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Indoor/Outdoor antenna, annoying symptoms, and making do

Mar 21st 2017, 17:46

KC1HBG

Joined: Jan 25th 2017, 18:57
Total Topics: 0
Total Posts: 0
Here's my setup, and I'll post my symptoms/questions below:

Due to limited space (and limited outdoor time during Winter in New England), I purchased as my first antenna a G5RV "Jr" antenna - total dipole length about 51', with 18' of ladder line. I have the feed point mounted in my attic, in the peak at the outside wall, with one arm stretching across the ridge pole and the last 4 feet or so moving down one of the rafters. The other arm extends out the vent at the end, through a metal screen, and down to a tie-off about 4 feet above ground. The two arms aren't quite in the same vertical plane, as the outside arm needed to be pulled in a little to stay within the property line, so the inside arm runs along an EastWest axis and the outside arm runs NW/SE at an axis of about 285/105 degrees. The feed point is about 16' high, from what I can tell; inside the attic is the usual foil-backed insulation, as well as a power line running along the ridge a few inches away from the inside arm. The ladder line is running straight down to the basement inside the wall.

As long as I haven't sent someone running in horror, I'll describe what I am experiencing. I have successfully contacted a number of DX countries, including Croatia, Hungary, Germany, etc, and have heard many more, via SSB 100W on 7 and 20m. I know that there's some sort of signal getting out there. However, I am seeing the following:
* I am not being picked up, on any band, by reversebeacon.net.
* I am not able to hear *any* of the beacons listed in NCDXF
* I get significant background noise - my rig (Yaesu FT-450D) has an internal S-meter, and the usual level is at about S7.

I have read some accounts which have suggested that a choke coil is necessary with this type of antenna; based upon those accounts I have 12' of coax wrapped around a 4" PVC pipe, for about 10 turns, which I have connected between the ladder line of the antenna and my coax feed. While this does seem to make a bit of difference on the tuning of the antenna, it doesn't seem to change the above symptoms.

I do indeed plan on a better antenna setup once the weather clears (and I can clear a downed tree from the last storm here), but if there are other things I should be doing I'd like to know so that I am not discouraged if other antennae give me similar results. Do these problems seem familiar to anyone?
Mar 22nd 2017, 04:38

WA0CBW

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Considering the description of your antenna system I would say it is working pretty good. Some of your problems could be distortion of the antenna radiation pattern due to the foil insulation, the wire mesh one end of the antenna passes through and the orientation of the antenna and feedline. The noise level could be from the nearby electrical wiring in the attic or other "RF" noise makers in your house.
Bill
Mar 22nd 2017, 08:56

KC1HBG

Joined: Jan 25th 2017, 18:57
Total Topics: 0
Total Posts: 0
I thought the insulation and wiring might be a problem, never mind passing through a screen. I'd think that would a blanket problem, though, and apparently at least some European countries are hearing me. The heavy noise I hear is like heavy white noise rather than the characteristic hum I would associate with 110v 6-Hz AC; are the bands just that noisy? Or perhaps there's an adjustment on my rig I don't understand, which is quite possible.
Mar 22nd 2017, 15:46

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

You don't mention CW operation. You need to accurately send your call via CW to be picked up the CW skimmers used by the Reverse Beacon Network.

hamspots.net can be used evaluate JT9 and JT65 signals. The digital modes are quite popular these days--they are a way of making contacts with compromise antenna installations.

Beacons typically use omnidirectional antennas and modest antennas. It isn't unusual to have trouble hearing them if you have a high noise level. The choke coil didn't help much because your antenna is so close to the noise sources. Stopping common mode interference may not help if the antenna is picking near field radiation from interference sources. I use the term "near field" because these signals are typically very short range. They often disappear very quickly as you move the antenna away.

Zack W1VT
ARRL Senior Lab Engineer
Mar 22nd 2017, 18:06

KC1HBG

Joined: Jan 25th 2017, 18:57
Total Topics: 0
Total Posts: 0
Good information, thank you. I *think* I'm sending CW accurately, though when I look at the reverse beacon list I try to look for possible permutations in case I'm either flubbing it or it's not being read correctly. I may work on some of the digital modes at some point, but I haven't gotten there yet. At the moment, the priority is getting a more established setup, and in working on portable arrangements for field work.

That said, I do hope to move the antenna (or set up another, better one) once I can actually get across the yard. It hadn't occurred to me that common mode noise would sound so... generic. I thought it would have more character to it; I just get a plain roaring. But I will see soon enough. Thanks again!

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