Question still open: are people still interested in such an article? Lots of DIY involved. nothing from shops except screws and N-connector.
Return loss measured and exceeding 25dB (which is VSWR<1.12).
Question still open: are people still interested in such an article? Lots of DIY involved. nothing from shops except screws and N-connector.
Return loss measured and exceeding 25dB (which is VSWR<1.12).
DL7UKM fair point. I changed the blockdiagram on the webpage.. new one is here as well for completeness. But you can still change to LO of 594 MHz as option as described in the text.
please check all recent information here
its no so much a matter of asking but a matter of measuring. If properly done, you would have to do it at the feed. Unfortunately, this is 7/16 coax connector there and even then we would require the precise antenna gain.
But as a guess, 3m is 35dBi and 100mW is 20dBm so we have 55 dBm EIRP, maybe 3dB more.
A 90cm dish has some 24dBi, so 2W should be equivalent. Which I believe experience has already shown.
ok, so quite comparable with known setups.. thanks for the test!
DB8TF was the freeDV text line correct? 80cm and 10W?
got you both now, freeDV 1600. what tx are you using (pwr and ant)?
mode 700D?
got the last few seconds when settings were correct could you please do another call?
We have in Bochum 3m uplink and the beacons are a few 100 mW each. Don't know more accurate now, sri.
me too.. another mode to present to users, would be willing to participate in rx test (no tx until at least weekend). software is ready.. need a test signal
After almost 2 months of operation of the transponders, I would like to make a survey which modes are being used on either transponder. This is especially true for the NB transponder, where I am learning every day about new digimodes! But also for the WB transponder I think it is time to collect data from people what setup they are using. SSB and CW are the well known ones but there are tons of other digimodes being used!
The goal of all this collection will be a talk for the Hamradio Friedrichshafen in June. It shall serve as a guideline for all newcomers what can be done on the satellite and what setup is required. Certainly, after the talk is complete I will upload it to the webpage as a general information 'leaflet'.
How can you contribute:
- send in your mode used and a description of your groundstation, both for uplink and downlink. Pictures are appreciated!
- give some estimate if you are at the limit of feasability or less power is possible.
- at minimum, send a waterfall screenshot of your mode. Please no audio files as they get quickly large and don't play well in a presentation
- give a link to the used software and/or the technical details of the digimode.
- describe from your own perspective what the pros and the cons of this mode are.
If used in the talk, all information will be credited to the original source. Please understand, that I will have to make a selection of entries, otherwise the talk could get boring rather easily (not all of the talk should be SSTV or FT8). And I need to stick to some time limit..
Looking forward to your contributions! You may post directly to this thread or (if you think it's too much) send directly to (mycallsign)@amsat-dl.org
73s Achim, DH2VA
Trust us, we would love to share more technical details. But we have only little insight ourself and the little information we have is heavily NDA'ed. But we get two transponders for this price, so I am willing to live with it.
When it comes to phase noise, a good TCXO can be better than a badly designed (or set up) GPSDO. Its advantage is the absolute frequency accuracy, so if you can live without it, I would go with the TCXO solution. Much less of a hassle as there are many errors one can make with GPSDOs.
Actually David G0MRF did this study many years ago:
Bottom line: you need some powerful propulsion to get from A to B.
Now here is the catch: launch providers are more and more unwilling to accept non-paying secondary customers (hamradio) with a high-energy detonation device (propulsion) just next to their multi-million dollar main customer. Both AMSAT-NA and AMSAT-DL (and others!) have tried to overcome these and other problems in the past decades with little success.
The term here is 'snowflaking' an amplifier (german term: Fähnchenschieben) and I consider it an art (and those who master it 'witches' .. hi!).
Any amplifier has a complex impedance it wants to see on both input and output to produce max. output power. The striplines on both sides transform the complex port impedance to our known and loved 50 Ohms system impedance.
Of course, real life is much harder. Matching the input influences the output matching and vice versa.. and matching for max. output is sometimes not identical for matching for max. gain.
Hi Andreas, the easy solution is to switch the PA 12V supply with the PTT line. Probably what I will do as well (looks like the 20W WiFi booster..).
another fine read on the stability of frequency references, written by Ulrich Bangert DF6JB (SK):
Über die Stabilität von Oszillatoren und Frequenznormalen
(sorry German only, but DeepL might be of help here).
@Mike5000 You need to be careful about using standalone GPS modules. By its working principle, the PPS output of any GPS module has some serious jitter (good one in the 10s of ns range), even the timing modules. To get the best of both worlds, any GPSDO needs two key components, a low-jitter timing module for the long term stability(>100sec) and a flywheel crystal oscillator (often OCXO) which determines the short-term stability and SSB phase noise. Rick Hambly W2GPS together with Tom Clark W3IWI have written some excellent presentations on it: www.gpstime.com (disregard the expired SSL certificate for now).
beacon seems to be back