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#14
November 16th 14, 11:08 AM
posted to rec.radio.amateur.equipment,sci.electronics.design
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Very Low Power Preamp
On Sun, 16 Nov 2014 03:47:44 -0500, rickman wrote:
On 11/16/2014 3:18 AM, wrote: On Sat, 15 Nov 2014 22:17:38 -0500, rickman wrote: On 11/4/2014 6:29 PM, rickman wrote: I am working on a project for receiving a very narrow bandwidth signal at 60 kHz. One of the design goals is to keep the power consumption to an absolute minimum. I'm trying to figure out how to run a pre-amplifier on less than 100 uW. So far I have found nothing. Any suggestions? I haven't seen the original post, but are you building some type of clock receiver ? Those work for a year with a single battery. Yes, it is a radio controlled clock. What kind of antenna are you using ? Do you really need a preamp ? I was planning on a loop antenna made from RG6 cable, but if I have to add an amplifier I may use a ferrite loop. Are you going to use a big (several meters) loop with the RG-6 center conductor as a loop and cutting the shield at the top and using the rest of the cable shield as a grounded static shield and using a small coupling loop into the receiver ? With the main loop resonated by a capacitor to 60 kHz, you should get quite decent signal without preamplifier. For anything smaller, a 5 cm ferrite bar is quite adequate due to the high band noise, even if the ferrite antenna gain might be -40 dBi or even -60 dBi. Do you have room for a tank circuit (L/C) on the collector/drain ? Room should not be a problem. But what is the point of a tank? 1. if you do not have a frequency selective antenna, this tank circuit will provide the selectivity. Since this stage has a low gain at unwanted frequencies, this reduces the risk of IP3 distortion, which becomes critical at low collector/drain currents. 2. you get at least twice the voltage swing compared to the battery voltage. Tapping the inductor or capacitor chain will provide nice impedance matching avoiding the need for a cascaded stage. |
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