Last week I stumbled across the Elecraft 2 tone oscillator kit and decided that it was something I could use. The Marconi RF generator I use on my tech bench is great, but can only produce a single audio tone. I'm sure most realize this, but you need two tones that are not harmonically related to test the linearity of a SSB signal using a scope or other equipment. This generator produces the standard 700/1900 Hz tones.
The Electraft kit can be found here: Elecraft Mini-Module Kits. The price is $69 + shipping.
This really is a "kit"; nothing is pre-assembled. All of the components arrive in a static bag and are loose. The first thing I noticed is that the instructions are excellent and detailed. They have complete specifications, parts inventory, step by step build instructions, test procedures, O-scope & spec analyzer print screens, and circuit schematic. The board has excellent, clearly readable markings. Here's a pic of all the components with just a few resistors attached:
The first thing you have to do is install all of the various resistors. Even though they come loose, the instructions tell you the color band codes for each resistor along with the install location. I double checked them anyway with my multi-meter just to make sure I was installing the correct resistor in the correct location. Here's a pic with all the resistors completed. One thing that is interesting to note in this pic is that you can clearly see how well the board is labeled for the installation.
Here is the completed project (battery is not included in the kit).
Even though it doesn't come with an enclosure, the unit does come with rubber feet to get the board up off of your work surface. In the picture you can see the on/off switch on the bottom left. Right above is the output and balance POTs (more about that later). On the right by the battery there are two jumpers blocks at the top and bottom of the board. These disable each tone if you move the jumper.
I hooked it up to a rig today to see how well it works. This is where my first complaint comes in. The AF output is a female RCA. All of my other test equipment and cables are BNC (except for the watt meter). I'm willing to bet that others will have this complaint, also. This isn't that big of a deal, so I just picked up an RCA/BNC adapter at radio shack.
It's important that you read the instructions to set the output level and tone balance properly. The manual outlines this procedure very well. It's pretty easy to do this, but this also leads to the second complaint: The jumpers for this purpose. To set the output levels properly, you have to disable each tone and look at your O-scope or watt meter. It would be much better if they just used a switch for each tone instead of the jumper. At a minimum, they should have moved them away from the battery, as the average person's fingers are too big for their location to be convenient.
Those are really my only two complaints. It would be really easy to put this whole thing into a project box if you desired. You would just have to get some different pots that you can case-mount and extend the jumpers and power switch. I sort-of wish they offered this configuration as an option. Even though it's a simple build, it's still fun to put together a little projects like this. The whole thing took me about 45 minutes to complete. I would recommend this little kit to anyone wanting a simple little device that will provide a little more accuracy to testing your station's SSB output.
The Electraft kit can be found here: Elecraft Mini-Module Kits. The price is $69 + shipping.
This really is a "kit"; nothing is pre-assembled. All of the components arrive in a static bag and are loose. The first thing I noticed is that the instructions are excellent and detailed. They have complete specifications, parts inventory, step by step build instructions, test procedures, O-scope & spec analyzer print screens, and circuit schematic. The board has excellent, clearly readable markings. Here's a pic of all the components with just a few resistors attached:
The first thing you have to do is install all of the various resistors. Even though they come loose, the instructions tell you the color band codes for each resistor along with the install location. I double checked them anyway with my multi-meter just to make sure I was installing the correct resistor in the correct location. Here's a pic with all the resistors completed. One thing that is interesting to note in this pic is that you can clearly see how well the board is labeled for the installation.
Here is the completed project (battery is not included in the kit).
Even though it doesn't come with an enclosure, the unit does come with rubber feet to get the board up off of your work surface. In the picture you can see the on/off switch on the bottom left. Right above is the output and balance POTs (more about that later). On the right by the battery there are two jumpers blocks at the top and bottom of the board. These disable each tone if you move the jumper.
I hooked it up to a rig today to see how well it works. This is where my first complaint comes in. The AF output is a female RCA. All of my other test equipment and cables are BNC (except for the watt meter). I'm willing to bet that others will have this complaint, also. This isn't that big of a deal, so I just picked up an RCA/BNC adapter at radio shack.
It's important that you read the instructions to set the output level and tone balance properly. The manual outlines this procedure very well. It's pretty easy to do this, but this also leads to the second complaint: The jumpers for this purpose. To set the output levels properly, you have to disable each tone and look at your O-scope or watt meter. It would be much better if they just used a switch for each tone instead of the jumper. At a minimum, they should have moved them away from the battery, as the average person's fingers are too big for their location to be convenient.
Those are really my only two complaints. It would be really easy to put this whole thing into a project box if you desired. You would just have to get some different pots that you can case-mount and extend the jumpers and power switch. I sort-of wish they offered this configuration as an option. Even though it's a simple build, it's still fun to put together a little projects like this. The whole thing took me about 45 minutes to complete. I would recommend this little kit to anyone wanting a simple little device that will provide a little more accuracy to testing your station's SSB output.
