Satellite, 30m and 40m APRS - A comparison

I’ve been interested in APRS from the early days, even before the proliferation iGates with the shift from dial-up to dedicated 24/7 internet connections.  I’ve run APRS in my car on both 2m and 30m whilst traveling and even sent the occasional APRS out on the 2m Satellite frequency. I have memories of being on the Nullarbor and reaching an iGate in Perth via the ISS (this on 2m), as well as having my 30m beacon being iGated by a station in Italy.  It’s all a lot of fun but it’s not for everyone!

Over the last couple of years, I’ve become friends with Joel VK8JG who shares my interest in APRS and has been living in Darwin.  Friday was his last day here before relocating south.  (Anywhere else in Australia is referred to as ‘south’ when you live in Darwin!) For this trip south Joel managed to set his car and caravan up with four separate APRS transmitters, one of 2m Terrestrial (145.175MHz) VK8JG-8, one on 2m Satellite, (145.825MHz) VK8JG-9, one on the 40m HF band (7.0452 Mhz), VK8JG-15 and one on the 30m HF band (10.1476 Mhz USB) , VK8JG-14.

It’s interesting to compare these side by side as Joel drives to Brisbane.   I have included screenshots of the Satellite, 40m and the 30m Beacons below (you can click on the image to in-large them). From memory, the 30m beacon is only 10watts.  (I’ll need to check this, and the output power on the other bands.)

The Satellite APRS is fascinating.  Joel has consistently beaconed through the ISS and also once through LAPAN A2 (IO-86).  The latter is understandable as LAPAN A2 is in an equatorial orbit, and its coverage of Australia is limited to the norther reaches. Joel has been heard by YD8VMS-6 and YB8VRA-4 in Ambon, Indonesia, via the ISS and IO-86.  VK8JG-9 to YD8VMS-6 was at a point-to-point distance of just under 2000km.  Even more impressive are the beacons into VK5ATN-3, at just over 2000km.   Joel’s beacons have been iGated 16 time during six passes in just under 48 hours.

2m Satellite - VK8JG-9

The 30m and 40m Beacons provide a good side-by-side comparison, although we must consider the difference in power between the two. (Again, I will need to check the power output on 40m). Nonetheless 30m seems to be more consistent, especially during daylight hours.  40m seemed better in the far north in the early evening and into the night but there are large gaps in reception during daylight hours. As Joel moved south and closer to the iGates the reception improved and there appears to be a more consistent pattern emerging.

40m - VK8JG-15

30m - VK8JG-14

 

A second point of consideration are the number and location of iGates on each band.  Joel’s 40m beacons were received by 5 stations located in VK2 (x3), VK6 and VK7, whist his 30m beacons were received by only two stations, one in VK5 and the other in VK4. There are, no doubt, a lot more iGates on both bands in operation.  In the past 30m was the preferred band but in light of the Standard Licence not having access to this band I suspect that 40m may end up with more uses and therefore more iGates. This may already be the case.  

In conclusion, it is my opinion that 30m is still the best band for HF APRS, it provides a more consistent path to iGates, this especially during the daylight hours.  40m seems to come into its own from just before sunset and through to mid-morning and may be better than 30m in the far-north during these hours.  For large pasts of Australia, that are less remote, 40m may proof to be just fine, especially if the number of iGates on this band continues to grow.

If you are planning a road trip into the great beyond (obviously not into or out of VK6), and you have HF in your car, why not give HF APRS a go. And if you only have 2m FM why not add APRS into the mix and set it on the Satellite frequency of 145.825MHz. If you do, it will keep me entertained for hours!

Cheers for now!