Posts by G4SAQ

    HB9SKA Hi Thomas. I can only speak about the Octagon Quad LNB Green which I have. Before modification, It drifted quite a bit for the first 15 minutes or so and then became manageable - only slight re-tuning required then. I suspect that the dual output version (for which I sent the link) will be the same as it also has a 25MHz Xtal. None of them are going to be rock stable on their own but these are acceptable. 73 Russ.

    HB9SKA Hi Thomas. I think the Octagon OTLSO has been discontinued. I bought one about two years ago and I can confirm it has PLL technology and a 27MHz Xtal. I have also tried the 'Octagon Quad LNB Green' which has a 25MHz Xtal. I see that a two output version is being advertised cheap on Ebay https://www.ebay.co.uk/itm/Oct…136100:g:gAMAAOSw6lpch~rp

    I have found that the PLL Octagons need 15 minutes or so to warm up and then the drift is acceptable for SSB. However, I have modified mine to accept an external reference to keep it really on frequency. I hope this helps you. 73 Russ.

    PA3FYM A bit more on the Si5351a. I had been using some code I found on the web to program the registers in the Si5351a. At 27MHz the output looked very clean (and that is what I reported earlier). However, when I generated 25MHz the output was awful. Then I used Silabs 'ClockBuilder' Windows program to produce a register map for 25MHz and the result was clean!

    I tried injecting this into my Quad Octagon (25MHz) and the QO-100 CW beacon sounded good (no raspyness). Then I tried 23.817,949MHz to put the bottom of the transponder on 1,200,550MHz. Again the CW beacon was clean. I am guessing that there is more than one way to produce a frequency from the Si5351a but only the 'ClockBuilder' method gives a clean output. Having said all this, I could not receive DATV on my Minitiouner with the Si5351a input. Probably the phase noise was the problem. I have ordered a sample Si5332E to have a play with (much newer device). 73 Russ.

    PA3FYM I don't have a definitive answer to that. However, i suspect that the noise comes from the micro's clock and that that a tiny amount of this gets onto the I2C connection. Putting the micro to sleep turns the clock off. I hope to modify my quad Octagon (25MHz) tomorrow. Then I will inject it with the si5351a output and see what the NB transponder beacon looks like on my SDR. 73 Russ

    A while ago there was some discussion about the si5351a device. I have just managed to find a link to some work done by Daniel Estevez EA4GPZ. He found the output from this device to be quite clean. Take a look: https://destevez.net/2016/07/p…ences-for-a-ku-band-lnbf/ As I said earlier, it is important to put the driving micro to sleep after a frequency command has been sent to the si5351a. I hope this is of use. 73 Russ.

    Yes, congratulations indeed! What an achievement. Very many thanks to His Excellency A71AU and to Peter, DB2OS, for whom this is a dream come true! (not forgetting numerous others. of course)

    73, Russ.

    Dear Peter (DB2OS), I wonder if the inauguration ceremony will be broadcast on the WB transponder? Are you able to give any indication of the timing (in GMT) and video parameters, please?

    73 Russ.

    My technical knowledge is shallow compared to most of you so I make this suggestion with care! I use a PIC micro to control my si5351a over the I2C connection. I have found that the output at 27MHz - as seen on my SDR - is very noisy. However, putting the PIC to sleep after a command has been sent seems to result in a clean output. I hope this helps. 73 Russ

    Yes, I agree with you. In itself that may be manageable. I guess we will find out. However, I have tried to speak on a local club top band net whilst listening on our web sdr (high local noise) and I just cannot get my brain to function! I was just curious in case anyone knows (and is allowed to say) whether the transponder is sdr based. Exciting times ahead!

    I have been thinking about the problem of digital latency in my receiving equipment as this will make it hard to listen to one's own signal. However, it has occurred to me that there may also be in-built latency in the satellite transponder, which we can do nothing about. Please can anyone throw any light on this matter?