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Sunday, February 26, 2023

First QSO with the High-School Receiver -- 100 mW to Dipole. (with videos) -- Homebrew to Homebrew!

Alan W4AMV in Raleigh NC

Dean KK4DAS and I have been working with a local high school.  The students are building a direct conversion receiver for 40 meters.  

We've been giving out prizes for the first team to complete each stage.   I wanted to give one of the teams a little oscillator that could b heard with their receiver.  So this morning, using a 7040 crystal from the AF4K (SK) company, I threw together a one transistor oscillator.  It has just 8 parts, including the key:
I had a low pass filter in the antenna tuner.  The antenna was a low-to-the-ground 40 meter dipole.  The transmitter was putting out around 100 milliwatts.   

N2CQR's Ten Minute Transmitter

The Reverse Beacon Network showed that I was getting out quite well: 

Then I thought, wait a second, let's make a contact with the prototype high-school direct conversion receiver.  

With the receiver hooked up, I again called CQ on 40 CW.  BOOM!   Very quickly Alan W4AMV in Raleigh NC  came back to my call.  Wow!  That's 222 miles.  And a quick check of QRZ.com revealed that Alan is a homebrewer.  Then Google reminded me that his work has been featured on the SolderSmoke blog.    TRGHS. 

I was so excited during this contact that I almost forgot to film it.  But I did manage to get some short clips of the QSO in progress.   You have to listen carefully, but you can hear our calls in there while Alan is transmitting (listen for the lower tone): 

And in this clip you can watch me transmit using the 10 Minute Transmitter: 

UPDATE (Feb 27 2023):  I asked Alan about the rig he was using:  "A PLL EXCITER DRIVING A PAIR OF FETS PUSH PULL ABT 50 w to an inverted L at 55 feet. The Rx a single conversion 9 MHz IF and it is connected to an active antenna in the trees out in the woods abt 25 feet up. Uses an automotive whip antenna about 3 feet long. "

Alan's Rig

This little contact is a reminder of the fun that can come from using simple, homebrew, QRP gear.  It is really amazing that the very first contact with this receiver was with another homebrew station.   This all reminds Dean and me of something we have been telling the students:  the little DC receiver they are building is not a toy -- it is capable of being used in real, long-distance contacts.

Thanks Alan!    


  1. The kids here and I have been having a blast with our little 20m Rockmite for similar reasons. Especially when we get out away from town, we make QSOs across the country on a simple half-wave dipole. It's a lot of fun.

  2. How did the students react to a reply being heard on their receiver?

    1. This contact took place on Saturday morning, so we haven't had a chance to tell the students about it. We will tell them about it in our next meeting. I will bring the transmitter with me. It is not heavy! 73 Bill

  3. Schoolkids making direct conversion receivers, and learning about crystal-controlled HF oscillators? This is marvelous stuff, and I'm encouraged to hear of this.


    1. And Dave: We were all very pleased by your return to the ham radio blogosphere. You were missed! 73 Bill

    2. This is really great Bill! Young people learning about the magic of radio. They are going to be so thrilled to get a reply on this humble design. Great job! - Steve M0ECS, Lincoln, UK

  4. Hi Bill. Yes I live the excitement of the first QSO on a newly completed radio.
    It's a great and very satisfying moment.
    I hope the students at the school the same feeling I do.
    Good luck to them all.

    De HS0ZLQ /G0MIH.


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