Making my APRS iGate

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This article was derived from two separate blog posts from my personal website that were originally published May 15th and July 1st 2016 under my old callsign, KD0TGA.

So this week I took the plunge and picked up a Yaesu FT1XD Handheld. This is one of the new Yaesu HTs that supports C4FM Digital (ie: Yaesu SystemFusion). Since we now have two SystemFusion repeaters here in Fargo (W0HSC at NDSU and W0JPJ in Moorhead) I thought it was worth picking up and trying out. I may do a full review later, but right now I’m still trying to get familiar with the radio.

One additional feature it has that I haven’t had in previous radios is APRS (Automatic Packet Reporting System).  APRS is a single frequency (144.390 MHz here in North America) that gives the mobile ham a place to monitor Announcements, Bulletins, Messages, Alerts, Weather, etc. It also takes location coordinates (if equipped with a GPS) and can map out stations across the web, such as My Icom ID-880H supports DPRS (which is kinda the same thing but with D-STAR) but I’ve never had any luck with it. There’s a lot more to APRS than what I just described. If you’re interested check out for more info.

So wanting to get my hands on APRS, I got it setup on my HT yesterday. But I quickly realized that I wasn’t getting anywhere, because for some reason there isn’t a single APRS reporting station (either iGate or Digipeater) in the Fargo area. APRS is only useful if there are stations receiving or transmitting info. The main thing I was trying to do was to get my coordinates onto, and you can guess where that got me thinking next.

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Bulding the KD0TGA APRS iGate

A little bit of googling later and I came across a video from KD8RTT that shows how to throw together a receive only iGate. This is all I would need to get my APRS info onto the web. All you need to do this is a computer, a sound card, and a radio or scanner that can tune to 144.390 MHz. Being the resourceful person that I am, I have all of that.

Since Tony’s video is very well done I won’t bore you with instructions. Go watch the video if you want to find out how make your own.

So I got to work and got it running in about an hour (most of that time was spent trying to find an audio cable for my scanner). I am pleased to report my iGate is gathering APRS data and successfully uploading it to the web.

The only I’m noticing is my limited receive strength. My scanner is hooked into my N9TAX Slim Jim that I’ve talked about many times, up in the corner of my office. It’s only a total of 25 feet off the ground, and that’s where the problem is. I’ve picked up some traffic on the iGate (I also live right by a major Interstate highway, so there’s that), but the range is limited.

If I could add some height to the receive antenna it would help a ton. And (again) being the resourceful person that I am, I have an idea on how to make a very large APRS iGate.

Outside of my office, we have a 120 ft tower that houses STL gear and a few auxiliary FM antennas. One of the FM bays on the tower is no longer in use and is used an FM receive antenna. This is routed to my office where I have a modulation monitor and FM tuner hooked up. This antenna is 85 ft up the tower and receives excellently. So, I tapped into this and attached another RadioShack scanner to a computer in my office.

In theory, this should blow the smoke out of my N9TAX Slim-Jim, right? Well, not so much…

If you compare the stations heard in the last six weeks between the iGate at my office and the iGate at my house, my home iGate, which is only 25 feet off the ground on an indoor antenna hears way more. Why would that be?

A tower crew working on the 120 ft tower at my office a few weeks ago.
A tower crew working on the 120 ft tower at my office a few weeks ago.

There are two explanations I can come up with. As mentioned, there is some Microwave STL gear on this tower… in the order of 5 STL dishes in the 950 MHz band. While that wouldn’t effect APRS on 144.390 MHz, it could certainly produce noise that would impede reception. Not helping is a few blocks away is the studios of a competing radio group, and they have STL dishes that point towards my office to get audio to their transmitters northwest of town.

The other possible issue is the fact I’m using an FM antenna bay to receive. This antenna is broad-banded, but is designed to operate between 88-108MHz. While I have put a 2m rig on this antenna before, there is a possibility that being slightly out of tune could hinder reception.

My guess is that it is a combination of the two here. I do have a 2m/440cm J-pole on the tower for my 2m rig (yes, I have one of those at work too) and  I could try that out and see if that helps. But personally I think there is just a lot of RF noise in the vicinity of the office.

So for the time being, my home APRS setup is my primary iGate. That being said there are a group of hams from the area club (me included) that are looking into finding a site for an APRS Digipeter. And perhaps that is the solution. But until then…