To: | "amps@contesting.com" <amps@contesting.com> |
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Subject: | Re: [Amps] Power metering in linears |
From: | craxd <craxd1@ezwv.com> |
Date: | Thu, 07 Oct 2004 16:49:59 -0400 |
List-post: | <mailto:amps@contesting.com> |
One other thing I forgot to mention about that toroid. Check to see if
that may be going into resonance at 80 meters or so with a dip meter.
You mentioned that there was hardly any output on 80 but was some on 160
and then from 40 on to 10 I take it? If it is going into resonance on a
needed frequency, you may have to change the turns on the transformer by
a few turns. This will move the resonant frequency to somewhere you
won't be using. Most I've seen had about 26-28 turns but seems like I
remember one with about 40. There's a different process for checking
toroids with a dip meter than there is with an air coil. This is due to
the self-shielding action of ferrite cores. Anyhow, you might want to
check that. If it's not, I'd say it's in the material of the ferrite itself. Will Matney Don't think any diodes in the circuit are linear from 160 to 10. Diodes are not linear. But, that is not the problem. The non-linearity does not depend upon frequency but is controlled by the rectification process. Non-linearity can be calibrated out easily with a meter scale. The change in levels due to frequency are caused by the frequency response of the toroid device. Both the core material and the number of turns can be adjusted. It is quite easy to determine what the bandwidth is by feeding the sensor with a wideband signal generator and measuring output of the sensor versus frequency. If adjusting the number of turns and the core does not give you the range you need, you can make frequency dependent compensation on the output of the sensor (for example, small value bypass caps on the output line will not charge the diode at the lower frequency and be useful if the voltage output of the sensor dropped off with frequency). The right combination of these three factors should allow you to construct a sensor that covers the range you need. This empirical approach is perfect for the amateur since it requires no math, no knowledge of physics and very little expenditure of money. You should be able to become an expert in this area with less than a 6 pack and one evening of bench work. Colin K7FM
Rob, You are correct on this. Most use a 1N270 or so, but I'm not sure what would be needed for that wide of a range. Will Matney robrk@echomatrix.net wrote: Don't think any diodes in the circuit are linear from 160 to 10.
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