Practice some multiple choice questions on resistors

 


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What is LMR SDR?

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See also (new post):   Standalone Versions of LMR SDR!  I have been hearing about LMR SDR during discussions among homebrewers for the past few days on 40m. Thought of learning a bit about it and my web searches told me that some of the persons behind the development of LMR SDR are YE3CIF, UT3MK and F5NPV. F5NPV has given detailed descriptions about homebrewing LMR SDR on his webpage, including videos. Even though I did look at the pages of YE3CIF and UT3MK, they seem to be in regional languages. I could not find the expansion of LMR on those pages, though I presume that it would stand for land mobile radio. LMR cables which many of us use were initially designed for land mobile radio. SDR stands for Software Defined Radio like my FT-710, which uses software to do many of the functions done by hardware in the conventional superheterodyne radio receiver . It is interesting to note that LMR SDR covers from 160m to 10m band, that is the whole amateur radio HF bands. There are a...
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Have you heard of zBITX?

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 Well, I had not heard till I read the program schedule of LARC-7 today. Most of you would be familiar with uBITX which has gone up to version 6. Some of you would be aware of sBITX, which is quite an advance over uBITX. Almost daily I am meeting a new uBITX user on the band, most of them using additional linear amplifiers. That made me join the BITX group on groups.io , where I am getting messages from uBITX and sBITX users from all sides of the globe. Still I was not aware of zBITX and that made me look around and came across two references. One was the video of a talk by VU2ESE at QRP ARCI . Another was an email in the BITX groups.io which was citing the former. zBITX is a new transceiver from VU2ESE based on Raspberry Pi Zero for 20W, having CW skimmer and FT8 modes in addition to the regular SSB mode and waterfall display which the sBITX also has. zBITX is quite small, just 3" x 3" x 1.5" in size. It is a Raspberry Pi Zero based 20 W software defined radio which h...
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Homebrewing a Slim Jim Antenna

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 Slim Jim antenna, as the name implies, has a very slim design and hence very little wind loading. JIM stands for "J Integrated Matching" as it uses a J type matching stub. Slim Jim antenna was described by Fred Judd, G2BCX in 1978. The antenna has a lower takeoff angle and hence reported to have better performance than 5/8 wavelength ground plane antenna. People have made it using half inch copper pipe, ladder line and many other options! Approximate gain in the horizontal plane has been mentioned as around 2  dBi. Slim Jim antenna should be insulated from the antenna mast with a 'free space' of at least quarter wavelength. Antenna itself can be supported on a PVC pipe. Though it can be made for any band, it is quite popular as a 2m VHF antenna which can be made easily with good performance. It is almost like a vertical asymmetric folded dipole with a gap between the half wave and quarter wave regions. The exact feed points on the long and short parts of the antenna ...
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