Review – BTech AMP-25 series for Analog & DMR

by John ‘Miklor’

The  AMP-25  series  VHF / UHF Amplifiers

The recently announced BTech Digital and Analog amplifier series puts a whole new spin on mobile operation. It performs more like a mobile than it does a power amp. The D series are true TDMA Tier2 DMR amplifiers.

Note: This review was done using an Anytone D868UV on both DMR and analog.

In the Box

Included with the 40W Mobile Amp are:

–  Mounting Bracket
–  3′  Interface Control Cable (Kenwood K1 connectors)
–  3′  RF connect cable (SMA-M to SMA-F)
–  Microphone and Hanger
–  All necessary mounting hardware
–  User Guide

General Description
–  UHF or VHF Power Amplifier

–  2-6W  >  20-40W  Output

                         Modes of operation include:

             V25  U25             V25D   U25D
Analog (FM)
C4FM (Fusion)
P25  (Phase 1)
 >  DMR Tier II (TDMA)
 >  P25  (Phase 2)
Analog (FM)
C4FM (Fusion)
P25  (Phase 1)

A Different type of Mobile Amplifier

I found these to be much more than a typical power amplifier. Although they can function as a simple ‘In and Out’ power amp, this is about as close to a full mobile as you can get. Although the driving force was my DMR handheld sitting in my cup holder, the transmit audio was that of the included hand microphone and the receiver audio out was coming through the built in speaker driven by a four watt audio amplifier.

Transmit Power

I tested the power on two different models. The VHF V25 (non TDMA) and the U25D for UHF DMR.  The power was tested using the analog side of both into a calibrated Bird Termaline wattmeter. The maximum current drain from my 13.6V 30A power supply was just under 6A. This is low enough for the amp to be powered by the 10A accessory jack in your vehicle.


The basic frame measures 4.6″W x 1.3″H x 5.5″D (excluding the SO-239) and weighs in at 26oz.  I was curious to see the internal layout of the amp and to no surprise, there was a 5/8″ finned heat sink spanning the entire length and width of the case along with air vent along the back of the enclosure.

Operating Modes

These are single band amplifiers.
V25(D) = VHF 136-174MHz
U25(D) = UHF 400-480MHz.

Note: The V25D and U25D were designed to include DMR Tier II (TDMA) and P25 Phase 2 along with all other modes. Their operation varies slightly.

V25  /  U25
To operate VHF through the UHF (U25) amplifier, or UHF through the VHF (V25) amplifier, simply power off the amplifier. This will allow you to run straight through directly to the antenna without power amplification on that band.

V25D / U25D
These amplifiers will only operate within their specified VHF or UHF range. This is due to the circuit switching design of DMR Tier II and P25 Phase 2.

Hook Up

The simplest configuration is using the included RF cable to attach the radio to the amp. You could add a Spkr/Micr to the handheld, but you would still be bypassing some of the best features.

I use the two included cables. The 3′ RF cable to attach the radio to the amp, and the control cable. This allows me to use the full size hand microphone as well as connecting the four watt audio amp powering the speaker. The power included power cable is compatible with handhelds using the standard two pin Kenwood style connector, such as an MD380, D868, GD77, UV5R, F8HP, UV82, etc.

I use an Anytone D868 on DMR as well as analog with the hookup diagrammed below. Depending on your radios antenna jack, you may need to pickup an SMA-M to SMA-M adapter.



All channel selection and volume adjustments are done using the handheld. No duplicate programming or code plugs are necessary. Whatever is in my handheld is what I operate in the mobile

Operating my handheld in the low power position, I still get 22W out on UHF and my handheld’s battery life remains excellent, but high power gives me a solid 39W.


I was glad to see someone finally develop what is a full featured mobile amplifier capable of  DMR as well as all other modes including C4FM and D-Star that is small enough to mount in the car, boat, and on top of your computer. This amplifier is Part 90 certified and definitely worth considering.

Available from Amazon:    V25     V25D     U25     U25D

Digital / Analog
Mobile Power Amplifiers



‘USA 1776’ DMR Talk Group

DMR-logoOne of the nice things of D-Star and DMR is the ability to talk all over the world without the need of an HF rig and a bunch of big antennas. While this largely reduces a radio to a simple Internet-driven communication tool – just like Skype or other VoIP apps – it’s definitely nice to use.

There are a few problems surrounding DMR, one of which is the lack of more than two time slots. For example, if hams are using the Dutch Hytera network and occupying talk group 204 on slot 1, World Wide (which uses the same time slot) will be unavailable. Because 204-1 is a busy place, world wide QSOs are often impossible. It’s one of the reasons I thought of dumping DMR all together — I can talk to the same Dutch guys on analog while enjoying a much better quality audio.

There are reasons to keep DMR too. DMR is maturing; there are more than enough possibilities to put less pressure on the nation-wide network by going local. Now if only hams would do that…. but most don’t. Another reason to keep DMR for now is the gateway we recently added, which connects D-Star to our DMR network.

Not available on the Motorola network, sorry — some people responsible for that network appear to be so scared of such innovations that they will ban a repeater from the network if such a gateway is detected.

Talk group ‘USA 1776’ could add to the appeal of DMR. It’s unclear on which network this talk group will reside, but my best guess is that it will be the Motorola network.  MITCON writes:

The “USA 1776″ (English preferred) Talk Group will be distributed worldwide to DMR networks upon request.  The spirit of “1776” is to continue the Amateur Radio tradition of international friendship and to push the boundaries of technology in the new frontier of digital communications.

USA 1776USA 1776 is intended to be a flexible, politically neutral, unrestricted Talk Group that can be used as Push-To-Talk (PTT) or Full-Time (FT) to meet the operating requirements of a DMR Network.  DMR subscribers are welcome to use 1776 as a universal meeting place to “Rag Chew” or as a jumping off point and QSY to an alternative Talk Group if desired.  To add USA 1776 to your DMR Network please contact us to schedule a time for configuration & testing.

Sub $200 D-Star radio in the making?

This was spotted on a D-Star Yahoo group:

Hi Everyone,

In case you do not know me, I am President of Connect Systems Inc. and I am responsible for getting to HAM market a commercial grade DMR radio for $180. This is about 1/4 the price you would pay for a New Motorola 6550 MotoTRBO radio. Beside running the company I am also a design Engineer.

I few days ago I had a long conversation with Mark Thompson (WB9QZB) and he convinced me I should seriously look into developing a DSTAR radio in competition with ICOM that has a selling price to HAMS for less than $200. He supplied me with three Documents named “D-STAR Uncovered”, “D-STAR System”, and “D-STAR radio packet structure for the Digital Voice (DV) mode. I studied the documents and at first glance I came to the conclusion that the development of this type of Radio is much simpler than either NXDN or DMR. So now I am seriously looking to develop the radio.

I have four questions I would like to ask. Put on the subject matter the word D-STAR someplace if you would like to e-mail me at jerry _at_

Question 1
What features would you like me to add to this radio that is not already in the ICOM radio?

Question 2
Given a choice for a commercial grade D-Star radio for about $200 (Such as Motorola or Kenwood quality) or an amateur grade D-STAR radio for about $30 less (Such as Wouxun) quality), which would you pick?

Question 3
Is there any software (Source Code) available that I could look at that would show how to design the radio part of a DSTAR System. Even better if someone made a working breadboard of a D-STAR radio.

Question 4
Is there anyone who completely understands the protocol of D-STAR down to the bit level?

Thanks in advance for answering these questions.

Jerry Wanger


Connect Systems Inc

Icom ID-5100 – D-Star dual-band with touch screen

Osaka Hirano, president of Icom Inc., recently announced a new VHF/UHF D-Star transceiver, the ID-5100. Two versions will be released at the end of February 2014: a 50W version, the ID-5100, and a 20W version, the ID-5100D.

Icom ID-5100Dual-band, dual receive
According to the preliminary specs this will be true dual-band radio with two separate VFO’s. This makes it possible to receive two signals simultaneously, and it doesn’t matter if the signals are analog or digital – any combination is possible.

Touch Panel
First seen on the IC-7100, now migrating to other models too: a touch panel. In an era where color touch screens are default on almost any device, Icom’s black & white screen seems a bit odd, out of place even. Readability seems to be good though.

Nearest Repeater Search
An interesting feature is “Nearest Repeater Search”, which acts a bit like the roaming function we know from cell phones and DMR radios. Strangely, this only works in analog mode.

Android support
With the help of an Android app it’s possible to control this radio from your Android device and (if my limited Japanese language skills didn’t let me down) even use it to make QSO’s. No word on iPhone support.

Bluetooth (option)
You can use a Bluetooth headset to operate the ID-5100. The necessary UT-133 interface and VS-3 headset are options, not standard.

Suggested Retail Prices (without taxes)
Icom ID-5100D (20 Watt): $779
Icom ID-5100 (50 Watt): $828