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New Antenna Worth Trying ?
Hi,
I have a Uniden 996 scanner and would really like to pick up some marine traffic from Boston Harbor. Live about 20 miles due west of the harbor. Have a Scantenna antenna which I think is "pretty good". It's up in my attic. It's omni directional, and broadband over the typical scanner ranges (supposedly). I can often pick up coast guard conversations, but very rarely (but ooccassionally) ship traffic. Do you think a dedicated, very directional, and tuned to the marine freq's would help, or am I just too far away ? Any thoughts on, or antenna suggestions would be most appreciated. No idea what to buy, if you feel it's worth a try ? Very interested in the AIS data being transmitted by ships at around 162 MHz, as well as general marine stuff. BTW: really surprised that I hear the CG at all. I would have thought that their antennas would be "focused" out to sea, with any propagation going the other way (towards me) minimized to maximize the effectiveness of their radiated power in the direction that it's needed. Thoughts ? Thanks, Bob |
New Antenna Worth Trying ?
On Tue, 12 Jun 2007 09:10:26 -0400, "Robert11"
wrote: Hi, I have a Uniden 996 scanner and would really like to pick up some marine traffic from Boston Harbor. Live about 20 miles due west of the harbor. Have a Scantenna antenna which I think is "pretty good". It's up in my attic. It's omni directional, and broadband over the typical scanner ranges (supposedly). I can often pick up coast guard conversations, but very rarely (but ooccassionally) ship traffic. Do you think a dedicated, very directional, and tuned to the marine freq's would help, or am I just too far away ? Any thoughts on, or antenna suggestions would be most appreciated. No idea what to buy, if you feel it's worth a try ? Very interested in the AIS data being transmitted by ships at around 162 MHz, as well as general marine stuff. BTW: really surprised that I hear the CG at all. I would have thought that their antennas would be "focused" out to sea, with any propagation going the other way (towards me) minimized to maximize the effectiveness of their radiated power in the direction that it's needed. Thoughts ? Thanks, Bob I suggest you get your antenna out of the attic and put it outside as high up as you can get it. For VHF height is everything. Danny, K6MHE |
New Antenna Worth Trying ?
Robert11 wrote:
Hi, I have a Uniden 996 scanner and would really like to pick up some marine traffic from Boston Harbor. Live about 20 miles due west of the harbor. Have a Scantenna antenna which I think is "pretty good". It's up in my attic. It's omni directional, and broadband over the typical scanner ranges (supposedly). I can often pick up coast guard conversations, but very rarely (but ooccassionally) ship traffic. Increasing your antenna height would probably improve reception more than increasing antenna gain at that distance. Theoretically, ships will switch to low power (~5 watts) when they enter the harbor, but you should still hear them. I think pilot-to-tug communication is done with portable, hand-held radios. Very low power is needed for distances on the order of a few hundred feet and antenna height is quite close to the water. So you may not be able to hear these communications from your distance. If you look he http://209.85.165.104/search?q=cache...lnk&cd=2&gl=us Chapter 11 â–* Coast Pilot 1 you will find some info on which VHF channels ships would normally use (#13) in their approach to Boston Harbor. Also, you can see that transmissions are brief and occur at specific points. Unlike the USCG, which recites a 1,000 word, mostly unintelligible, preamble to every announcement, ship traffic in a crowded harbor is likely to be terse and easy to miss. A call to the Harbormaster or a posting to a marine newsgroup (rec.boat.electronics) could get a more definitive answer. Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
New Antenna Worth Trying ?
On Jun 12, 7:10 am, "Robert11" wrote:
Hi, Do you think a dedicated, very directional, and tuned to the marine freq's would help, or am I just too far away ? Sure, I did the same thing once. Except I'm 55-65 miles from the gulf, instead of 20.. I built a 4 el yagi for 162 mhz. Worked great, and I could hear boats that didn't exist on the omni vertical. MK |
New Antenna Worth Trying ?
"Robert11" wrote in message . .. Hi, I have a Uniden 996 scanner and would really like to pick up some marine traffic from Boston Harbor. Live about 20 miles due west of the harbor. Have a Scantenna antenna which I think is "pretty good". It's up in my attic. It's omni directional, and broadband over the typical scanner ranges (supposedly). I can often pick up coast guard conversations, but very rarely (but ooccassionally) ship traffic. Do you think a dedicated, very directional, and tuned to the marine freq's would help, or am I just too far away ? Any thoughts on, or antenna suggestions would be most appreciated. No idea what to buy, if you feel it's worth a try ? Very interested in the AIS data being transmitted by ships at around 162 MHz, as well as general marine stuff. BTW: really surprised that I hear the CG at all. I would have thought that their antennas would be "focused" out to sea, with any propagation going the other way (towards me) minimized to maximize the effectiveness of their radiated power in the direction that it's needed. Thoughts ? Thanks, Bob Hi Bob Do you want to try building your own antenna? If so, I'd think a simple antenna like a J-pole ( http://www.hamuniverse.com/jpole.html ) would be worth trying. Jerry |
New Antenna Worth Trying ?
wrote in message ups.com... On Jun 12, 7:10 am, "Robert11" wrote: Hi, Do you think a dedicated, very directional, and tuned to the marine freq's would help, or am I just too far away ? Sure, I did the same thing once. Except I'm 55-65 miles from the gulf, instead of 20.. I built a 4 el yagi for 162 mhz. Worked great, and I could hear boats that didn't exist on the omni vertical. MK I used to pick up tons of stuff about 20 miles away with just a vertical antenna at about 50 ft. My experience with VHF/UHF in the attic has not been good. I think asphalt shingles are pretty good RF absorbers at that frequency. Jimmie |
New Antenna Worth Trying ?
In article ,
Robert11 wrote: Have a Scantenna antenna which I think is "pretty good". It's up in my attic. It's omni directional, and broadband over the typical scanner ranges (supposedly). I can often pick up coast guard conversations, but very rarely (but ooccassionally) ship traffic. Do you think a dedicated, very directional, and tuned to the marine freq's would help, or am I just too far away ? Could very well help, especially if you can get it up above the attic into clear air. In fact, the height of the antenna may make more difference than antenna gain/directionality. My guess is that your current antenna is high enough up to pick up the shore antennas (which are probably tower- or building-mounted) but is too low to be in good line-of-sight to the ships themselves. Review the page at http://www.connect802.com/height.htm - it has a chart showing the required height-above-ground of an antenna, to "see" another antenna past the earth's curvature. Any thoughts on, or antenna suggestions would be most appreciated. No idea what to buy, if you feel it's worth a try ? Take a look at http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf Simple, decent-performing Yagi antennas that you can throw together with a piece of one-by-two wood for the beam, some stiff copper wire, and a soldering iron. I'd suggest taking the dimensions for the simplest (3-element) 144 MHz antenna, and rescaling them all by a factor based on the _highest_ marine-band frequency you want to receive. You'll need to rescale the element lengths, and the distances between the elements. You'll end up with a Yagi which is intermediate in size between the 144- and 220-MHz versions. Very interested in the AIS data being transmitted by ships at around 162 MHz, as well as general marine stuff. BTW: really surprised that I hear the CG at all. I would have thought that their antennas would be "focused" out to sea, with any propagation going the other way (towards me) minimized to maximize the effectiveness of their radiated power in the direction that it's needed. At most, I'd think that they'd use an antenna with a cardioid or off-center-circular pattern, so that a single shore station's signal would cover the whole half-circle with fairly equal power. There's probably still quite a bit of back-spill towards shore - plenty enough for you to receive. They wouldn't use (or need to use) an antenna with an extremely high front-to-back ratio, because they have no need to "reject" transmissions from shore-side... since there probably aren't any. Increasing the front-to-back ratio would just add complexity and expense to the antenna, reducing its overall reliability (more things to break), at no significant benefit in received-signal quality or desired-direction output power. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
New Antenna Worth Trying ?
On Jun 12, 11:10 pm, "Robert11" wrote:
Hi, I have a Uniden 996 scanner and would really like to pick up some marine traffic from Boston Harbor. Live about 20 miles due west of the harbor. Have a Scantenna antenna which I think is "pretty good". It's up in my attic. It's omni directional, and broadband over the typical scanner ranges (supposedly). I can often pick up coast guard conversations, but very rarely (but ooccassionally) ship traffic. Do you think a dedicated, very directional, and tuned to the marine freq's would help, or am I just too far away ? Any thoughts on, or antenna suggestions would be most appreciated. No idea what to buy, if you feel it's worth a try ? Very interested in the AIS data being transmitted by ships at around 162 MHz, as well as general marine stuff. BTW: really surprised that I hear the CG at all. I would have thought that their antennas would be "focused" out to sea, with any propagation going the other way (towards me) minimized to maximize the effectiveness of their radiated power in the direction that it's needed. Thoughts ? Thanks, Bob hi bob ..if you want really good reception on vhf marine band ,you should consider buying a ham 2mtr band base antenna . these work on 147mhz and will work just as good on the marine band for receive. hope this helps ... bob vk4la in australia |
New Antenna Worth Trying ?
"Robert11" wrote in message . .. Hi, I have a Uniden 996 scanner and would really like to pick up some marine traffic from Boston Harbor. Live about 20 miles due west of the harbor. snip No idea what to buy, if you feel it's worth a try ? snip Thoughts ? I googled for marine band colinear and got this near the top: http://buyreliant.com/marine/5102.htm It's way cheaper than some name-brand competitors, like Shalespeare, but you're not going to be stressing it on a boat, so give it a try on your rooftop or chimney. |
From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
Hi,
Thanks for link to the Shakespeare Vertical Antenna. Know very little about antennas, but was wondering. Is this vertical whip , or any vertical, a better bet to try as compared to perhaps a "simple Yagi for the Marine bands ? Why ? This Shakespeare vertical whip is described as: It's a 6dB collinear phased 5/8-wave antenna of 8-foot nominal length. Again, I'm about 25 miles due west of Boston Harbor, but would sure like to at least try to pick up some Marine VHF comms from the harbor. Hard for me now at my age to try a whole bunch of antennas, so would like to limit it to what you experts feel would offer the best "chance". Thanks again, Bob -------------------------------------- "Sal M. Onella" wrote in message ... "Robert11" wrote in message . .. Hi, I have a Uniden 996 scanner and would really like to pick up some marine traffic from Boston Harbor. Live about 20 miles due west of the harbor. snip No idea what to buy, if you feel it's worth a try ? snip Thoughts ? I googled for marine band colinear and got this near the top: http://buyreliant.com/marine/5102.htm It's way cheaper than some name-brand competitors, like Shalespeare, but you're not going to be stressing it on a boat, so give it a try on your rooftop or chimney. |
From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
On Fri, 15 Jun 2007 08:01:34 -0400, "Robert11"
wrote: Hi, Thanks for link to the Shakespeare Vertical Antenna. Know very little about antennas, but was wondering. Is this vertical whip , or any vertical, a better bet to try as compared to perhaps a "simple Yagi for the Marine bands ? Why ? This Shakespeare vertical whip is described as: It's a 6dB collinear phased 5/8-wave antenna of 8-foot nominal length. Again, I'm about 25 miles due west of Boston Harbor, but would sure like to at least try to pick up some Marine VHF comms from the harbor. Hard for me now at my age to try a whole bunch of antennas, so would like to limit it to what you experts feel would offer the best "chance". Thanks again, Bob -------------------------------------- A 5/8-wave collinear has 3dBd gain. Danny |
From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
On Jun 15, 7:54 am, wrote:
On Fri, 15 Jun 2007 05:59:55 -0700, Danny Richardson wrote: On Fri, 15 Jun 2007 08:01:34 -0400, "Robert11" wrote: Hi, Thanks for link to the Shakespeare Vertical Antenna. Know very little about antennas, but was wondering. Is this vertical whip , or any vertical, a better bet to try as compared to perhaps a "simple Yagi for the Marine bands ? Why ? This Shakespeare vertical whip is described as: It's a 6dB collinear phased 5/8-wave antenna of 8-foot nominal length. Again, I'm about 25 miles due west of Boston Harbor, but would sure like to at least try to pick up some Marine VHF comms from the harbor. Hard for me now at my age to try a whole bunch of antennas, so would like to limit it to what you experts feel would offer the best "chance". Thanks again, Bob -------------------------------------- A 5/8-wave collinear has 3dBd gain. Danny However, a 5/8 is only 48inches, that antenna is a stacked 5/8s colinear and at 8ft 6db would be correct. Allison A stacked dual 5/8 collinear will give appx 3dbd.. A single 5/8 GP will do appx 3.3 dbi give or take.. I recommend a small yagi myself.. It will eat the verticals for lunch if both are in the attic. Course, you have to point it though.. MK |
From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
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From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
I was under the impression that a 1/4 wave was approx 0 dBd, a
5/8ths was approx 3dBd, and a collinear dual 5/8ths was approaching 6dBd Nick |
From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
On Jun 15, 2:10 pm, "Nick" wrote:
I was under the impression that a 1/4 wave was approx 0 dBd, a 5/8ths was approx 3dBd, and a collinear dual 5/8ths was approaching 6dBd Nick Most the textbooks rate the 1/4 wave GP at .3 dbi. The 1/2 wave at 2.1 dbi or 0 dbd. The 5/8 GP appx 3.3 dbi, or 1.2 dbd. The dual 5/8 collinear appx 5.1 dbi or 3 dbd. But.... If you model the antennas, the sloping radial 1/4 GP actually does a bit better.. Appx 1.8 dbi, which is within .3 db of the 2.1 dbi you would see from a 1/2 wave. BTW, these are "free space" numbers. I don't like to confuse people by adding ground effects... Besides, if you do model over ground, you will see the same comparison spread.. It doesn't really change anything.. The gain from a 5/8 GP can be all over the map depending on the radial length used.. Most 5/8's use 1/4 wave radials. No bueno. At an old page I put up, you can see the effect of radial length on the performance of the 5/8 GP. http://web.wt.net/~nm5k/acompari.htm Many people rag on the 5/8 antenna, but the largest problem is due to an old lousy obsolete design which uses the short 1/4 wave radials. If you use longer radials, such as 5/8 or 3/4 you will see the rated gain you would expect from a 5/8 GP. If you use 1/4 wave radials, you can often see less gain at the desired angles than either the 1/2 wave, or 1/4 GP. Of course, all these examples assume no common mode currents on the feedline.. On VHF/UHF, decoupling of the feedline can be as important as the antenna design itself. So if I were to build say a dual 5/8 collinear, or a 5/8 GP with steep 5/8 radials, I would add a decoupling section below the lower element. IE: like an isopole, or whatever.. It used a lower 1/4 wave cone as the decoupling device. You could also add a section of 1/4 wave radials for decoupling.. 6dbd from a dual element vertical? Good luck..A 3 el NBS yagi is only good for about 7.3 dbd, and it will thrash a dual 5/8 collinear. If the height is limited, I would use the highest gain antenna I could scrape up. Even if you have obstructions, it's going to do a heck of a lot better than most any vertical at the same height. MK |
From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
Nick wrote:
I was under the impression that a 1/4 wave was approx 0 dBd, a 5/8ths was approx 3dBd, and a collinear dual 5/8ths was approaching 6dBd Nick 5/8ths isn't what it's advertised it to be. I'd explain it, but I have to finish watching SG1 and then F1 practice session 2. It has to do with "ground planes" and the fact that they are mostly fictional in this case. And that the second 5/8ths doesn't have the needed "ground plane". I'm sure someone else will explain fully. tom K0TAR |
From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
On Jun 15, 6:46 pm, Tom Ring wrote:
5/8ths isn't what it's advertised it to be. I'd explain it, but I have to finish watching SG1 and then F1 practice session 2. It has to do with "ground planes" and the fact that they are mostly fictional in this case. And that the second 5/8ths doesn't have the needed "ground plane". I'm sure someone else will explain fully. tom K0TAR In my opinion, a 5/8 vertical should be set up to be a complete antenna, which means it needs 5/8 on the "other" side.. Running a 5/8 over 1/4 wave radials is fairly perverted.. It's no wonder it doesn't live up to expectations. But a dual 5/8 collinear is a pretty stout vertical, as far as verticals go. I think 5/8 ground planes should use either 3/4 or 5/8 wave radials if one uses actual radials, to more closely simulate a collinear. A dual 5/8 collinear is a complete antenna, and requires no radials at all. I compared all the usual types "lengths" on 10m a few years ago, and my 5/8 GP with four 3/4 wave radials handily beat a base fed half wave, with and without decoupling. I used 3/4 wl radials because I wanted a low Z.. But if I made one with real steeply sloped radials, I think I would make them 5/8 wave. But, I never got around to trying one with 5/8 radials, so not sure how it would compare to my last version. BTW, all my tests were done using "ground/space" wave locally, and were pretty accurate as far as telling which was best. I'm using a low angle path for that type of thing too.. Many of the people I talked to were 20-30-40 miles away. MK |
From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
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From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
On Jun 15, 8:01 pm, John Smith I wrote:
wrote: ... In my opinion, a 5/8 vertical should be set up to be a complete antenna, which means it needs 5/8 on the "other" side.. ... Obviously, OCF antennas must set you off also. JS Fer sure... MK |
From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
John Smith I wrote:
wrote: ... In my opinion, a 5/8 vertical should be set up to be a complete antenna, which means it needs 5/8 on the "other" side.. ... Obviously, OCF antennas must set you off also. JS Yes, they are certainly counter-intuitive ... there is form and beauty in symmetry alright. JS |
From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
"John Smith I" wrote in message ... John Smith I wrote: wrote: ... In my opinion, a 5/8 vertical should be set up to be a complete antenna, which means it needs 5/8 on the "other" side.. ... Obviously, OCF antennas must set you off also. JS Yes, they are certainly counter-intuitive ... there is form and beauty in symmetry alright. JS ....and how about OFC antennas ? Nick |
From OP: Vertical Or Yagi ? New Antenna Worth Trying ?
Nick wrote:
... JS ...and how about OFC antennas ? Nick Surprisingly functional? An ugly duckling? JS |
New Antenna Worth Trying ?
"Jerry Martes" wrote in message news:TYAbi.3722$O15.28@trnddc03... "Robert11" wrote in message . .. Hi, I have a Uniden 996 scanner and would really like to pick up some marine traffic from Boston Harbor. Live about 20 miles due west of the harbor. Have a Scantenna antenna which I think is "pretty good". It's up in my attic. It's omni directional, and broadband over the typical scanner ranges (supposedly). I can often pick up coast guard conversations, but very rarely (but ooccassionally) ship traffic. Do you think a dedicated, very directional, and tuned to the marine freq's would help, or am I just too far away ? Any thoughts on, or antenna suggestions would be most appreciated. No idea what to buy, if you feel it's worth a try ? Very interested in the AIS data being transmitted by ships at around 162 MHz, as well as general marine stuff. BTW: really surprised that I hear the CG at all. I would have thought that their antennas would be "focused" out to sea, with any propagation going the other way (towards me) minimized to maximize the effectiveness of their radiated power in the direction that it's needed. Thoughts ? Thanks, Bob Hi Bob Do you want to try building your own antenna? If so, I'd think a simple antenna like a J-pole ( http://www.hamuniverse.com/jpole.html ) would be worth trying. Jerry Yes it is worth trying. I can pick a telemetry transmitter nearly 30 miles away that only puts out about 5 watts on just above 400Mhz. There are 2 transmitters there and I can only pick up one .The one I cant pick up has its antenna at about 20ft above the ground , the other is a 50 ft. Just an example of what a difference heigth makes. Jimmie |
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