RF down to the I. As an example, the transmitting mixer is examined to show how the 3. VFO is mixed with 4. The term "heterodyne" refers to the mixing function, where two different frequencies are combined in a non-linear way to generate an output waveform of a different frequency. Keep in mind that the process is non- linear: there is no way to linearly add two frequencies to get a third. An audio "mixer" is an entirely different animal: it simply adds signals together linearly.
If it did output other frequencies, an audio mixer would be considered faulty, and in need of repair. An internal Colpitts crystal oscillator generates the 4. The heart of the mixer uses a circuit known as a Gilbert Cell. Inputs are represented as voltage sources V4 and V A simple Gilbert Cell requires six identical transistors.Lg v530 firmware
Q1 and Q2 accept one of the mixer's input - in our case 3Mhz. The upper four transistors accept the other mixer input - in our case it is from the internal 4 MHz. Colpitts oscillator connected to pins 6. V4 represents a 4 MHz.
V5 represents a 3 MHz. I1 is a DC current source, inside the SE If V5 were zero amplitude, half of I1's current would flow into Q1's emitter, and half into Q2. V5's input voltage unbalances current so that it flip-flops back and forth between the two transistors at a 3MHz.
Another way of looking at it is that Q1 and Q2's collector currents have equal amplitude, but opposite phase. The real mixing action occurs at Q3, Q4, Q5, and Q6. The 4 MHz. Their collectors connect directly to SE output pins 4 and 5. Notice how their collectors are cross-coupled together - part of the magic of double-balancing.Authored by Ian C. Text size: increase decrease. My personal recommendations, thanks.
Philips describe their NE mixer SAA circuit as "a low-power VHF monolithic double-balanced mixer with input amplifier, on-board oscillator, and voltage regulator. It is intended for high performance, low power communication systems. The guaranteed parameters of the SAA make this device particularly well suited for cellular radio applications.
The mixer is a "Gilbert cell" multiplier configuration which typically provides 18dB of gain at 45MHz. The oscillator will operate to MHz.
It can be configured as a crystal oscillator, a tuned tank oscillator, or a buffer for an external LO. For higher frequencies the LO input may be externally driven.
The noise figure at 45MHz is typically less than 5dB. The gain, intercept performance, low-power and noise characteristics make the SAA a superior choice for high-performance battery operated equipment. It is available in an 8-lead dual in-line plastic package and an 8-lead SO surface-mount miniature package ". The later NE or SA is an improved pin for pin improved equivalent so if you can't find a then look for a I am particularly indebted to Philips Components and Semiconductors Australia for their most generous assistance in giving me access to material presented on this page.
Figure 1 - mixer pin configurations. IN a Pin 1 One half of the balanced input. IN b Pin 2 The other half of the balanced input. Ground Pin 3 Output high is about 1.Paraffins and olefins
Oscillator base Pin 6 This is the input to the base of the oscillator transistor. See data sheet for comprehensive explanation. Oscillator emitter Pin 7 This is the input to the emitter of the oscillator transistor.
Note comments about effective supply filtering and bypassing this pin below under "General considerations with using a mixer". Block diagram of the mixer Figure 2 - block diagram of the mixer. Vcc should lie between 4.Ios reject binary
Input signal frequency is typically up to about Mhz, while typically the oscillator will work beyond Mhz. At 45 Mhz signal input the noise figure is quoted as 5. The output impedance of the mixer pins 4 and 5 is 1K5 1, ohms and the mixer needs to see that impedance. The SAA is designed for optimum low power performance. The RF inputs Pins 1 and 2 are biased internally. They are symmetrical.
Red Wave Radio
The equivalent AC input impedance is approximately 1. Pins 1 and 2 can be used interchangeably, but they should not be DC biased externally.Welcome, Guest. Please login or register. Did you miss your activation email? This topic This board Entire forum Google Bing. Print Search. SouthPark Contributor Posts: 28 Country:.
Hi all! Anybody here used these Gilbert cell double-balanced mixers before for generating AM signals? I have managed to generate AM signals with the NE very nicely.
However, I don't know if my set-up is the 'correct' approach even though it is working very nicely. The situation is - the data sheets seem to indicate that the internal differential amplifier circuits are internally biased.
And, usually a double balanced mixer takes in AC voltage inputs. And the data sheet doesn't seem to indicate how we can add some DC voltage level to the low frequency AC input signal eg. For generating AM, we usually need to add a certain amount of DC to the message signal before mixing this combo with the local oscillator carrier signal.
Anybody know if the NE NE actually generates AM by default, without needing us to actually do anything extra ie. And I assumed that it would be necessary to somehow follow some procedure to offset the message with a DC voltage in order to then generate AM.
So far, I haven't found procedures for setting a DC offset on the message. Obviously if the inputs have capacitors on the inputs, we can't add DC before the capacitors.
But we also can't add DC after the AC coupling capacitor - because the data sheets say that external bias should not be applied. Thanks in advance! Just keep the signal levels small, etc. The following users thanked this post: SouthPark. Zero Super Contributor Posts: Country: What's the difference between the NE and NE?
I've looked at the data sheets but they seem the same to me. They are basically the same - now Some time later, the design was refreshed to allow the internal oscillator to operate up to MHz and the RF path to work to MHz. This part was designated the NE The ' was intended to replace the ' But, customer demand for the ' forced Signetics to label some devices as and some aseven though they were now the same part.
This is why the current datasheets list the same specs for both. The following users thanked this post: Zero Thanks very much Alan! This particular situation had me stumped.
I was thinking of deliberately applying a tad of offset at the immediate base input for offsetting the messagebut didn't go ahead with it - due to the data sheet. But I'll definitely try that out now that you kindly indicated it can be done. I'll just add a tad, following your recommendation.Mark Neugebauer from Hamburg, Germany built this circuit and this how it looks.
This is a schematic for a straightforward direct-conversion heterodyne detector, having a tuning range of about 10 kHz to kHz.
It has been optimised for the use of an electret microphone. The current consumption is very low at only 8 mA, which allows it to operate for about hours with a set of rechargeable batteries. When the frequency is set to about 35 kHz, it is even possible to hear the 32, Hz vibrating crystal inside an electronic wrist watch held close to the microphone!
Circuit is still experimental! Circuit Introduction The signal from the MCE electret microphone is amplified by the pre-amp, then it is mixed with a square wave from the variable oscillator and finally low-pass filtered and amplified for headphones.
Microphone The microphone is a special small type of electret. It is able to pick up sounds up to at least 60 kHz and possibly even further although the signal-to-noise ratio gets worse with higher frequency. My microphone draws about 0. By feeding it with a 4k7 resistor, its DC voltage sits around 2. Because of the current-source behaviour of the microphone, the 4k7 resistor will dominate the source impedance.
Pre-amplifier The pre-amplifier has been optimised for low noise and has a rising gain with frequency to compensate for the high-frequency roll-off of the microphone. The amplifying element is the leftmost transistor, which is a low-noise type BCC.
The 'C' indicates a high current gain, which is desirable because it means that the base current will be low. In the datasheet a low noise setpoint has been given of uA collector current for a source impedance of 2k. Since in this case we have a higher source impedance of 4k7 ohms, a lower collector current of uA has been chosen.
The capacitor from emitter to ground has been chosen to give a rising gain vs. Maximum gain about 50 is reached at about kHz. The rightmost transistor is used as an emitter-follower to buffer the signal from the amplifier and provide a low output impedance to the mixer.
This IC is very convenient, because of its linear relationship between voltage and frequency and its low power consumption. The resistor and capacitor values have been chosen such that a frequency can be set from 10 kHz to approx.
The signal of the VCO in the is buffered by feeding it into the internal phase detector. At pin 2 it exits the and is fed into a resistive divider to give a signal of about mV amplitude, suitable for input into the NE mixer.
Mixer A NE is a mixer multiplierwith a low current consumption of about 2 mA. Besides multiplying, it also provides a conversion gain of about 7. Input coupling is done with 10 nF capacitors, which means that frequencies below 10 kHz are attenuated. By multiplying the bat signal with the oscillator signal, an output signal containing frequencies of the sum and difference of the input frequencies, are generated. Low-pass filter and audio amplifier After being mixed in the NE, the signal passes through a simple first-order low-pass filter with a cut-off of about 3.
The volume of the output is set by the volume potmeter, which should be a logarithmic potmeter. Finally the signal is amplified 20 times by the LM audio amplifier and can be used to directly drive a pair of headphones.Ateez reactions
Perhaps a small loudspeaker can be connected instead of headphones, by connecting a 1 uF capacitor between pins 1 and 8 of the LMto boost the gain, but I have yet to try that. For the 47uF capacitors, I used electrolytics watch the polarity! Update Several small changes can be made to this circuit to significantly improve it: Balanced mixer input The addition of a single resistor to the output stage of the preamp makes it into a balanced circuit.
Problems with feedback will be smaller while the total gain of the bat detector is doubled.RadioLabRio Pesquisar o site. Atlas x or x HF Frequency Counter. NE Experiments. Power Meter Digital. RF Power Meter. Atividade recente no site. The NE is an fantastic integrated circuit, complete one chip radio! It can be used too as the 2nd mixer in a dual conversion receiver, and as a balanced modulator.
SE612 Integrated-Circuit Double-balanced Mixer
With addition of the TA, increased simplicity of the circuit, contributing with IF high gain, selectivity and demodulation for AM signals. After the implementation of an good match at input circuit with wideband core T, the sensitivity go to 1. Teste with the loopstick antena can be done in two band, MW and SW. To achieve great performance, was used the cascode preamplifier.
The above loopstick antenna and oscillator coil was removed. With the schematic below, the T core broadband tranformer was used in the input cascode preamplifier and T for the oscilator. This filter was selected to the best low insertion loss.
Near fluorescent lamp with electronic reactor, computer and switching mode power supply, introduce noise and reduce drastically the performance performance test! For guarantee, all this devices near the radio must be in off, during the test and operation too!Hi have redesigned my hardware with the data in the PDF and results are improved, I can confirm the mixer conversion gain audio out when RL is above 3.
I had 1k of load at the mixer output, now changed to 8k2 and got some gain, also I left one RF section out the RF path as I was getting compression due to over amplification, confirmed with your data and working now as expected, with a clean and linear RF path. Evaluation schematic of RF section is shown in Fig. Measurements were made by reading output voltage amplitude by a oscilloscope. Figure 5 represents the results and Therefore, actual gain is determined by Transconductance is then calculated as Google doesn't give me any useful info about it.
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Here is the full copy of the evaluation. Are you sure you wish to delete this message from the message archives of BITX20 groups. Cancel Yes. Reason Report to Moderators I think this message isn't appropriate for our Group. Cancel Report.Audio record of DIY SSB HF HAM NE612 based Radio Receiver with DDS
The new topic will begin with this message. Subject of the new topic:. Cancel Split Topic. Messages More. Toggle navigation.The RadioBoard Forums Forums for radio builders and experimenters. Beginners and Experts Welcome! Skip to content. Quick links. The amplitude of the audio out is surprising. Unlike the normal NE receiver circuit, in this circuit, the oscillator coil is connected to the input of the mixer. The regen control potentiometer varies the bias of the oscillator.
It still needs some work but I am certain there are many NE receivers out there that can be modified to test this out. I built one up on an old Vectronics NE receiver board. It had a slightly different oscillator configuration with which I didn't have success. For this reason I used the setup in the enclosed schematic. I was interested in the 7MHz. No external antenna is necessary.
Regeneration was simply controlled by a 10K pot across the inductor. A smaller value pot in series as a vernier control would be an asset. I would be grateful for any suggestions or improvements. It appears that the NE operates in 2 modes depending on the position of the regen control. With the oscillator gain at max, the circuit acts as a regen receiver. As the oscillator gain is decreased, the oscillator behaves as a Q-multiplier. The oscillator is still switching the output transistors which act as a product detector, effectively rectifying the amplified RF input signal.
You do not have the required permissions to view the files attached to this post. Last edited by Selenium on Sun Oct 06, pm, edited 18 times in total. Last edited by Selenium on Fri Oct 04, pm, edited 4 times in total.
Last edited by Selenium on Fri Oct 04, pm, edited 2 times in total. Most have been regenerative receivers or receivers with Q multipliers, perhaps this is the mitigating factor. Me too. I worked in Santa Clara for a year in Marvellous weather!
The audio gain of this receiver when followed by a standard LM audio amplifier in single ended mode is so great that it is earspliitting on many stations even without an external antenna. If the oscillator output has not been attenuated with the regen control, the receiver operates as a standard regen receiver.
As the oscillator portion of the NE is attenuated with the regen control, the oscillator section begins working as a Q-multiplier and the switching section as a synchronous detector. I'm hoping that others may build it and make suggestions on how it may be improved. I have been using it from 6 to 12 Mhz. It would be interesting to try it on the medium wave broadcast band by changing the input coil. Last edited by Selenium on Sun Oct 06, pm, edited 6 times in total.
After examining the circuit, it appears that as the oscillator portion of the NE is attenuated with the regen control, the oscillator section begins working as a Q-multiplier and the switching section as a synchronous detector. He used a significantly lower value for one of his oscillator caps and suggested using a trimmer cap to reduce the oscillator gain. The second suggestion was to use a potentiometer across the entire oscillator coil. Shorting the feedback section is a technique that I have used on many of my receivers, but at the present time, the softest control is given by altering the oscillator bias on pin 6.2010 ford f250 fuse panel diagram diagram base website panel
I did try a crystal earphone without success.
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