sloping vertical single ended antenna for SWL , questions

[Opcom]

I put this single wire SWL antenna up today. Already it is working much better than what was there before. I can only try reception at this point. In a few months the tower guys will be back to put up the dipole but for now this is it.

I tried to fix this so that I can leave it disconnected from the house when not in use. When the connector is unplugged, the wire just hangs down by the plastic (rubbermaid) utility shed. That ought to be non-flamable and non-conductive. The house is then disconnected from the wire.

Inside the shed are some plastic containers of diesel for the generator. Is this a bad idea, or is it decently safe because the shed is plastic and any lightning ought to not go inside, but down the loose end of the wire to the earth? I have to say it won't be helpful to have the lightning avoid the house but ignite the fuel in the shed next to the house.

When disconnected from the house and radio, should that loose end of the high wire be grounded for lightning avoidance when not in use?

[kb3ouk]

Since the tower itself is grounded, wouldn't lightning be more likely to travel down it than a piece of wire that is not grounded.

[KL7OF]

Take the diesel out of the hut...

[WD5JKO]

Patrick,

I'm no antenna guru, but looking at that triangle suggests something. Using your image as drawn, and if the bottom is 10' off the ground, we have a triangle dimensioned 44' + 20' + 48' = 112'. That is almost a full wave on 40m. Heck wire it up, vertical wire maybe 1' away from tower, and feed it at the bottom left with open wire line to a Johnson Matchbox, or similar tuner. Might do fine on 40-10m. If you open up the wire at the midpoint (relay), then you get 80m too. Just a thought.

Jim
WD5JKO

[Opcom]

Jim, do you mean add more wire so that I bring the loose end away from the house to within 1FT from the tower and feed it there? That is a good idea to try for transmitting. But I found out I got a big problem detailed below, not sure how to attack it. The image is 10 pixels per FT. The lower end of the wire is 7FT high at the roof of that shed but it ought to be close enough.

There some kind of huge noise here. I thought this would go away if I had a decent antenna up away from it all. Seems like a really nasty power line noise but it is not coming from any one place according to my Alinco DJ-X2 handheld (LW-UHF RX) and very short rubber duckie. I've been walking around the place and It seems to be on every power line and it's also on the cat5 cable coming in. The noise is so strong that these results appear:

R390 with a 1FT clip lead on the coax port connected to chassis: meter reads 0dB, audio is silent enough
R390 with a 1FT clip lead on the coax port just hanging in air: meter reads 20dB, very loud harsh buzz
The strongest ham AM transmission I have picked on 3885 a few minutes ago makes the meter hit 40dB but with the broad banded buzzing racket I can't make anything but a few words out.
From worst problem to least: 160M, 80M, 40M.. A 1-FT piece of wire picks up enough racket to ruin the listening.

The way the antenna is set up, the wire is not shielded at all and comes straight in. I could try a 50FT section of coax to shield the signal path until it is out of the house but would that really help when only 1FT of wire at the radio is enough to pick up this terrible racket?

I guess the next step is to bring in an IC706 with a battery, tune it to the most annoying noise and kill the main power to the house and lab (and shut off all UPS's and battery backed devices) to eliminate those as culprits. If the racket persists, it's got to be the power lines. Unless I can find this interference and get it stopped I will never be able to use 160M or 80M. 40M is not too bad but that's no answer.

I don't know what to try really, just start trying different things. I have no experience chasing down this kind of noise but it looks like the 60 year old power lines here could be a problem.

[Ed/KB1HYS]

I fan into a similar situation here. Strong PL noise in a WIDE area.  It was due to multiple sources, bad insulators on some poles, rusted/corroded connections, a couple of bad streetlights etc. Lack of Utility maintenance for some years (decades?) had allowed things to get pretty ugly.

DFing with an Aircraft band reciever (VHF AM) and a HB yagi is a good way to go. you can almost pinpoint a bad insulator, certainly a bad pole. 

[WD5JKO]

Jim, do you mean add more wire so that I bring the loose end away from the house to within 1FT from the tower and feed it there? That is a good idea to try for transmitting.

Patrick,

  I did some digging, and an antenna that describes what I said is from W9JJV in QST March 1983, and also in the "ARRL's Wire Antenna Classics" book published 199-2002. Here they call it "The Two Band Delta Loop Antenna". It is also supported by a large tower. The loop is a right triangle with the 90 degree angle at the bottom of the tower. The vertical run is 18" away from the tower (insulated by 2" X 2" wood with 'U' bolts). The dimensions they used were 40' vertical, 42' horizontal, and 58' diagonal. The total was length 140'.

  Having a closed loop antenna will drop the noise when you have a lot of local e-field noise present. I bet you have 10 sources of noise, and at least 3 of them on your property. :-)

Regards,
Jim
Wd5jko

 

[Opcom]

wow that is quite an antenna. I can study that a bit.