simple to work properly.
The original article said to buy the cheap kid's walkie-talkies or cheap child's toy remote controlled car and use their parts.

Half-duplex does not work in a noisy environment (paint ball shootings?).

 

[wookie]

Come back with a 1 page detailed list of requirements.

27MHz is the CB band and you don't need a license. Is there something else that makes this circuit illegal apart from "appalling[ly] poor circuit[ry]"

Below is my spec, copied from my specification powerpoint:

this list is noticeably more concise than a normal spec, due to the fact it was for a powerpoint and I would talk about each of the sections in detail. I hope it provides the necessary information. if not, let me know and I will add it to the spec.

Market

• 4-Man semi-pro + pro team

Competition

• Motorola radio + RAP4 mic

Shipping + Packing

• Must ship in large AirMail packet
• ESD shielded + conductive foam

Industry Standards

• UK Ofcom regulations
• Lead free solder (RoHS)

Economy

• 4 Units,1 Product. £75

Performance

• All weather conditions, 50m range
• Paintball durable (300fps)

Manufacturability

• CAD, Workshop + lab (PCB)

Lifespan

• 2 Years with regular use (caps will die)

Dimensions + Weight

• 50x30x40mm + aerial
• Up to 150g

Ergonomics

• No sharp edges
• Easy to clean

Design

• 6 weeks
• Matt black with coloured trim

Testing

• Paintball team at Mayhem SE
• Full working functionality
• Magnified inspection (4x)

Safety

• No voltage over 50V
• Never exceed 50*C or -5*C

Law

• CB Radio band (27MHz)
• Must accept interference
• Mustn’t generate interference

Also,

In the other thread I said the "receiver" is a Mickey Mouse super-regen. Mickey Mouse circuits are too simple to work properly.
The original article said to buy the cheap kid's walkie-talkies or cheap child's toy remote controlled car and use their parts.

Half-duplex does not work in a noisy environment (paint ball shootings?).

I most likely will do exactly that and buy some kids walkie talkies, I had a pair a few months ago but i harvested the transistors and 4PDT switches from them for another project - doh!

Bare minimum functionality is all that I care about. Paintball isn't that noisy when everyones using electromechanical guns and pumps. But old style mech guns are hideously loud, I agree.

 

[Nigel Goodwin]

27MHz is the CB band and you don't need a license. Is there something else that makes this circuit illegal apart from "appalling[ly] poor circuit[ry]"

You don't need a licence, but you have to meet the fairly strict requirements needed - that appalling 'circuit' is going to radiate all over the place, and has no accurate frequency anyway.

 

[JimB]

27MHz is the CB band and you don't need a license. Is there something else that makes this circuit illegal apart from "appalling[ly] poor circuit[ry]"

Licence free does not mean a free for all to use whatever equipment you like.
There are specifications issued by the licencing authorities, (OFCOM in the UK) which specify the frequencies to be used, the modulation type and the limits on output power and spectral purity.

Have a look here:
https://stakeholders.ofcom.org.uk/b...s-tech-info/interface-requirements/uk2027.pdf
Also be aware that there are further specifications to be taken into account as listed in the References section of that specification.

As a general rule, only type approved equipment may be used.

JimB

 

[Nigel Goodwin]

If you want something cheap and easy, and probably about as 'nasty' as your existing circuit

Have a look here:

**broken link removed**