Double Sideband Novice 10 - Part 2

In Part 2 of the Novice 10 Double Sideband Radio Project we make some DSB and develop the receive section and listen to some stations on the band.

[@gretalaube91]

Woo! 10 meter walkie-talkie? "Space Patrol DSB"!

[@MIKROWAVE1]

Playing with the 1 dollar BD139 audio bipolar transistor at 28 MHz and whoever figured this out that this thing could make power at HF has to be commended!

[@Dazzwidd]

At 28MHz it can? Now that's a revelation

[@m0dad]

A brilliant project for 10m and following this with great interest. Great to watch the construction in stages. 73...David M0DAD

[@MIKROWAVE1]

I need comments and guidance from many of you who have done a lot of work with QRP phone projects.

[@jamesmoffat9754]

I like your thoughtful approach to the design process. A PCB would help less experienced builders achieve success.

[@nandrews8412]

Not only that but a ground plane or double ground plane can greatly improve performance and cure some RF bugs.

[@CARL557511]

Love the microphone !! I have only had success with the AN612 balance modulator chip (getting) hard to find. I've used this chip in connection with the tx mixer in a cobra 29 cb to achieve dsb but I I had to bias the bases on the driver and final amp transistors. It was a pain but it worked ok. Good job on all your projects!!! They work!!

[@PapasDino]

So when you said "Peter Parker" I filled in the next with "Spider-Man"...the comic book collector in me without thinking took over! ;-) 73 - Dino KLØS

[@Dazzwidd]

This is a fantastic introduction to this. I liked your trial modulator experiment. I think that a one transistor amplifier stage would definitely be beneficial for the microphone, you play with the gain to get what you want through the emitter degeneration resistance. I'd probably go one step up and do a two transistor dc coupled preamp with global negative feedback which rolls off the high audio frequencies steeply. Love the strive for simple circuit principles though

[@mikesmuseum]

Son of Beach! 😂😂😂 I like that!

[@acestudioscouk-Ace-G0ACE]

I had seen Peter Parker's videos on double sideband and this build is fascinating me. I'm hoping my very basic skills may be up to building it and no high voltages for me to get anxious about. Thanks Mike!

[@MIKROWAVE1]

Yes 12V, but already I have managed to smoke two transistors and pop a fuse in my Fluke!

[@acestudioscouk-Ace-G0ACE]

@@MIKROWAVE1Oh dear!

[@TheGmr140]

Nice dsb rig 😊😊

[@arnoldschmidt2753]

I have no knowledge about anything but the basic physics of frequency spectrum other than what I learned from physics 13,23 while I was in high school. So now you have a non critic watching your channel. But I wish upon you encouragement and success in your study.

[@Steve-GM0HUU]

👍Thank you Mike. As usual, very interesting. I like the common base RX amplifier. I built a single stage common base amplifier for 10m (2N3904). Mine did not have a tuned circuit and gave only about 15dB gain. Although not bad for a single general puprpose transistor, maybe not quite enough gain for 10m. Shall maybe try adding your tuned circuit. I may even splash out on a toroid core 😂.

[@amilion01]

Great project, what is the inductance value of the NP filter in the receiver RF amplifier : between the common base first transistor and the buffer ?

[@migsvensurfing6310]

Very good performance,

[@Dazzwidd]

I was thinking you could use diode based solid state TR switching easily enough. That way it can be automatic with no clunky relay

[@ornithopterindia]

👍Thank you sir.

[@gd2329j]

Using just a LM386N you can get over 70dB +of gain . A article in PW by JF10ZL has more information . But its just a 100uf cap & a resistor string hanging of pin 1 . The resistor is setting the gain & a 820R is around 40 dB 6R2 is 74 dB if you can keep it stable that is ….........

[@JackKC8QPG]

Great detailed explanation of the thought process . You could call it "Son of Peter Gunn" You could pirate the great Henry Mancini sound track.

[@Chris_Grossman]

Did you use any lacquer or nail polish to hold the turns in place on your transformer?

[@MIKROWAVE1]

The center tap usually stabilizes the ends. The broadband transformers are ridiculously stable. The high Q transformers on powdered iron used in military radios like the GR106 were repeatedly soaked in Q Dope and bake stabilized over days. You can do as far as you want.

[@gd2329j]

Maybe a BS170 / 2SK3476 type PA . I haven't looked if that works at 10M but some power fet will ! Playing with the pre driver transformer could save one stage . All you need is correct drive voltage into the pa ….

[@MIKROWAVE1]

Yes! The RD06HHFI and other RF capable Mosfets are tempting. I managed to do it with an old school CB Narrowband approach with the BD139 as a driver and 2SB2078 Final.

[@SergiuCosminViorel]

You a priest now?

[@MIKROWAVE1]

After you reach a certain point in your radio education and experience, clergy is really the final step that the RF designer can take! Plus if this thing works, it will be a miracle.