Posts Tagged ‘Monitor Sensors’

LF / MF News From Monitor Sensors





A note from Roger, VK4YB of Monitor Sensors, reports some interesting news.








You might recall that his company manufactures a very versatile and well-engineered 630m transverter which was used at both ends of our two 630m JT9 contacts last year during the fall equinox propagation peak between North America and down-under.

Roger now reports that Monitor Sensors will be producing a new 2200m transverter, with all of the bells and whistles found on the 630m unit which has proven to be a real workhorse.


Monitor Sensors 2200m Transverter

The Monitor Sensors TVTR2 2200m Transverter enables any Amateur Radio Station, equipped with a conventional HF transceiver, immediate, all mode, access to the new 135.7-137.8 kHz, 2200m band.
The receiver design incorporates a 7pole Chebyshev filter, 3kHz wide roofing filter and a 5 pole Chebyshev filter in cascade before the double balanced, commutating mixer, fed by an ultra stable, temperature compensated, extremely low phase noise, MEMS local oscillator. The mixer is followed by a Chebychev band pass filter into an ultra linear, low noise, current feedback, IF amplifier. The receiver noise floor, in a 500Hz bandwidth, is -125 dBm and yet the onset of compression is not reached until +11dBm. A front end 20dB attenuator can be switched in for even higher signal handling. Overall receiver gain is set to +6dB, or -14dBm with attenuator in.


The transmitter input circuit incorporates a 0-14 dB switched step attenuator to prevent over driving. The same mixer and local oscillator are used on the transmit side. The PA uses 6 rugged lateral FETs in class AB push-pull to easily achieve the 50 watts rated output. Lateral FETs are inherently linear and thermally stable. The transmitter can be run at full power, indefinitely, into a dead short or open circuit without any danger of damaging the FETs. Transmit-receive switching is automatic with user selectable VOX delay. Alternatively the PTT line may be used.


The transverter employs extensive and accurate metering. Power input and output, SWR, Frequency, Attenuation in use, Temperature, Supply Voltage, Current and Resistance are displayed.
Transmission is inhibited if carrier frequencies outside the 135.7-137.8 kHz band are detected. A tuning screen may be selected which displays SWR in digital and graphical form for easy antenna adjustment. The menu system is self explanatory and users report no manual is needed, although one is supplied. A USB socket is provided for future code upgrades (free of charge) from the Monitor Sensors web site.


The transverter has been designed for the best possible protection against accidental mishaps. It will survive reverse polarity supply and the injection of 100 watts of HF into any of its ports whether in transmit or receive mode. If supply current exceeds 25 Amps, the supply is cut in 3 microseconds. This electronic breaker can be reset by simply switching off and on again. The transmitter will shut down in the unlikely event that the internal heat sink reaches 90°C. The cooling fan is under the proportional control of the microcomputer and begins operation above 35°C. Any unusual operation will cause the screen to turn red and an appropriate warning will be displayed.


TVTR2 Specifications


RF frequency range 135.7 to 137.8 kHz
IF frequency range 1805.7 to 1807.8 kHz (others available in the 160m band)
Transmission modes CW, SSB, WSPR, and all other data modes
Output Power 50 Watts Continuous, 100% duty cycle @13.8V supply
Input and Output Impedance 50 Ohms
Supply voltage 13.8 VDC @ 15 Amps nominal, 10-16 VDC operational
Rx noise floor -125 dBm (500 Hz bandwidth)
Rx 3dB compression point +15 dBm (Rx attenuator out)
Rx IF rejection better than 75dB
Rx conversion gain +6dB nominal
Roofing filter in-band ripple +/- 0.5dB
Tx 3rd order IMD -33 dB below PEP, typical at 50W output
Tx 5th order IMD -45dB below PEP, typical at 50W output
Tx harmonics and spurii All better than -50dB
Tx conversion gain +10dB nominal
Power input connector 2 * Anderson Power Poles (one Power cable supplied)
RF connectors 3 * SO239 (one PL259 to PL259 cable supplied)
PTT connectors 2 * RCA (one RCA to RCA cable supplied)
USB connector Micro B USB, (matching cable supplied)
Dimensions 12½ * 4¼ * 3 inches, 320 * 120 * 76 mm
Weight 3.4 lbs, 1.6 kg


In addition to the transverters, Monitor Sensors will also be manufacturing solid state amplifiers for both the 2200m and 630m bands with power levels at around the 450W output level. Like the transverters, these will be 'linear' devices as well. It is possible that a duo-band amplifier will also eventually be produced.

It will be interesting to see if any other new gear becomes commercially available from other manufacturers once the LF / MF ham bands are introduced in the U.S.A. , something that is expected to happen fairly soon.

LF / MF News From Monitor Sensors





A note from Roger, VK4YB of Monitor Sensors, reports some interesting news.








You might recall that his company manufactures a very versatile and well-engineered 630m transverter which was used at both ends of our two 630m JT9 contacts last year during the fall equinox propagation peak between North America and down-under.

Roger now reports that Monitor Sensors will be producing a new 2200m transverter, with all of the bells and whistles found on the 630m unit which has proven to be a real workhorse.


Monitor Sensors 2200m Transverter

The Monitor Sensors TVTR2 2200m Transverter enables any Amateur Radio Station, equipped with a conventional HF transceiver, immediate, all mode, access to the new 135.7-137.8 kHz, 2200m band.
The receiver design incorporates a 7pole Chebyshev filter, 3kHz wide roofing filter and a 5 pole Chebyshev filter in cascade before the double balanced, commutating mixer, fed by an ultra stable, temperature compensated, extremely low phase noise, MEMS local oscillator. The mixer is followed by a Chebychev band pass filter into an ultra linear, low noise, current feedback, IF amplifier. The receiver noise floor, in a 500Hz bandwidth, is -125 dBm and yet the onset of compression is not reached until +11dBm. A front end 20dB attenuator can be switched in for even higher signal handling. Overall receiver gain is set to +6dB, or -14dBm with attenuator in.


The transmitter input circuit incorporates a 0-14 dB switched step attenuator to prevent over driving. The same mixer and local oscillator are used on the transmit side. The PA uses 6 rugged lateral FETs in class AB push-pull to easily achieve the 50 watts rated output. Lateral FETs are inherently linear and thermally stable. The transmitter can be run at full power, indefinitely, into a dead short or open circuit without any danger of damaging the FETs. Transmit-receive switching is automatic with user selectable VOX delay. Alternatively the PTT line may be used.


The transverter employs extensive and accurate metering. Power input and output, SWR, Frequency, Attenuation in use, Temperature, Supply Voltage, Current and Resistance are displayed.
Transmission is inhibited if carrier frequencies outside the 135.7-137.8 kHz band are detected. A tuning screen may be selected which displays SWR in digital and graphical form for easy antenna adjustment. The menu system is self explanatory and users report no manual is needed, although one is supplied. A USB socket is provided for future code upgrades (free of charge) from the Monitor Sensors web site.


The transverter has been designed for the best possible protection against accidental mishaps. It will survive reverse polarity supply and the injection of 100 watts of HF into any of its ports whether in transmit or receive mode. If supply current exceeds 25 Amps, the supply is cut in 3 microseconds. This electronic breaker can be reset by simply switching off and on again. The transmitter will shut down in the unlikely event that the internal heat sink reaches 90°C. The cooling fan is under the proportional control of the microcomputer and begins operation above 35°C. Any unusual operation will cause the screen to turn red and an appropriate warning will be displayed.


TVTR2 Specifications


RF frequency range 135.7 to 137.8 kHz
IF frequency range 1805.7 to 1807.8 kHz (others available in the 160m band)
Transmission modes CW, SSB, WSPR, and all other data modes
Output Power 50 Watts Continuous, 100% duty cycle @13.8V supply
Input and Output Impedance 50 Ohms
Supply voltage 13.8 VDC @ 15 Amps nominal, 10-16 VDC operational
Rx noise floor -125 dBm (500 Hz bandwidth)
Rx 3dB compression point +15 dBm (Rx attenuator out)
Rx IF rejection better than 75dB
Rx conversion gain +6dB nominal
Roofing filter in-band ripple +/- 0.5dB
Tx 3rd order IMD -33 dB below PEP, typical at 50W output
Tx 5th order IMD -45dB below PEP, typical at 50W output
Tx harmonics and spurii All better than -50dB
Tx conversion gain +10dB nominal
Power input connector 2 * Anderson Power Poles (one Power cable supplied)
RF connectors 3 * SO239 (one PL259 to PL259 cable supplied)
PTT connectors 2 * RCA (one RCA to RCA cable supplied)
USB connector Micro B USB, (matching cable supplied)
Dimensions 12½ * 4¼ * 3 inches, 320 * 120 * 76 mm
Weight 3.4 lbs, 1.6 kg


In addition to the transverters, Monitor Sensors will also be manufacturing solid state amplifiers for both the 2200m and 630m bands with power levels at around the 450W output level. Like the transverters, these will be 'linear' devices as well. It is possible that a duo-band amplifier will also eventually be produced.

It will be interesting to see if any other new gear becomes commercially available from other manufacturers once the LF / MF ham bands are introduced in the U.S.A. , something that is expected to happen fairly soon.

The New VK4YB 630m Transverter


For the past several months I have been beaconing overnight on 630m WSPR mode. I've been using a new transverter designed by Roger Croft (VK4YB) and Ralph Loveday, in Queensland, Australia. One unit was sent to me for beta testing and I have been hammering it as hard as I can ever since setting it up in the spring ... no problems have been experienced after several months of 12 hour nightly beaconing punishment. Nightly signal reports often range from Hawaii / Alaska and eastward to New England ... all during the 'not so good' summer band conditions.

Now that beta testing is complete, production units are now ready for distribution from Monitor Sensors, a family environmental-sensor manufacturing company of which Roger is Governing Director.

The introduction of the VK4YB 630m Transverter presents another new option for those wishing to get on the band, or in the case of American amateurs, to get prepared for the band ... soon expected to be implemented in the U.S.

When I first started using the test unit provided, I was immediately impressed with how simple it was to set up and to get operational. It sits inconspicuously beside the main station's transceiver, taking up less space than the typical station speaker unit.

One usually associates 'transverter' operation with a rat's-nest of cabling or re-cabling to accommodate the new addition. The transverter arrived with all necessary cabling, even a nice Anderson power pole connector to connect the user-supplied 12V power source. A second pair of 12V contacts is also available for sharing with other station needs. One feature that I quickly appreciated was the dual RCA jack on the rear panel for controlling the transverter's PTT keying line. With my transceiver's PTT line already being used for another purpose, it was simply a matter of plugging-in (cable supplied) and sharing the line with the second jack ... no need for unplugging or using an external adapter to split the PTT line. Switching from 630m to normal HF operation is simply a matter of turning the transverter 'off' ... all HF operations are back to normal with antenna routing taken care of. There appears to be a lot of thoughtful engineering packed into this little box.


A look under the hood shows a well-planned and efficient use of space as seen in this pre-production prototype shown below. If Collins Radio were to manufacture a 630m transverter for the military, I can't imagine it being any better than this!


prototype board under test
Although rated at 50W output, my transverter produces ~ 70W output when run at 12.6 volts. More output can be realized at higher voltage, up to as much as 16 volts. Power is generated with six carefully-matched Lateral MOSFETS, three aside, in a parallel / push-pull configuration.

"... we carefully match the FETs into three pairs. Each pair is matched to its opposite number but the pairs are chosen so 2 have low gain, 2 have mid gain and 2 have high gain. This improves the IPs and also the harmonics. With matched FETs we are getting the 2nd harmonic at typically -60dB. That's 10dB better than the stringent FCC requirement." 

Roger's unit is running at 16 volts and produces 90W output, with his 630m WSPR signal being the one most often heard in North America from down under.

The transverter's multi-colored screen combines with a multi-function menu, allowing a visual on-screen display of numerous parameters such as RF output power, DC supply voltage and current draw, SWR, exciter drive power, heatsink temperature, graphic SWR display and various warning screens.

The transverter requires 3-5 watts of 160m drive from the station transceiver for full output power. Built-in safety circuits prevent overdrive from causing any damage. Similarly, transmitting into a high SWR or with no antenna connected is no cause for concern. Temperature sensors will trigger shutdown should the heatsink rise above 100 degrees C. Software also prevents out-of-band transmission.

This is a microprocessor controlled linear-transverter. This means that operating system software can be readily updated (via the supplied micro USB cable) as new features are implemented. It also means that any mode your transceiver is capable of operating on can be produced on 630m. At present, the most popular modes on the band are WSPR, CW and JT9 but I suspect this order may change once the band is opened up in the U.S.


A shortened eight-page Operator's Manual can be downloaded from the Monitor Sensors web site but units will ship with a more comprehensive 22-page manual. For more information regarding pricing and shipping, please contact Monitor Sensors here. For technical questions, please contact Roger here.

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