Category: Technical

74HCT240 transmitter

I’m working on a new QRP transmitter based on the 74HCT240 octal buffer, the circuit has been described on many places, even in ARRLs books.

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Video: Measuring antenna return loss with SDR receiver

By virtue of how they present information, SDR receivers can also function as spectrum analyzers. Receivers from SDRplay and Airspy blur the line between receiver and test equipment in a way that is beneficial to hams who don’t have thousands of $$$ to spend on dedicated equipment. SDRplay will soon be releasing a dedicated spectrum analysis program for use with their receivers. But no need For the full article

Need help with transmitter coils

This is embarrassing to ask, but I need help with some transmitter coils. (I guess even after 41 years in the hobby, I’m not too old to need an Elmer). I have a homebuilt 6AG7 – 807 CW rig on 80m and 40m that uses plug-in coils for the oscillator and PA tank. The rig is based on an article in a book which gave the 80/40 coil specs, so I just wound what they suggested and tweaked them as necessary. I just acquired a nice handful of FT-243 crystals for 30 meters

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An fm transceiver from an unexpected chip

The Si47xx series of integrated circuits from Silicon Labs is a fascinating series of consumer broadcast radio products, chips that apply SDR technologies to deliver a range of functions that were once significantly more complex, with minimal external components and RF design trickery
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A recent article on the popular Hack-a-day website showed readers how to build a very simple ADS-B ‘Cantenna’ to use with their SDR USB dongle radio

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Yaesu ft-225RD Mode Issue

I just got a yaesu 225rd all mode 2m transceiver and right now it appears to only work in CW mode. If I am in any other mode besides CW (LSB, USB, AM, or FM), the display just reads 14 to the far left and the VFO light isn’t on. Also there is no output through the speaker on these modes no matter where I turn the squelch or AF gain. I have attached a picture of what the rig looks like when it is having this issue. Do you think something could have come loose when it shipped or do I just…

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