Review – BTech AMP-25 series for Analog & DMR

by John ‘Miklor’
K3NXU

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)
NXDN
IDAS
dPMR
MPT1327
 >  DMR Tier II (TDMA)
 >  P25  (Phase 2)
Analog (FM)
C4FM (Fusion)
P25  (Phase 1)
NXDN
IDAS
dPMR
MPT1327

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.

Enclosure

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.

 

Convenience

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.

Conclusion

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
and     

VHF /UHF
Digital / Analog
Mobile Power Amplifiers

 

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‘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.

BFDX MT-7250 DMR Mobile

We knew BFDX already as a manufacturer of affordable DMR hand helds, and now a 30 Watt mobile radio popped up on the screen: the BFDX MT-7250. Grapevine Ham Radio sells this model for $329.99.

I find the number of channels/zones (160/50) a bit disappointing, but the price is right.

BF_MT7250-0BF_MT7250-1

General Specifications
Frequency range VHF: 136-174MHz, or
UHF: 350-390 MHz, or
UHF: 400-470 MHz, or
UHF: 450-520 MHz
Channel Capacity 160
Zones 50
Channel Spacing 12.5KHz
Voltage DC 13.8V (±15%)
Frequency stability ±1.5ppm
Antenna impedance 50Ω
Dimensions 150(L)*160(W)*40(H)mm
Weight 1.29Kg
Transmitter
RF power output VHF/UHF high power:30W
VHF/UHF low power:15W
4FSK Modulation 12.5kHz (only data):7K60FXD
12.5kHz (data and voice):7K60FXE
FM Modulation 12.5 kHz:8K50F3E
Modulation Limiting +/- 2.5kHz @ 12.5kHz
FM Noise -40dB
Conducted  Emission -36 dBm≤1GHz/-30 dBm≥1GHz
Adjacent Channel Power ≤-60dB
Audio Response +1/-3 dB
Audio Distortion 3%
Digital Voice coder Type AMBE+2™
Receiver
Digital sensitivity 5% BER:0.25 uV
Analog sensitivity 0.25 uV (12 dB SINAD)
Inter-modulation 60dB
Adjacent Channel Selectivity 60 dB
Spurious Response Rejection 70 dB
FM Noise -40dB
Audio Response +1/-3 dB
Audio output 3W
Audio Distortion 3% (typical)
Conducted Spurious Emission -57dBm
GPS Accuracy Horizontal Accuracy≤-10m
(with well signal)
TTFF (Time To First Fix) Cold Start < 1 minute(with well signal)
TTFF (Time To First Fix) Hot Start < 10second(with well signal)
Environmental Specifications
Working Temperature -20℃—+70℃
Storage Temperature -40℃—+80℃
Humidity MIL-STD-810C/D/E/F
Vibration & Shock MIL-STD-810C/D/E/F

Samhoo DMR

More and more Chinese manufacturers dive into the DMR market. This e-mail from Samhoo shows that there’s still room for more.

Greetings form Samhoo Sci & Tech Co.,LTD (Samhoo).

For the coming International Wireless Communications Expo (IWCE 2015), taking place March 18–19, 2015 in Las Vegas, USA, Samhoo wishes to invite you to visit our company booth NO. 2027. We look forward to welcoming you at the show. At the same time, we wish you will have a good trip in IWCE2015.

Attachments are the introductions and details of our DMR radio products. If you want to know more, please feel free to contact us and we will do our best to further our understanding. You can also find more information via our website: www.samhoo-pmr.com.

DMR—-  Samhoo is delighted to formally launch our DMR Portable SPH6000 serial, SPH2000 serial and DMR Mobile SPM6000 serial, which all fully compliant with ETSI DMR Tier 3 & Tier 2, and be available in UHF (350-400MHz, 400-470MHz) and VHF (136-174MHz) bands will release soon. 

TETRA—  Samhoo could provide fully integrated all feature industry TETRA module(smart size :86 X 43x 8) for Portable and Mobile devices, and be available in 806-870MHz,350-400MHz,380-430MHz,410-470MHz bands.

Samhoo is willing and open to work with all kinds’ partners, who could be distributor, dealer, ODM, OEM and technical cooperation etc, to explore Digital PMR radio business opportunity.

Best Regards

Alex YE
Oversea Sales Assistant
Samhoo Sci&Tech Co.,Ltd

Address: Room 601,Building 2th,Huaqiangyun Industrial Park,No.1-1,Meixiu Road,Meilin,Futian District,Shenzhen,China

Tel:+86-755-8316 0260 Fax:+86-755 8226 3733

What I find interesting about these Samhoo SPH6000 series is that ordinary TF cards are used for storage. This makes it possible to copy the configuration of one radio to another, just by transferring files. It would also be the few brands I know of who’s developing a VHF model.

Samhoo DMR ModelsFull specs can be found in this PDF document: Samhoo DMR SPH6000 Series DS-en

Also interesting (but probably very expensive and not really for hams) is their LK838 portable base station. When power goes down, this would still work — at least for a while.

Portable Ad hoc BS_samhoo-P1