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

 

CHIRP Support now available for the new Anytone 8R series

By John ‘Miklor’ K3NXU

CHIRP, software that now supports over 80 different models of transceivers, is now providing basic support for the two newest models of the Anytone series, the TERMN-8R and the OBLTR-8R.  CHIRP’s Latest Daily Build can be found HERE.

The advantage of the basic settings is the “spreadsheet memory editor” which will allow owners to:
– import channels from a *.CSV file
– import channels from an *.img file
– copy-and-paste the stock config file
– load from external sources like RepeaterBook and RadioReference.

That is a BIG step and additional settings will be added in small groups.

SUPPORT:
Development of CHIRP is an all-volunteer effort and is offered as open-source software, free of charge. If you like CHIRP, please consider contributing a small donation to help support the costs of development and hardware.

More Information:  CHIRP, Miklor.com

 

Baofeng squelch: measurements

Erik PE1RQF offered to do measurements on his Baofeng BF-F9, before and after changing default squelch levels with Chirp. As expected after field tests, the differences are substantial. Here they are:

VHF (default settings, thresholds in dBm)

SQ Set	BF-F9 setting	Threshold
1	40	-124,6
2	41	-123,8
3	42	-122,2
4	43	-120,8
5	44	-120,6
6	45	-119,9
7	46	-119,4
8	47	-118,8
9	48	-118,4

VHF, Default thresholds

VHF (new settings, thresholds in dBm)

SQ Set	BF-F9 setting	Threshold
1	24	-130,4
2	29	-131,4
3	34	-130,9
4	39	-129,6
5	44	-125,5
6	49	-120,1
7	54	-115,3
8	59	-110,2
9	64	-105,1

VHF, new thresholds

UHF (default settings, thresholds in dBm)

SQ Set	BF-F9 setting	Threshold
1	29	-140,1
2	30	-130,9
3	31	-129,0
4	32	-127,4
5	33	-126,6
6	34	-125,4
7	35	-123,8
8	36	-123,0
9	37	-121,6

UHF, default thresholds

UHF (new settings, thresholds in dBm)

SQ Set	BF-F9 setting	Threshold
1	24	-133,1
2	29	-133,1
3	34	-125,6
4	39	-120,7
5	44	-114,1
6	49	-108,6
7	54	-103,6
8	59	-97,6
9	64	-93,7

UHF, new thresholds

Adjusting Baofeng squelch, first results

This morning I re-programmed some Baofeng radios using the latest Chirp Daily Build.

Confirmed to be NOT compatible: firmware BFB231 and BFB251. You need BFB291 or higher. You can check this by powering up the radio while holding the ‘3’ button.

Confirmed, no issues:

Model no: / Firmware version according to Chirp:
UV-82, B82S25,
GT-3, BFS311
GT-3 Mark II, N5R-213 / BFB297
GT-3TP, N5R3401 / BFP3-25
GT-5, B82S25

The actual effect on the squelch varies from model to model. The UV-82 and GT-5 for example stay more sensitive than the Sainsonic GT-3/MKII/TP versions. The latter are nearly deaf at SQ9.

Fixing poor squelch levels on Baofeng radios

After reviewing the GT-3 Mark II, a radio in which many problems were solved, the poor, sometimes meaningless squelch levels on various Baofeng models were one of the few things left on my ‘The Perfect Baofeng’ wish list.

Squelch levels improved somewhat over time, but it just wasn’t enough. The slightest whisper of a modem, router or switch still opens up the squelch, whatever the setting. It seems that this annoyance will become something of the past. No, not thanks to Baofeng, but thanks to the efforts of the Chirp development team.

A new ‘daily build’, available within a few days, will let you decide when the squelch opens up – either when receiving a tiny noisy signal, or when a repeater around the corner starts transmitting. The image below (courtesy Miklor.com) shows how the the new ‘Service Settings’ option will look like in Chirp:

As you can see you can set a personal threshold for every individual squelch level (1-9), and enter different settings for VHF and UHF. The higher the number, the more signal you need to open up the squelch.

I’ll keep you posted regarding the compatibility with old and new models.