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Old 24th Jan 2023, 6:16 pm   #1
Iangebbie
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Join Date: Oct 2013
Location: Alconbury, Cambridgeshire, UK.
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Default Two Radios and a PA system controlled by one operator

Two Radios and a PA system controlled by one operator,
Let’s go through the basic requirement,
1. To enable communications on the VHF marine band (154-174 MHz) FM modulation
2. To enable communications in the UHF band (413-423 MHz) TDMA modulation
3. Single P/A amplifier up to three speakers
4. Control head for operator to use / select any of the above (Note the operator is non-technical or a professional radio operator).

So why would you want this strange selection of radios and equipment,
If you were a crane operator on a offshore platform, you need to communicate with the supply boat your unloading (VHF Marine)
The deck crew assisting with the unloading on the platform (UHF TETRA)
The P/A system is there just in case any of the deck crew miss or are exposed to a potential hazard, the crane driver can warn them.
You would think this is an easy system to make, but the main issues relate to the crane operator (Non-technical radio wise) and limited use of his hands while operating the crane.

PTT foot switch can be used, but will still have to somehow select what system Marine / TETRA / PA
Nudge switch using elbow to select system is the norm.
Headset with boom mic for all systems

Fortunately, the radio channels are pre-set and in most cases, do not have to be changed, a control head is also fitted , this is just an indicator as to what radio or system is active or selected

One other issue / due to offshore regulations and were the crane is located / all of the equipment must be zone 1 approved (Intrinsically safe and in an explosion proof enclosure).
The enclose is a pain large a heavy containing all radios, with feeds to the antennas, the PA amplifier and to the indicator control head, these units are not mass produced, so the radios tend to be Motorola, Sailor, Sepura or any approved supplier , the RF output power is restricted to 1.2 W (Deemed safe to work in a gas cloud)

They tend to use handheld portables in this application / advantage is battery is used as a backup / although the radio is on charge while being used, the battery can form a backup for 1hr + this also gets around the use of a UPS system,
See typical http://www.cdt-ltd.co.uk/EX-CCR.htm

This type of design is now 25 years old and is in my view vintage, new type systems may well switch to DMR but that would only cover the deck crew, shipping VHF systems I guess will remain in place for many years

Question, has anyone used combined technologies that have to work together

Has any one had to consider the end user or give an example of good simple to work equipment

This could also branch to software packages (Excel) and the difference in function buttons / menus between one release and the next (Drives me mad and takes me 6 months + to get used to)

Regards Ian Gebbie
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Old 24th Jan 2023, 7:13 pm   #2
Roger Ramjet
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Default Re: Two Radios and a PA system controlled by one operator

Interesting insight yet again Ian,

I understand UHF but could you explain TETRA in more detail please as I am sure I have seen this in reference to previous generation police radios.

Would the supply helicopters use marine band also ?

Do the lifeboats / escape pods have radios also ?

Rog

Last edited by Roger Ramjet; 24th Jan 2023 at 7:14 pm. Reason: add words
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Old 24th Jan 2023, 7:47 pm   #3
Cobaltblue
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Default Re: Two Radios and a PA system controlled by one operator

Sadly this isn't vintage.

So the thread will be closed.

Cheers

Mike T
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