Ham Radio didn't start with an Appliance Box! Another DCR Example
Another DCR Approach. An Active Mixer.
What was presented in earlier posts and in the m0ntv video was a passive mixer, meaning no gain but an actual conversion loss. The passive mixer takes more drive like 7 dBm (1.414 Volts Peak to Peak) and often can exhibit 6 or 7 dB of conversion loss. You can verify this by looking at the datasheet for the Mini-Circuits ADE-1.
The J310's connected as a Dual Gate MOSFET does have device gain and requires less LO Drive. That was in Nick's video presentation. There are however several active device Double Balanced mixers including the NE602 (and variants like the SA612) and the Motorola MC1496. [In 2023 Nick the Vic might look to adding the Audio Diplexer to the J310 detector to alleviate the BC Band break through. I will keep you posted.]
Many commercial radios (like Ten Tec) of the late 1970's early 1980's used the MC1496 for frequency mixing, as balanced modulators and as Product Detectors. Through hole and SMD versions are still available today for less the $2 for the through hole and less than $1 for an SMD. So, this part is still pocket change.
About two years ago now, I built a MC1496 Direct Conversion Receiver not for the purpose of a DCR but actually as a test bed for a bag of through hole MC1496 IC I had stashed away. The real intent was to build a mostly MC1496 SSB transceiver based on an IF Module found in SSDRA (Scroll Down to the bottom to see that project). The result was so good that this test bed was the basis for an article in the G-QRP Club SPRAT Issue #187.
I have received over 110 requests for the Arduino sketch code and about maybe 15-20% have actually turned into radios. Folks at SPRAT tell me that 110 requests for the code represents a high degree of interest using similar project benchmarks that they are privy to.
The requests themselves are telling in that the requests from US Hams were far less than other countries. The highest number of requests were from the UK. This reflects the 50% of US hams being Tech Class licenses and homebrewing being out of step with the Baofeng UV5. A general conclusion -- more homebrewing going on in the UK!
You can see the project and hear how it sounds below. The MC1496 version uses the same block diagram of the earlier post including the BPF, the RF Amp (2N3906) and the Audio Amp Stage and of course LO. The real difference is the MC1496 in place of the Diode Ring Mixer.
MC1496 DCR
Despite how really good this rig sounds the one issue is (like the Tayloe Detector) that it is not bilateral. But on the other hand, the Motorla datasheets show how to configure the MC1496 as a DSB transmitter. So, a DSB transceiver would require two devices. But given the low cost of the device --a $5 Bill would get you there for all of the DSB Generator parts.
The MC1496 and Audio Amp Stage
The MC1496 DCR
The NE602 has been used in DCR's and there is a host of info on this and typically the naysayers bash the NE602 on its signal handling qualities. But by building in Modules, it would be as NTV did to swap in various modules and thence select the best for your application.
Those who complain, Lack the Knack!
For those who celebrate here is wishing you a very Merry Christmas. For those who don't, Peace be unto you.
