Mtr4b V2.3 Mountain Topper

From LNR’s site:

Update: 2/24/22: MTR4 V2.3 online ordering is now active! We are releasing 100 units and they will be available as first come, first served. We have a handful of units built now but are expected to quickly have a 3-4 week lead-time before they ship. This could be LONGER and we can’t guarantee shipment in that timeframe but will do our best. We have enough parts in hand for 250 units so there will be another release of this model once we have shipped the first 100.

Also, the MTR4b pricing was increased slightly (up $20) to cover part cost increases. The overall costs were much higher but we know how bad overall inflation has been so we want to be as reasonable as humanly possible. Thanks so much for your continued patience and we know you will enjoy this radio!


The old 3B is far superior for SOTA. LNR needs to ditch 80 and give us a band that is more useful like 15, 17, 12, 10.


12 and 10m is too high in frequency, the rig would need a re-design. I’m guessing that an SI5351 would be more useful these days.

73, Colin

Agreed… but 17 wouldn’t require a redesign. I converted the 30m on one of my old MTR3’s over to 17 and it works great! An MTR4 with 17/20/30/40 would be much more useful for SOTA.


I vote for this as well, in the same form factor as the MTR-3B and with a SWR meter :slight_smile:


For about half the cost you can get the three most useful bands with a Venus SW-3B…plus an encoder!…/sw-3b-qrp-cw-transceiver/ Etienne-K7ATN

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I look on the used market every now and then for a MTR-5b… that would be my favorite :blush:

73 Armin


I have both but the MTR-3B is a special beast. Not sure what it is… the boxy look, the color, the logo, the polished UI, the history behind the the MTR series? Probably all of this actually!

The lack of encoder doesn’t bother me at all for SOTA activations. For QRP SOTA chasing I would prefer the SW-3B indeed.


Short history of the MTR’s ancestors (the ATS series) by the man himself.

Group: AT_Sprint Message: 2427 From: Steven Weber Date: 12/11/2007
Subject: Re: History of ATS series

The ATS series started out as a SMT project in an attempt to build a trail
friendly rig into an Altoids tin. It was built on two boards which plugged
in together, was a dual band 20/40 meter rig with relay switched filters.
The PA was a NPN SOT-223 device with a fairly low Ft, so power out wasn’t
very good, even at 12 volts. Maybe 2 watts on 40 and 1 watt on 20.

Besides the low power output, the most serious problem was mechanical. The
two boards were the same size and had common connections along both edges
of the boards. Both boards had to be connected together for anything to
work, so it was very difficult to trouble shoot if something wasn’t working
right. Longish jumpers had to be soldered between the boards so they could
be placed next to each other, instead of being stacked so it could be
worked on.

Dispite this, I put picutres of the rig on my then new web site on
It wasn’t long before I was getting requests to kit the rig. Since what I
had wasn’t real practical to kit or build, I went back to work on it.

The breakthrough which made the ATS rigs possible was the invention of the
square wave, logic gate driven 2N7000 PA. At last I had a PA which was
simple, took up little board space, was effiecent, had consistant power
output on different bands, worked at low voltages and used common,
inexpensive parts. The second innovation was to use the now familer band
filter module boards. I was now able to fit everything on a single board,
dispite using mostly 1206 sized passive parts.

As for functions, it only had the basics, because the processor used was an
Atmel 90S2313 with only 2K of memory. It had RIT, keyer with one memory,
Tune up mode, the push button tuning and frequency annunciation.

Only about 50 of the original ATS rigs were produced.

A year or two later, some new parts became available, or I became aware of
them, like the low power AD9834 DDS chip, the TI MPS430 processor and
LM4808 low power headphone amplifier. I decided to try these new parts in a
new ATS design to see if the current consumption could be significantly
reduced. The ATS-1 drew some 50 ma on receive, which was a significant
amount of current.

Thus, the ATS-2 was born. With the new parts, receive current dropped to a
much more modest 25-26 ma, half of what the ATS-1 took. I also made the
board much larger and put it in a plastic box which could also hold AAA
batteries. The larger board allowed parts to be spaced farther apart,
making it easier to build, adding a few slide switches and little volume

With more memory available in the MPS430 processor, DFE mode was added,
along with XIT and the calibration modes. 80 meters was also added, making
it a 4 band rig, instead of just the three bands the ATS-1 did. (40/30/20)

About 100 of these were produced. I might have did more, but the plastic
box which was supplied had the front silk screened. This I did myself,
which turned out to be a mistake. Most of them turned out okay, but not
great. It was a lot of work. I resolved to go back to the Altoids tin
formate. While some liked the larger form factor of the ATS-2, most still
wanted the smaller Altoids size rig. Besides, the KX1 came out about then
and I wanted to have the smallest, lightest rig there was.

So, back to the Altoids sized rig with the ATS-3, followed by the 3A and
finally the 3B, each which had incermental improvments from things learned
from the previous design.

Steve, KD1JV
“Melt Solder”
White Mountains of New Hampshire


I long for Steve to do another MTR type CW rig kit. I’ve really enjoyed building Steve’s kits. I have a Soda Pop kit and 40m Paraset kit in storage, but after that I don’t have any of Steve’s kits left. :frowning:

I want another 2B to put in a mint tin!

73, Colin


When I started amateur radio again almost 5 years ago - thanks and because of SOTA - I quickly came across the KX2 when looking for a TRX. That was the tool of choice.

But pretty soon I also wanted to have a very small CW TRX. In this process, I came across the Mountain Topper and was immediately enthusiastic about it… but like so many others, it was no longer available. Not to mention the Altoid or similar. The only TRX that was really available was the QCX. In the meantime I have a nice set for 60, 30 and 17m.

I looked at the MTR4b page from time to time… but it was never available. For my birthday at the beginning of the year, I got myself the SW-3b, which I am also happy with.

I also consider 80m to be jewellery on a nightgown… I don’t know who the target group should be here… 60m yes! In my opinion, the band has established itself in SOTA, although the frequencies are not coordinated. It allows nice short ranges… e.g. also within the Alps. Space for antennas for 80m is already a problem… maybe it’s different in NA.

Lately, the 10m band is fantastic… and we are not even at the maximum of sunspots yet. You can convert the QCX though… but a small TRX covering the higher bands would be great of course.

The classic endfeds work on 10,15, 20 and 40m - If there was a small CW-TRX with these bands… I think that would be a hit.

73 Armin