My APRS IGate VK2MES-5 and a Flowerpot High Gain antenna

Something I’ve been wanting to muck around with since I got back into the hobby is APRS. I used to have a Kenwood 710 previously, and honestly, I should have hung onto it. When I first moved to NSW back in 2015 I figured I wouldn’t be doing any HAM radio again, so I got rid of all my radios in the move. Hindsight is 20:20, I wish I’d kept the gear.

I checked up on aprs.fi and noticed there was an IGate in Bathurst and one of the things I wanted to play with is messaging. I sourced a Yaesu APRS HT (FT2DR), setup APRS, and sent a test message via SMSGTE to my phone. I had a message! I replied and … nothing. Infact, the silence on 145.175 was deafening. Not just no reply message, but no beacons from the local IGate, no Digi traffic, nothing at all? What’s going on here, Ah, the IGate in Bathurst is a Rx-Only IGate.

I made some pretty feeble attempts to get in touch with the HAM running the IGate to see if Tx could be enabled, but eventually just decided that, more is more, and to setup my own IGate/Digi. I found a cheap Yaesu FT-212L which coupled with a modified version of one of my 817iPad interfaces and Dire Wolf, would do the job nicely. Next was to source/build an antenna. I’m in a rental so anything I put up needs to be temporary and I prefer to build rather than buy. I stumbled upon the plans for a flowerpot antenna and decided that the high-gain version would do the trick. Now I had the concept all that was left was to build it all.

The Radio/IGate/Digi

I setup the FT-212L on the bench and googled the microphone pinout, made a custom cable to go to one of my iPad interfaces via the mic connector (There’s no data port on this radio, and fortunately the speaker is send via the mic connector) and used a break-out cable from the TRRS out, to plug into my soundcard. To mute the radios audio I plugged a blank 3.5mm connector into the speaker port in the back of the radio, unfortunately the speaker out on the front panel must be designed for a speaker mic and the volume on this connector varies with the volume control, so couldn’t simply be turned down like it could if you were using the DATA port on a more modern radio. PTT is done via the VOX circuit on my interfaces that I designed and it’s fast. I mean really fast. With the standard Dire Wolf setup I’ve seen no packet corruption, at all.

The server is a Dell PowerEdge T620 running CentOS 8. Absolute overkill for this job, but it’s in my office and it’s running anyway so why not?

One note on the Dire Wolf setup, I opted to configure it to start via systemd using the article linked here https://www.f4fxl.org/start-direwolf-at-boot-the-systemd-way/ as I think it’s a better way to run services than what’s suggested in the Dire Wolf manual. I’ve configured my station as VK2MES-5 as it’s a dedicated IGate/Digi, it’s NOT a home station. It’s configured to IGate incoming and outgoing messages for stations on RF, Gate from APRS-IS to RF weather, position and station traffic within 50km and Digipeat WIDE1-1/2, WIDE2-1/2. If that becomes too noisy for our area in the long run (it’s pretty quiet out here) I’ll take the APRS-IS to RF traffic somewhat.

This is a really good example of how versatile the interfaces I’ve produced are, and that they work for not only their intended purpose (FT-817/818 to an iPad) but all manner of other things as well.

The Antenna: Flowerpot High Gain Antenna

I was looking for a discrete antenna that provided high gain for 2m for my IGate. I initially looked at the feasbility of building a coaxial colinear, and then courtesy of the Ham Radio On A Budget Facebook group I found the Experimental Dual Band Flowerpot Antenna. I decided to build one for 2m only (leave out the sleeves that make it work on 70cm), so I sourced the parts, put it together and threw the antenna up and it was on air. The SWR is a *little* high at the low end of the band, but right on 145.175 it’s around 1.5:1 which is good enough for my application. It could be tuned by lengthening the two exposed sections of the antenna, but for me for now, near enough is good enough.

Rather than wrap the coils of my antenna in insulation tape and use an end-cap on the end of the antenna I opted to instead use dual wall glue lined heat shrink over the coils and the end. That, as it turns out, comes with a bit of danger. The heatshrink temperature is close to the temperature of the transition temperature of the PVC tubing and care has to be taken not to bend the PVC tubing as it softens when the heatshrink shinks. I used 40mm OD heatshrink here which fits nicely. I’m gonna be honest though, it was expensive, but I think the end result and added weather protection was worth the expense. Instead of using a fishing wire to the exposed top end of the antenna I drilled a small hole in the end of the tube at the top and poked the wire through the side of the tube and secured it with some glue lined heatshrink, which I also used a couple of layers of to seal off the top end.

The antenna is secured to the side of the verandah with a couple of very inexpensive conduit clips that mount with a single screw, so easy to remove when I eventually buy a house. I’ve set the height of it so that it stands on it’s own without any extra support. I originally had it a bit taller but it was leaning a bit under it’s own weight.

And now we have an APRS IGate/Digi that’s fully working

If anybody has any suggestions for improvements here I’m always open to ideas. Feel free to comment and let me know!

73 de VK2MES