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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/YZYOLDAUGGM2GYBVXACJ7MSQY2NE66T3/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "YZYOLDAUGGM2GYBVXACJ7MSQY2NE66T3",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/DXYC2GUJLN5TXNQT5Z2DGNSWT454J32F/?format=api",
    "sender": {
        "address": "tosca005 (a) tc.umn.edu",
        "mailman_id": "ddd1e012a31843ce830c5bc7888b5fea",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/ddd1e012a31843ce830c5bc7888b5fea/emails/?format=api"
    },
    "sender_name": "John P. Toscano",
    "subject": "[amsat-bb] Re: Test Gear for 1.2/2.4Ghz Equipment",
    "date": "2008-05-31T04:29:00Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/DXYC2GUJLN5TXNQT5Z2DGNSWT454J32F/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "John Henderson N4NAB wrote:\n> Need some advice  on test gear, signal source, swr  measurement for L and S\n> band. Just got 1.2 board for 910H and have unit on order for 2.4 from SSB.\n> Home brewing antennas and need some way to check/adjust. My MFJ is only good\n> for up thru  70cm.\n\nYou might want to consider some surplus HP equipment.\n\nThe HP432a power meter will cover any frequency you are likely to need.\nIt requires the additional purchase of a thermistor head. The 478A head \nis good to 11 GHz, and 8478B head is good from 10 MHz to 18 GHz. You \nalso need the thermistor cable.\n\nThis setup covers a power range of 10 microwatts to 10 milliwatts full \nscale. So you would also want a few precision attenuators so that you \ncan measure power levels higher than 10 mW without destroying the \nthermistor head.  A -30dB, 10 watt attenuator would bring a 10 watt \nsignal down to 10 mW, or full-scale at the maximum power range of this \ngear.  I also found a -40dB, 50 watt attenuator that brings 50 watts \ndown to 5 mW or half the power rating of the thermistor. If you were \nbrave (or foolish) you could put 100 watts through this attenuator very \nbriefly and the thermistor would be happy at 10 mW maximum. But \nprecision attenuators don't retain their precision qualities if \noverheated with excessive power, so go easy there.\n\nNow, this still doesn't get you the ability to measure SWR, or measure \nforward and reflected power into/out of an antenna. To do that, you need \none more piece, which is a directional coupler.  Power goes into the \ndirectional coupler and its output is connected to the antenna or other \ndevice under test (DUT). You connect your power meter's thermistor to \nthe forward or reflected coupling port. By measuring forward and \nreflected power, you can determine the SWR.\n\nSure, the Bird 43 wattmeter is convenient -- power in one side, antenna \nconnects to the other side, and you can read the SWR right off the main \ndial. The \"problem\" with the Bird is that you have to buy additional \n\"slugs\" for every frequency band and every power level of interest. With \nthe HP system described above, you only need one meter, one cable, and \none thermistor to measure power at any frequency between 10 MHz and \neither 11 or 18 GHz.  Although some precision attenuators are frequency \nspecific, you can easily buy only attenuators rated to 18 GHz and you \nare good for any frequency that the meter can measure.  Likewise, \ndirectional couplers have highest precision at specified ranges of \nfrequencies, but in many cases, you can calibrate one with the above \nsetup plus a good 50 ohm dummy load. By calibrate I mean that if the \ndummy load is near 1:1 SWR, the forward power coming out of the coupler \nat the frequency of interest can be easily measured with the dummy load \non the output, and you now know what the coupling level of the forward \nport is, whether -10dB, -30dB, -16.2dB, or whatever it turns out to be. \n  Then you physically rotate the device (put power into the output port, \nput the dummy load on the input port, and measure the forward power \ncoming out of the \"reverse\" coupler port).  Now, even though the coupler \nmight not have been designed to work at 2400 MHz, if the coupling is \nmeasured in this way, the coupler is usable unless the coupling you \nmeasure is extremely poor.\n\nThat may be a bit more of an answer than you were looking for. But this \nsetup seems to be much more versatile to me than a Bird 43 with a box \nfull of slugs.  I actually bought a couple of HP432a meters, thermistor \ncables, and 8478B thermistor heads, and 18 GHz attenuators of -10, -20, \n-30, and -40 dB, plus a two-way directional coupler. With these pieces, \nI can measure power from microwatt levels to tens of watt levels at any \nfrequency for which I have equipment, as well as forward/reflected power \nand (indirectly) SWR.  No, I don't have any 24 GHz equipment and this \nsetup would not test it if I did, but you'll not find a 24 GHz slug for \na Bird 43 either! On the other hand, it is possible to buy a K486A \nwaveguide thermistor for the 432A and measure 18 to 26.5 GHz too!\n\nIf you're interested, the following HP/Agilent operator's manual for the \n432A would be a good place to start reading:\n   http://cp.literature.agilent.com/litweb/pdf/00432-90079.pdf\n\n73 de WØJT\nAMSAT-NA LM#2292\n",
    "attachments": []
}