Ne602 direct conversion receiver circuit under rf receiver. In searching my parts drawers i discovered an fm receiver kit which i had bought about 10 years ago but had not yet built. The local oscillator is the original part of my project. I was just getting back into ham radio, getting married and starting a medical practice so i was more of am observer, not ready to. If you are a minimalist and like to mess with small electronics projects then you should meet the sa602 chip. The direct conversion receiver, also called zeroif receiver, is similar to the superheterodyne in that a local oscillator and mixer are used, but in this case the if frequency is zero. Direct conversion receivers function by directly converting. Yet direct conversion receivers have also earned a reputation for a set of particularly obnox. The signetics sa602 ic is a double balanced mixer and tunable oscillator in one shot. The schematic, below, is relatively simple, but to make things easier i have broken it up into 5 sections, outlined by the thin blue blocks superimposed over the schematic itself. With a conventional mixer, youd have to add a tuned lc circuit to eliminate the.
Ne602 or ne612 double balanced mixer electronics tutorials. Worst thing to ever happen to direct conversion circuit topology was widespread adoption of the ne602 in hobbyist designs in the 80s and 90s. Increased pressure for low power, small form factor, low cost and reduced bill of materials in such radio applications as mobile communications has driven academia and industry to resurrect the direct conversion receiver. Oct, 2014 simpler singlesignal direct conversion receivers. When 4sqrp brought out a version of the david cripe nm0sdesigned hipermite filter, i noticed that it could be configured to give up to 50db of gain. Ever since direct conversion receivers became popular in the late 1960s, authors have raved about the clean direct conversion sound, like a window on the band.
Figure 5 shows three singleended output configurations and a balanced output. All that is needed to make a complete highperformance direct conversion receiver is an. This receiver is built to show how good a direct conversion receiver can be. Like many others, im sure, my next thought was that it would make the process of building a simple direct conversion receiver even simpler. It eliminates a lot of the problems with superhets, such as alignment, the birdies, and the crystal filter. The main part of a direct conversion receiver is a single mixer stage. Nic hamilton, g4txg, has underlined that considerable care needs to be taken in the design and construction of directconversion receivers to obtain a performance, on the higher frequency bands, truly rivalling that from a ne620 superhet improving direct conversion receiver design radcom, aprilpp this cannot be undone. Direct conversion receiver an overview sciencedirect topics. This circuit has not been tested but a very similar circuit was successfully built for a recent a2 project. Life after death experience nde with steve gardipee, vietnam war story one of the best ndes duration.
The receiver figure 1presents the schematic for the dc receiver. Feedback capacitors between a, b and 0v will be around 150pf for 9mhz. Many people are surprised at the nice clean sound of a direct conversion receiver, compared to the superhets they are used to. All the gain is at audio, so they can suffer microphonics and power line hum issues. I have used both ne602 and ne612 interchangeably and not noticed any obvious difference. Jan 06, 2019 ne602 pdf posted on january 6, 2019 by admin the ne is an integrated circuit for processing of signals, such as in the transmission of radio the ic belongs to a family of the following ics. Ive built a couple ne602 based dc radios, and they work fine for casual use.
The ne602 contains an lo and dou blebalanced mixer in an 8pin dip, as shown in fig. Tasic sinisatasa yu1lmqrp first receiver i was ever built for hf was tube receiver without rf. Jul 26, 2012 ne602 based 40m cw direct conversion rx with hipermite filtering from 4sqrp aa7ee. That said, the effects mentioned in the article you. This is important in direct conversion receivers, where the lo frequency is so close to that of the input, that the two cant be isolated by. High performance single signal direct conversion receivers. Ne602based 40m cw direct conversion rx with hipermite filtering from 4sqrp aa7ee.
Those were very simple units using a ne602 and an lm386 audio amp. Its not a monster of performances but it provides some gain, its cheap and easy to find. In this page well discuss the image problem in ifbased receivers, and well also look at an alternative approach that eliminates this complication. Direct conversion receivers are the most popular qrp receivers for the reception of ssb or cw modes. Ne602 mixer, is designed to cover the frequency range between 7. Very high performance image rejecting direct conversion receivers or how can an 11 ma receiver out perform the worlds best. A local oscillator is mixed with the frequency one wants to receive and the product of this mix is the sum of the two sidebands around this frequency. The short answer is no, it will not ruin your listening experience. Tasic sinisatasa yu1lmqrp first receiver i was ever built for hf was tube receiver without rf amplification called ov2. Modern qrp rigs and the development of the qcx cw transceiver kit. A directconversion receiver is similar to a superheterodyne, except that the lo and rf frequencies are. In the previous page we explored benefits associated with the use of an intermediate frequency if. Modernization of qrp radios and development of the qcx.
Many popular radios, including the elecraft kx1 and any number of direct conversion receivers see under ne602 lm386, use them to good effect. Jun 01, 2001 on the direct conversion receiver a tutorial. Building a frequency converter is easier now than its ever been because of a new iic, the signetics ne602. The sa602 chip is a mixer with a builtin local oscillator. Nov 14, 2015 i have had success with using cmos switch ics 74hc4051, 2, 3 etc as direct conversion receiver mixers. I no longer had the general coverage receiver i had used that last time i checked the calibration. Note that input impedance of ne602 is around 1k5 so do not connect to the top of a tuned circuit but tap down. I find them to be a lot more predictable and less prone to overloading than for instance ne602 612 designs. The guaranteed parameters of the sa602a make this device particularly well suited for cellular radio applications.
It is a through hole kit that uses the popular ne602612 mixeroscillator and an lm386 audio amplifier for ear buds or a small speaker. Receiver build this simple receiver and bridge the gap between regenerative and direct conversion receivers. Weak input signals cannot be demodulated if the receiver noise within the demodulated bandwidth is larger than the received signal itself. From vision to reality 4 may 2015 receiver sensitivity receiver sensitivity is a measure of how well it can recover and process very small input signals. Pg1ns ham radio site multiband hf projects receivers.
Renaissance of hf dc direct conversion receivers part1 dipl ing. The cost of direct digital synthesis dds is falling rapidly, and many ofthe dds chips offer two outputs 900 out of phase. The values for other frequencies and the tunable version will. It is intended for high performance, low power communication systems. Here is another circuit design from cliff donley, k8tnd he calls lucky strike. A much better indication of the poten tial for highperformance directconversion receivers is the excellent design by lewallen, an optimized qrp trans ceiver. The availability of ics, improves their performance, and reduces parts count, making them simple to build, and easy to use. Googling it should reward you with plenty of circuit ideas. Direct conversion direct conversion utilizes only a single mixer, straight from rf to baseband audio. Superheterodyne, 1or multi conversion, receivers were invented in 1917 and were followed by the invention of the homodyne, or direct conversion receiver, in 19322.
Progressive receiver design direct conversion receiver. Despite the wellknown drawbacks of regenerative receivers, the elegance and simplicity of the regenerative detector is still appealing. A direct conversion short wave receiver is used as a laboratory capstone. The superheterodyne receiver has been the staple of most receivers for the last 90 years due largely to challenges in implementing a direct conversion receiver. The ne602 is a lowpower vhf monolithic doublebalanced mixer with input amplifier, onboard oscillator, and voltage regulator. Jul 27, 2012 when 4sqrp brought out a version of the david cripe nm0sdesigned hipermite filter, i noticed that it could be configured to give up to 50db of gain. Ne602 application note ne602 philips double conversion narrow band fm receiver 10. The following article appeared in radio electronics, april. While were on the topic of direct conversion receivers. I love the sonic impact of a welldesigned direct conversion receiver. The rest of audio amplifier is common to other direct conversion receiver. Very high performance image rejecting direct conversion receivers. I had a couple of vectronics direct conversion receiver boards that a friend had given me a few years ago. This permits direct output termination yet allows for balanced output as well.
Lets get into the nittygritty of the new direct conversion receiver. Jun 10, 20 compared to the ne602, the tda7000 chip contains a simpler oscillator circuit and mixer which i realized could likely be used in a shortwave direct conversion am receiver. Each output is connected to the internal positive supply by a 1. I wouldnt recommend an ne602 for a 40 meter receiver, and even with a diode ring, you may need a. Ne602based 40m cw direct conversion rx with hipermite. Ne, sa, ne and sa it is widely used in amateur radio applications, i. A five pole lc filter with 50 ohm output termination was used at the output of dds. Block diagram of mixer output circuit used in direct conversion receivers. This is a single chip superhet receiver with an intermediate frequency of zero hertz.
The phasenoise performance of lowcost dds chips is not good enough for a highperformance direct conver sion receiver, but that will change in the future. The image frequency, a potential problem in the superheterodyne, coincides with the desired signal, so it is no issue in this. Direct conversion receiver cleaner sound than a superhet avoids superhet alignment issues no unwanted mixing products birdies main disadvantage. Im always looking for a better way to implement armstrongs brilliant design. Image rejection and directconversion receivers selected. It is a sensitive direct conversion receiver kit that covers the 40m band for cw or ssb reception. The sudden direct conversion receiver was described by rev george dobbs, g3rjv in sprat number 58, back in 1989, and has proved to be a popular little receiver, for which a. Or how can an 11 ma receiver out perform the worlds best. Oct 28, 2015 to get good stability on higher amateur hf bands and to keep simplicity of direct conversion receiver, the receiver circuit was redesigned and a ad 9850 dds vfo with at mega 328 chip control having band switching output and 16.
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