What do I need to set up an iGate and digipeater?

[ClemsonSCJ]

Looking at setting up an iGate and digipeater at my house. I bought a BTech UV-50X2 a while back and was not very impressed with it so it’s been sitting aside doing nothing. I figured it would be the perfect radio to use for my iGate and digipeater assuming I can make it work. This is only concerning the hardware…the software I’ll figure out later cause I’m watching YouTube videos to figure all that out.

So my plan is to use a UV-50X2 radio and a DBJ-1 antenna. Ham Made Parts makes an adapter for the BTech to connect the mic jack to a Mobilinkd. So then the Mobilinkd should connect to a Raspberry Pi and from there it should be all software configuration from there, correct?

I guess That’s my biggest hang up is figuring out what hardware is needed for what, and what can be handled through software. I’ve seen some people saying you need a sound card, like a Signalink USB, but I would assume that’s what the Mobilinkd is replacing? Any help would certainly be appreciated.

 

[AK9R]

I'd use something other than an inexpensive radio with questionable filtering.

I'd also suggest using a dedicated iGate/digipeater rather than a Mobilinkd and software, though that would be doable.

Let's start with the radio. A high-profile digipeater is going to be bombarded with lots of RF and it is also probably going to be transmitting a lot. You need a robust radio that has sufficient front-end filtering to deal with the off-frequency RF. And, you need a robust radio that can deal with being keyed down a lot. If your planned digipeater is at a lower profile, you can back off these requirements a bit. I'd suggest scouring the used market for a Kenwood TK-790 or TK-7180. I'd also suggest a Motorola mobile radio, but I'm not as familiar with them. I know of one high-profile digi (the antenna is at about 480 feet AGL) that uses a Motorola, I think it's a CDM-1250, with very good performance. If you are talking about a lower profile digi, a Yaesu FT-2600 or Alinco DR-135T would work and be easy to interface with.

The second thing you need is a TNC. A lot of hams don't understand what a TNC does, so let's review. A TNC has two functions: 1. modulate and demodulate the audio to/from the radio, 2. construct and deconstruct the packets and interface with the world usually over a serial connection. In the old days, the mod/demod function was done by a Bell 202 modem (remember, we are talking about 1200 bits/second AFSK here), but more modern TNCs do the mod/demod in firmware running on some sort of small-scale CPU. With any TNC, audio from the radio goes in the radio port, the audio is demodulated, the packets are examined to make sure they are intact (CRC check), and serial data comes out the serial port. The transmit path is just the reverse.

I do not recommend the Signalink for packet radio, though it will work. It is not a TNC. It's merely a sound card interface between your radio and your computer. The TNC functions would have to be done in software. Yes, lots of people make this work with sound card TNCs like AGW or Direwolf, but, in my experience, the settings can be a little fiddly.

So, what TNCs are available. The old standby and still a workhorse in the packet radio world is the Kantronics KPC3 or KPC3+. They are expensive new, but you can buy used ones for less than $100. With a KPC3, you connect the radio (Tx audio, Rx audio, PTT, and ground) to the radio port and a computer to the serial port (usually RS-232 on older TNCs). Note that later KPC3 models with the APRS firmware can be configured as digipeaters. It's all done in hardware/firmware with no need for an external computer. Aside from the KPC3, the Argent Data Tracker 4, Byonics TinyTrak4, and the Mobilinkd are also capable TNCs with APRS functions including digipeaters.

An Igate is going to require a computer to interface between the TNC and the Internet. In the Windows PC world, UI-View32 and APRSISCE/32 are software that can be configured as digipeaters. In the Linux world, I think Xastir or BPQ32 are the primary candidates.

For a Raspberry Pi, you can use an external TNC and run either BPQ32 or Xastir. BPQ32 has a steep learning curve, but it's very flexible. When Coastal Chipworks was still in operation, they produced the TNC Pi which was a TNC in Pi daughterboard. I have a couple of these and they work very well with BPQ32 running on the Pi.

Another option is an all-in-one TNC/digipeater/Igate. Take a look at the Microsat WX3in1 as it has everything built into one box. No computer or external software needed. Just add a radio.

 

[R8000]

AK9R gave you some great input. I have two Igates up using the Microsat WX3in1's. The Microsat has one job in the world, to be an Igate/Digi. Simple and reliable.

 

[ClemsonSCJ]

I'd use something other than an inexpensive radio with questionable filtering.

I'd also suggest using a dedicated iGate/digipeater rather than a Mobilinkd and software, though that would be doable.

Let's start with the radio. A high-profile digipeater is going to be bombarded with lots of RF and it is also probably going to be transmitting a lot. You need a robust radio that has sufficient front-end filtering to deal with the off-frequency RF. And, you need a robust radio that can deal with being keyed down a lot. If your planned digipeater is at a lower profile, you can back off these requirements a bit. I'd suggest scouring the used market for a Kenwood TK-790 or TK-7180. I'd also suggest a Motorola mobile radio, but I'm not as familiar with them. I know of one high-profile digi (the antenna is at about 480 feet AGL) that uses a Motorola, I think it's a CDM-1250, with very good performance. If you are talking about a lower profile digi, a Yaesu FT-2600 or Alinco DR-135T would work and be easy to interface with.

The second thing you need is a TNC. A lot of hams don't understand what a TNC does, so let's review. A TNC has two functions: 1. modulate and demodulate the audio to/from the radio, 2. construct and deconstruct the packets and interface with the world usually over a serial connection. In the old days, the mod/demod function was done by a Bell 202 modem (remember, we are talking about 1200 bits/second AFSK here), but more modern TNCs do the mod/demod in firmware running on some sort of small-scale CPU. With any TNC, audio from the radio goes in the radio port, the audio is demodulated, the packets are examined to make sure they are intact (CRC check), and serial data comes out the serial port. The transmit path is just the reverse.

I do not recommend the Signalink for packet radio, though it will work. It is not a TNC. It's merely a sound card interface between your radio and your computer. The TNC functions would have to be done in software. Yes, lots of people make this work with sound card TNCs like AGW or Direwolf, but, in my experience, the settings can be a little fiddly.

So, what TNCs are available. The old standby and still a workhorse in the packet radio world is the Kantronics KPC3 or KPC3+. They are expensive new, but you can buy used ones for less than $100. With a KPC3, you connect the radio (Tx audio, Rx audio, PTT, and ground) to the radio port and a computer to the serial port (usually RS-232 on older TNCs). Note that later KPC3 models with the APRS firmware can be configured as digipeaters. It's all done in hardware/firmware with no need for an external computer. Aside from the KPC3, the Argent Data Tracker 4, Byonics TinyTrak4, and the Mobilinkd are also capable TNCs with APRS functions including digipeaters.

An Igate is going to require a computer to interface between the TNC and the Internet. In the Windows PC world, UI-View32 and APRSISCE/32 are software that can be configured as digipeaters. In the Linux world, I think Xastir or BPQ32 are the primary candidates.

For a Raspberry Pi, you can use an external TNC and run either BPQ32 or Xastir. BPQ32 has a steep learning curve, but it's very flexible. When Coastal Chipworks was still in operation, they produced the TNC Pi which was a TNC in Pi daughterboard. I have a couple of these and they work very well with BPQ32 running on the Pi.

Another option is an all-in-one TNC/digipeater/Igate. Take a look at the Microsat WX3in1 as it has everything built into one box. No computer or external software needed. Just add a radio.

I really appreciate the info provided but I’m really not looking to just buy a one-and-done device. Part of the fun of this hobby is experimenting and building your own stuff. Plus I simply don’t have the budget that it will take to buy all the high dollar “proper” equipment.

So basically the UV-50X2 is going to be the digipeater and the RPi is going to be the computer, I’m just trying to figure out the parts between the 2. I’ve seen one video where he uses an RTL-SDR for the receive/iGate side, and he uses a Baofeng UV-5R for the transmit/digipeater side. What I’m curious about is with the TNC cable that Ham Made Parts makes that interfaces the RJ-45 mic jack on the UV-50X2 with a standard 3.5mm TRRS plug, can I plug that straight into the headphone jack on the RPi and let Direwolf and whatever other software do what they do, or am I over simplifying it? Obviously the main purpose of this cable is to allow the PTT function for the digipeater, however will it also receive signals through the mic jack on the BTech? If it will Rx through the radio mic jack then I shouldn’t need much else, and I would be able to use the same radio and antenna for the iGate and digipeater. If not, then I’ll have to use the RTL-SDR for my iGate side and the radio for the digipeater and just utilize more hardware.

 

[AK9R]

Here's the problem with the Signalink and many similar knock-offs: There is no command from the software that keys the radio. The Signalink has what amounts to a VOX circuit. If the VOX circuit detects enough signal in the Tx audio coming from the computer, it keys the radio. But, there's always going to be a delay. In sound card digital modes, like PSK31, it's not much of a problem because the data rate is slow. But, with 1200 bits/second packet, every millisecond of delay can mean incomplete packets get sent if the radio isn't keyed up when the data starts flowing.

The alternative is a hardware PTT circuit controlled by the computer or TNC so that when it wants to start transmitting, the software (or firmware in a TNC) keys the radio, then starts sending data. This is a much more reliable means of transmitting packet, in my opinion.

Very few mobile radios have receive audio on the mic jack. You may need another cable that plugs into the external speaker jack.

Your digipeater needs to be able to receive incoming packets. Otherwise, it'll have nothing to digipeat.

You can use your SDR to set up a receive-only Igate, but the real value of Igates is that they both transmit and receive. That would allow users to send and receive APRS messages with distant users through the APRS-IS.

 

[dwhit29689]

Clemson, you're getting good advice here. I used to live along Lake Hartwell in Townville. Then I moved to FL and did exactly what you're looking to do. Lotsa reading led me to a Yaesu 2980R and a WX3in1 mini. It was wildly successfulI at 30watts and a Comet GP-3 at 40' handling over 32K databurts/month. The funny thing is I got bored after awhile and became irritated with my internet connection being tied up. That and there were already enough igates and digi's here I found I wasn't really supplying a need. I sold everything as a package to a guy in MO who is doing something wrong and is wildly unsuccessful. The learning and doing experience was interesting and worthwhile. When everything is running as it should it was "gee...what's next"? My station lasted two months. I recovered about 80 percent. You will need a really good connection to the net. If you're now experiencing throttleling and holes in flow you'll get frustrated. Constantly moving data taxes a network connection. I still play APRS but I'm not transmitting data for others anymore. KN4YBP

 

[nd5y]

If the VOX circuit detects enough signal in the Tx audio coming from the computer, it keys the radio. But, there's always going to be a delay. In sound card digital modes, like PSK31, it's not much of a problem because the data rate is slow. But, with 1200 bits/second packet, every millisecond of delay can mean incomplete packets get sent if the radio isn't keyed up when the data starts flowing.

In addition to that if there is any delay in transmmitting valid data it will be way more likely that you will double with other stations and cause interference.

Also some CCRs might have excessive tx-to-rx turnaround time (too long of a delay between unkeying and the receiver coming back on). That will also cause problems.

 

[vagrant]

Is a digipeater, or a receive only IGate in your area needed? What city are you in? We can look and advise.

Also, you want to use a radio you were "...not very impressed with..." to TX/RX APRS data packets. Additionally, that antenna you plan on using makes me think you are not serious about APRS and running a digipeater. There is nothing wrong with experimenting, but I question the use of those items. Flooding 144.390 MHz with unnecessary or wonky RF is damaging to the network and is definitely not needed.

If you want to experiment, see if you can successfully setup a RX only IGate. You do not need to pass the traffic to the Internet/APRS network if it is not needed, but it will allow you to learn and observe the beacons in your area and the extent of your RX. It will also not congest your personal Internet connection.

1. Use a simple RTL-SDR $25 USB dongle as the receiver. They have a TCXO so the frequency will be stable enough.
2. A Raspberry Pi 3B+ is fine. You don't really need a 4.
3. Direwolf 1.6 is the software to use.
4. You can use that DBJ-1 antenna, a discone, or something that will RX 144.390 MHz.

* Alternative to using 1, 2 and 3 above, you could use your mobile radio as the receiver for #1. A windows computer for #2. Finally for #3 you could use APRSISCE/32. To get the received signal audio to the computer, just use an audio cable that fits the radio output and your computer sound card input. ( You will need to disable computer noises )

If you are able to get the above going, you will observe the packet information on the screen. It will display if you are receiving packets directly, or from a nearby digipeater, as the word "Digipeater" will appear in front of the station callsign. You can also observe signal levels, quality of the packets and other information the initiator might be sending along with their GPS coordinates.

At this point you may still not need to connect your Pi to your local network, especially if the traffic is already being passed to the Internet by someone else. If the RF traffic is not being passed, you could connect and pass that data and see how much it impacts your Internet connection. Also, there would not be anything wrong with that if you are not congesting the APRS network. Remember, APRS is about RF first and foremost and must be protected from erroneous stations. Passing the data to the Internet is not the point, but it can be helpful.

 

[dwhit29689]

Yeah...you can see by my "circle" of coverage my station was not needed...interesting learning it all.

 

[ClemsonSCJ]

Ok, so I think I’ve got it figured out but I just have to iron out a few more details. For the receive/iGate side, I CAN use the rtl-sdr blog v3 that I already have, however that just means I’ll have to have one antenna for receive and one antenna for transmit. I would prefer to be able to use one antenna for transmit and receive, and as has been stated and as I initially suspicioned, the cable made by hammadeparts is for the mic jack which doesn’t carry rx signals. But I *think* I’ve found a solution.

The cable made by hammadeparts is for a Mobilinkd which would handle the PTT from the pi to the radio to transmit the packets. So I still have the issue of how to get the rx signal from the radio into the Mobilinkd and into the pi. For whatever reason BTech uses a full TRRS with audio out, PTT, and everything with their UV-25X2, but with the UV-50X2 (what I have) it’s just a mono audio out. However looking at schematics all day today, it appears as though the “tip” of the trrs plug on the Mobilinkd is for the audio out of the radio and into the TNC. So I should be able to get a TRRS splitter cable and have the “common” plug of the splitter going into the Mobilinkd, the hammadeparts cable going from one side of the splitter to the mic jack, and a TS cable going from the other side of the splitter into the speaker jack on the back of the radio.

That should cover rx going into the Mobilinkd as well as the tx going back into the radio through the mic jack. I now just need to iron out the details on the software side of it.

 

[ClemsonSCJ]

Well, even better news. I spent my day at work going back and forth between BTech and Hammadeparts and got them to send me their pinouts the interface cable and the RJ-45 on the radio. In the UV-50X2 manual they have the 8 pin labeled as “null” on the RJ-45, however Hammadeparts has their diagram labeled as “audio input” for that pin. This would essentially mean that I wouldn’t need to rig up a way to get audio into the TNC3 from the rear speaker jack. I contacted BTech and they sent me the updated pinout and it is in fact “AF out” so no rigging needed. Looks like the only additional item I need to make this setup work now is the TNC3.

 

[K5MPH]

First of all make sure a Igate/digi is needed in your area it wont do any good if its not needed and more so if a digi. Where i live we have three igates and 3 digi in a 12 mile circle area its so stupid .........

 

[tweiss3]

I know the digipeater/iGate system in our area uses a mixmatch of equipment:
Dig 1: Kantronics KAM+ and Moto Radius GM300 (5W, 125'AGL)
Dig 2: Kantronics KPC-3 and Moto CMD-1250 (20W, 160'AGL)
Dig 3: Kantronics KPC-3 and Yaesu FT5200 (40W, 300'AGL)
iGate: RPi w/Direwolf and Yaesu FT8900 (10W, 20'AGL)

Power is pretty low, but the digipeaters are placed such that they all can reach the iGate while providing great coverage.

If you plan on putting it at 30' AGL or lower, it's not going to receive the traffic you think it will, and won't have the 2-way coverage you want. If you are going to make a digipeater out of it, it might work, but you need to make sure you are going to be able to reach the iGate.

Also note, there isn't a CCR radio in the mix, but they Motos are cheap, GM300 is about $80 and CDM1250 is about $120 on ebay, and worth the money.

 

[ClemsonSCJ]

First of all make sure a Igate/digi is needed in your area it wont do any good if its not needed and more so if a digi. Where i live we have three igates and 3 digi in a 12 mile circle area its so stupid .........

We’re pretty baron.

 

[ClemsonSCJ]

I know the digipeater/iGate system in our area uses a mixmatch of equipment:
Dig 1: Kantronics KAM+ and Moto Radius GM300 (5W, 125'AGL)
Dig 2: Kantronics KPC-3 and Moto CMD-1250 (20W, 160'AGL)
Dig 3: Kantronics KPC-3 and Yaesu FT5200 (40W, 300'AGL)
iGate: RPi w/Direwolf and Yaesu FT8900 (10W, 20'AGL)

Power is pretty low, but the digipeaters are placed such that they all can reach the iGate while providing great coverage.

If you plan on putting it at 30' AGL or lower, it's not going to receive the traffic you think it will, and won't have the 2-way coverage you want. If you are going to make a digipeater out of it, it might work, but you need to make sure you are going to be able to reach the iGate.

Also note, there isn't a CCR radio in the mix, but they Motos are cheap, GM300 is about $80 and CDM1250 is about $120 on ebay, and worth the money.

Mine will be just above 30’ and power will be about 70-75W. There is an iGate very close to me but the closest digipeater is in Clemson and I don’t know how high up it is but the terrain itself isn’t very advantageous. I don’t pick up their repeaters well at all. The next closest is Paris Mountain and that’s about 30ish miles from my house but it’s up on a mountain way above me so I pick up those repeaters quite well.

 

[tweiss3]

What is the coverage of the iGate close to you? Will the new iGate create APRS loops/dupication? Would you be better off with a digipeater to expand the coverage of the iGate near you?

BTW, here is an excellent writeup from one of the local clubs on building an APRS iGate: Building an APRS IGate | Wayne Technical Fanatics

 

[jeepsandradios]

How are you planning 75 watts from a 50 watt radio ? Personally you should look for a better radio. My Digi is running a motorola M120 at 25 watts. I picked it up on ebay for $50 programmed. Much easier to interface to as well.

 

[K5MPH]

We’re pretty baron.

In that case how far are you from WD4EOG-1,if not to far you might want to but up just a Digi to expand the APRS coverage bit if to far in distance a Igate/digi would do your area good..........

 

[dwhit29689]

I didn't see enough traffic in the area to justify a station there...even along I-85. And that Clemson igate...I only intermittently caught it even at 50 watts.

 

[ClemsonSCJ]

How are you planning 75 watts from a 50 watt radio ? Personally you should look for a better radio. My Digi is running a motorola M120 at 25 watts. I picked it up on ebay for $50 programmed. Much easier to interface to as well.

If you watch YouTube videos and read reviews, the UV-50X2 actually puts out around 75W on 2m unless you key up longer than about 30 seconds continuous. Then it drops to around 35ish I think. Granted by the time it hits my antenna at 35ish feet it will be a bit less.