We are MAKERS, so we should build our own radios!

[wandrson]

To get more people started with building their own radios I am going to be offering a series of classes. In each class you will construct (from scratch, no kits) a radio for the 80M amateur band. By the end, if your diligent, you should have the skills to build a radio for any of the HF bands and any mode,

We will start with building a morse code transmitter, which is a repeat of a few classes that @zmetzing and I taught last fall. I plan on talking a little about the process on this thread and hope this encourages people to try their hand at these classes. Since the transmitter we build has a permenantly attached dummy load, you don’t need to have a HAM license to take and build any of this.

So starting with a direct conversion receiver, we have a total of five blocks in its design:

We will be starting with the block on the right, and work our way left, skipping the local oscillator (LO). The LO will be the last since that module will have multiple options, including an Arduino with digital frequency display…

I have already created the first two; audio amplifier & product detector, and shown those on the Show and Tell thread. Yesterday, I modeled the third module; a band pass filter, in LT Spice to verify the performance of the design and built it this morning.

So this afternoon, I was modeling the fourth module in LT Spice. This is a broadband RF amplifier that will function as the receiver’s front end.

So this is what I have built so far, I plan on having a working radio soon and will display this in Electronics during open house to represent the Amateur Radio special interest group.

[Josh_Melnick]

lets do it!

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[Bill]

@Josh_Melnick

lets do it!

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dddddddddddddddddddddddd

Don’t you mean

dit dah dit dit
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dit dit dit
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dit dit
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[artg_dms]

Where’s the math??
Surely you did the equations to find the component values before doing the sims.
On a more serious note - how do the sims compare to the actual ckt?

For those that might be interested, LT Spice is now on the jump srvr.
Thank you Stan.

[wandrson]

I have not built the broad band rf amp, yet so I don’t know how they compare.

For the band pass filter, when built with the values shown in the schematic the filter response was shifted up from the simulation by a hundred or so kilohertz.

Most likely this was due to stray capacitance and inductance in the circuit. By reducing C2 and C4 by about 30pF, I was able to get the band width I wanted. The upper frequencies are not matching the simulation, but again that is likely due to stray capacitance and inductance not in the model.

[wandrson]

@zmetzing

Don’t believe everything the simulator tells you.

Dang, your telling me I can’t trust the simulation of my energy adjusticator when it says, I get three orders of magnitude more out then I put in?

[artg_dms]

Agreed. Some of the sim results are amusing. Working on Vreg ckt that has 3 term reg w/ pass ckt. Replaced diode brdg rect w/ LT’s active brdg and sim went nuts. Did you know you can pass 90 A through a 15 A pass transistor? Still trying to sort this one out. May have found a sim anomaly…

[wandrson]

I finished assembling the broadband RF amplifier I described above.

Which means we have four of the five modules assembled

With the addition of a signal generator in the lab to fill in for the as yet unbuilt variable frequency oscillator, this is a complete radio. I plan to test it next week with the output from a Michigan Mighty Mite in preparation for the class on the 13th.

https://calendar.dallasmakerspace.org/events/view/3488

If you want more information on these designs, I would suggest following the blog of the man who designed them.

N6QW -- Left Coast Radio

[Josh_Melnick]

ok thanks I plan on taking the class, I tried to register today only to find out I had already.

[wandrson]

@zmetzing

The class should be a good one.

First, thank you!

This will be multiple classes, one for each module. At a minimum you will need to attend five classes (one for each module) to have a complete radio receiver.

[kbraby]

I really want to get these and the mighty mite into my schedule. Of course I really need to learn Morse code along the way, or I can’t even use the transmitter simply because I can’t ID myself.

[Josh_Melnick]

if the radio isn’t working are you still going to have the class?

[wandrson]

The radio works. I will need a few weeks to prepare the class material for the first module, then order the parts, at which point I will put the class on the calendar.

[wandrson]

So, the company in India that sells the BitX40 SSB radio kit has started selling their Raduino product separately. This is an Arduino nano, 16x2 LCD, and an SI5351 VFO/BFO board all in one package for $25 delivered.

As such, I will not be teaching a class on how to assemble this module in the radio, but rather cover only how to program it. If you want one they are extremely cheap for what you get. The company has proven reliable the 3-4 times I have ordered from them.

http://www.hfsigs.com/buy_paypal.html