Recently, I took a short excursion through the city of Guimarães with the objective of conducting a brief APRS test using my Kenwood TH-D75. The purpose of this test was to map the coverage areas of the Braga digipeater, CQ0PBR, which is installed on Mount Santa Marta at an elevation of 562 meters ASL.
Aware from the outset that the antenna is not yet in its final location due to certain technical constraints, I was fully conscious that, in lower and more obstructed areas without a direct line of sight to the digipeater, it would be exceedingly difficult for my packet to be relayed.
For this test, I used a Super-Elastic Signal Stick™ antenna from SignalStuff, and the transmission power was set to the High level of the TH-D75, which, theoretically, corresponds to approximately 5W.
Below, one can observe a map extracted from the aprs.fi website, displaying the locations where my transmissions were successfully repeated by CQ0PBR.
The signal was relayed in six distinct locations:
- Largo do Toural
- Weekly Market Area (adjacent to GuimarãeShopping)
- Ascent towards Mercadona
- Elevated area between Mercadona and Hotel de Guimarães
- Avenida D. João IV (open area facing NW)
- Avenida D. João IV (open area facing NW, near the avenue’s end)
As illustrated by the horizon map below, at each of these six locations, the signal “traveled” through the opening oriented towards the northwest (NW).
The distance between the transmission point and the digipeater is approximately 11 km in a straight line.
Below is the list of stations received between 1330z and 1335z.
My experience was also the subject of a tweet.
A quick city walk for #aprs fun pic.twitter.com/g8QZNehNJs
— CT1ETE 🛰 (@CT1ETE) January 21, 2025
I conclude this brief article with a video of one of the transmissions carried out, along with its corresponding repetition. I hope this encourages you to experiment with APRS.
73 de CT1ETE, Paulo