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Vertical Antenna And ALA 100 Comparisons
Telamon wrote: In article .com, "R390A" wrote: Telamon wrote: In article .com, "R390A" wrote: To Whom It May Concern: Additions and revisions have been made to two of my articles about vertical antennas and the ALA 100 on the www.kongsfjord.com web site. The articles are (1) "Measurements Of Some Antennas Signal To Man Made Noise Ratios In The Daytime MW And LW Bands," and (2) "Some Of My Favorite Small Antennas For MW And LW." In the first article an additional comparison of the ALA 100 was made with an active whip antenna. The ALA 100 and active whip had about the same signal to man made noise ratio. In the second article some information was added about reducing noise in active whip antennas due to what are believed to be ground loops in the DC feed. The link is dead. http://www.kongsfjord.no/dl/Antennas...ome%20Antennas %20Signal%20To%20Man%20Made%20Noise%20Ratio.pdf Try www.kongsfjord.no and then click on The Dallas Files. That link worked. Looking at your data I'm at a disadvantage not knowing which are radio stations and which are computer noise other than KNOE 540 kHz you specifically pointed out. Another problem for me is the loop antenna gain looks to be about 10 dB less than the other antennas. While actually not a problem for signal to noise measurements it does make the sweep look different to a person that did not make the measurement. Antennas in different locations around your house is not exactly apples to apples comparison. If your spectrum analyzer has a max hold on the trace that would be a help in measuring the top of the noise floor. A clear difference in S/N would be the last pair on page three 1500 to 2000 KHz where the ALA-100 looks to be 22 dB (-42 S to -60 N) compared to the vertical 33 dB (-32 S to -65 N). One problem for me here is I don't know what the analyzer noise floor itself is at this point and I can see that the loop has 10 dB less gain than the other antennas. Assuming that the analyzer noise floor is -70 dBm and lower would make this comparison valid. A simple check of just disconnecting the cable from the analyzer at those settings would show the instrument noise floor. Using max hold would make the noise floor less ambiguous. Due to my disadvantages noted I can't draw any firm conclusions based on the analyzer pictures. ************* I have to take exception to the wording you ascribe to other people such as myself about a "belief in magnetic field sensitive antennas". I rely on belief only when I have no other choice as a fall back to no being able to test a thesis empirically. An electrically small shielded loop antenna will respond very poorly to a local electric induction field and very well to a magnetic one. An electrically small dipole would be just the opposite in response to induction fields. This is theoretically and empirically correct. I have much experience using these types of antennas monitoring for induction fields and they behaved as theory predicted. When poorly designed electronic devices generate induction fields the electric fields have the tendency to spread farther from the source than the magnetic fields. This is a generalization but knowing this leads to the conclusion that a loop would pick up less of the locally generated noise most of the time or in other words it would be an advantage to use over a dipole. Most people that have local noise problems and purchase a loop antenna such as the Wellbrook find that their listening situation is greatly improved. I use a non-amplified folded dipole and non-amplified shielded loop. The loop picks up much less of the local noise and picks up as much signal as the folded dipole depending on the band. Notice that belief is not required for any of the foregoing. ************ You have the right idea about field impedance vs distance but that relationship is appropriate for transmitting antennas that are efficient. Here the subject is inefficient noise sources. Here the induction fields fall off rapidly compared to an efficient antenna. ************* I just noticed that your ALA 100 is pretty big and not electrically small at SW frequencies. This means it will also respond to electric fields and being broadband will raise the noise floor. Your 60 foot amplified loop is 10 feet bigger than my passive loop. Why do you need an amplifier with a 60 foot loop? Normally when I consider an amplified loop it more like 1 to 3 foot in diameter. -- Telamon Ventura, California How the hell am I going to put up a 45 ft vertical antenna? I see this article is from the guy that claims elliptic filters reduce fading. Well, enough said. Next! |
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