Posts by G8UGD

    I would be very doubtful of getting a good VSWR at 2.4GHz by using resistors in parallel, at these frequencies dummy load resistors tend to be co-axial in nature. Have a look at this page http://millimeterwave.free.fr/ATT_DISPONIBLES.htm and see if anything takes your fancy, it really depends on if you can deal with 7/16 connectors. Also you will need more that 40 dB in total to not damage your power sensor. A quick look on Ebay (UK) and I see some 50 Ohm loads 25 watts for about £11, they will only be rated for intermittent use I would suggest, but they say they are good to 3GHz or even some resistors that can be bolted directly to a heatsink that will take a lot more power if cooled correctly, so please do have a look around various outlets before you decide.

    I am probably guessing wrongly, but wonder if you will be trying to test a Pyrojoe 20 watt amp or similar, if you can give your self some margin in case it is 25 or 30 or even more Watts output.


    What ever you do be careful at these frequencies and powers as you are taking microwave frequencies now and soft tissue damage is always a possibility.

    Very carefully! with the aid of something like a Ebay 30 dB directional coupler, a 30 dB attenuator and a 50 Watt dummy load good for 2.4GHz. The directional couplers seem to be very good are are covered by a few posts on the forum, they cover 800 to 2500MHz and are cheap to buy, I picked up a 50 Watt dummy load for around £30 UKP and you can get a N connector'ed attenuator for similar money, so probably not a cheap option but one which could save your power meter.


    Amp through directional coupler to the load, -30dB port to another 30 dB attenuator to your power meter, so if you assume 43dBm with your 20 Watts you will get a signal at the power sensor of +43 - 60 = -17dBm

    Adrian

    More prep work going into things


    I made another ID filter for 2.4GHz and tried to neaten things up by putting some of the gear into a box. This is the present stage.

    The box layout


    The Bison amp has now got a cowl over the heat-sink fins to help cooling for a fan to be directed in at one end. Only using one of the two amps, the other is there in case of mishaps!



    Next is to get an outside enclosure to house it all in and fit the PSU's and control.


    Adrian

    I do not need to use wide scan or for that matter do I need to use the low SR button although I generally have it ticked.

    If the offset for the LNB worked in Version 0.8 then it should be working in Version 0.9.


    It is a bit of a pain setting up the new minitiouneConfig.ini for version 0.9 but I had two editor windows open to make it easier to copy frequencies from minitioune.ini to the new config file.

    I can not remember having to do any special changes to the ini file to make it work, so a bit baffling why it does not work for you if 0.8 was OK. Hope you get it sorted soon.

    Click on the Oscar 100 button to get a selection of frequencies for different SR rate. Also 3 memory buttons you can use for frequencies and SR rates which can make it easier when jumping between a couple of specials for yourself say during a QSO!

    You also have 8 presets rather than 5 and I believe some fine tuning internally particularly for QO-100 although what I am not sure. I do find the dials at the bottom easier to read.


    Adrian

    OK I have to ask a question here regarding OXCO's if you are more knowledgable, I use a 10Mhz Oscilloquartz type 8661 which is a double oven style unit, it seems to be reasonable for my up converter. The board it is mounted on would have been internally installed in test gear and I have wrapped it in 5 or 6mm styrofoam not a lot of foam and I can feel heat though the foam. It dropped the power requirement by 0.5 watt. So is this a bad idea?


    Adrian

    Do not worry! I am only in to a dummy load and sniffing into my Spectrum analyzer at present, still some time from going to air.


    I have been playing with my Hackrf generating a 1000K SR DATV test signal.

    This is my line up at present

    Hackrf, to RF2126 amp to MHL21336 Amp through 2.4GHz filter to 30 dB coupler and dummy load with the sample port to the spectrum analyzer.

    The line up:-

    Everything for testing is from a 12 Volt PSU so the the RF2126 amp has a DC converter down to 5 Volts and the MHL21336 has an DC buck to 26 Volts.


    This is a spectrum display at present with 10 MHz per division Horizontal and 10 dB per div vertical, so I am looking at present with around 50 dB down on any spurious signals.


    This is the same view but now at 2MHz per division.

    I think I may be able to reduce the spikes there as they are the sample rate used on the Hackrf so I believe increasing it from 10 to 12Mhz may reduce the spikes to an even lower level.


    I was trying to use this small amp stage after the Hackrf,


    but, the frequency response is so wide that it amplifies any and all spurious outputs from the Hackrf and helps pass them to later stages so unless I build another ID filter, (Which I may well do!) then I will not use it in the line up.


    But I still do not have anywhere near enough signal going this way to actually drive the main PA into any sort of power level.


    I put the bisonelectronics amp on the output as it was for a test and was disappointed. The shoulders increased to at best -40 dB at worst -35 dB below peak signal.

    A 1000SR test signal



    A simple test shows that the amp has around 20dB increase


    But we are still taking less than 1 Watt!;(


    That is a far as I got tonight playing with it all across the bench I need advice on how to proceed and what are realistic figures I should be expecting on shoulders, yes i have seen some saying -35 dB down are OK and some saying that is not good enough?


    Is anyone using a bisonelectronics amp as the final stage and how does it perform and what drive level do you need to get to?


    Adrian

    I have been playing again and made a 2.4GHz ID filter.

    The top line is with a back to back connection and the bottom trace 10dB per div vertical and 50MHz per division Horizontal.

    Not brilliant as I guess loss is around 1.5 dB. It still could be useful between a driver stage and main PA for DATV to clean up things before the output stage.


    I am pondering placing a few more screws in there to allow a small change in the coupling between stages, but not sure if it would give any benefit.


    Adrian

    OK thanks guys for the feedback, there has been posts about letting operators know if they are putting out bad signals, but it is good to have confirmation of what I see and think is the cause.


    What I would like to see if possible from the Amsat team is a General post/sticky of problems with signals and what could be the likely cause of the effect. Put it with the Operating guidelines so that operators can easily find it and look for themselves, it may or may not be of use, but may help.


    Adrian


    @G0MRF It's an 8 hour drive round trip for me so I doubt it.

    General question about the WIFI amps and pushing them, how can operators tell they are being pushed to hard? Am I correct in thinking that they then generate additional side-bands especially at the low audio frequencies as they hit compression as in this effect typically seen on the satellite:-



    I guess it is not just the WIFI amps but any amp that can do this.

    Or am I mistaken in what I am thinking?

    Adrian

    Gentlemen, I was joking !!! :D:D


    At least for me, our hobby still is about wireless radio..


    73s Peter

    It is about wireless to me, but I bet it is possible to do and something that Amsat as a governing body could operate for schools and colleges if they wanted to show the technology, and my questions were actually genuine. How would you authenticate licenced operators?

    I have not used echo-link, D-Star or any of the other web gateway systems as it has never appealed to me, (I hate DMR with a passion as it was part of my job at a radio dealer's) So I do not know how these system is controlled or policed from abuse over the Internet I have it in my mind a sort of timed token system to a particular IP address, but it's just a guess.


    Actually sat here in front of SDR console on the Laptop, I bet it is possible with that software?


    What may be a joke could have merit in some quarters to both boost the hobby and industry, just a thought. But I am also happy to be shot down.:)


    Adrian

    Is there any plans to reduce the beacon to 1M SR, that may be useful the wider bandwidth users and also have the benefit of reducing the average power consumption, even if only slightly that the transponder takes?


    Adrian

    To the original poster, to me it is a good idea to have your own downlink as:-

    1) it's yours

    2) Should be less latency then Internet based

    3) May be fun to put together

    4) build it portable enough and you could use it anywhere.


    As to the point of monitoring ones own transmissions, it was good to notice that many have the gear to make the checks and where doing so before the satellite was live, I would surmise that many are old hands at satellite working. I was not, but thankfully had a Hackrf that works to 6GHz to hear my output directly.

    What I was trying to suggest was that a dish, 10GHz LNB and say a SDR with software does not necessarily provide compliance with licence conditions.

    But I thank you for the link to the 2.4GHz transmission test as I just decided to get two of the MMDS converters at £8.50 each that were mentioned by PA0P together with mod instructions.


    Adrian

    Not trying to be awkward here, but how many actually have a receiver to monitor the transmit frequency on 2.4GHz and not what have been rebroadcast through the satellite. To me that is what 7(6) means. It is correct in that QO-100 is not test gear, but the assumption is that if sounds clear through the satellite then it is OK on transmit. Although down at 2.4GHz who knows what spurious side-bands or image frequencies are being transmitted, they are going upwards so will not effect anyone, will they?????


    There was an interesting read on QRZ at one time about a security camera effecting a 1.8GHz sat band,

    https://forums.qrz.com/index.p…nterference-issue.659731/

    and a pdf about the levels of interference

    https://www.itu.int/en/ITU-R/space/workshops/2017-Bariloche/Presentations/23- Elena Daganzo - ESA.pdf

    I wonder if we can do harm to systems on other satellites.


    Adrian

    I have an aluminium filter that was designed for above 23cms that I retuned, I was surprised it was aluminium as it was copper coated.

    Aerial Facilities, as was, built their band pass filter systems from aluminium, some would have copper clad board top and bottom but the sides stayed aluminium. I used to work for them and build them many years ago.

    I did a bit of web reading before I started and apparently the issue is not the necessary aluminium which will oxidise very quickly and protect it self to an extent but the fasteners that can be used in construction, Keeping away from stainless and some other metals seems to be the key, Zinc plated basic steel appears OK with aluminium.


    But all in all it was easier to get hold of aluminium in block form, it is relativity easy to machine if not a little sticky on the tools, so my little milling machine could cope OK. The issue was how to solder connectors. I would love to be able to Nickel and then copper plate things like this but for the odd job it is not worth it. But what I have tried seems to work OK, time will tell.


    I also use a retuned Block filter at 2.4GHz that was intended for LTE gear, that is also aluminium, but is silver coated, now that would cost a bit to do, but RF losses at the higher frequencies would probably be worth while for the manufacturer.