When operating SAT-portable, the automatic Doppler correction of 2xFT-818 can be conveniently performed by a #RaspberryPi Zero W running #Gpredict and #Hamlib. Proven solid and reliable in DXing over the last 2 years. Read on for details 🧵

#amsat #hamradio #amateurradio #hamr
Doppler adjustment can be made manually but beyond calling CQ things get cumbersome. An automated tracking allows to quickly hop between different stations in the very limited time of the pass. For DX skeds this setup brings you spot on on the transponder frequency. 2/8 #amsat
RasPi connects to the WiFi hotspot of my iPhone enabling control and time sync. RTCZero backs up the system time. 2x CH340 USB-TTL converters connect the FT-818s to the Pi through Zero4U hub. 3/8
#amsat #hamradio #amateurradio #hamr #raspberrypi
Precise timing is crucial for overhead passes and CW. When cell coverage is absent I plug a GPS dongle into the spare port of Zero4U to feed the GPS time to NTP. The only limitation: FT-818 can't change frequency during TX 4/8
#amsat #hamradio #amateurradio #hamr #raspberrypi
RealVNC offers excellent GUI access to the Pi from iPhone. I load two instances of rigtcl deamons via shortcuts (can be loaded at startup) and from here the workflow resembles that on a desktop. 5/8
#amsat #hamradio #amateurradio #hamr #raspberrypi
RasPi Zero W has the humblest specs in the line. Yet it is capable enough to have Gpredict track 6-7 sats at a time. I work more than 7 sats and overcome the CPU limitation by utilising the module feature of Gpredict. 6/8
#amsat #hamradio #amateurradio #hamr #raspberrypi
RasPi Zero W doesn't consume much energy. A 1500mAh 9.6V battery gets me through 12-15 passes of RS-44 (without GPS). There are lighter batteries. I use an inefficient linear regulator and hence bulky heatsink for all-weather operation. The switching ones I tried were noisy 7/8
Worth to note that this was a prototype that I continue to use as is. It is bulky. It can be optimised and dolled up. The extra circuity on the lower board is for audio switching and TX breaking for Doppler control. It works but I don't use it casually. 8/8
#amsat #raspberrypi

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More from @M0SKN_SA5IKN

Feb 25, 2023
Recently, tens of #amsat ops made their 1st #moonbounce QSO. The thrill of #EME with a biggun creates an illusion of similarity to other modes. EME is different. How small a station you can hear? This thread elaborates on accurate predictions. No magic, only Physics! #hamradio
2/10 #EME is the only field in #hamradio that allows reliable predictions of station sizes that one can work. No smaller station beyond this prediction can be contacted under any conditions! You cannot bend the theory. The link budget can be expressed in Signal-to-Noise ratio-SNR
3/10 SNR represents the ratio of System Gain to Noise Temperature. #WSJTX in Q65 computes SNR in the bandwidth B=2500 Hz. That is the report that you exchange with each other. We want to maximise it by increasing the numerator and decreasing the denominator
#hamradio #moonbounce
Read 11 tweets
Jan 31, 2023
This is a simplified guide describing a bare minimum (!) for #EME operation of WSJT-X in Q65-60B on 432 MHz. A few settings are TRX-specific. Consult to your rig's manual for those

Step 1: Download stable version of WSJT-X at pulsar.princeton.edu/wsjtx.html

#amsat #moonbounce #hamradio
Step 2: Install WSJT-X and open Settings
1) Fill in "My Call" and "My Grid"
2) Tick "Enable VHF and Microwave submodes"
3) Tick "Decode after EME Delay"
Step 3: Navigate to Radio tab
1) Choose your rig model
2) Choose your serial port and baud rate
3) Choose CAT as PTT
4) Mode and split operation depends on your rig. A minimum non-destructive set: Non and Fake it, respectively
You test CAT by a button
Read 8 tweets
Jan 31, 2023
Bernd DL7APV asked me to QSP to the #AMSAT community that he will QRV this coming Thu, Sat, Sun and listen especially for #satellite setups. Use your chance to make your first ever #EME QSO - biggest challenge in #AmateurRadio 🌗

See how this can be done⬇️

#hamradio #moonbounce DL7APV and his EME antenna. Credit: DL7APV
Read 5 tweets
Jan 28, 2023
If you work via #GreenCube, try #EME with big guns. I promise, you will be amazed! As a proof of concept, I made a quick #moonbounce QSO with DL7APV with just a Yaesu FT-818, 40W, 1dB NF LNA and 15 el Diamond antenna held by hand! Easy QSO. Read on🧵
#amsat #io117 #hamradio #hamr Diamond A430S15 Yagi antennaEME QSO with DL7APV using 40W, Yaesu FT-818 and 15 el Yagi
2/9 There are a number of extremely capable #EME stations on 70cm: DL7APV, HB9Q, NC1I. If you are enjoying decode rates above 80% on #GreenCube, don't wait and try #EME. You will likely complete your first QSO over the Moon faster than on the congested #IO117
#amsat #hamradio Credit: HB9QCredit: DL7APVCredit: NC1I
3/9 I used my portable #Greencube set: Yaesu FT-818ND - 40W amp / 1dB NF preamp - Diamond A430S15 14.8dBi on wooden extension, held by hand and pointed visually. With a low NF frontend you can go with a 7el Arrow
#EME #amsat #hamradio #hamr #moonbounce
Read 10 tweets
Nov 1, 2022
LNA / preamp is an unpopular topic of the portable SAT discourse. Noise figure (NF) is assumed to be low due to absence of long cables. But what if NF of the system inherently is not top tier? Any benefit in using LNA with FT-817 & FT-818? 🧵
#hamradio #amsat #amateurradio #hamr ImageImageImage
NF & MDS are determined by the quality of the signal chain and the venerable FT-818 is not a star in that department. Under exact same conditions (antenna, cable etc) a very weak signal readable from IC9700 would not be copyable from FT-818. 2/7
#hamradio #amsat #hamr Image
The comparison of NF & MDS of IC705, IC9700 and FT-818 assumes favourable IMD performance of the FT-818 with a 500 Hz filter. In the field this is rarely true and even less so with a passband of 3 or 2.7 kHz in SSB. 3/7
#hamradio #amsat #amateurradio #hamr Image
Read 8 tweets
Jun 3, 2022
How portable can a #QO100 station be? Ultraportable, when running #FT8. No dish, <100 mW out (note the 3dB attenuator) and a 5000 mAh battery can power it for the whole day. 486 FT8 QSOs using this setup from JO89🇸🇪 so far. Few notes and thoughts
#amsat #hamradio #GHz_bands #hamr

Image
Image
Image
This is neither the most light-weight nor elegant setup, yet it takes less backpack space than my LEO gear (2xFT-818 & Arrow). The size can be further cut down if an SDR is used. I don't do #SOTA or #POTA but have not heard of anyone adopting similar approach in their activations
1) 13dBi RHCP cavity-backed patch antenna on TX (FPV drone racing antenna will do)
2) Bare, modified single LNB on RX
3) Primitive bias tee and high-pass filter to enable GPSDO input and IF out from LNB via one cable
4) DXPatrol upconverter
5) Leo Bodnar GPSDO
6) Cheap SDR dongle
Read 4 tweets

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