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Comms options?


Warthog
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Have had the standard CB setup in the truck for ages. But find it a pain in the arse to use the standard mic when trying to drive/winch etc. Plus the winch bitch's handheld is cumbersome and awkward. Been in the mud more often than anything :blink:

Whats options are available to me for using a headset type set-up on the CB instead of the mic. Something with a voice activated set-up, like you get on PMRS?

Have tried PMRS and would prefer to stay with CB.

Cheers for any response :)

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The trouble with most radios is lack of bandwidth - which leads to lack of clarity, particularly in noisy environments. PMR is less than 2.5kHz (giving a 5kHz channel spacing), CB has about 6kHz and FM Radio about 15kHz.

You need to find one of the wireless intercom sets used in rallying. I've seen these quote 12.5kHz voice bandwidth which should be very clear - but they are kind of expensive as well.

For the best clarity, running 'full duplex' helps a lot as well. You know how, with a CB only one person can talk at a time whereas on the phone you can both talk over one another. You can achieve the same with radios by transmitting & receiving on different channels. You can then leave the mike keyed and hold a fairly 'normal' conversation.

A lot of Amateur transceivers can operate full duplex and can give decent audio bandwidth. Maybe if you found a pair capable of operating in the 446MHz PMR band, although they would not be totally legal (exceeding the bandwidth, spanning several channels), at least you would not be disturbing anyone as most people have discovered it's rubbish.

Many of these rigs are smaller than mobile phones and brimming over with features.

'Novice' Amateur licenses come free with packs of cornflakes these days - so you could operate on amateur bands legally if you desired.

The last option is just using mobile phones with hands-free earphones. You can get these 'friends & family' deals where you can talk to one number for hours for next to no money. So long as there is coverage, you could just dial up and leave the call open for the whole event.

Hopefully, when 'Push to talk' mobiles take off, this kind of walkie-talkie crossover usage will be much easier and cheaper.

Si

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The trouble with most radios is lack of bandwidth - which leads to lack of clarity, particularly in noisy environments. PMR is less than 2.5kHz (giving a 5kHz channel spacing), CB has about 6kHz and FM Radio about 15kHz.

Si

Hmmmm……………….. not strictly true ………… ;)

The AUDIO bandwidth of any analogue radio based communications system is 3K ………… 300Hz to 3.3Khz.

Frequencies below 300hz are used for sub audible tone signalling (CTCSS …… Continuous Tone Coded Squelch System). It is not sub audible to the ear ……… it is sub-audible by the fact that every thing below 300Hz is filtered. However, an experienced radio comms engineer would be able to detect by ear CTCSS on a signal as it has a characteristic very low level hum.

The RF bandwidth is determined by the method of modulation and currently all VHF / UHF channels are either 12.5 Khz or 25Khz bandwidth (also referred to as the channel spacing. The above is due to the simple fact that the Frequency modulation is used to super impose the audio onto the RF carrier. OK …….. for the purists amongst you, pure FM is rarely used, it is actually angle modulation. It should be remembered that we are talking about NBFM (Narrow Band FM) . Wide band FM is reserved for the broadcasters where the audio bandwidth is larger 15hz to 15kz, thus resulting in a 180khz RF channel, although this does carry some overheads with the stereo sub carrier and a little bit of data thrown in for good measure.

The channel spacing, or bandwidth can be reduced to 6.25Kz channels by using phase modulation, although this was abandoned in favour of digital technologies.

The audio quality between a 12.5khz channel and a 25 khz channel will be undetectable to the human ear. In Comms audio quality is subjective and is measured using PESQ (pronounced ‘Pesk’)…….. Perceptual Evaluation of Speech Quality.

With the older system of Amplitude modulation the audio band width is the same and the RF band with (i.e Modulated carrier) is 10Khz.

With Radio comms equipment, these days the actual equipment perforamce is pretty much the same across the board. The quality differences are usually down to the quality of the accessory attachments ………… some are good, and some are atrocious.

High noise environments are very unkind to analogue radio, and the only real solution is to use noise cancelling headsets ……..typical uses are Rally cars and helicopters.

PMR 446 is fine as long as you understand that the power output (ERP – Effective Radiated Power) is limited (IIRC 500mW ) and it is 8 shared channels, although the use of CTCSS is permitted, it will not solve co channel interference.

PMR (normal Professional Mobile Radio) is licence by Off-Com and you would need a wide area licence …… go look on the Off comm Site for the PDF’s

For our application PMR446 is fine for close in winch monkey type comms and CB is fine for the wider area type comms (CB has lost a lot of is popularity over the years and is now relatively quiet).

PMR 446 has an odd channel spacing when compared the ‘normal’ PMR channels, therefore it is not easy to reprogramme a commercial PMR Hand Portable to use this RF spectrum …………… although illegal (because the ERP will be 1 to 5 watts) it can be done ……… ;)

Errr ……….. what was the question :lol:

:)

Ian

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Les,

Its been my job for the last 30 years ............. so it comes sort of natural like .........

All typed...............I am just waiting in a London restraunt for a customer to arrive ........... its quite pleasant here watching the activity on the Thames ..............I'll have a nice lunch then I think I'll jump on the train and return home again.

Its a hard life being a RF communications consultant.......... :rolleyes:

:)

Ian

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As a man who knows very little about this, how easy would it be to use bluetooth headsets with some sort of transmitter reciever (not mobile phone)?

The main reason I ask is that there are some good headsets out there and wires will also be a PITA. Also, I can see helmets coming in at some point and ski helmets offer reasonable protection, are bloody comfortable and a fair few have built in (and reasonably water resistant) bluetooth headsets.

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FWIW, we use a boom mic/mono earpiece assembly, where the earpiece slips inside one cup of a pair of ear defenders, also positioning the mic in front of your lips. We use them for landing helicopters, with both ear cups down you can concentratre on comms with however many dB of noise a Seaking makes hovering 30ft above you. also, with one cup taken off an ear, you can hear ambient noise and hold conversations, whilst also getting comms in the other ear.

I've not seen any CB base sets with VOX, but you could put a PTT switch on the gear level or wheel etc.

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So the top 4 "legal" options so far are :P

Barbie Twin Telephone Walkie Talkies

With duplex technology allowing 2 way speaking

Kids Station Toys Superman Walkie Talkies

empty baked bean cans work well, as long as you use twine not string

Moglite uses tomato soup tins with 4mm Dyneema Bowrope

:wacko:

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on a slightly serious note theres a bike-to-bike system sold in the US called chatterbox (GPRS?) that I think offers duplex, its waterproof, built to be used on a crash helmet, can be bought with a boom mike and operate on vox or ptt configuration - might be worth a look but can be pricey

HTH? :)

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on a slightly serious note theres a bike-to-bike system sold in the US called chatterbox (GPRS?) that I think offers duplex, its waterproof, built to be used on a crash helmet, can be bought with a boom mike and operate on vox or ptt configuration - might be worth a look but can be pricey

HTH? :)

A spot of searching and found this from UK supplier. Could be promising..............

http://www.bikersweb.co.uk/Features/Featur...?ArticleId=1221

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'Novice' Amateur licenses come free with packs of cornflakes these days - so you could operate on amateur bands legally if you desired.

Oh no they don't, you have to complete & succesfully pass a exam & morse appreciation assesment, before being granted a licence, -- there's no novice grade now it's Foundation/Intermidiate/Full

more here www.rsgb.org.uk

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here's a review Interphone Review

We Have tried them here in Denmark at Challenge events, they work very nice as long as you can more or les se each other but not very good if "line off sight" is broken, and then when they lose contact one has to sort off syncronize them again, wich is a pain in B*** in the middel off a timed stage.

I use a Peltor Microphone and a cheaper earphone built into my helmet, the advantage off the Peltor Mic is that due to the way it is constructed with two membranes it do outphase a lot off noice, here in DK I paid 250£ to have them built into the two helmets.

I am currently using mobiles as com device but are looking into some fancy 900Mhz Us spec things with 1/4 mile range wich I am trying to get hold off, you will hear more about this if I succed.

The drawback off the mobiles is the same as with the BlueToth system you have to do two much to re-establis the connection but it is simply just invaluable two be able to speak both ways at the same time( full duplex)

Kind regards

Oddball

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