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Improved 134GHz Rx



    Cluster Activity

    Spots per uW band today:
    UK spotter or spotted only.

    Solar data:
    SFI
    76
    A-Index
    6
    K-Index
    2
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    26
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    qui
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    My Weather

    Date:18/11/17 Time:17:25
    Temp:3C
    Wind Speed:2.5mph
    Wind Dir:202deg
    Pressure:1017.29mB
    Humidity:118%
    Dew Point:6.6C
    UKHASnet
    Improved 134GHz Rx

    Improving the receiver:
    Thanks go to Terry G1LPS for ordering some more diodes and boards for us to test :-)
    Firstly i mounted a MA4E1317 diode on a new board and fitted it in place of the current Rx board which was using the suspect DBES105A.
    This proved to be similar in Rx performance but needed a lot less LO drive, comfirming my suspicions about the DBES105A to be damaged.. oh well!

    Now i knew the diode was faulty i replaced it with a MA4E1318 anti parallel diode. Instantly i could tell this was far more sensitive and again I needed even lower LO level to make it work.
    After numerous repeat tests i found that the MA4E1318 diode has around 12dB Rx sensitivity improvement over the MA4E1317.
    I guess this value is also dependent on the phase noise of the 11GHz source.


    Short range tests 50m:
    I setup the Tx (now with a sight fitted to the box and using the 58G Horn) ~50m away from the house and roughly aimed at the Receiver at the back porch.
    The receiver (using the Channel Master 35cm dish) was lined up on the Tx signal and a fully quieting signal in NBFM was heard, initially to find the signal i used an rtlsdr dongle and SDR# software to look in a 250KHz span on the waterfall, then moved to the handheld scanner for monitoring once the frequency was found.
    To align the sight on the tx i used a wireless headset to send the Rx audio to the tx end and then adjusted the cross hairs to match the best signal.


    Longer range test 1.4km:
    I have a clear view to the south from the house, there is gap in one of the hedgerows along a road 1.4km away where i have close to LOS apart from the edge of one tree, how typical!.
    I setup the Tx to point at this location using the sight and then drove there in the van with the rx setup using the 35cm dish.
    Finding the signal was not as easy, but i managed after a few minutes using the sdr receiver. The signal was peaked up and was quieting quite well in NBFM, the weather was not ideal for 134G, Humidity 75%,Temp 15C, Air Pressure 1004.
    There was a few dB of variation on the signal but I think this was probably due to the tree in the path.
    This was a big step forward in signal strength at any distance and would have been extremely difficult without the MA4E1318 Rx diode!!
    S/N was 25dB in ~100Hz Bandwidth, so i thought this would go to 10km....

    Even longer range test 10.3km:
    Failed to find the signal on two outings so far.

    Hopefully more updates to follow when the weather conditions are better.








    Last page added:16/08/17 15:45
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