- 1. Topband: Measuring field strength (score: 1)
- Author: "Dan Zimmerman N3OX" <n3ox@n3ox.net>
- Date: Wed, 20 Dec 2006 15:06:58 -0500
- I've had lots of good responses regarding putting radials out to the front yard. I'm going to run radials around to the front of the house, possibly by putting a perimeter wire around the house. I'd
- /archives//html/Topband/2006-12/msg00205.html (7,427 bytes)
- 2. Re: Topband: Measuring field strength (score: 1)
- Author: Greg - ZL3IX <zl3ix@inet.net.nz>
- Date: Thu, 21 Dec 2006 19:35:34 +1300
- The park will be more than enough, Dan. All you need is for the wave impedance to settle close to 377 ohm, and that happens inside a wavelength. By the way, how are you going to measure the field str
- /archives//html/Topband/2006-12/msg00210.html (8,304 bytes)
- 3. Re: Topband: Measuring field strength (score: 1)
- Author: Herb Schoenbohm <herbs@surfvi.com>
- Date: Thu, 21 Dec 2006 10:40:08 -0400
- Dan, If you use the distance of one mile to make your FSM you can tap into the wealth of FCC (www.fcc.gov) and other enginneering data that use measurements at one mile with 1KW into a vertical. If y
- /archives//html/Topband/2006-12/msg00214.html (8,217 bytes)
- 4. Re: Topband: Measuring field strength (score: 1)
- Author: Telegrapher9@aol.com
- Date: Thu, 21 Dec 2006 11:05:07 EST
- Dan, five wavelengths will be far enough. An indirect measurement can be as good as a field strength measurement. If you can accurately measure the base impedance at resonance you can calculate the c
- /archives//html/Topband/2006-12/msg00215.html (7,721 bytes)
- 5. Re: Topband: Measuring field strength (score: 1)
- Author: Herb Schoenbohm <herbs@surfvi.com>
- Date: Thu, 21 Dec 2006 12:18:34 -0400
- I mentioned the www.fcc.gov website where there is an excellent inverse distantce field strength caculator in the last post. Even though its frequency data entry tops out at 1700Khz it is close enoug
- /archives//html/Topband/2006-12/msg00216.html (8,341 bytes)
- 6. Re: Topband: Measuring field strength (score: 1)
- Author: "Tom Rauch" <w8ji@contesting.com>
- Date: Fri, 22 Dec 2006 18:31:02 -0500
- I measured dozens of systems and that method will not work except by pure luck. As an example just a few moths ago Roy Lewallen and I measured a series of 40 meter vertical radial system. We had a v
- /archives//html/Topband/2006-12/msg00233.html (8,651 bytes)
- 7. Re: Topband: Measuring field strength (score: 1)
- Author: David Gilbert <xdavid@cis-broadband.com>
- Date: Fri, 22 Dec 2006 18:23:07 -0700
- It is even quite easy to create models in EZNEC that support Tom on this. The relative base impedance of a vertical monopole fed against ground does not accurately predict relative field strength in
- /archives//html/Topband/2006-12/msg00235.html (9,222 bytes)
- 8. Re: Topband: Measuring field strength (score: 1)
- Author: "Tom Rauch" <w8ji@contesting.com>
- Date: Fri, 22 Dec 2006 21:56:34 -0500
- Because radials, like antennas, have standing waves on them. What we measure at one point doesn't tell us much about something some distance away. A sample of what we measured on 7 MHz shows: Two ra
- /archives//html/Topband/2006-12/msg00237.html (9,607 bytes)
- 9. Topband: Measuring field strength (score: 1)
- Author: "Thomas Damboldt" <Thomas.Damboldt@T-Online.de>
- Date: 23 Dec 2006 06:39 GMT
- Hi, I dont think Tom is right on this one. You can not measure field-strength, even if your meter is calibrated in FS. You can only measure voltage or power and calculate field strength, which is a
- /archives//html/Topband/2006-12/msg00240.html (8,425 bytes)
- 10. Re: Topband: Measuring field strength (score: 1)
- Author: Telegrapher9@aol.com
- Date: Fri, 22 Dec 2006 22:01:57 EST
- Dave, let's see if we can obtain an accurate change in field strength from added base resistance in NEC-2. Here's a 7 MHz vertical mounted 1' above average Sommerfield GND. The vertical has 16 resona
- /archives//html/Topband/2006-12/msg00243.html (9,302 bytes)
- 11. Re: Topband: Measuring field strength (score: 1)
- Author: "Tom Rauch" <w8ji@contesting.com>
- Date: Sat, 23 Dec 2006 07:46:40 -0500
- <SNIP> I'm sure we all agree if a lumped resistance component is placed in series with a fixed load resistance-- Ohm's law will work as expected. I think the point being missed is the "ground resist
- /archives//html/Topband/2006-12/msg00245.html (8,984 bytes)
- 12. Re: Topband: Measuring field strength (score: 1)
- Author: "Dan Zimmerman N3OX" <n3ox@n3ox.net>
- Date: Sat, 23 Dec 2006 09:59:46 -0500
- This is what I'm planning on doing when I return next week. I'm thinking of doing the following, and I'm interested in comments. I have a small CW transmitter (about 110mW) that I can set up 1 wavel
- /archives//html/Topband/2006-12/msg00250.html (9,266 bytes)
- 13. Re: Topband: Measuring field strength (score: 1)
- Author: Telegrapher9@aol.com
- Date: Sat, 23 Dec 2006 21:53:16 EST
- Tom, thanks for the excellent data.We have two things were are discussing; whether a decrease in input impedance follows the field strength trend and how well NEC-2 can model all of this. I ran a sim
- /archives//html/Topband/2006-12/msg00263.html (10,056 bytes)
- 14. Re: Topband: Measuring field strength (score: 1)
- Author: "Tom Rauch" <w8ji@contesting.com>
- Date: Sun, 24 Dec 2006 07:52:17 -0500
- I actually use a "pinger" to measure my receiving antennas. It is a battery powered oscillator using a cheap 1843 kHz time base crystal that drives a six-foot whip. A 555 timer pulses the source off
- /archives//html/Topband/2006-12/msg00268.html (9,842 bytes)
- 15. Re: Topband: Measuring field strength (score: 1)
- Author: "Rick Karlquist" <richard@karlquist.com>
- Date: Sun, 24 Dec 2006 06:44:42 -0800 (PST)
- I also have one of these oscillators. It works well for many purposes, but since you asked the question: there are two reasons why you would want to transmit on the antenna under test instead of rece
- /archives//html/Topband/2006-12/msg00271.html (10,877 bytes)
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