discone antenna question

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Aircargo

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i got a discone antenna. bout 8 years old (when i joineded maybe) on roof on a 100 ft line i guess. just scanning locally in newark nj about 2 miles from airport straight line. wanted to get more DISTANCE on receiving. should i RAISE antenna? its about 8 ft on highest point on 45 ft roof. house on left,right and rear are taller then antenna. bc355n i use. i did own a uniden digital...on antenna which reached i-95 along FAR side of airport. MAYBE IM FINE but is higher better? mines antenna has i THINK center whip 20 inches maybe or better and those 4-5 going around it on bottom. txs all in advance....nice scanning again.
 

Aircargo

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reg cable i think. difinitly the right coax. maybe 75 ft. did it years ago. more then half is coiled up,guess i bought to long. WOW....maybe 15 years ago. im looking at my account here. its when i had digital handheld bc250d,lol.
 

stantorres

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A few years ago I went through something similar. Here is the story and my take-aways. Maybe you will find this helpful.

I live 5 miles away from an airport. But my house is on the lake which is a low area. I have always listened to air traffic using rubber duckie antennas on base and portable scanners in the house. I have always heard the planes, never the tower.

1st attempt:
MFJ disconne that came with R/G58 coax. A good deal at $100. Mounted the antenna on the upper balcony of the house. Results: Tower very weak in the static, comes and goes with the weather and seasons. Very disapointing.

Advice I was given:

1. If you are trying to get good performance at a specific frequency, get an antenna designed for that frequency. Wideband antennas are good for repeater based hi power public safety scanning, but have varying performance characteristics elsewhere. Get the right antenna.

2. If you are using coaxial cable longer than 25 ft start thinking about the signal loss of that cable. Look up the model number of the cable and see what the loss is at the frequency and length you are trying for.

3. Try to get your antenna above the roofline if at all possible.

2nd attempt:
DPD Omni airband antenna $160
LMR400 cable $50 ($1 per foot)
Good connectors pre-assembled $15
Mast & mounts from Channelmaster $40

Results: Like a miracle. Can hear planes horizon to horizon practically. Can hear the tower crystal clear. Can hear ground crew on walkies talking simplex even. All the public safety and railroad scanning still recieves well, even though the antenna is out of band.

Good luck
 

stantorres

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Concerning your existing set up, all that extra coiled coax strikes me as a place where you might be getting a lot of signal loss. Couldn't hurt to shorten that cable up as a first attempt to solve your problem.
 

JoshuaHufford

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reg cable i think. difinitly the right coax. maybe 75 ft. did it years ago. more then half is coiled up,guess i bought to long. WOW....maybe 15 years ago. im looking at my account here. its when i had digital handheld bc250d,lol.
We need to know the specific type of cable that you have, look at it, it should have it printed on it every so often.

You need to get rid of the cable that is coiled up in excess. You loose signal in long cable runs, I suspect that is your problem.

My advice is to get a custom length of high quality coax made to the length you need and only a short amount of extra to spare.

Having half of it coiled up shows clearly it was not the "right coax."
 

mmckenna

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i got a discone antenna. bout 8 years old (when i joineded maybe) on roof on a 100 ft line i guess. just scanning locally in newark nj about 2 miles from airport straight line. wanted to get more DISTANCE on receiving. should i RAISE antenna? its about 8 ft on highest point on 45 ft roof. house on left,right and rear are taller then antenna. bc355n i use. i did own a uniden digital...on antenna which reached i-95 along FAR side of airport. MAYBE IM FINE but is higher better? mines antenna has i THINK center whip 20 inches maybe or better and those 4-5 going around it on bottom. txs all in advance....nice scanning again.
Others have answered you really well. Here's what I'll add.

Most of the frequencies that your scanner will receive work by line of sight. If your antenna can "see" the transmitting antenna, it'll work. There are some slight variations to this, but it gives you a general idea. Raising the antenna up higher will increase what the antenna can "see".

However, raising it 3 feet probably isn't going to make a big difference. It won't hurt, and if you can safely do it, go for it, but don't expect that to solve your issues.

All coaxial cable has loss. As frequencies go up, losses go up. As cable gets longer, losses go up. Lower grade coaxial cable has more loss than higher grade cables. Without knowing what type of coaxial cable you are using, it's hard to say, but you may want to consider a higher grade cable.
Also, if you have a bunch of unused cable coiled up, that is not doing you any favors. The right amount of coaxial cable you need is exactly the amount to get from your antenna to your radio. No more, no less.

Other issue we often see on the hobby side is that people rarely waterproof the outdoor connections. If your coaxial cable connection to your antenna was not properly waterproofed at installation, then expect that some water intrusion happened. That water will get into the connectors and potentially into the coaxial cable itself and start corroding the copper.

If I was in your shoes, here's what I'd do….
Sure, raise the antenna that extra 3 feet, it's not going to hurt.
Disassemble everything and inspect. Make sure the antenna is in good shape, no rust, corrosion, etc.
Replace the coaxial cable. Get enough to reach from your antenna to your radio, with a few feet of slack. The type of cable you need depends on your budget, the actual length needed, and which frequencies you need to listen to.
-On the antenna end, get the connector that matches what is on the antenna base. Use no adapters.
-Properly waterproof the connection. Use coaxial cable sealing tape. Electrical tape/duct tape/chewing gum is not sufficient.
-Properly secure the cable to make sure there is no stress on the connector.
-On the radio end, terminate the cable with a female N connector. Use a short length of flexible cable with a male N connector on one end and a connector on the other end to match your radio. This short 'whip' of flexible cable will take the strain off your scanners antenna connection.
If installing coaxial connectors is not your strong point, there's nothing wrong with buying coaxial cable with pre-installed connectors.
 

gmclam

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Everything from the antenna to the radio is part of the "antenna system". Even with great signal at the antenna, it doesn't do any good if you use cheap and/or high loss coax. The system needs to be designed to fill your needs. Will the antenna feed more than one radio? Are you close to "high power" transmission sources (AM/FM radio, TV, cell towers)? What distance do you want to receive from (10, 50, 100 miles)? What's your antenna's elevation (above terrain and sea leve)?

- Use the best coax you can find. Most people recommend LMR-400. I am using a clone of that AIR-802.
- Keep the coax run as short as reasonable (don't coil up unused coax).
- If you're near high power RF sources, you may need to insert a filter inline. Otherwise your receiver will automatically attenuate all signals.
- From ground level, antenna height adds greatly (difference between 0 and 25 feet).
- Increasing antenna height further only helps if there's something blocking the signal or you are "in a hole".

Generally I use the formula of the following to determine how far my antenna can see. This only relates to getting past the curvature of the Earth and does not take into consideration of other factors. Square root of transmitting antenna's elevation + square root of receiving antenna's elevation equals miles. Example: My antenna sits at about 350 feet above sea level and I want to receive a signal where the transmitting antenna is at 2100 feet above sea level. The antennas can "see" each other for about 64.5 miles.
 

Xray

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May 24, 2005
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A 15 year outdoor cable run needs replacement regardless of what it is, IMO.
If you are only 2 miles from the airport, I can't see that raising the antenna 3 ft would help, seems to me a rubber ducky would work fine that close. If you don't think you are receiving all that you should be that close, issue is most likely with the cable and/or connection. But if you really must assure yourself that you are pulling in everything that you possible can, which I understand, then get an omni like another poster suggested, along with some quality coax.
[No reason why you couldn't use both antennas on the same mast]
 

Aircargo

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I copy guys.... getting new cable,easy replace. Getting different scanner bcd996p2... digital like one i owned on profile. Be here next week. Txs all for replys. Miss here!
 

Aircargo

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hi guys...i get the line of sight thingy. DOES LINE OF SIGHT APPLY TO DIGITAL FREQUENCES? anyway.... im raising it higher yes AND UPON being up on roof i c that only and closes wall is next doors house. othe 3 directions im over there roof line and more or less line of sight would be east/south. towards varazano bridge,ny. i do catch 495 lie highway patrol/cops which is further. TXS for advice on cable,inspection.(y)
 

mmckenna

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hi guys...i get the line of sight thingy. DOES LINE OF SIGHT APPLY TO DIGITAL FREQUENCES? anyway.... im raising it higher yes AND UPON being up on roof i c that only and closes wall is next doors house. othe 3 directions im over there roof line and more or less line of sight would be east/south. towards varazano bridge,ny. i do catch 495 lie highway patrol/cops which is further. TXS for advice on cable,inspection.(y)
Propagation of radio waves will be the same for digital and analog.

However, analog signals will become scratchy and slowly continue to degrade over distance. Digital CODECS are pretty good at recovering clear audio right out to the edge of coverage and then disappearing completely.
So you will likely get better audio from digital whereas analog will get pretty lousy.
 
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