added two new blog posts

content/post/qo100-gpsdo.md

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+---
+title: "Adding a GPSDO to the Pluto+"
+type: post
+author: micha
+date: 2023-04-13T17:00:00+02:00
+url: /qo100-gpsdo/
+tags:
+ - Ham Radio
+ - QO100
+ - DIY
+---
+
+While [SDR Console](https://www.sdr-radio.com/Console) is doing a great job stabilizing the frequency with the help of locking to the middle beacon of the QO-100 narrow band transponder, it still has some inaccurancy. Because of this and because I might try out other SDR software in the future, I've decided to enhance my [QO-100 ground station](/qo100-pluto-sdr/) with a GPSDO. The product I have chosen for this is the well known "Mini Precision GPS Reference Clock" from Leo Bodnar.
+
+First thing to do is to add a SMA socket to the Pluto+. There is a small IPEX UFL socket on the board next to the built-in TCXO. I've ordered a 10cm long IPEX to SMA female cable, drilled a 6mm hole above the 5V micro USB socket and installed the cable by connecting it to the IPEX UFL socket and mounting the SMA socket into the newly drilled hole.
+
+![image](/img/gpsdo-2.jpg)
+
+In addition to this it is also required to set a jumper to connect EXCLK to GND so the Pluto+ knows we want to use an external clock reference (Please see https://github.com/plutoplus/plutoplus).
+
+![image](/img/gpsdo-1.jpg)
+
+Before connecting the GPSDO to the Pluto+, it should be configured first to deliver an output frequency of 40000000Hz with the help of the configuration software that can be found on the official product web page. It is also a good idea to reduce the output drive strentgh to the lowest needed settings, in my case 8mA.
+
+![image](/img/gpsdo-3.jpg)
+
+After connecting everything and powering up the Pluto+, it is necessary to connect to the Pluto+ via SSH and execute the following commands to make it work:
+
+```
+fw_setenv refclk_source external
+fw_setenv ad936x_ext_refclk_override 40000000
+```
+
+As soon as the GPSDO has gained its GPS lock, the Pluto+ is then properly frequency stabilized with the help of the external GPSDO.

content/post/qo100-pluto-sdr.md

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+---
+title: "Building a QO-100 SDR Ground Station"
+type: post
+author: micha
+date: 2023-04-12T06:00:00+02:00
+url: /qo100-pluto-sdr/
+tags:
+ - Ham Radio
+ - QO100
+ - DIY
+---
+
+Frustrated by local QRM on HF, I finally decided to build a ground station for the geostationairy satellite Es'hail 2 aka Qatar-OSCAR 100 - or short - QO-100. Since I don't own a full duplex capable SSB VHF/UHF transceiver and did not want to purchase such an expensive radio, the remaining option was to go down the SDR route.
+
+After searching the web, I've found a setup based on the Pluto+ SDR transceiver which I've then built. It consists of the following components:
+
+* Pluto+ SDR
+* Analogue Devices CN0417 pre-amp
+* SG Labs 2.4GHz v3 power amplifier
+* 12V to 5V DC-DC converter (for Pluto+ and CN0417)
+* 12V to 26V DC-DC converter (variable, for power amplifier)
+* metal enclosure for industrial use, 30x25x15 cm
+* 80mm fan
+* lots of SMA adapters
+
+The components have been mounted on the metal plate that came with the enclosure. To fit the enclosure, I've chosen the following layout:
+
+![image](/img/qo-100-1.jpg)
+
+For mounting the Pluto+ I've remixed a 3D printable holder that can be found [on Thingiverse](https://www.thingiverse.com/thing:5888064).
+
+The 20W PA can handle up to 70C but I'd rather like to have it cooled down. First test also have shown that the Pluto, which is sitting next to the PA, gets pretty warm from the radiated heat of the power amp. The solution was to cut a 80mm hole into the enclosure's door right in front of the PA and mount a fan on the inside. The enclosure is mounted indoors so I did not have to take care of waterproofing. The air is blown from the front directly onto the PA and then flows out on the top side of the enclosure wich is open.
+
+![image](/img/qo-100-3.jpg)
+
+I have chosen the following tried and tested configuration for the antenna:
+
+* 80 cm offset dish
+* Bullseye LNB
+* Ice Cone Helix antenna with 3.5 turns
+* 5m Ecoflex 10 coax
+
+![image](/img/qo-100-2.jpg)