The Legendary Mountain Topper HF Radios

The Mountain Topper Radios (MTR) are the most svelte top down radio some one can have in their kit without goong full stripped down home brew. They are effective, efficient and tiny. If you’re interested in Morse Code, you should probably check them out.

Features:

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

Specifications:

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.