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73 de SV1JRF
George

Popular posts from this blog

Delta Loop Antenna 10m-11m + Balun 4:1

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As i really enjoy using the 10m band and sometimes the 11m band to talk with friends around Athens, it came as a must of constructing a new antenna. Also i wanted to do this because i have an Albrecht 5890EU ,which operates in these frequencies and i didn't have an extra antenna to operate it. Due to the lack of space in my QTH(that is why i 'm using the long wire + UnUn antenna), i was trying to find a solution of a vertical polarization antenna ,with high efficiency and as small as possible.
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FM Band notch filter with coax cable

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Usually the case is that we are close to a radio station transmitter(for repeaters) transmitting with some kilowatts, or near an airport and this is causing problems!!! In such case you need to have a filter cutting out these bands. The filter described here is for the VHF Band (2m) and it is really easy to construct. You will need the following: Notch filter block diagram Coax cable (good quality LMR-240,400,600) T connector ,bnc or n-type Signal generator & spectrum analyzer so you can tune your filter to the desired frequency A plastic electrical box to use it as enclosure (if you wish) I personally wanted to create a Notch Filter for a near by Radio Station that transmits on 94.5Mhz. So after some quick calculations: The Wavelength of 94.5Mhz is 3.17m LMR-240 VF = 0.84 So for the 1/4λ coax stub: 1/4*3.17*0.84 =  0.6657m = 66.57cm For the 1/2λ coax section between the 2 stubs: 1/2*3.17*0.84 = 133.14cm = 1.33m Personally i constructed a one st...
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