Implemented coupling coefficient is always in question, thus the choise between tuning for maximum signal versus tuning for minimum distortion. Loose coupling for one (implemented by distant placement of the coupling coils). The link you provided on the above post is a good example. And these characteristics depend on various aspects of a practical implementation, so much that a theoretical approach can not envisage all. This can't be so of cource if the tuning/filtering characteristics of each stage are not specified. I anticipated your wording in post#30 as a reference to a theoretically derived minimum number in tuned RF stages and filter IF stages. Probably it was a miss-understanding from my side. Try searching VFO frequency readouts, that might be the key words.ĭon't look any further. Ive also got a vauge memmory of just such a circuit being avalable in an ARRL radio handbook. Then again some car radios are so cheap that for 25 bucks, you can take the parts you want and scrap the rest.
#PASSIVE AUDIO TUNER MANUAL#
Might pay to get a peak at the service manual and copy a design that works. Some 'comercial' tuners still use the VFO style receivers and have digital readouts. In transmit they read 'direct' and in receive the display the LO +/- some value. You still see these counters avalable today on some CB radios. The same deal if it was a 'low side' injector radio. The chip would subtract 10.7 and display 107.7. So if your radio was a high side injector, a normal counter chip would see 118.4 mhz. You could select standard offsets to be applyed to the reading. Years ago I worked for Mr Kahn of AM Stereo Fame, and some of our early conversion radios (pre PLL days) were of the LO being a standard tuner and a frequency counter chip. There are/were chips avalable that did an automatic offset correction with the right jumpers set. Any help on this will be greatly appreciated. I have ordered a Bourns potentiometer and I am in search for a cost effective way for implementing an appropriate frequency counter. For a descent user-friendly tuner though, a 10 turns 100Kohm tuning potentiometer and a frequency indicator are required. Easy to make it work and at a fare price as well. Compared to a Kenwood KT-660L in mono and stereo, highs are clean, very good lows, detailed mids.Īs is (I am in the process of doing some minor mods), the kit sounds very good.
Compared in mono to a Tivoli, sound is more clean and detailed. In stereo there is a hiss (Scope trace shows 38KHZ remains and on strong modulation 57 KHZ as well). Output cups required! It is stable, no drift even with AFC off. Around 600mV RMS AF output, superimposed on 800mV DC. 92mA consumption with LED and the two meters connected, 80 mA without. With this loose implementation (80cm single wire for antenna, flying long leads), it works fine. Kit arrived pre-adjusted with components for stabilized PSU, LED, RCA outlets and a few electrolytics generously supplied as a bonus.įor start, I tried it with a 12V 7.2 Ah lead battery. There is a buffered output for a frequency counter as well. Signal strength meter, Centre-Tuning meter, Stereo LED, Stereo/Mono switch, AFC On-Off switch, Mute On-Off switch (mute level adjustment is on board) can be directly wired to the appropriate output points of the PCB. Basic kit components are: TDA1062 front end IC, two broadband (250KHZ) IF ceramic filters, CA3189 IF IC (with a single discriminator coil), CA 741 for the AFC drive, CA 1310 stereo decoder IC.Ī 100Kohm tuning potentiometer, 2 10Kohm trimmers, 2 resistors, 2 output cups, and a 12V DC PSU is what is required for a dry start. This is a superheterodyne receiver in a single sided pre-assembled PCB. There are a few weeks now that I have received some FM Tuner kits (Larsholt LH7254) from Mr.
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