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#297059 - 09/19/20 09:53 PM Radiooddity DB25 shortwave transceiver
Blast Offline
INTERCEPTOR
Carpal Tunnel

Registered: 07/15/02
Posts: 3609
Loc: TX
After being left without reliable communications during hurricane Harvey I final got my technician's level amateur radio ticket. This allows me to use voice communications on the 2m (144MHz-148MHz) and 70cm (440MHz) radio bands. These are line-of-sight radios that under ideal conditions and a good antenna can reach out about 25 miles. When repeaters (to be explained in a bit) are used the range can be extended drastically, especially when a repeater is connected to the internet.

A repeater is simple a special transceiver which, when it receives a signal at a very specific frequency and including a special code, immediately transmits it at a different frequencies. Repeaters are generally mounted high up on buildings, watertowers, and piggybacked onto other large antennas. This makes their line-of-sight contact footprint extremely large. To use the repeater, you need to know its specific receive and transmit frequencies along with the special code that tells the repeater to repeat the signal.

The Houston area has a lot of ham radio operators which I'd listen to while driving. The radio I had in my vehicle was a small Baofeng, 5 watt unit and a magnetic-mounted antenna. I could hear people well but know one could hear me du to the low power of my unit. So I upgraded to a Radiooddity DB25 radio.

Radiooddity DB25 by Dr. Mark Merriwether Vorderbruggen, on Flickr, on Flickr, along with extra antenna cable and connectors.

The unit is small.
5" deep by Dr. Mark Merriwether Vorderbruggen, on Flickr

4" wide by Dr. Mark Merriwether Vorderbruggen, on Flickr

2.25" tall by Dr. Mark Merriwether Vorderbruggen, on Flickr

Also in the box was the 12VDC power cord and the computer programming cable. This type of transceiver requires a lot more than just turning a dial to use. All the necessary data for each channel can be added using the keypad on the microphone but with a memory of 200 channels that would take FOREVER. Radiooddity makes a PC-compatible programing software for this radio, free with purchase but that software doesn't work on my Mac. Luckily, the free, user-developed software CHIRP can be used to program the radio's channels. Just download and install it on your computer, plug in the special USB-radio cable into the your computer and radio, attach the radio to a 12VDC power supply...and now the fun really begins.

The first step in programming your radio is to find the repeaters you think you'll be able to reach. The best source for this information is the website www.repeaterbook.com

To get the data, first go to its link for North American Repeaters which brings up a map of the United States. Click on your state.
I'm in Texas
Screen Shot 2020-09-19 at 3.38.30 PM by Dr. Mark Merriwether Vorderbruggen, on Flickr

This leads to a page where you can then see all the repeaters based on band (frequency), location by county, town, or along major roads, and which ones may be linked to other repeaters for even greater range.

Screen Shot 2020-09-19 at 3.39.24 PM by Dr. Mark Merriwether Vorderbruggen, on Flickr

I want to start programming the Radiooddity DB25 with 2m bands around Houston so I click on "Houston" under towns and it brings up a list of repeaters. At the top of the page I click on "Export" and choose the CHIRP format.
Screen Shot 2020-09-19 at 3.40.28 PM by Dr. Mark Merriwether Vorderbruggen, on Flickr

This puts a file on my computer that I can import into CHIRP and then upload it onto my new radio. So let's do that.

Opening up CHIRP gives a very boring gray box. The first thing you need to do is download the current channel programing from the radio into CHIRP. To do this click on "Radio" at the top of the program and then choose "Download From Radio". You'll have to pick the particular brand and model of radio so CHIRP knows how to do this. A box pops up with choices. For the Radiooddity DB25 you need to pick "Port" as /dev/cu.usbserial, the vendor as QYT and the model as KT8900D which doesn't make sense until you remember you're dealing with a Chinese clone.
CHIRP by Dr. Mark Merriwether Vorderbruggen, on Flickr

A small progress box should pop up showing you're Cloning data from the radio.
IMG_2995 by Dr. Mark Merriwether Vorderbruggen, on Flickr

When the data from the radio has finished downloading the CHIRP box will now look like this:
IMG_2996 by Dr. Mark Merriwether Vorderbruggen, on Flickr

Those cells are where you need to put data to make the radio work. Luckily, CHIRP will do that. Open a New file on CHIRP and import the file you exported from Repeaterbook.com into this new file. It'll look like so:
[img]https://live.staticflickr.com/65535/50358171662_987f3e4c2b.jpg[/img]IMG_2996 by Dr. Mark Merriwether Vorderbruggen, on Flickr

Now, copy all those cell and paste them into the blank data file you had cloned from your radio. Save it with a file name that makes sense to you, then you need to upload it to the radio. To do this click on "Radio" at the top of the screen then click on "Upload to Radio". You'll get the same cloning box for a bit then all the data will have transferred. Your radio will turn of then on again all by itself.

The Radiooddity has the ability to scan all 200 channels while at the same time monitor three of those channels in case anything interesting pops up on them. I monitor three local emergency dispatch frequencies while scanning all the other channels. When you first upload all the channels of interest to the DB25 it shows the channel frequency. I find the channel call sign (name) to be more useful and so switch the display as directed in the manual.

Scanning repeaters plus monitoring Houston EMS and fire dispatches.
[img]https://live.staticflickr.com/65535/50357307343_29a81c7e75.jpg[/img]IMG_3006 by Dr. Mark Merriwether Vorderbruggen, on Flickr

I'm sure this little writeup has caused more questions than answers. I like this radio. It seems durable and solid. It puts out around 25watts which means people will definitely hear me now. It took about an hour to set up because I had to figure some things out myself. I already had CHIRP files setup from similar radios so I didn't have to spend a lot of time on Repeaterbook getting the information.

After it was all set up and working I decided I like it enough to order a second to use as a basestation inside my house. One of the features of the DB25 is it supports DTMF codes which allow you to use one radio to control another programed with the same codes. This will be good when I'm out working for the Red Cross during disasters but want to send periodic "I'm okay!" signals to the wife and kids even though they don't have ham radio licenses.

Note, as an Amazon affiliate, if you purchase the radio from the link I provided Amazon will pay me a small sales commission .
_________________________
Foraging Texas
Medicine Man Plant Co.
DrMerriwether on YouTube
Radio Call Sign: KI5BOG
*As an Amazon Influencer, I may earn a sales commission on Amazon links in my posts.

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#297060 - 09/19/20 10:08 PM Re: Radiooddity DB25 shortwave transceiver [Re: Blast]
Phaedrus Online   content
Carpal Tunnel

Registered: 04/28/10
Posts: 2788
Loc: Big Sky Country
Wow, thanks for a very thorough write-up!
_________________________
ďI'd rather have questions that cannot be answered than answers that can't be questioned.Ē óRichard Feynman

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#297062 - 09/19/20 11:49 PM Re: Radiooddity DB25 shortwave transceiver [Re: Blast]
chaosmagnet Offline
Sheriff
Carpal Tunnel

Registered: 12/03/09
Posts: 3437
Loc: USA
Great write-up Blast!

I actually own the same radio, although it is set up for backpack mobile rather than being installed in a car.

Iíve been a licensed ham for over thirty years, and have taught a number of beginning ham radio classes. Iím happy to try to answer any questions that anyone has.

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#297069 - 09/21/20 12:28 AM Re: Radiooddity DB25 shortwave transceiver [Re: chaosmagnet]
Blast Offline
INTERCEPTOR
Carpal Tunnel

Registered: 07/15/02
Posts: 3609
Loc: TX
Originally Posted By: chaosmagnet

I actually own the same radio, although it is set up for backpack mobile rather than being installed in a car.


That makes me feel even better about the purchase. smile
-Blast
_________________________
Foraging Texas
Medicine Man Plant Co.
DrMerriwether on YouTube
Radio Call Sign: KI5BOG
*As an Amazon Influencer, I may earn a sales commission on Amazon links in my posts.

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#297070 - 09/21/20 03:51 AM Re: Radiooddity DB25 shortwave transceiver [Re: Blast]
haertig Offline
Pooh-Bah

Registered: 03/13/05
Posts: 2222
Loc: Colorado
I have one of the Baofeng UV-5R radios. My amateur radio club gave them away to new members as a welcome gift. I hate to say it, but my personal experience with the Baofeng was dismal. I consider it a totally useless radio. Sorry. Don't mean to knock something that you have, but they're just not very good radios. You can improve them by installed a better antenna though. Unfortunately, the improvement only upgrades them from "is this thing a joke?" to "throw it in the trash".

I did a mini comparison of the Baofeng to a well known Yaesu radio on a different forum (link below). The Baofeng was totally outclassed. This comparison was not about features, it was only about performance.

On that other forum, I also did a post about an antenna stand I made for a J-Pole antenna. J-Poles perform well. You can mount one on your house or take it portable (mine is a two piece takedown model). You can't mount a J-Pole on your car however.

Link to my Baofeng vs. Yaesu comparison:

https://www.homesteadingforum.org/thread...479/post-242325

Link to my antenna stand for the J-Pole:

https://www.homesteadingforum.org/threads/whats-everybody-doing-today.474/post-269020

Where I got my test antennas from:

https://www.jpole-antenna.com/

https://signalstuff.com/product-category/antennas/

(Note that the Baofeng required an SMA-F antenna whereas the Yaesu requires an SMA-M, besure and get the correct connector type, or buy an adapter.)

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#297071 - 09/21/20 04:19 AM Re: Radiooddity DB25 shortwave transceiver [Re: Blast]
haertig Offline
Pooh-Bah

Registered: 03/13/05
Posts: 2222
Loc: Colorado
It's nice that your radio came with a programming cable included. That's somewhat rare based on what I've seen. Usually you have to buy them separately. And then you wonder, "Why does this one cost $3.95 and this other one costs $40?" One thing to note, many of these programming cables, especially the cheap Chinese ones, do not work with Windows unless you go through all kinds of gyrations to load the correct driver.

I had zero problems with a cheap cable when running CHIRP on Linux. Linux speaks many different languages, including the "Cheap Chinese Cable" dialect. Sounds like Blast didn't have any trouble using a MAC either. For Windows users out there, try the cable - if it works, great. If it doesn't you can buy a high end cable, but they are not cheap. A free alternative is to run Linux in a virtual machine on your Windows host. There is even a Linux distribution that is specific to ham radio - named "Skywave Linux". Google it to find where to download it. This distro contains lots of programs for ham radio preinstalled. Including CHIRP. So you can install a free virtual machine manager ("VirtualBox" is one such free one) and then run a free Linux distribution in a virtual machine (Skywave Linux) and you've got everything you need to work with your Cheap Chinese Cable, and don't have to worry about Windows drivers and identifying which specific driver you need and downloading it. OK - if you understood what I just said there about virtual machines and Linux distros, you're probably equally capable of installing appropriate Windows drivers. But I present this as an alternative.

"RT Systems" makes good cables and programming software. BUT, their cables are proprietary, they intentionally mess with the innards to incorrectly identify the chip inside. This is to force you to buy THEIR software. And you have to buy different software for each radio. This is their "gotcha". Well made stuff, but with a big catch. CHIRP is generic software - works with most every radio and most every cable (and it's free). As a test, I tried using an RT Systems cable with CHIRP software. No go at the start. However, when running Linux as I was, it is trivially easy to inform Linux about the lie that RT Systems hardware is forcing on the OS, and the OS then loads the correct driver. This magic, while trivial in Linux, is extremely difficult in Windows. In Windows, the OS is in control, not the user. Linux is just the opposite, with the user being the one in control. Not trying to turn this thread into a Linux vs. Windows thing, but for what we are talking about here - programming ham radios with either Cheap Chinese Cables or expensive proprietary cables - you gotta say, Linux wins if you don't want to pay through the nose for the privilege of programming your radio. So we have a second use case for a virtual machine running Skywave Linux - so you can use CHIRP with an RT Systems cable.

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#297072 - 09/21/20 06:37 AM Re: Radiooddity DB25 shortwave transceiver [Re: Blast]
haertig Offline
Pooh-Bah

Registered: 03/13/05
Posts: 2222
Loc: Colorado

Is this thing a radio, or a weapon?



Attachments
radio.jpg



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#297075 - 09/21/20 05:46 PM Re: Radiooddity DB25 shortwave transceiver [Re: Blast]
Famdoc Offline
Member

Registered: 04/29/09
Posts: 135
Loc: PA
It probably depends on how hard it is thrown.

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#297084 - 09/22/20 03:28 AM Re: Radiooddity DB25 shortwave transceiver [Re: Blast]
chaosmagnet Offline
Sheriff
Carpal Tunnel

Registered: 12/03/09
Posts: 3437
Loc: USA
The Baofengs arenít useless, IMO. Theyíre REALLY hard to program without a cable and CHIRP, but once programmed theyíre reasonably competent, pretty rugged, have good battery life, and almost disposable in price.

I handed out a few of them at a mass casualty car wreck hoping to get them back but not worried about it ó all of them came back to me.

Blastís radio is similarly hard to program and frankly not incredibly easy to use, but itís ridiculously inexpensive and works well once programmed and the quirks are learned. I was able to hit a repeater over 50 miles away backpack mobile with a roll-up J-pole about 30 feet in the air and have a decent QSO with it. If I were made of money would it be my top choice? No. But for an inexpensive 70cm/2M mobile setup itís small and cheap.

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#297085 - 09/22/20 03:29 AM Re: Radiooddity DB25 shortwave transceiver [Re: haertig]
chaosmagnet Offline
Sheriff
Carpal Tunnel

Registered: 12/03/09
Posts: 3437
Loc: USA
Originally Posted By: haertig

Is this thing a radio, or a weapon?


Silly (IMO) features to turn it off remotely.

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