A Wideband Field Strength Meter
One of the more common pieces of equipment that lots of amateur operators make use of may be the industry strength meter. Most typically contain a diode sensor (often germanium with regard to awareness), followed by a micro-ammeter, and usually tend to be restricted to frequencies in the HF area, even though some VHF and even UHF versions are available. Along with measuring the output of the transmitter, the area strength meter can also be helpful for antenna radiation pattern dimensions, concealed transmitter areas (for example inside a sibel search), and also general RF detection.
This particular 30 days we would like introducing you to definitely a far more contemporary edition of the industry strength meter, one that addresses the number from 10 kHz to in excess of 1 GHz (1000 MHz) and it is almost as simple to construct since it’s many predecessors.
Our signal utilizes the Linear Technology LTC5507, which is explained the organization as an Power Sensor.”It includes a Schottky diode maximum detector and acquire of 2 barrier amp all contained in a tiny SOT type surface attach package. The nick works through 2.7 to 6 volts DC and therefore can be driven from a handful of AA batteries. The sensitivity from the signal stretches from-thirty four dBm (regarding 1/2 microwatt) to +14 dBm (about 20 milliwatts) over the entire rate of recurrence range. The ensuing DC result has a frequency response of DC up to about 1.5 MHz, so it can even be utilized being a wide-band AM sensor, if you wish. Fig. 1 is a chart displaying the input power vs. result DC degree (in millivolts) over the entire selection of the chip. While not particularly linear, the range is quite remarkable.
Fig. 2 may be the basic working schematic from the LTC5507. C1 couples the input to the chip and really should become chosen for the rate of recurrence variety preferred. It should be a porcelain type for the best outcomes, and you should be careful of self-resonances, especially from high frequencies. Remember, if you use a 0.1 uF, for example, it doesn’t consider significantly lead duration to resonate above several tens of MHz. As a result, it is not a good idea to use any sort of electrolytic capacitor, because the inner turning from the foil components within the capacitor package is inductive and will definitely resonate at some rate of recurrence over the wide range of the device. C2 is the filtration system capacitor for that output of the maximum detector and can affect the pace of reaction from the result. Usually of thumb, each C1 and C2 ought to be selected based on the following guidelines suggested simply by Linear Technology:
C1 = C2 = 1/30 x F
F may be the cheapest rate of recurrence preferred in MHz, and each C1 and also C2 have been in uF.
Obviously, you could test out these types of ideals.
Fig. 3 is the schematic of a total industry strength meter since the whole 10-kHz to at least one-GHz variety while using LTC5507. You will note that we now have combined the enter for an flexible telescoping mix antenna and the output to a 100-microampere solar panel meter along with a adjustable ”control. Power is actually provided by a couple of AA or even AAA batteries, and the whole gadget is actually mounted in a small light weight aluminum enclosure. Power deplete is very low, and also the batteries will last for a lot of hours of measurements. Because of the little size of the components and also the frequencies included, attempt to keep all input qualified prospects as brief as you possibly can. We regularly use person lengths from common 16 stranded home cable, plus they are perfect for the job. A totally free 1-foot ”from the local home center will give you enough jumpers with regard to numerous experiments. Finally, be sure to download the data sheet from the Linear Technology web site for more information.
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