In this post I would like to share with you the Motorola SM50 specifications among other exciting things that I like about this small commercial radio from the Motorola Radius family. 

This small radio has only two channels, so it is very limited if you are planning to use it as ham radio equipment unless you have a specific use case. I found some cool uses for it:

• Digital nodes (Packet or APRS)
• Digipeaters
• Have a radio programmed with a frequency of meetings with friends
• Have a radio programmed with the frequencies of the repeaters that we have close of us
• Have a radio for testing and laboratory

If you follow the blog you already now that I like playing with commercial radios, this is not an exception.

Motorola SM50 specifications

As said before, this is a 2 channel radio. There are various versions of this radio:

VHF	UHF
136 – 156 MHz	450 – 470 MHz
150 – 170 MHz	470 – 490 MHz

Regarding power we have versions of the radio that work in 10-15 watts and up to 40 watts. These parameters are also adjustable via software. Also, you will find narrow (2.5 kHz) and wide (5.0 kHz) bandwidth

Something interesting about this radio is that being idle, only turned on and not transmitting, it has a current consumption of only 300mA, which makes it excellent standalone equipment to run as a digipeater.

We have a consumption of 1.5A with the maximum volume in reception and 12.5A of maximum current transmitting 40 Watts.

The Radius SM50 can be programmed using this cable or this cable. If you ask me, I will always choose the Jiykr cable because it supports more brands and models than the specific for Motorola.

With very simple front panel this radio is very easy to operate.

The only drawback is that programming this radio is not simple as programming other brands. The concept seems to be very different, and it takes time to understand the programming software of the Motorola SM50.

Once you get familiar with the software it’s an easy ride, it just takes time.

Like many Motorola radios of that time, this one also uses mini-UHF antenna connectors. Unless your antenna has one of this male connectors, you will have to get an adapter.

The adapter you will need to get is mini uhf male to  UHF PL259 female. You can find it on amazon. This adapter allows you to connect almost any amateur radio antenna.

And just because we are on the back of the radio, in case you have a broken power cable, get the the replacement here.

How to identify the Motorola SM50 model

As many radio manufacturers, Motorola created an identification method for the different models of the Motorola SM50.

To identify the model of your Motorola SM50, first you will have to take a look at the label placed on the bottom of the radio.

So, not my case, on the bottom of your radio you will find a readable label including a code to identify the specific model of your SM50. 

Here you have a chart that will help you identify the model

Mount Type	Power	Band	Series
M always	3: 10-25w	3: VHF-HI	DGC always
	4: 25-40w	4: UHF

The next characters describe the following

Spacing (kHz)	# of Channels	Split (MHz)	Version	Options
00: 12.5	A: 2 (SM50)	1: 136-156	A always	A always
20: 20/25/30 (VHF)	C: 16 (SM120)	2: 150-170
20: 20/25 (UHF)		2: 450-470
		4: 470-490

In my case the unreadable label indicates the code M33DGC20A1AA which means that this is 25 watts, 2 channels, VHF radio with a 20/25/30 KHz spacing that works on 136-156 MHz.

Simple, right?. This would be hard to identify for me without the guys at Repeater builder that took the time to publish this table for the SM50 and SM120. Thank you guys.

Motorola Radius SM50 accessory port

One of the things I like the most about this radio is the accessory port.  This is a 16 pin port, with very different functions we can use to extend the radios functionalities.

You can build a repeater using two of this radios. In case you want to build something like this, this is the cable you need to buy for the connection of the radios.

Based on the service manual, this is the pinout of the accessory port:

Pin	Direction	Function or Signal Name
1	Out	External Speaker
2	In	External Mic Audio
3	In	External Mic PTT
4	Out	External Alarm / Programmable
5	In	Flat TX Audio
6		Spare
7	In/Out	Ground
8	In/Out	Programmable I/O pin
9	In	Emergency Switch / Programmable
10	In	Ignition Sense
11	Out	RX Audio
12	In/Out	Programmable I/O pin
13	Out	Switched A+
14	In/Out	Programmable I/O pin
15	In	Internal Speaker
16	Out	External Speaker

If you want to build or connect something through this port, this are the connetors you need.

Pin marked as programmable are modified throuth the programming software of the Motorola SM50.

Motorola Radius SM50 characteristics

These are some characteristics of this little radio:

• Simple Controls
• Compact
• Programmable power per channel
• Wide area/local programmable sensitivity
• Auto disconnect timer
• Busy channel lock
• Front mounting
• LED indicator
• Radio to radio operation
• Repeater operation
• Monitor
• Channel scan

Motorola SM50 additional information

Here you have additional information about the Motorola SM50 radio

• Motorola SM50 original brochure
• Motorola SM50 service manual
• Programming cable (supports other models and brands)

Hope this post presented properly the Motorola SM50 specifications. If you have any questions please feel free to leave a comment below.