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 not ( “pre-compliance”). Only in special circumstances the transmitter PCB can be equipped with the AX5043. The AX5043 option is not actively promoted because of the limited stock.

 

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

A2: Currently there are three types of  receiver PCBs:

• A receiver PCB with digital outputs (NPN) based on the Radiometrix LMR0 is currently available.

• Only in special cases an AX5043 based receiver PCB with digital outputs (NPN) is available. This design has been tested and is ready for production, but is not actively promoted due to the limited stock of AX5043 transceiver ICs.

• A smaller, LMR0 based  receiver PCB without digital outputs is currently being developed.

 

Q3: What about remote control with telemetry?​

A3: This is a future project based on the AX5043 transceiver IC only. Note it requires a larger PCB.

As such more room is needed in the model submarine. A dimensional case study has been carried out to see if the PCB fits in my model submarine the “Patrick Henry”. Conclusion: it will be a challenge.​

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Q4: Are AX5043 and Radiometrix (LMR0/LMT0) based PCBs interchangeable?​

A4: Yes

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Q5: Why are for remote control purposes without telemetry Radiometrix modules used instead of the AX5043?

A5: See the about page.

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Q6: What is the range with the Tx and Rx antenna both submersed?

A6: The range is approximately 5 metres with vertically polarised antennas positioned a few metres below the water surface. The range can be greater with both antennas just below the water surface. The greater range is due to radio waves crossing the boundary between water and air. This despite refraction losses.

 

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). The latter option is the better choice. 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 antenna setup should I use for maximum range?

A8: Use the dipole antenna on the outside of the hull of the model submarine. Use a (telescopic) whip antenna with a length of approx. 100cm for the transmitter (in air). While doing so the majority of radio waves travel the distance to cover through air (less attenuation). Note the ideal length of a whip antenna is a 1/4λ. Unfortunate a ¼ λ wave length whip antenna is not very practical (long).

 

Q9: What is a practical antenna setup?

A9: Like A8, but then with a dipole antenna in the WTC.

 

Q10: Except for the antenna what other factors affect the range?

A10: 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 exceptions).

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Q11: What about antenna polarization?

A11: The maximum range can be achieved with antennas that have aligned polarisation. Unfortunately, this is often not possible with model submarines. The antenna in the model submarine will usually be horizontally polarised and that of the transmitter 45 degrees vertically. As a result, a shorter range must be taken into account.

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Q12: What range can I expect in practice?
A12: As far as you can see the vessel.

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Q13: What is the formula for estimating attention of radio waves in water?

A13: dB/m=0.0173√(F x ø)  [27MHz=28dB/m]

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Q14: What is the formula for estimating refraction losses?

A14: dB=20log (  ( 7.4586 / 1000000 ) x  (  (F / ø ) ^ 0.5 )  )   [27MHz = 18dB]​