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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/WXUSKOEX3GJO6M2M25G76AT3SBZRWFQR/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "WXUSKOEX3GJO6M2M25G76AT3SBZRWFQR",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/WXUSKOEX3GJO6M2M25G76AT3SBZRWFQR/",
    "sender": {
        "address": "pe1rah (a) yahoo.com",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "William Leijenaar",
    "subject": "[amsat-bb] Re: P3E transponder and launch",
    "date": "2007-03-27T19:21:49Z",
    "parent": null,
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "\nHi AMSATs,\n\nI am supprized to see that my mode-uv work for the P3e\nis still remembered :o) I wonder what happened with\nthe mode-uv transponders designed by the other (New\nealand, Russian, German and ??) groups ? Lately I only\nread about the SDX work of NA, UK and DL, but what\nabout the other parts made by other (none NA,UK,DL)\nhams ?\n\n\n>From the messages I feel that the SDX seems to be the\nbest radio at all, with a larger dynamic range, better\naligator killer, better HELAPS etc...\nSDR technology is very interresting and it should be\nexplored, but somehow I feel that only its advantages\nare named. So I like to \"flip the count\" to its other\nside to have \"the pair of scales in balance\".\n\nAbout the dynamic range, I wonder how it can be better\nthan an analog receiver. I suppose the RX side (UHF)\nwill not directly be digitalized (it would need an\nhigh speed and high power ADC) so there is still an\nanalogue\namplifier and down-mixer needed in front. Then there\nis only the IF part where it can be dynamically be\nbetter. I guess with analogue electronics this can\nalso be done :o)\n\nI also seen someone mentioned about 1970 electronics,\nas if todays electronics is only better in IC form.\nTodays 2007 transistors are much better than in 1970,\nthey are much smaller, and have a better performance.\nEven analogue style transponders can be made better\nand smaller size than those in Ao-10, with todays\ntransistors. Have a look at my modern analogue\ntransponder system at: http://www.observations.biz \nWhen talking about old technology then HELAPS (or\nofficially called EE&R) is even more older, from 1952\n;o)\n\nThat the HELAPS works better only due to the \"modern\"\nSDR system is not compairing in a fair way. Then you\ncompair 2007 SDR electronics with 1975 transistor\nelectronics. I believe with todays modern discrete\nelectronics the HELAPS system will work equally or\neven better.\n\nThe SDR system with zero-IF is a nice system which is\nvery flexible. However zero-IF can have problems with\nDC-drift over time what gives unefficient ADC use or\neven ADC clipping. It is also more sensitive for low\nfrequency 1/f noise, and the high frequency digital\nprocessing signals are a serious threat on sensitive\nreceiver inputs... (also a problems in modern\ncell-phone systems)\n\nA Near-Zero-IF system might be a solution but is more\ncomplex to integrate.\nThe filters at such low frequencies (zero-IF) can be\nmade very sharp, but the same trick can be done in\nanalogue way, with an RC low pass filter :o) Several\nyears ago I present such a bread-bord system as\n\"Quadrature transponder\" where I could easily change\nthe transponders bandwidth and change from inverted to\nnone-inverted :o) The difference is that it takes far\nless power than a DSP does, and it was extreemly\nKISS...\n\nI agree that digital DSPs are more flexible which is\ngood when you like to use the same radio for other\nmodes also.\n\nThis was my vote for the analog transponder systems\n:o)\nI hope the digital SDX works well and hope that its\nanalog sister will also have a chance to do its work\nand gets its technical respect...\n\n73 de William\n---\n\n\n \n____________________________________________________________________________________\nBe a PS3 game guru.\nGet your game face on with the latest PS3 news and previews at Yahoo! Games.\nhttp://videogames.yahoo.com/platform?platform=120121\n",
    "attachments": []
}