Yet another guy who tried a discone antenna in his attic

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Mister-Ed

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I am 2 months new to scanner receiver radios. I wanted to monitor local air traffic at DIA (about 18 miles away), Front Range Airport, (about 16 miles away) Buckley Airbase (about 5 miles away) and Centennial Airport (about 10 miles away.) I also wanted to receive CB, MURS and FRS bands.

I knew I would have an uphill battle with my shop in the basement. Even though Aurora, Colorado appears very flat, our home is in quite a gully. My first mistake was not reading more about frequency use. I purchased a BC355N that I am happy with but then soon realized the military air frequencies could not be covered. I then purchased a BC125AT and now have coverage of all the frequencies I am currently interested in. I realized soon into research that police or fire monitoring would be difficult in this area due to our departments using various higher end and encrypted equipment. Even if I went up the food chain and bought a BCD436HP or a TRX-1 I do not believe I could even monitor theoi communications yet so the BC125AT is all I seem to need for now with the BC355N covering everything except military air.

When I drive up out of our neighborhood to the "normal" street level, I get good reception even with the stock antenna on either of these scanners. (The BC355N has a telescoping metal whip and the BC1q25AT a rubber duck.) In the shop, much less traffic is received. I bought a discone and placed it in the attic like our TV antenna is. Perhaps there is a cold solder joint on the cable end or the fact that our south attic wall (just one wall) has a foil liner, regardless, I get no (I mean zero) reception from that cable that took me three hours to run down into the basement shop. One post here was correct that predicted that result. I still went ahead with it all because so many others yet had reported such great success with discones for receiving a wide range of frequencies.

My next move will be to move the same discone antenna onto a pole atop the back deck that will allow the bottoms of the "umbrella" part to be about 2 ft above the gutters on the top roof of the house. I will check the cable better to be SURE it is not cold soldered or otherwise bad.

MY QUESTION is, if this discone still does not help once remounted outdoors and away from that one foil covered attic wall, what do you experienced guys think the result would be if I just put a regular whip antenna (like a 14" rubber duck replacement antenna) on a PVC pipe up there above the gutters with a good coax cable coming down to the scanner in the basement? Do you think is would just be a waste of time?

One other thing I considered is the "car antenna" the BC355N came with. It looks like a stranded copper wire perhaps 18" long with two suction cups you place on the windshield. When I use it it is an improvement over the BC355N whip antenna when I use it in the car. Maybe I can fashion something as simple as that vertically along the side of the house up on the outside wall of the second floor. I have Masonite siding on the home. Does anyone think that could make a significant (hoping for 3x) improvement over using the standard whip antenna on the back of the scanner in the basement?

Again, I want to receive the wide range of frequencies on my scanner that I mentioned above but not transmit. Any recommendations for better scanner reception over a wide frequency range will be welcomed.v (I realize my question sounds like "Scanner Antenna 101" to most experienced guys.)
 

mmckenna

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MY QUESTION is, if this discone still does not help once remounted outdoors and away from that one foil covered attic wall, what do you experienced guys think the result would be if I just put a regular whip antenna (like a 14" rubber duck replacement antenna) on a PVC pipe up there above the gutters with a good coax cable coming down to the scanner in the basement? Do you think is would just be a waste of time?
The VHF High, UHF and 700-800MHz frequencies you want to listen to are (for the most part) line of sight. Being down in a gully might be part of the issue. Either way, the higher up the antenna is, the more it can se.

A rubber duck outside isn't going to help unless you get it high enough. It's not going to work better than the discone, and it's not designed for long term outdoor use. It's not weatherproof and will likely fail quickly.

One other thing I considered is the "car antenna" the BC355N came with. It looks like a stranded copper wire perhaps 18" long with two suction cups you place on the windshield. When I use it it is an improvement over the BC355N whip antenna when I use it in the car. Maybe I can fashion something as simple as that vertically along the side of the house up on the outside wall of the second floor. I have Masonite siding on the home. Does anyone think that could make a significant (hoping for 3x) improvement over using the standard whip antenna on the back of the scanner in the basement?
Probably not going to help. The reason it works better in your car is because it's up against the window. Usually running a radio inside a car without an external antenna suffers from blocking by the steel body. This is referred to as a "Faraday Cage". Basically you have your antenna shielded. Putting it agains the window helps quite a bit. If you want even better performance, get a proper multi-band antenna, like the Larsen NMO-150-460-800 whip and you'll see an even greater performance.

Antennas work best when they are resonate at the frequency you want to listen to. Random lengths of wire can work, but you'll do better with a correct antenna. Running wire outside your home probably isn't going to help as your are still down in the gully, and the line of sight thing isn't there.

Again, I want to receive the wide range of frequencies on my scanner that I mentioned above but not transmit. Any recommendations for better scanner reception over a wide frequency range will be welcomed.v (I realize my question sounds like "Scanner Antenna 101" to most experienced guys.)
It's all about the antenna system.
The antenna system is:
1. The coax between your radio and your antenna. Needs to be low loss for the frequencies you want to listen to. All coax has attenuation. The attenuation increases as the cable gets longer AND as the frequency goes up. Different types of coaxial cable have different loss properties. Lower loss cable tends to be more expensive.

2. Your antenna support structure. The common frequencies used by public safety all are dependent (mostly) on line of sight. To get reliable coverage your antenna needs to be able to "see" the transmitting antenna. No amount of witchcraft, marketing claims or magic pixy dust is going to make an antenna work when the line of site is impacted. You need to get your antenna up high if you want to hear more. There's no way around that with your current setup.

3. Your antenna. Your antenna needs to be more or less resonate at the frequencies you want to listen to. It'll work if it's not, just not as well. Random length antennas will work, but it's going to be hit or miss. Something like a discone is a good compromise. While it doesn't have any gain, it does cover a wide amount of frequencies. They are not perfect antennas, but they are a suitable compromise for hobby use. A better solution is to use multi band vertical antennas, or better yet, dedicated single band antennas for the frequencies you want to listen to. This would be expensive, so that's one of the reasons a discone is a good compromise.

You didn't tell us anything about the exact antenna model/brand you have. You also didn't mention what type of coaxial cable you are using. Those sorts of details might shed a little more light on things for us.


What you are trying to do is probably doable, unless you are really deep down in a hole. It's just going to depend on how high you can get your antenna.
 

Mister-Ed

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The VHF High, UHF and 700-800MHz frequencies you want to listen to are (for the most part) line of sight. Being down in a gully might be part of the issue. Either way, the higher up the antenna is, the more it can se.

A rubber duck outside isn't going to help unless you get it high enough. It's not going to work better than the discone, and it's not designed for long term outdoor use. It's not weatherproof and will likely fail quickly.



Probably not going to help. The reason it works better in your car is because it's up against the window. Usually running a radio inside a car without an external antenna suffers from blocking by the steel body. This is referred to as a "Faraday Cage". Basically you have your antenna shielded. Putting it agains the window helps quite a bit. If you want even better performance, get a proper multi-band antenna, like the Larsen NMO-150-460-800 whip and you'll see an even greater performance.

Antennas work best when they are resonate at the frequency you want to listen to. Random lengths of wire can work, but you'll do better with a correct antenna. Running wire outside your home probably isn't going to help as your are still down in the gully, and the line of sight thing isn't there.



It's all about the antenna system.
The antenna system is:
1. The coax between your radio and your antenna. Needs to be low loss for the frequencies you want to listen to. All coax has attenuation. The attenuation increases as the cable gets longer AND as the frequency goes up. Different types of coaxial cable have different loss properties. Lower loss cable tends to be more expensive.

2. Your antenna support structure. The common frequencies used by public safety all are dependent (mostly) on line of sight. To get reliable coverage your antenna needs to be able to "see" the transmitting antenna. No amount of witchcraft, marketing claims or magic pixy dust is going to make an antenna work when the line of site is impacted. You need to get your antenna up high if you want to hear more. There's no way around that with your current setup.

3. Your antenna. Your antenna needs to be more or less resonate at the frequencies you want to listen to. It'll work if it's not, just not as well. Random length antennas will work, but it's going to be hit or miss. Something like a discone is a good compromise. While it doesn't have any gain, it does cover a wide amount of frequencies. They are not perfect antennas, but they are a suitable compromise for hobby use. A better solution is to use multi band vertical antennas, or better yet, dedicated single band antennas for the frequencies you want to listen to. This would be expensive, so that's one of the reasons a discone is a good compromise.

You didn't tell us anything about the exact antenna model/brand you have. You also didn't mention what type of coaxial cable you are using. Those sorts of details might shed a little more light on things for us.


What you are trying to do is probably doable, unless you are really deep down in a hole. It's just going to depend on how high you can get your antenna.
Thank you for the great, detailed, reply!! Very good information for me.

The discone I ordered is a Tram 1411. I selected it because of the CB top tip addition it has. It arrived from amazon apparently complete but without a lick of identification nor information in the box. Apparently this was a return from a previous buyer. I did find other sources for information on it online, however, but I have temporarily set aside the "adjustment" pieces and items as I have not yet studied how to do the "tuning" nor do I understand yet what frequency ranges the tuning will be effecting.

I thought I was getting RG-8 coax based on my search on eBay but when it arrived it was clearly marked RG-8/X. Reading the description again it was, indeed, what I had ordered. I did not realize there was a difference until I read in the Uniden BC125AT manual where they recommend RG-8 for up to 100 ft and this RG-8/X for only 50 ft use. Here I presumed (there is that word that I should never uses in the world of radios again) that the "X" meant it was better yet. :-( My bad. Yet another mistaken investment to chalk-up to this learning curve.

The new run of this cable up to the back deck roof from the basement will be right at 50 ft max so I will live with this RG-8/X for now. If I can then see better results on the scanner when I use it in the basement shop with the moved discone using this coax I may consider upgrading the cable.... which appears to be yet another topic on which there are varied experiences and opinions.

Thanks Again for your help!! - Ed
 
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I have my antenna up in the attic, although not a discone. Check the "basic" stuff first, make sure all the parts you're using to connect the scanner to the coax as well as the connections to the discone are nice and tight. I was using a BNC to coax connector that wasn't making good contact with the scanner...switched it out, that alone instantly made a difference.

Also, for the aviation stuff, think about getting one of these:

NIB RADIOSHACK FM TRAP Improves TV Picture Quality 75 ohm coax connector | eBay

a radio shack FM trap

that was my ticket. As soon as I put one of those between my scanner and the antenna it was the golden ticket. Keep in mind this does mean you will have to cut your coax in two.
 

dsalomon

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You will definitely benefit from better coax. If you have the budget, you might consider something like LMR400 or LMR600 types of coax, both of which will give you significantly less loss at higher frequencies. They're also more expensive than RG8. The antenna system is the most important part of any radio system. Put up the best you can afford for the long haul. Dx Engineering makes and sells LMR400 type coax (their own brand), which is less expensive than many other places. For example, a 100ft. length of DX Engineering 400MAX is $120. I use this for my discone antenna and get much less loss than the previous RG8. I use Times Microwave LMR-600 for my 2 meter/440 antenna with even better results (however, the 600 coax is thick and does not bend well, so know that in advance).

If you're in a really deep valley (like I was in my previous home), you might need a wide band amplifier at the antenna. Most installations do NOT require an amp. However, if you do use an amp, it MUST go right at the antenna. Putting it at the radio just amplifies noise as well as signal. The result will be no better SNR than before the amp. If you do use a wide band amp, again, it should be a good one. Many inject too much noise, so you don't get the expected benefit. Also, since you're planning to move your antenna outside, obviously, the amp must be waterproof. You'll also need a way to power the amp, which will mean injection power up the coax. That's easy to do, but yet another expense. So, consider this a last resort, after a better antenna, better coax, and better mounting location.

At higher frequencies, roofing material very well could be blocking some signal (the higher the frequency, the more is lost to obstacles). If your monitoring targets are mostly in the 800MHz range, then getting that antenna outside and higher up will definitely help.

Good luck - David
 

Mister-Ed

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Thank you, David. I read a bit about LMR400 and originally decided against it because some mentioned it is stiffer and harder to "run" through a home. With this new run out the back wall of the basement and up to the back deck roof it is a much simpler run. It sounds like LMR400 it will be a great choice and improvement over the RG8x I ended up with. Now I need to do research to see if the compression tool and connectors I purchased and that worked well with the stranded copper core RG8x coax will work with the LMR400 coax. I saw someone mention that coax uses solid core aluminum in the center so the tool simply may not work. DO you have any experience with that?
Thanks again, - Ed
 

Mister-Ed

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Sounds like a great little device to know about. I'd never hear of these. I "cut the cable" on our TV service perhaps three years back and have been using a TV antenna (also in the attic of our home) with great results. I do have what was advertise as a "TV signal splitter and booster" on the line from that antenna so the one line feeds a number of TVs in the house. On certain days it can lose channels so I wonder if this FM trap could also help that.(?)

I will research what these do specifically and probably try one of these as well but on both the TV and scanner coax.

Thank you fopr your input!
- Ed
 

gmclam

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?

ZERO reception sounds suspicious to me. Do you have an NOAA channel in your area? I'd use that as a starting point to see if you can get anything. Coax is AS IMPORTANT as the antenna (maybe even more). If your coax is shorted, the signal from a perfect antenna will go nowhere. I can't help but feel there is something significantly wrong with your install.
 
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