Thursday, September 4, 2014
Check Inductors With This Simple Q Meter
The tuned schema so formed is buffered by JFET Q2 and transistor Q3 which form a cascode stage with about 3dB of gain. The JFET provides a high impedance so that the loading of the tuned schema is minimal (note: an MPF102 can be substituted if you cannot obtain a 2N5485). The RF output from Q2s collector can be monitored by an oscilloscope to easily find the point of resonance and read the frequency. Alternatively, the RF output can be read by an external frequency meter. Diodes D1 & D2 and the 5.6nF capacitors form a voltage doubler rectifier to drive a 100µA DC meter so that the resonance can be found (in the absence of an oscilloscope).
Trimpot VR1 provides a sensitivity adjustment for the meter. Transformer T1 is wound on a 12mm diameter ferrite toroid core. The primary winding consists of 50 turns of 0.2mm diameter enamelled copper wire, while the secondary is a single turn consisting of a strip of brass 0.5mm thick and 2.5mm wide bent into a horseshoe shape and threaded through the centre of the toroid. VC is a small AM tuning capacitor with both gangs connected in parallel.
To measure Q, the output of the RF signal generator should be around 0.5V peak. Adjust the frequency until the meters reading peaks, then adjust VR1 so that the meter reads full scale (100µA). Read the resonance frequency F0 from the frequency scale of the signal generator or better still, the reading on a frequency meter.
Next, increase the signal frequency until the meter reads 70µA and note this frequency as F2. That done, reduce the frequency on the signal generator below the resonance frequency until the meter again reads 70µA and note this frequency as F1. The Q can now be calculated as:
Q = F0/(F2 - F1)
While using a variable tuning capacitor will enable a wider range of inductors to be tested, the main advantage is estimating the distributed capacitance of the inductor as well. To do this, you have to calibrate the tuning scale with a capacitance meter, by measuring the capacitance across the tuning capacitor with no inductor connected. This is done with the unit switched off. Marking off increments of 20pF should be sufficient.
Set the tuning capacitor to say ¼ of its maximum value and note this value as C1. Adjust the RF signal generator frequency so that the inductor under test is at resonance and note this frequency as F0. Now set the RF generator frequency to half F0, adjust the tuning capacitor until resonance and note this capacitance as C2. The distributed capacitance of the inductor is (C2 - 4C1)/3.
Saturday, August 30, 2014
Q Logic Car Audio Sub Enclosures
All the equipment installed in your car to play tracks through your stereo system is individually important. Component speakers or full-range speakers are there in your car to play your favorite tracks while doing justice to all the tunes. Naturally, the more you spend the more you are going to get a great result while there are some tips and tricks that can boost up sound production of your speakers at the same time as subwoofers are there to emphasis on bass. Baffles and foam placed between your speakers has great importance as well as they make sure the body of the car and speakers to not bump into each other all the time and producing noises that will be irritating to the ears. Enclosures that are box shaped to place your speaker’s in. the main function of these enclosures is to produce sound that is accurate and tight while they keep your speakers safe from dirt, prolonging their life.
The two kinds of enclosures that can be found in the market are sealed and ported enclosures. Like the name suggests, sealed enclosures are air tight making sure no air leaves or enters the box while ported enclosures have holes in front of the box to equalize pressure within and outside the box. This enclosure may increase the efficiency but the sound production is less accurate and tight than the sealed enclosure. The only thing that matter is that the different manufacturing of these enclosures do really make a difference in the sound production. If you want an enclosure for your speakers then Qlogic car audio enclosures is the best. Their carpeting around the box makes sure it keeps your speakers away from dirt while the box itself maximizes the productivity level. Now keeping in mind the importance and role played by the enclosures, these things come with the speakers themselves although you can pick from one of the types mentioned above according to your own taste and requirement. Sealed enclosures are actually easier to make yourself and produce sound that it should while ported are way complicated and do not have more fans. Qlogic also offers every other car audio accessories to jazz up your stereo system.
The thing that attracts every customer to purchase Qlogic car audio equipment is as they are way much cheaper with warranty and result that will make you its fan. The shipping for this product is very cheap than the rest of the electronic devices. The carpeting of Qlogic looks like they are made not just to play but to look good as well. The stylish styles and boxes will dazzle up your car interior as well. You can purchase this product from the links listed below.
http://www.qlogicenclosures.com/
http://www.crutchfield.com/
http://www.carstereoworld.com/
http://www.hifisoundconnection.com/