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[CQ-Contest] IC-756 Tests

Subject: [CQ-Contest] IC-756 Tests
From: w2vjn@rosenet.net (George Cutsogeorge)
Date: Thu Mar 13 10:00:24 1997
            IC-756 PERFORMANCE TESTS S/N 01020          3/8/97

K6AW and W6OTC were nice enough to lend me an IC-756 to run some lab tests on.  
K6AW has covered the operator impressions and features very well in a prior 
note, so my intent here is to provide some performance numbers.  Where 
possible, performance numbers of an IC-765 have been included.  You may note 
that some performance numbers usually given are absent.  This is due to the 
lack of certain types of test equipment such as a spectrum analyzer in my home 
lab.  

Conditions: stock SSB filters, CW-optional 500 Hz@9 MHz and stock SSB@455 IF.
            (Numbers in parentheses are for a reference IC-765 S/N 4616)    

SENSITIVITY-    SSB Noise Floor = -130 dBm, Preamp OFF  (-128)
                                = -135 dBm, Preamp 1 IN (-134)
                                = -137 dBm, Preamp 2 IN

                CW Noise Floor = -134 dBm, Preamp OFF   (-133)
                               = -139 dBm, Preamp 1 IN  (-140)
                               = -141 dBm, Preamp 2 IN

SELECTIVITY-    Small signal, AGC off, SSB = 1900 Hz @ -3 dB    (1020 Hz)
                ?        ?             CW  = 480 Hz             (330 Hz)

                Large signal, AGC on,  SSB = 2570 Hz            (2260 Hz)
                ?        ?              CW = 1070 Hz            (680 Hz)

BLOCKING-   Noise limited for both radios within a few kHz of the desired 
            signal and not enough generator output to measure at 500 kHz 
            offset.  Both radios are quite good.

    Additional conditions: The third order, blocking and reciprocal mixing 
    tests were performed with a home brewed two tone generator using low noise 
    FET crystal oscillators.

THIRD ORDER PRODUCTS-   

    Tone spacing = 100 kHz;
        Intermod products at the noise floor for two -32.5 dBm tones.   (-29.5)

        Third order intercept = +18.2 dBm   (+22.7)

        Dynamic range = 101.5 dB            (103.5)

AGC - Extremely flat from minimum to maximum signal .

       Rise       = 1 - 3 ms, Fast to Slow.         (3 ms.)
       Undershoot = 20%, all speeds.                (none)
       Overshoot  = 20%, all speeds.  Small signal to large.(7% Fast, 17% Slow)
       Recovery   = 100 ms Fast, 400 ms Med, 1.4 sec Slow (30ms Fast, 0.6s Slow)

RECIPROCAL MIXING -phase noise
    Measured with the radio offset from a crystal oscillator by the amount 
    indicated and adjusting the input level to raise the noise floor 3 dB.

            Offset         IC-756              IC-765
    
            3 kHz       -56 dBm, S9+16      -44 dBm, S9+38
            5 kHz       -48                 -37
            10 kHz      -39                 -30
            15 kHz      -34                 -26
            20 kHz      -31                 -23
            50 kHz      -22,  S9+52         -16,  S9+65

    S meter readings above are for the indicated tone level on the respective 
    radios.

POWER OUTPUT-power supply set to 13.8 VDC

            Band        Tuner off       Tuner on
            1.8 MHz      98 watts       90 watts
            3.5         100             93
            7.0         101             95
            10          102             95
            14          102             93
            18          103             95  
            21          104             92
            24          103             91
            28          103             87  
            50           85             77

KEYING - tested at 40 meters, no frequency effects noted.

    Rise time = 0.7 ms for the first dot and 1.0 ms thereafter
    Fall time = 3 ms down to approximately 3% , then drops rapidly to zero.
    Delay to RF out, full break in = 6 ms to a 3% pedestal, 16 ms to start of 
    rise.
    Delay to RF out, semi break in = first dot as above, then 6 ms to a 3% 
    pedestal, 10 ms to start of rise.  
    Note: the pedestal level stays constant as the power output is reduced.
    Key up to RF off = 0, starts fall time immediately.

    There is a pronounced dip or undershoot in power output approximately 75 ms 
    after key down to about 60% of full power at 100 watts and substantially 
    lower for lower power outputs.  The good news is, it is virtually 
    unnoticeable over the air.

    The keying is shortened as the delay to the rise and from  the fall are not 
    the same.  It is quite noticeably light.  At 40 wpm the duty cycle of dots 
    is 40%.  The so called ?weight control? for the built in keyer only adjusts 
    dash length, not both dots and dashes as it should. The side tone is a true 
    representation of the key down periods.  There are some key clicks in the 
    side tone (not terrible) which are  more noticeable during full break in 
    operation. 

SPEECH PROCESSING -average power increase due to processing.
    Peak power output is 100 watts.  White random noise is put into the mike 
    input and the level is adjusted for an ALC reading according to the 
    instruction manual.

    Average power output, no processing   = 17 watts    (17 watts)
    Average power output, with processing = 23 watts    (42 watts)
    Average power increase                = 1.3 dB      (3.9 dB)

COMMENTS - Good Features.
    1. Sensitivity is excellent and compares to the best radios.
    2. Selectivity is good if cascaded filters are used.
    3. AGC performance is excellent.
    4. Dynamic range is very good.

COMMENTS - Could use improvement.
    1. Phase noise performance is  not as good as it could be.
    2. CW keying needs improvement.  Side tone clicks should be eliminated.
    3. The audio compressor is not adequate for competition.
    4. The AGC is too flat.  A few dB of tilt helps when picking signals out of 
       a pile up.

This radio comes very close to being a competitive contest radio, but in my 
opinion it doesn?t quite make it.  An RF speech processor, improved keying and 
better close in phase noise performance would make the difference.  There are a 
lot of us out here that would pay a bit more to get that kind
of performance.

George Cutsogeorge, W2VJN@rosenet.net
Umpqua, Oregon
http://www.qth.com/topten











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>From Joe Subich" <W8IK@ibm.net  Thu Mar 13 02:29:49 1997
From: Joe Subich" <W8IK@ibm.net (Joe Subich)
Subject: [CQ-Contest] Log Windows
In-Reply-To: <c=US%a=_%p=TCI%l=TCI/HERMES/00017C46@brahms.tci.com>
Message-ID: <199703130232.CAA167885@out1.ibm.net>

In <c=US%a=_%p=TCI%l=TCI/HERMES/00017C46@brahms.tci.com>, on 03/12/97 
   at 02:28 PM, "Fatchett, Mike" <Fatchett.Mike@tci.com> said:

>I saw an earlier post that the developer of the software may start
>selling it on his own.  Any confirmation of this.  Anyone know how to
>contact them?

Yes, LogWindows has returned to direct marketing following the failure 
of AEA.  Check the LogWindows Home Page at: 

         http://www.hamhead.com/~ira


73, 

   ... Joe Subich, W8IK  ex-AD8I
       <W8IK@ibm.net>
       <jsubich@ibm.net>


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