ARRL

KO0Y

Joined: Sat, Apr 7th 2012, 19:22 Roles: N/A Moderates: N/A

Latest Topics

Topic Created Posts Views Last Activity
antenna close to metal roof: effects? Jan 9th, 14:52 3 47 1 week, 1 day ago
Window line impedance Feb 4th 2016, 16:53 1 340 on 4/2/16
CW ID necessary? May 14th 2015, 14:32 2 929 on 14/7/15
SWR and metal roof Mar 15th 2015, 23:47 6 1,055 on 17/3/15
Twin Lead and metal mast? Oct 31st 2014, 16:12 2 912 on 31/10/14
Dipole or loop? Aug 19th 2014, 03:02 11 2,773 on 5/9/14
dBmicrowatts? Jul 16th 2014, 19:51 3 932 on 17/7/14
Dipole crossing vertical? May 2nd 2014, 00:01 3 1,042 on 5/5/14
Ground Plane antenna near metal roof? Jul 6th 2013, 15:28 4 2,645 on 9/7/13
Does paint affect a Yagi? Jan 17th 2013, 02:40 4 1,484 on 25/1/13

Latest Posts

Topic Author Posted On
antenna close to metal roof: effects? KO0Y 1 week, 1 day ago
Thanks, Zack; that page is helpful. I'm going to try it fastened to the eave, as being more secure and closer to my shack. We are getting a capful of wind today, enough to blow semi-trucks over down on I-25. My current mast is guyed in three places and is swaying a bit, but so far standing. I lost our doormat, however, blown down the mountain apparently.
antenna close to metal roof: effects? KO0Y 1 week, 1 day ago
I am planning to put up a 3-wire terminated folded dipole and have a question about placement. I have a mast made of aluminum sections with a total height of up to 45 feet. I would like to fasten the lower sections to my roof at the eaves, guy the sections above, and run the antenna as an inverted-vee from the mast head with an angle between the legs of around 90 degrees. The center of the antenna would be about 38 feet above the eave (34 feet above the peak which is 14 feet away horizontally) and the antenna would run about five feet from the corner of the roofline as it descended toward the ground. The ends of the antenna would terminate about 13 feet above the ground, being fastened to trees or stakes with rope. I hope this makes sense.

The thing is, I have a metal roof, the kind that consists of curved pieces that look and feel like stone-coated tiles, and I wonder what if any effect this would have on the antenna’s performance. The antenna would not be above the roof, but rather parallel to it.

I could site the mast farther from the house and guy it to the ground, but fastening it to the roof would be much more secure. Is the close presence of a metal roof likely to degrade the antenna’s performance, or change its impedance? If so, how far away from the roof should I place the mast to avoid any degradation? Thanks for your input.
Window line impedance KO0Y on 4/2/16
I have a long non-resonant dipole fed with 300 ohm twin line. I want to construct my own feed line using 14 gauge stranded wire. I could set the distance between the conductors from one inch to three inches, using spreaders I have. Measured at the 1:1 balun, impedance of the current feed line and antenna ranges from 20 to 1200 ohms (4-10 MHz), with most points below 800 ohms. What would be the ideal distance between the conductors for the new line? Thanks for any help.

Buck ko0y
CW ID necessary? KO0Y on 14/5/15
Fldigi offers the option of CW ID, but this adds overhead to each transmission. When running an ARES directed net, we generally use MT-63 and our call signs are a part of each transmission in that mode.

My question is whether the CW ID is still required. FCC Part 97 says that ID may be made by "a RTTY emission using a specified digital code when all or part of the communications are transmitted by a RTTY or data emission."

We seldom use RTTY Baudot. Does transmission of the call sign in another data emission, such as MT-63, satisfy the ID requirements?
SWR and metal roof KO0Y on 17/3/15
Quote by WA9WVX


If you had a known good 50 Ohm Dummy Load and disconnected the RF cable from the GP-6, connected it to the 50 Ohm Dummy Load, re-measured the VSWR again and it read high, this would point the problem directly at the transmission line.

Dan


I have an oil can dummy load, and I will do that when the weather clears again. Nice yesterday, but foggy today, and I stay off the roof in bad weather; it's 35 feet from peak to ground!

In the meantime, I rigged a signal generator and got these results.

MHz SWR
144 >10
145 >10
146 7.0
147 4.5
148 2.5
149 1.7
150 1.1
151 1.1
152 1.7
153 2.3

Resonance has shifted upwards 4 MHz. Cold moisture produce such a neat result?

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