Dear All,
The Online AMSAT-UK Convention takes place on Sunday, October 11, from 11am BST (10:00 UTC) to approximately 5pm, with a break for lunch, and several short breaks during the day. You don’t have to be a member of AMSAT-UK to participate, and the event is free of charge but please register.
Details at https://amsat-uk.org/2020/09/1…e-colloquium-open-to-all/
Registration: http://tinyurl.com/amsatukreg2020
Regards
Mike
AMSAT-UK offers an eMembership with a journal in PDF for download. Would this not be a good solution for AMSAT-DL and their new members in oversea ? With QO-100 I think we gained a few new members.
The journal is in German. I think that would limit the appeal outside the EU of a printed version. However an online PDF would be excellent for those of us who need to use translation services to get the most out of it. There are many interesting articles.
Would we send 73s in CW?
There is a problem in with assumptions on bandwidth as not all driver radios have SSB filters able to meet a 2.7 kHz limit.
So why wasn't the limit set to be compatible with the "standard" 300Hz-3.4kHz ? It's not as if there is a lack of bandwidth available with the extension to 500kHz.
Rec. ITU-R BS.640-3 might have been more sensible.
"The upper limit of the audio-frequency bandwidth (-3 dB) of the transmitter shall not exceed 4.5 kHz with an attenuation slope of 35 dB/kHz and the lower limit shall be 150 Hz with lower frequencies attenuated at a rate of 6 dB/octave."
However that is for SSB broadcasting and even though QO-100 is a broadcasting satellite, amateurs don't broadcast.
ITU Report M2478 which although related to the 6m allocation, does mention the bandwidths required for narrow band modes (CW/SSB/Digimodes) to be between 500Hz and 3kHz depending on the mode. So for 6m at least maximum of 3kHz.
Then there is the handbook: https://www.itu.int/dms_pub/it…HDB-52-2014-OAS-PDF-E.pdf which is where I assume the 2.7 kHz comes from though the definition of SSB:
SSB – Amateur single sideband suppressed carrier telephony has virtually replaced double-sideband amplitude-modulated telephony in the amateur service. The emission symbol is 2K70J3E, although there is some use of narrower and wider bandwidths. SSB is used on frequencies from 1.8 MHz through 47.2 GHz.
So we see where it comes from and there's not hard and fast number. Most radios people might try to use from the (Yaesu, Icom, Kenwood, Elecraft) have filtering to 2.7 kHz or less at -6dB anyway.
Display MoreHi There,
does anyone can explain me how is the CN / MER parameter on Minitiouner affected?
How can i increase it?
TNX
Giovanni pa1kek
It is an approximation to the level of signal above the noise. To improve it, improve your receiver. Bigger dish, better LNB. Compare with others to make sure your setup is operating effectively. You will need a large dish for DATV, at least 80cm and preferably 1.2m.
Mike
Indeed - what would be good would be a IC705 with just a few milliwatts output and fully duplex and full coverage. Not impossible. Several SDRs already do that, they just lack the filter banks and integrated computer that generates the look and feel of a traditional radio. Then a bolt on amplifier would allow whatever was needed, from 1mW to 1kW. This will be an unpopular statement but I think the IC-705 is disappointing. The fact it can't do duplex means it is essential to have a second RX for the linear satellites. Even if Icom don't produce an update we can be sure someone in China will and it will be considerably cheaper with "good enough" performance for most people and yet bad enough performance to annoy VHF weak signal operators. Icom missed an opportunity, let's hope they fix it.
So to the point. There has been several times now "I know my frequency comments". We don't have to just know our frequency but also our power and if not listening or looking at the waterfall of the downlink how do we know if we are not too low or too high power? I can imagine "I know my power" comments. Well, evidence seems to suggest far too many clearly don't know their power and ignore Lila as they don't hear it. Remember, the owner of the transponder probably doesn't care if you drift or have a poor signal, or trample on top of someone else, but they absolutely care when someone sends too much power. Too much too often and it will be switched off. So lets be clear about this. If you are not operating QO-100 duplex, you should not be operating at all, period.
Mike
It is really important to actively monitor your downlink, not just to be able too. When I mentioned this in the UK there was a lot of pushback. Out of the bad signals I see, almost none of them are from people using SDRs and almost all of them from people operating simplex. The IC705 is an SDR so hopefully it will be good, but I fail to understand why ICOM did not make the radio duplex! It makes no sense. The IC9700 is almost the same price and must have much in common in its design and is duplex.
Mike
Some of these SDRs use sound cards. These are not locked to GPS. An error of 130Hz in a sound card would be - shall we say - disappointing and quite obvious but it's possible. Meanwhile, does anyone know how to gold plate a Lily?
Thanks to all for the responses. We are in an early stage of the project and your part is only to set up the antenna and RX/TX system. The communication part is done by someone else and we just know that part of it will be a high speed downlink on 13cm. To our calculations we are on the limit with a 2 m dish. So at the moment we are investigating the optimum for this setup regarding dish-size / rotator accuracy and speed / system costs. We also have to account for future developments as this institut will not be able to make a similar investment within the next 10 years.
Anyway, further informations and reports are welcome.
In that case, if you intend to use for professional missions I would strongly recommend a much larger dish - or X-band and a proper professional dish mount. They do come up second hand and if you have a mechanical shop then perhaps it could be refurbished. You might want to talk to TU Graz - experts in this area.
You should be using 10m dishes on s-band. This is to allow for the many missions there are to co-exist. Narrow beams are necessary. Amateur S-band is different of course.
I am sure he knows. I will ask next time. The reasons for these errors are probably interesting and subtle.
Display MoreHi all,
Half a year later, the issue remains unchanged. The Goonhilly WebSDR now seems to be off by around 130Hz. Apart from the offset, there is a visible jitter of quite a few Hz.
The screenshot below shows the same audio signal as received simultaneously by the Brazil WebSDR (trace at the left side), the Goonhilly WebSDR (trace at the right side) and by my own receiver (trace at 762Hz).
The Brazil WebSDR (http://appr.org.br:8902/) is shown just for comparison as Thomas mentioned it above and I guess it uses a simple TCXO as a reference. Both offset and drift are heavily dependent on the time of day.
73 Jean DJ0VL
130Hz in 10 GHz? Shocking. Don't think anyone said it was a standard frequency reference, but don't forget to account for Doppler and relativity.
Hi PY2RN - I tested it last night and it works, but you need to power off the box when not using it or change it's IP as it sends multicast as you discovered. It does seem work with the new patch from M0DTS as H264 and H265. The audio via HDMI works fine for me. Video quality is quite good, not as good as you can get with an Nvidia graphics card encoder, but quite adequate at high bit rates - say above 125kb/s. These are very useful boxes.
I found when switching between H264/5 and various rates the box crashed on occasion. It recovered but this prompted windows to re-arrange the open windows in that unique and unhelpful way windows is so fond of doing, so beware.
Mike
Wait a bit - I have been testing the same thing with issues. They are being worked on. You need to check the force compliant box. Audio via HDMI works for me.
Mike
PS, if you don't want the pluto to control the box and use your own settings, simply don't let the pluto know where it is. Configure the box to send UDP to the pluto, it won't know any different.
What happened with ITU Resolution COM6/19 ? This problem was recognized in 2015 or earlier and should have been addressed at WRC 2019.
Against the odds we were largely successful, due to a huge effort by many, in identifying spectrum for short duration missions. The result was:
The frequency band 137.025–138 MHz may be used for short-duration missions, if they do not cause harmful interference and if they do not claim protection from other services. In this case, simplified filing procedures apply. For most countries, the coordination requirement Art. 9.21 was removed from the uplink band 148–149.9 MHz which enables it's use for these missions.
It's not perfect but a good outcome given the circumstances.
Mike
I will raise this with my ESA contacts to find out what has really happened.
Regardless of what the IARU say, they don't have a veto over administrations who will always be able to authorise what they wish. Normally administrations do follow IARU guidance, so for one to not do so, is quite a problem. However, if a university or individual has acted independently here and for example claimed a permission they did not have, that needs to be dealt with appropriately.
You say 95% of cubesats have nothing to do with amateur radio. That's not really true. More like 95% of cubesats have been enabled to exist through the creativity and work of radio amateurs. It's a sign of the value of amateur radio that such a large market for them now exists and this is evidence that justifies our continued access to these bands more than anything else. In fact, I can't think of any satellite that has not had a radio amateur significantly involved in the mission at some point.
Mike
I expect you broke the tiny power chip. It can't be changed. If it is working with USB power via the power connector and USB data via the USB port then count yourself lucky and leave it like that. If not, have a look a the schematic to see how you can bypass it and feed 5V. That might work.
Mike
It's a still from a broadcast made this afternoon for several hours on QO100 DATV transponder. Copyright material. Music.
I wonder what we need to do about people persistently violating copyright and amateur regulations? It's true it is not doing any harm, that is until some administration perhaps not so supportive of amateur radio objects and we are taken off air permanently.
It would be better to make a complaint of interference via your administration - but I am afraid commercial startups are using the amateur bands because they can and it's cheap and their administrations are prepared to accept it, so your argument is really with the country.
