FAQ

Q1: What transmitter PCBs are there for remote control purposes without telemetry?​

A1: There is one type of transmitter PCB which can be equipped with the AX5043 (transceiver IC) or the Radiometrix LMT0 module (10/100mW). Both options require different software. Note the LMT0 is CE approved while the AX5043 is “pre-compliance”.

 

Q2: What receiver PCBs are there for remote control purposes without telemetry?​

A2: For an overview of receiver PCBs, click here.

 

Q3: What about remote control with telemetry?​

A3: This is a project based on the AX5043 transceiver IC only. There are several options which are currently investigated. One of them involves a receiver PCB in the model submarine with 3mW transmit power. A telemetry solution using Radiometrix modules is considered too bulky and too expensive.

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Q4: Why would I want telemetry?

A4: There can be many reasons, but depth , battery voltage and status of the radio communication link are the main parameters. If one of these parameters is out of range, the vessel temporarily takes over control from the user. Under these circumstances telemetry helps to understand unexpected vessel motion and how to respond to it.

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Q5: Are AX5043 and Radiometrix (LMR0/LMT0) based PCBs interchangeable?​

A5: It does on the work bench but this has still to be tested in practise.

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Q6: Why are for remote control purposes without telemetry Radiometrix modules preferred over the AX5043?

A6: See the about page.

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Q7: What antenna options are there for the model submarine?

A7: For the model submarine a non-folded isolated wire dipole antenna is used. This for reasons of simplicity, make-ability and to avoid counter poise issues. There are two antenna options: a dipole antenna in the WTC (in air) or one on the outside of the hull (in water). From the perspective of an antenna's reception characteristics, the last option is the best. Because the antenna is located in water, the length can be reduced by a factor of approximately 10, which results in a ½λ dipole antenna. The lower propagation speed of electromagnetic waves in water is responsible for the factor 10.

 

Q8: What is a practical antenna setup?

A8: Use the dipole antenna inside the hull of the model submarine and a (telescopic) whip antenna with a length of approx. 100cm for the transmitter. Note both antennas need a small impedance matching PCB.

 

Q9: Except for the antenna what other factors affect the range?

A9: These are mainly receiver sensitivity and selectivity, antenna impedance matching circuitry, water conductivity and to a lesser extend transmit power. Note more power can help to battle interference. In most countries 100mW is allowed for 27MHz remote control applications (there are however exceptions).​

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Q10: What range can I expect in practice?
A10: As far as you can see the vessel.

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Q11: What is the formula for estimating attention of radio waves in water?

A11: dB/m=0.0173√(F x ø)  [28dB/m@27MHz]

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Q12: What is the formula for estimating refraction losses?

A12: dB=20log (  ( 7.4586 / 1000000 ) x  (  (F / ø ) ^ 0.5 )  )   [18dB@27MHz]​

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Q13: What happens if the model submarine no longer receives a signal?
A13: After a few seconds (adjustable) without reception, the propeller is stopped. This reduces the speed of the vessel, causing it to rise to the surface (if the trim is adjusted correctly). Contact is usually restored automatically when the submarine rises to the surface. If contact is not restored and the vessel has a ballast system, the ballast system will be emptied after a few tens of seconds (adjustable). Emptying stops as soon as contact is restored. It is possible to start emptying the ballast system immediately if there is no signal (configuration option).

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Q14: What does ‘no signal’ mean?
A14: This concerns digital radio communication that uses a protocol. A CRC is calculated over the payload of the protocol. This calculated CRC is added by the transmitter at the end of the protocol. The receiver also calculates a CRC over the received payload. If both CRCs match, the data is valid. If reception is good, valid data will occur regularly. If reception is poor, there will be gaps in the regular pattern of valid data. If these gaps become too large in time, this is considered ‘no signal’.

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Q15: What are the differences between the AX5043 transceiver IC and the Radiometrix LMR0/LMT0 modules?

A15:  AX5043  

- small

- cheap

- limited stock

- CE pre compliance

- for telemetry need one device

       

LMR0/LMT0

- large

- expensive

- sufficient stock

- CE approved

- for telemetry need two devices

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