After spending months on Vienna Wireless Society Makers projects and the SolderSmoke Direct Conversion receiver project I wanted to get back to building a rig just for me! Several months ago Pete, N6QW sent me an ebay listing for a very nice Yaesu VFO module, for only $35. I jumped on it, not knowing what I was going to do with it. The module is complete with reduction drives and dials. It even came with the dial window that proclaims it to be from a Yaesu FT-401B.
Earlier versions of the VFO run on 6V but this one needs 9 to fire up and oscillate. After getting the voltage right it fires right up and tunes from about 9MHz to about 9.4MHz. So with a 5 MHz IF this will make a 20 meter SSB rig. Bill, N2CQR has built two of his Mythbuster rigs using this VFO module and I am following in his footsteps. Like Bill I found the output was too low to drive a 7dBm diode ring mixer so I build a 6dB gain Termination Insensitive Amplifier (TIA) to boost the drive to the required level.
I'm doing things deliberately this time around - I'm starting with the end-layout in mind including placement of all the modules. Its going to be in a homemade plywood case. I'm using copper plumbers tape to provide the ground plane and case shielding. After 5 years of continuous homebrewing I have built up a collections module boards that are just waiting for the right project come along. Bill calls these "boards that could be rigs." I already have the transmit chain built - it is two stages of 2N3866 drivers followed by a Mitsubishi RD16 MOSFET final - which should give me 10-15 wattts or more on 20 meters. This was the transmitt module I had built for my SBITX build before I went to a push-pull final for 25-30 watts. I have the diode ring mixer built (one of several build during the DCR projectg testing.) For the IF I have ordered 5MHz crystals from Mouser and am using 4 TIA boards that Todd, K7TFC of mostlyDIYRF kindly sent me some time ago. I assembed the TIA boards the other night. In addition to being termination insensitive which means that what you hang off the output doesn't load down the amplifier, they are also variable gain - anywhere from 7dB to 24dB by changing a three resistors. I had a 20 meter BPF built that was looking kind of ratty so I build a new one last night - I just used the component values from the QRPLabs BPF filter kit instructions. Tested on the NanoVNA less than 1dB of insertion loss and almost no ripple across the entire band.
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| 20 Meter BPF - less than 1dB of inserstion loss acrosss 20 meters |
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| 20 meter SSB rig in progress VFO, buffer amp and diode ring mixer |
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| VFO and mixer test - 14Mhz RF, 9Mhz VFO, products at 5MHz and 23MHz! |
I have a couple of different ideas for the audio chain - I might use a kit (shocker) from Kitsandparts - as part of my ongoing desire to master surface mount construction. The balanced modulator will be a 2 diode version straight out of Solid State Design for the Radio Amateur. The mic amp will be identical to the electret version I build for the SBITX. The transmit LPF will be a W3NQN filter again with the values from the QRP labs LPF kit instructions.
After five years of building I am finally starting to feel like I know enough to do stuff! Thanks Pete and Bill for all the encouragement over the years.
Dean
KK4DAS
