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Tuesday, March 12, 2024

Justin's Receiver -- A 40 meter Superhet from AC8LV

FB Justin!  I really like the board that you are using as a base for the project.  And you have some great mentors in Nick and Loren.  

It is wonderful that you have that receiver working.  But I would tweak and peak quite a bit before taking on the transmitter.  Get a decent outside antenna -- even a dipole or a 1/4 wave with counterpoise would be a big improvment.  Like this one:  

And try to square away the grounding on the board (maybe some copper tape from Amazon) and the power supply you are using (I hope it is not one of those noisy wall warts).  When  you are experimenting, it can be useful to power varous stages with 9V batteries -- this is a good way to find out where noise is coming from.  If your AF amp is squealing at 12 volts, you need to break the feedback loop that is leading to oscillation.  Often the feedback is through the power supply.  Finally, try to get that homewbrew crystal filter working -- if the bandpass is uneven, you just need some impedance matching at the input and output.  

Great work Justin!   Keep at it.  73  Bill 


I am sending video and pictures of my 40m  superhet that I built. I have it on the floor in an extra room in the house. The antenna is a stock vhf dipole that came with my rtl sdr which I use as a spectrum analyzer. In one of the clips I am receiving RW7K. I have been working on the station for the past year with help from Loren Moline, WA7SKT through texts when I have a problem. The LO / VFO is from Nick Woods Videos.

Next, I will build an outdoor antenna and the transmitter section. I first started homebrewing at the beginning of the pandemic, but this is by far my largest accomplishment. I would like to thank you and Pete for the soldersmoke videos which have been a great inspiration.

I will send more updates when the transmitter section is finish along with a much longer description of the projects

Thank you

Justin Elliott

Bill, Pete, and Dean 

Thank you for the compliment. Pete, I want you to know, I’m a huge fan and I enjoy the one-liner jokes. I enjoy your contributions to the videos when you’re on Dean. 

Here are pics / videos of my superhet. 

The bandpass filter is a homebrew version of qrp labs design for 40m, I had to add an extra capacitor to get the bandpass where I wanted it. It is 6.9mhz to 7.32mhz. 

Mixer / demods are ade-ask.

The rf amps are kits i bought online, assembled, then used the schematics to replicate. They are the W7OI created and which have been mentioned on the channel

The LO/VFO are arduino driven from Nick Woods (M0NTV) YouTube channel. I believe episode 26

The crystal filter was built for 9MHz, but when I swept it I found the bandpass was saw toothed, so I used a commercial filter that Loren Moline WA7SKT sent. 

The audio amplifiers are a Common Emitter Amp I found on YouTube, I can’t recall the channel and a commercial amplifier, which I can now reproduce as I have the schematics. 

The speaker is a 2W 8 ohm speaker. 


Justin Elliott

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