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Sixkiller505
| | Posted on Thursday, February 27, 2003 - 5:29 pm: | 
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do you think that the top one ant would be better than the antron etc etc ground planes for tvi problems,because the higher up over 25 ft.the more the signal travels skyward? will that mean less signal to travel unwanted places?? sixkiller505 love country |
Tech833
| | Posted on Friday, February 28, 2003 - 10:18 am: |
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A Top One will not have any less TVI than another antenna since TVI itself is not caused by the radiating antenna unless it has loose connections in or near the RF path. Scuffing the aluminum connections and using Penetrox will easily solve that in any aluminum antenna. Not possible on a fiberglass antenna.
However, to answer the question about reducing TV receiver blanketing interference by getting the signal over the receiver, that is mixed. Either way, if you raise your antenna higher above the ground, you are effectively getting the radiation source farther away from the receiver being affected. It is the same effect as moving the antenna farther away in any plane or angle. Blanketing interference is solved by spacing the radiating antenna further away from the affected receiver or reducing power.
Now as for the design of the Top One removing the antenna's current node further from the receiver, yes. But only by the length of the antenna mounting bracket itself. Not really enough to worry about. If you are experiencing blanketing TVI, you are better off with a 5/8 wave ground plane antenna or an Imax 2000 w/GPK to reduce the downward radiation. Then, you need to ground the antenna system extremely well. A 4 foot ground rod is not good enough in most parts of the country. An 8 foot 1/2 inch minimum rod is better. |
Sixkiller505
| | Posted on Friday, February 28, 2003 - 6:27 pm: |
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thanks tech833. how do you feel about the maco v quad beam it suppose to talk vertical and horizontal at the same time,how do you feel about this.and how much do you think you lose in signal out the back door.and what about unwanted signal from other base stations,about how far(blocks, miles etc.do you think you can reject them. |
Tech833
| | Posted on Friday, February 28, 2003 - 8:48 pm: |
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The V quad is a miserable device, in my opinion. It is NOT vertical and horizontal at the same time, it is not circular, it is merely slant polarized.
A Signal Engineering 2 element quad will outperform a V quad hands down and give you your choice of vertical, horizontal, or with proper phasing, true circular. |
Tech833
| | Posted on Saturday, March 01, 2003 - 10:53 am: |
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Now to get off my soapbox and answer your other questions...
The F - B ratio on a V quad will be similar to a regular quad with the exception of being able to reject a specific polarity. In other words, a vertical signal will still 'get through' the 'back door' more than it would with a true quad in vertical polarity.
Rejection can't be measured in miles or blocks. Rejection is a ratio based on the level of signal coming to the antenna from different directions. If someone were hitting your antenna with -50 dB/m of signal and your antenna had a F/B ratio of 30 dB, then you would have -80 dB/m signal if you turned the back to them. This is roughly 5 S-units difference on your signal meter.
Therefore, in theory, if someone was hitting you with 5 S-units off the front and you turned your beam with a 30 dB F/B ratio the opposite direction, they would disappear into the noise.
On the other hand, if someone were hitting you with +10 S-units and you turned the same antenna the opposite direction, they would now be hitting you with +5 S-units. Still 'in the red'.
Another thing to consider is reflections. An antenna's F/B ratio is calculated in 'free space' That means, if there were nothing around the antenna but vacuum, then the F/B is accurate. In the real world, there are buildings, trees, power lines, cars, rivers, hills, etc. A signal from a station across town may be coming at you from many different directions depending on how may things it reflected off of. This is called 'multipath'. If you ever want to see how bad multipath is on a radio signal, find the local ham club and ask to ride along on a transmitter hunt. It would be a real eye opener! With this information in mind, a beam's F/B ratio becomes relevant only to signals with no multipath. For a beam antenna, the gain out the front should be the first consideration since getting the most signal to and from your intended station is more important.
Changing gears.
Although I do not talk on the CB, I do listen. I heard something really interesting the other day. Two people on base stations were trying to talk to one another on the CB and someone kept interfering with them by 'walking on' them when they tried to talk. This jammer followed them around no matter what channel they moved to. Instead of give up or run illegal power, one of the stations called the other on his cell phone (I also scan the analog cell phone bands, it is an illness). My receiver stopped on a cell phone channel with the phone ringing (also known to a cell phone scanner as 'fresh meat') The next thing I know, I hear the same CB conversation on the cell phone at the same time. You guessed it, they were simulcasting on the CB and the cell phone at the same time! They did not mention that they were on the phone at all. The jammer just figured he wasn't getting in between them any more and gave up! Then the cell dropped and they continued their conversation on the CB, never once mentioning anything about the cell phone 'linear'. It was really funny! I had to share that. |
2ec837
| | Posted on Saturday, March 01, 2003 - 12:22 pm: |
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Why does Maco and why did Wlison call them V-Quads when they are three sided? Was Delta Loop too long or confusing?
In my area analog traffic has just about disappeared.
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Sixkiller505
| | Posted on Saturday, March 01, 2003 - 3:30 pm: |
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tech 833 you are funny ha!ha!ha! that goes on in my neiborhood too.and if i had to give up my cb or my scanner,cb goes bye bye!IAM A SNOPER FOR LIFE ha!ha! it is and illness and and iam a junky!!a while back on the forum a guy from NC. mentioned "big bubba" sounding like 90000.00 watts to his station.well guess what?? "big bubba" lives 3 miles on the back side of me in va. go figure huh!! since you mentioned the two element quad by signal engineering i went to there web site, it may look like a PDL but from the specs. a PDL is second two it. dont you think so? iam buying it and keeping my back door to "bubba". i know it want get him all the way out of my radio,but it will keep him out enough for me to hear out of my front door. thank for your help 505 love country |
Tech833
| | Posted on Sunday, March 02, 2003 - 11:14 am: |
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The PDL II is a close second to the Signal Engineering 2 element quad. However, the PDL II is no longer made and the Signal Engineering quad is. |
Bigbob
| | Posted on Monday, March 10, 2003 - 12:48 am: |
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I have a PDL II it's not much better than an antron 99 w/gpk it offers some rejection and gain over the latter but not enough to warrant the added cost of more coax and rotor and antenna,that's why a WHITE LIGHTNING is going up this spring.Tech 833 a former radio bud said he added two verticals to either side of the ref. on his astro beam at the same spacing and increased both his side and rear rejection,huh? |
Tech833
| | Posted on Monday, March 10, 2003 - 12:40 pm: |
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Yes, that is possible. Have you ever seen a corner reflector type of antenna? The more reflectors you add behind the driven element, the more F/B ratio you will get. However, you reach a point of diminishing returns as you add more and more reflectors. You finally reach a point where more reflectors no longer make a difference.
Adding 2 more reflectors less than 1/4 wave apart from the existing reflector will make approximately 2 dB F/B improvement. |
Crafter
| | Posted on Monday, March 10, 2003 - 12:54 pm: |
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Dont believe everything you read, either 9.9 db gain on a A99 over what a milk can. Dont get me wrong there good antennas but That pdl2 is for the money a good system buy a antron and put it up on the top of your mast between the pdl. I noticed no effect on either antenna Im sure there is but it was nominal. I used the antron for local talk and pdl for DX. Also isnt a pdl a full wave antenna ? |
Tech833
| | Posted on Monday, March 10, 2003 - 11:50 pm: |
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A PDL 2 is not a full wave antenna. It is a quad. A quad does have a full wavelength wire which forms the driven element. Electrically speaking, a quad's driven element is actually 2 1/2 wave dipoles in phase.
An A99 is nowhere near the gain of a PDL 2. If both antennas are at the same elevation above ground, the PDL 2 will stomp all over the A99. Using round figures, the front of a PDL 2 has about 7 dB gain over an A99. That's a bunch.
Mounting a PDL 2 real low to the ground will devistate its performance. |
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