Added diplexer to build doc

build_doc/aprs_digipeater.html

@@ -55,8 +55,8 @@
 <main>
 <article>
 <p><b>Abstract </b><p>This project is a collection of former (and some
-new) projects connected together to make an APRS digipeater, which
-doubles as an APRS weather station, with PE1RXF telemetry server
+new) projects brought together to make an APRS digipeater, which doubles
+as an APRS weather station, with PE1RXF telemetry server
 capabilities.</p></p>
 <figure>
 <img src="./images/block_diagram_overview.svg"
@@ -218,13 +218,26 @@ alt="Alinco DJ-580" />
 </figure>
 <h3 id="diplexer">Diplexer</h3>
 <p>The LoRa APRS transceiver (70cm) and the APRS transceiver (2m) are
-connected to a triplexer, making it possible to use one dual band
-antenna for both radios. Why a triplexer? Well, I had one laying around.
-I terminated the unused 1200MHz connector with a 50 Ohm load. But a
-diplexer would have been sufficient, of course.</p>
+connected to a diplexer, making it possible to use one dual band antenna
+for both radios. The diplexer is designed specially for this project.
+The port isolation is not great, but because of the small transmit power
+of the two transceivers, this is not a big deal. And even so: it
+outperforms a commercial Diamond triplexer on the 70cm band.</p>
+<p>All the inductors are made from 1mm copper wire (preferably silver
+plated) and wind around a 6mm rod (a screw driver or a drill bit for
+example).</p>
+<h4 id="adjustment-procedure">Adjustment procedure:</h4>
+<ul>
+<li>Connect a dummy load to the combined 2m/70 cm port</li>
+<li>Connect an SWR meter and a 70cm transmitter to the 70cm port</li>
+<li>Adjust C1, C2 and C3 for the best SWR</li>
+<li>Connect the SWR meter and a 2 meter transmitter to the 2m port</li>
+<li>Adjust C4 and C5 for the best SWR</li>
+<li>Repeat the two steps, as both ports influence each other</li>
+</ul>
 <figure>
-<img src="./images/triplexer.png" title="Triplexer" alt="Triplexer" />
-<figcaption aria-hidden="true">Triplexer</figcaption>
+<img src="./images/diplexer.svg" title="Diplexer" alt="Diplexer" />
+<figcaption aria-hidden="true">Diplexer</figcaption>
 </figure>
 <h3 id="antenna">Antenna</h3>
 <p>This is a simple 2m/70cm dual band antenna from Diamond, the X30.</p>

build_doc/aprs_digipeater.md

@@ -99,9 +99,21 @@ The 2 meter transceiver is an old Alinco DJ-580 hand held radio with an output p
 
 ### Diplexer
 
-The LoRa APRS transceiver (70cm) and the APRS transceiver (2m) are connected to a triplexer, making it possible to use one dual band antenna for both radios. Why a triplexer? Well, I had one laying around. I terminated the unused 1200MHz connector with a 50 Ohm load. But a diplexer would have been sufficient, of course.
+The LoRa APRS transceiver (70cm) and the APRS transceiver (2m) are connected to a diplexer, making it possible to use one dual band antenna for both radios. The diplexer is designed specially for this project. The port isolation is not great, but because of the small transmit power of the two transceivers, this is not a big deal. And even so: it outperforms a commercial Diamond triplexer on the 70cm band.
 
-![Triplexer](./images/triplexer.png "Triplexer")
+All the inductors are made from 1mm copper wire (preferably silver plated) and wind around a 6mm rod (a screw driver or a drill bit for example).
+
+#### Adjustment procedure:
+
+- Connect a dummy load to the combined 2m/70 cm port
+- Connect an SWR meter and a 70cm transmitter to the 70cm port
+- Adjust C1, C2 and C3 for the best SWR
+- Connect the SWR meter and a 2 meter transmitter to the 2m port
+- Adjust C4 and C5 for the best SWR
+- Repeat the two steps, as both ports influence each other
+
+
+![Diplexer](./images/diplexer.svg "Diplexer")
 
 ### Antenna