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Sinker
Intermediate Member
Username: Sinker
Post Number: 452
Registered: 8-2005
| | Posted on Sunday, June 29, 2008 - 4:27 pm: | 
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Well the subject might tell you I have NO CLUE so once again seeking the advice of you fine folks.
I am interested in redoing my Base Antenna and want to do it RIGHT.
I have a 30' heavy duty tower in place with a 10' mast from there to the Antenna for just shy of 40'. Imagine when I add a rotor I will be looking at somewhere around 36' to the feed point.
I am very interested in beam antennas to bring in some of those distant stations and get rid of the noise from adjacent ones in the wrong direction. Also want to focus my signal toward those I am trying to reach. So first question - Am I on the right path here?
What is the difference between vertical and horizontal beam antennas? Trying to figure which I should go with. Also have seen units that are both vertical and horizontal but not sure if they operate at the same time or are switch between. HELP
If I end up with both vertical and horizontal beams do I still need an Omni Directional antenna for when I want everything open for listening to later switch to a beam to dial things in?
I am thinking of a 4 or 5 element beam but am looking for QUALITY. I will enlist the help of a local ham antenna guy for assistance on the install although I only operate 11 meter.
I want a good solid rotor that is HEAVY duty as my mast pipe is 2" galvanized steel plumbing pipe (I think), plus antenna weight and routine 60mph winds. Well, you get the idea.
Not even sure how these rotor and control boxes work but would love to be able to either direct to a specific magnetic bearing or operate through a computer to do the same or even enter a GPS Coordinate but not even sure if they have either.
So, rotor ideas?
Will run new Coax and want to run the very best - What would that be?
I have run a dedicated electric circuit for my radio. Polyphasers are in place and all grounding to include the tower and each and every single piece of radio equipment is also in place tied into a central ground.
This is obviously in the early stages of throwing ideas around as I am learning about this but am looking for a good solid start of ideas from you folks - Antenna Suggestions, Rotor Suggestions, Coax Suggestions etc., etc.
I figure if I have a solid antenna system then I can upgrade my radios later. I want OVERKILL (but not overprice)and something that will work 10 meters should I ever get my license.
Sinker
CEF-634
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Patzerozero
Senior Member
Username: Patzerozero
Post Number: 4309
Registered: 7-2004
| | Posted on Sunday, June 29, 2008 - 7:42 pm: |
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and something that will work 10 meters should I ever get my license-just what i like to hear! and with a tuner, 12 meters, too!
to avoid a book ( ), let's just deal 'antenna' for NOW. and NO change to the tower you have.
1st, signals propagated by BOUNCING from the 'sky' back to earth have a tendancy to 'flip' polarity, vertical to horizontal, even more then once sometimes. the benefit to horizontal {flat} is elimination of SOME vertically polarized noise, man made electronics, and, to some extent on CB, cbers. flipping polarity was evidenced numerous times today on ch 13 as MANY of the skip stations i was talking to heard me better-and sounded better to me-when they went flat side. i was vertical in my truck, or, on 10m, my base too.
and YES you ARE on the right path both focusing rcv & xmit as well as 'finding' what you want with the omni, then switching to the beam. of course switching to a flat side beam when trying to talk local to a vertical isn't going to help.....sometimes concessions need to be made to appease wives, neighbors, and even your own view of what your house looks like with tons of metal flying around.
i don't have much room to do directional antennas here, so that is how i think for those who may be in the same boat, so to speak. so unless you say 'damn the neighbors, full steam ahead', tim, i'd concentrate horizontally polarized beam ONLY. do i remember you having an imax2k, or was it a maco v5/8? BOTH will work WELL when placed on a tower ABOVE a flatside beam. don't use the ground plane kit on the imax or take the ground radials OFF the maco. the beam will be your groundplane. usually 1/4 wave ABOVE the beam is best, you may want to experiment based on your-or anybody's soil conditions.
as for WHAT size beam to use...
Transmitter Power, Antenna Gain, and Coax Loss Trade-offs
By Ken Larson KJ6RZ
In the 1950s and 60s many hams built their own transmitters for the simple reason that commercial transmitters were too expensive. For example, a Johnson Viking II transmitter cost $300, which doesn’t sound too bad until you stop to consider that a new Ford or Chevy cost $1,000. The alternative was to buy cheep war surplus radios and use the parts to build one of the transmitters shown in the Radio Amateur’s Handbook. In a way, that was more fun. As far as power was concerned, you had control! You could push your transmitter as hard as you dared, to squeeze every bit of power out of it, even to the point where the plates of the transmitter’s output vacuum tubes glowed cherry red.
I was convinced in those days that if I could just get another 20 watts of output from my transmitter that it would make all the difference in the world at the receiving end. If I could just get those extra 20 watts that rare DX operator in a distance land would see my signal jump from a pitifully weak whisper to a loud boom that he could not ignore, and I would get that contact. Today I know that little extra power would not have made any difference at all. However, I still have an intense desire to push my transceiver to its maximum power output to get a DX contact. But it doesn’t stop there. I want every db of gain that I can possibly get out of my antenna. As far as coax is concerned, I want that big, heavy, hard to handle, expensive coax because I don’t want to loose any of my valuable watts getting from my transmitter to the antenna. Does all of this pushing, shoving, and optimization really make a difference? Probably not!
It turns out that you must increase the output power of your transceiver by at least 3 db in order for the person you are talking with to notice any change in your signal strength. For your signal to sound twice as loud, you must increase your power out by about 9 db.
How much is a 3 db increase in power? A 3 db power gain is equal to a times 2 increase in power (3 db = x2). So, if your transceiver is running 100 watts, you must increase your transceiver’s output to 200 watts in order for the person you are talking with to notice any increase in your power. If you wanted your signal to sound twice as loud, you must increase your power to 800 watts (9 db = 3 db + 3 db + 3 db = x2 x2 x2 = x8)!. Clearly, increasing power by 20 watts, say from 100 to 120 watts, is not going to make any difference at all to the person receiving your signal. On the other hand, if you cut your power in half from 100 watts to 50 (a 3 db decrease in power), the other operator will hardly notice any drop at all in your signal strength. So why beat your transceiver into the ground by running it at full power? If you run at 75 watts instead of 100, your transceiver will run cooler and no one that you talk to will know the difference. There is someone who may notice the difference however, your neighbors. If you are having interference problems, cutting your power level in half could solve those problems without having any noticeable affect on your ability to make contacts. For example, when I operated on 10 meters at 100 watts, my lawn sprinklers would turn on whenever I keyed my transceiver. When I dropped to 50 watts, the problem went away. Running at 50 watts turned out to be a great water conservation technique.
What about antennas? The same 3 db rule applies. You can go to a lot of trouble and expense on 40 and 80 meters putting up phased vertical arrays to achieve 2 or 3 db of gain. But 3 db of gain will hardly be noticeable to anyone listening to your signal, so why bother? The threshold in antenna cost verses performance gain is around 6 db. If your antenna provides 6 db of gain, operators listening to your signal will notice a difference. Your signal will not be twice as loud, remember you have to get 9 db of gain for that to happen, but at 6 db the gain will be noticeable. The table below puts antenna cost verses performance gain somewhat into perspective. This table compares various yagi beam configurations to the performance of a dipole. The table shows the db gain, relative to a dipole, achieved by each of the antennas. The antennas get more expensive as you go down the table. The table also indicates the increase in signal strength observed by the S-meter on a distant transceiver that is receiving your signal.
Antenna db Gain S-unit Increase Comment
Dipole 0 0 Baseline
2-element Yagi Beam
4 0.6 Marginal performance increase
3-element Yagi Beam
6 1.0 Good performance increase
10-element Yagi Beam
12 2.0 Excellent performance increase
The cost verse performance trade-off for the transmission line connecting a transceiver to an antenna is similar to the antenna cost trade-off. However, this time the trade-off relates to the difference in loss between two types of transmission lines, for example, between two different grades of coax cable. As an illustration, 100 feet of LMR 400 coax used to connect a transceiver with a 10 meter antenna will produce a loss of 0.7 db. If standard RG-8/X coax is used instead, the loss will be 2.0 db. The difference in loss between the two types of coax is 1.3 db. Is it worth buying the more expensive LMR 400 coax to reduce loss by 1.3 db? Probably not. The strength of your signal in this example will sound the same to other hams regardless of which type of coax you use. Notice in making a comparison between two types of coax (or two types of antennas, etc.) it is the difference in loss (or gain) that is important, not the actual loss (or gain). At UHF frequencies, the differences in loss will be greater. 100 feet of LMR 400 coax at 440 MHz has a loss of 2.7 db. In comparison, RG-8/X has a loss of 8.1 db. The difference in loss is 5.4 db. In this case the more expensive LMR 400 coax may be worth the money. LMR 400 coax is relatively thick, stiff, and difficult to work with compared to RG-8/X, particularly inside the radio shack. Suppose that you use 75 feet of LMR 400 to get from your 440 MHz antenna to the wall outside your radio shack. Then you use a 25 foot length of RG-8/X to come through the wall and into the radio shack because RG-8/X is smaller and easier to handle in the shack. What performance penalty will you pay for doing this? The loss of 25 feet of RG-8/X is about 2.03 db. If you brought the LMR 400 all the way into the shack, the loss associated with the additional 25 feet of LMR 400 would be 0.68 db. The difference in loss is approximately 1.36 db, a negligible amount. Using RG-8/X within the radio shack is thus a good choice since it simplifies cable management within the shack and provides negligible additional loss.
In making trade-off comparisons, you have to look at the total system as well as the individual components. For example, a 2-element 10 meter yagi antenna (4 db gain over a dipole) feed by LMR 400 coax (1.3 db gain over RG-8/X coax) produces a total system gain of 5.3 db compared to a 10 meter dipole feed with RG-8/X coax. The total system gain of 5.3 db probably is worth the effort, even thought the gains between the individual components was not that attractive. The system trade-off can easily go the other way as well. At 440 MHz, 100 feet of LMR 400 coax has a 5.4 db performance gain over RG-8/X coax and is clearly better. However, if your transceiver has power settings of 5, 10, and 50 watts, and you can hit all of the area repeaters at 10 watts using RG-8/X coax, why upgrade to LMR 400? Unless you are running off of batteries, using LMR 400 coax so that you can drop your transmit power to 5 watts probably is not worth the trouble or cost.
In conclusion, when making trade-offs between transmitter power, antenna gain, coax loss, and total system performance, it is the db difference between the options available to you that is important. A difference of 3 db will not be apparent to the hams that you are communicating with. They will hardly notice the difference if you run your transmitter at 50 watts instead of its maximum 100 watt output power. A difference of 3 db or less between two antennas, two types of coax, or two system implementations is usually not sufficient to justify higher costs. However, a difference of 6 db may justify the more expensive approach.
i hope that-and the table-makes sense, had to cut & paste as it contained too many links. try to google 'yagi antenna', 'yagi antenna gain', etc. signal engineering also has a page with good info.
unfortunately, there is WAY TOO MUCH BAD info regarding antenna gain. i'd guess 90% of gain info by antenna manufacturers is BS! ham antennas too! and by reputable manufacturers! maybe that's too extreme, but your best bet is to read a bit about antenna gain if you want an HONEST idea of what you're getting. in truth, gain is MORE then just HOW LONG & HOW MANY ELEMENTS, but-how high off the ground, how the elements are spaced, and as i noted above, the quality of the SOIL underneath the antenna!
so HOW involved do you want to get now? how about HOW BIG? commercially available cb beams range from about 11' to 40' in length. i could probably squeeze in a 16' boom personally, maybe you can fit the next size, 26'. maybe not. next, remember that the more elements you have, the more you pinpoint the signal, which may be good, may be bad. 5 elements on the 26' boom may be just right. then again, maybe you can fit a 31' boom, which on a maco antenna has 6 elements. HOWEVER, different spacing of only 5 elements on that 31' boom may get you better GAIN.....maybe we just want to stay with what is commercially available, rather then modifying it, huh!
maco says 14, 15.5 & 17 db gain in their 16', 26' & 31' booms. which is not described as 'gain compared to what' (dbd or dbi). skipping ahead, remember, 3 db gain gets you 1/2 of an S-unit, 6 db 1 S-unit, etc. HOW it reads on your meter is LESS important then knowing that 6 db is effectively doubling your signal, or making 100 watts sound like 200. FORGET all antenna manufacturers claims as to 'power increase'.
ok tim, so what antenna do you want????? . we'll continue once you answer THAT question  |
Sinker
Intermediate Member
Username: Sinker
Post Number: 456
Registered: 8-2005
| | Posted on Sunday, June 29, 2008 - 8:29 pm: |
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OK now my head hurts. 
Just got a call from the local Ham guy. He just got a bunch of stuff from an estate sale. He has a YAESU G-450A rotor for a good price that he says will work for me and also a Yaesu G-800SA if I need something bigger. 
I am using LMR 400 coax now so maybe I do not need to upgrade that.
Presently running a Maco V5000 antenna with Ground Plane.
Thinking maybe a 4 element (is that the 16' boom as I don't think I want to go 26') horizontal beam with a SIGMA MANTOVA TURBO omni directional above it. As for the 4 element though I have NO IDEA what make or model as I know nothing about them. I will take recommendations though.
Looks like the 4 element needs to be decided on first, then purchased. Then I need to get my hands on a SIGMA MANTOVA TURBO (hurry up Copper) and then the install is ready to move forward.
I already have two runs of LMR 400 going to the tower. One with a IS-B50LU-CO Polyphaser and one with a IS-B50HU-CO Polyphaser.
Also if/when I get my ticket I do have an old Galaxy Saturn Turbo with an X-Force 60012HD amp. I was selling this but might keep a hold of it now or maybe still sell it to help fund the new antenna system. So I guess both antennas should be able to handle 2000 watts.
Just thinking that a good solid designed, installed and grounded antenna system will be the key component and I can worry about the radio, amps etc. later.
Oh yeah, I live in Florida, my dirt is SAND
Sinker
CEF-634
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Big_m
Junior Member
Username: Big_m
Post Number: 12
Registered: 9-2007
| | Posted on Monday, June 30, 2008 - 8:44 pm: |
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Patzerozero, Thank you for the very informative info. I anyone armed with this info can have a Super Performing Station even on a small budget. I see some Giant DXing stations on the rise. |
Sinker
Intermediate Member
Username: Sinker
Post Number: 458
Registered: 8-2005
| | Posted on Tuesday, July 01, 2008 - 9:49 am: |
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Of course it looks as though we may have an issue with the tower - Go Figure. I had picked it up as a You come get it you can have it and had to fix some welds, sand and paint it but it has worked well.
The top section is cracked where the mast goes through. Not sure I can weld it and still have a good circle for the bearing.
It also is only about 6' above the peak of my roof so not sure a beam at that height will do much.
If I can get it all to work I may go with the Maco M104 C 4 element beam antenna and use the Maco V5000 I already have above it for my omni.
As for the info Pat has provided - Yup he is great and very kind. It is because of him that any of you can hear me. He has given me a ton of advice freely and every Sunday Net you can hear him out there recruiting new folks to Copper. Definitely one of the GOOD GUYS.
Sinker
CEF-634
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Patzerozero
Senior Member
Username: Patzerozero
Post Number: 4316
Registered: 7-2004
| | Posted on Wednesday, July 02, 2008 - 6:30 pm: |
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you can probably persuade some sort of thrust bearing to fit ON TOP of the hole where the mast goes & get sufficient support for a 4 element beam. or you may be able to cut away part of it & reweld a new tube.
if the TOWER is 6' above the roof, adding a few feet for the mast will be fine at 27 mhz, and of course the maco 9' above....just use some high tensile steel mast, not aluminum from rat shack!
and tim , if i was just a little less humble then i REALLY am, i wouldn't be smiling right now  . by the way, if YOU start to consistantly 'own' ch 13 like YOU did 2 weeks ago, i'll start rethinking my suggestions |
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