Mtr4b V2.3 Mountain Topper

Out of stock
Product Details

Update: 2/25/22: MTR4 V2.3 ordering now paused. We appreciate the big response and fast sellout of first 100 units in about 24 hours! We have parts inventory in house for another run after these and will open up ordering again as soon as we ship all existing orders.

For those that have placed orders, we will process those in the order received. We are already shipping units and expect to have them all shipped in the next 3-4 weeks but could be LONGER. We will do our best to get units to you ASAP. Thanks so much for your patience and we know you will enjoy this radio!

MTR4B V2.3

4-Band Mountain Topper

KD1JV "Steve Weber" Designs - Produced by LNR Precision

80M, 40M, 30M, 20M

The LNR Precision MTR transceivers are designed to be efficient portable CW rigs. Whether climbing a mountain and operating SOTA or just out for an afternoon in the park, the MTR’s small size, light weight and meager battery requirements makes it a great choice for these activities.

Dimensions: 5.150″ Length x 3.0″ Wide x 1.075″ Thick

Weight: 7.95 oz


  • Side tone Frequency Adjustment (New in version 2.3)
  • Side tone Volume Adjustment (New in version 2.3)
  • Improved access to coin battery (New in version 2.3)
  • Red Gloss enclosure (New in version 2.3)
  • Switch selected 80/40/30/20 meter bands (no band modules to lose or change out)
  • Heavy Duty Slide Switches
  • Machined Aluminum Enclosure
  • Four bands – 80M, 40M, 30M and 20M
  • Very low receiver noise floor
  • Low current for maximum battery life
  • Wide operating voltage range – 5.5V to 13V
  • Full 5W “QRP” gallon with 12.0 Volt supply
  • 2 line, back lighted LCD display
  • SWR – RF Power display
  • Built in Real Time Clock
  • Internal Iambic B mode keyer, 5 to 31 WPM in 1 WMP increments.
  • Three Morse message memories with beacon mode


  • 80 meter, 40 meter, 30 meter and 20 meter operation.
  • Receiver sensitivity : ~ 0.5 uV
  • Receiver audio bandwidth: ~ 400 Hz centered at 600 Hz.
  • Receiver current: ~ 27 ma
  • Transmit output power: 5 watts typical at 12.0 Volt input
  • Transmit current: 750 ma Max with 5 watt output
  • Transmit spurious outputs: -50 dBc or better
  • Supply voltage 5.5 volts minimum, 13 volts maximum. 6 to 12 recommended.
  • Antenna Jack: BNC
  • Power Jack: 5.5mm with 2.5mm pin

Online Manual Click HERE (same as MTR4b V2)

An automatic email will be generated once your unit is ready and will be sent to you with FULL tracking detail from USPS Priority Mail. Also, we do plan on international shipping (to most countries) but please note that it is almost impossible to guarantee timely delivery until COVID-19 shipping/customs issues are resolved. Also, LNR does not sell external batteries or power supplies and please contact your preferred supplier for battery options.

Power supply options:

The MTR-4B V2.3 is designed to put out about 5 watts with a 12.0 V supply. This makes it a good match to a 3S Li-ion pack which produces a bit over 12V when fully charged.

A 2S pack can also be used, with reduced power output. But also with reduced transmit current draw, which will extend battery life. Operation is possible down to the minimum discharge voltage for the cells, about 6V, and still produce over 1 Watt of output power.

A 4S pack produces a bit too much voltage to safely power the rig, but a low dropout regulator can be added to bring the voltage down to one more suitable for the rig.

A 9V smoke alarm battery (once used in transistor radios) can power the MTR-4B V2.3 for several hours. A tad expensive to do regularly though. But it is fun to see how many contacts you can make using one during a contest sprint. A 9 or 12V battery pack made of AA cells is more long lasting.

A 13.8V bench supply can be used, but this will bring the output power up to 6 to 7 watts. This is fine so long as the SWR is low. At 7 watts, the transmit current is near the maximum the PA FETs can handle and near the point at which the resettable internal fuse will trip (1 A). A high SWR will increase the current in the PA and either trip the fuse or damage the PA.

A simple way of making a 13.8V supply safe to use is to add two silicon rectifier diodes in series with the positive power lead, such as 1N4001 diodes. This will drop the supply voltage to the MTR by about 1.5 volts.

In-line Volume Control accessory: LNR does not sell this, but a popular add-on option is the Koss 155954 VC20 Volume control. It can be purchased from Amazon for $9.99 by clicking HERE.

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