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eHam Forums / Antennas and Towers and more / RE: ARRL Antenna Book
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on: May 17, 2013, 02:31:10 PM
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Hi Randy,
I am one who likes to keep the "latest and greatest" tools on hand, but I would not purchase the newest Antenna Handbook if I already had one that was less than five or ten years old. The most basic theory of antennas goes back a gazillion years and is not likely to change much. The newer Handbooks I have looked over have updated drawings and somewhat better photos for the most part, but the formulas and graphs are basically the same. You can learn to understand antennas by reading the 1968 version of the Handbook or the very latest one.
That said, there are always a few "nuggets" in each new addition and I try to get my hands on one for a quick preview just in case there is something new. But, generally not worth the price of a whole new book.
73,
Terry, WØFM
Good comments. I agree. I buy a new one about once every ten years. I also use EZNEC 5+ and find that most of the antennas in the antenna book are in the eznec library. |
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eHam Forums / Antennas and Towers and more / RE: Unhooking Station Equipment Before A Thunderstorm
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on: May 17, 2013, 02:27:28 PM
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If your antennas come in through a bulkhead, you should ground everything at that point when you are not using the radio. If you have a remote antenna switch outside, as I do, wire the switch so that when it's off every antenna is grounded at that point. Disconnect the coax going to your shack at the switch. Make sure you also disconnect the control cable for the switch at the switch. Just disconnecting things is not enough...you also have to ground everything.
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eHam Forums / Antennas and Towers and more / RE: 40 meter Double Extended Zepp
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on: May 08, 2013, 08:16:59 AM
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I once had a 40 meter DEZ, but mine was 178 feet long, center fed with 450-ohm window line. I started out with 110 feet of feed line and had problems with 40 meter RF in the shack. I reduced the length to 90 feet and it worked great on all bands, including 160, with no RF in the shack. If you have a program such as the ARRL TL you can probably figure out what length you need, but it also works to do the cut-and-try method.
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eHam Forums / Amplifiers / RE: Icom IC-PW1 Power Output Meter Modifications
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on: April 09, 2013, 06:16:37 PM
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Even though there might not be any "user" adjustments, that doesn't mean that a slug can't be defective. The Navy used to require (and may still require; it's been a while) that slugs used for testing had to be identified to a specific Bird meter by serial number. No mixing of slugs was allowed. If a meter didn't meet the manufacturer's specifications and a new slug fixed the problem, the old slug was "retired" and the new one appropriately marked for use with THAT meter only. "User adjustments" -- depends on the user: http://www.repeater-builder.com/projects/bird-element-tour/bird-element-tour.htmlThanks for the link. Now I know how to calibrate my 15 year old Bird 43 elements if they ever go out of calibration. I'm sure Bird calibrates every element before it leaves the factory, but you never know when someone may be sleeping on the job and missed one or two! Ron, W4VR |
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eHam Forums / Amplifiers / RE: Icom IC-PW1 Power Output Meter Modifications
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on: April 09, 2013, 03:14:16 PM
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Ah, yes -- the "Bird". Probably talking about the Model 43, which is a decent, rugged meter which is still only accurate within ±5% of FSV. And if you add the "Peak" kit, making it a Model 43P, it's only ±8% FSV. And like any other measurement device, it requires periodic calibration - along with any slugs used with it.
The Bird 43 is not a "lab standard"; however, many seem to think it's the touchstone for "accuracy".
There are no user adjustments on the slug or pickup of the Bird 43 that I am aware of. The 43 may not be a lab standard for some but it is certainly more accurate than any wattmeter in any amplifier that I've ever seen or owned. The only manufacturer that I am aware of who used a Bird wattmeter in its amplifier was the old Henry 3K Ultra. |
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eHam Forums / Amplifiers / RE: Icom IC-PW1 Power Output Meter Modifications
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on: April 09, 2013, 07:57:51 AM
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I know of none, but would question the accuracy of the meter in the IC-PW1 to begin with (yes I have one). It varies significantly from my Wavenodes WN-2s with NIST traceable sensors.
Yes indeed, the power meter is certainly not a Bird. Compared to the Bird it's about 100 watts low on certain bands. |
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eHam Forums / Antennas and Towers and more / RE: What would you do with 215' at 70 feet?
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on: April 05, 2013, 12:51:49 PM
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With a span that long between the two ends you would end up with very significant droop at the center of the antenna if that's where you feed it with your transmission line. Anything longer than 100 feet I use a center support to get away from the droop problem. Also, you have to consider the tree sway, so you really can't pull the wire too tight...the supporting ropes or wire will stretch and break under high wind conditions. I once used a center-fed wire 178 feet long (extended double zepp for 40 meters) and fed it with 90 feet of window line; it worked great on all bands, including 160 meters. I used 90 feet of window line to avoid getting a voltage max on the transmit end.
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