| Author |
Message |
    
mikefromms
| | Posted on Monday, July 07, 2003 - 8:06 pm: | 
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I was searching the web the other day and ran across a product advertised as a round dish style antenna for 27mhz. Anyone heard anyone on the air using one of these? Does it use a rotor?
mikefromms |
Alpha1
| | Posted on Monday, July 07, 2003 - 9:16 pm: |
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I've seen one called the CB-SAT by President Electronics.
I tried to get further spec info from President
but they refered me to one of their U.S. distributors.
But I really got no further technical info from them than what was available on the web sites themselves. It was as follows:
PARABOLIC CB BASE ANTENNA.
*TYPE, 1/2 WAVE
*IMPEDANCE, 50 OHMS-ACCEPTS STANDARD PL-259 COAX CONNECTOR
*FREQUENCY, 26-30 MHZ
*GAIN, +3 DBI POLARIZATION, VERTICAL-REQUIRES NO
GROUND
*ADJUSTABLE SWR, 1,1/1
*MAX POWER, 100 WATTS
*BAND WIDTH, 1200KHZ
* DIAMETER, 17in"
Also, the contact stated the following:
"This antenna is used mainly where you have a limited use of antennas,
such as in an apartment. If you are able to use another antenna such as
some that you have mentioned (i.e. A99, Big Stick, TopHat/AstroPlane, etc) I would suggest you do so. This antenna
has a mount for attaching to a mast pipe. I'm sure you can improvise
and attach it some other way".
Was this the same antenna that you saw?
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Tech833
| | Posted on Monday, July 07, 2003 - 9:56 pm: |
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It would need more than a standard rotor. A dish for 27 MHz. would have to be a MINIMUM of nearly 40 feet across. |
mikefromms
| | Posted on Monday, July 07, 2003 - 10:45 pm: |
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How about shooting skip off satelites in space? CB the year 2050--which part of the world do you wish to talk? Point you cb dish at satelite 11 and talk to Spain. Wouldn't that be something? Of course, a cell phone might be just as good. LOL.
mikefromms |
Tech808
| | Posted on Monday, July 07, 2003 - 11:03 pm: |
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mikefromms,
Mike,
Pay $12.00 and take a 35 question TECHNICIAN CLASS Test and get your Ham License and you can talk anywhere in the world without a radio or Antenna on ECHOLINK thru your computer. When conditions are DEAD you can't beat it and it's FREE. 
Right now there are 1376 Stations on Echolink and only 20% are busy.
Lon
Tech808 |
Kc0gxz
| | Posted on Tuesday, July 08, 2003 - 12:13 am: |
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Tech 833
How can they make a claim of their parabolic being a 1/2 wave when it only has a diameter of 17 inches? Hmmmmm. Maybe it's all coil!!
A bandwidth of 1200Khz. And can handle 100 watts of RF power? What the heck, is this thing made out of plastic or what???
Hold me back, I gotta have one!!
PS: Do you think a Ham-II rotor will have enough intestinal fortitude to turn it?
Jeff, kc0gxz. |
bruce
| | Posted on Tuesday, July 08, 2003 - 4:43 am: |
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Jeff ... this is how they get a 17 inch dish to work at 27 mhz
Now they have discovered RF COMPRESSION Yes they are compressing the radio waves down to 17 inches!
And the best part is like jogunn by compressing the RF thay have achived AUDIO GAIN! Im waiting for the 1750 meter band one 24 inches across wow will that make low band mobil easer.....
Anyone want a bridge in Brooklyn? How about a 300 foot statue in New York harbor? |
mikefromms
| | Posted on Tuesday, July 08, 2003 - 12:09 pm: |
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I thought this would make an interesting conversation piece. I really wouldn't expect much performance from a 17" dish and was just making a joke about hitting a satelite with it to talk to Spain in the year 2050.
I'm aware of most of what we can do in Ham radio now days. I still like cb and talk only on cb, 10 meters and sometimes 2 meters.
I really like to take subjects apart and look at every angle. I try to forget what I know and see what I can learn from others, and you guys seem to really know your stuff well. That's why I ask (some apparently dumb) lots of questions about I-max antennas and others because it intrigues me.
I do have a Ham license. I have the Extra class. That certainly doesn't mean I know anything. I don't claim to know much.
I went through a divorce a few years ago that turned my world upsidedown. I basically got out of radio for awhile and now I'm taking an interest in things I used to like once again. The 1990's were tough for me. I'm only starting to live again now. I'm trying to make new contacts in radio and enjoy the hobby again.
Can't say enough how much I enjoy Copper's forum.
mikefromms |
Kc0gxz
| | Posted on Tuesday, July 08, 2003 - 12:16 pm: |
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bruce
If the price is right, I might be interested in your statue. Let me know what shipping costs would be to Lincoln Nebraska.
Jeff, kc0gxz. |
bruce
| | Posted on Tuesday, July 08, 2003 - 2:38 pm: |
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Just for fun lets see a review of this wonder antenna......o Jeff do you want it USPS or UPS.... 11,000 boxes...... kinda like a heathkit. |
Znut
| | Posted on Tuesday, July 08, 2003 - 3:10 pm: |
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Bruce,
I have an even better antenna. This one has more gain than that parabolic.http://www.copperelectronics.com/cgi-bin/checkitout/checkitout.cgi?catalogSTORE:CKIE:prodV10-05776+
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Tech833
| | Posted on Tuesday, July 08, 2003 - 5:34 pm: |
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I have found that the CB market is the worst in the world for truthful descriptions and specs of items. In my world, if someone misquoted specs like that, they would be out of business.
When a broadcast antenna saya 6 dB gain, it has 6 dB gain. End of story. If someone disproves that (like a competitor), then the FCC renders that antenna incapable of use in the broadcast band, and the company doesn't sell any. If they don't sell any, they go out of business. |
Alpha1
| | Posted on Tuesday, July 08, 2003 - 7:22 pm: |
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If you haven't already looked, a photo of the infamous "Dish" in question, can be seen at the President-Electronics web site. Or you can do a search for CB-SAT on the web (I would give the URL's but apparently that is taboo).
As for the spec's, that's what they advertise. Certainly NOT what I think or believe. I've found over the years that Antenna manufacturers are almost as trustworthy on their claims as software vendors. |
Kc0gxz
| | Posted on Tuesday, July 08, 2003 - 10:45 pm: |
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Tech833
When a broadcast station buys a antenna that has a claimed gain of 6 dB, and later proven it to have a actual gain of (lets say) 5.5 Db, how can the FCC step in and then "render that antenna incapable of use in the broadcast band"?
I'm NOT doubting you. I just didn't know that the FCC had that kind of authority over what antennas broadcast stations can and cannot use.
Could you clarify on this a bit. Your statement was almost scary.
Jeff, kc0gxz. |
Tech808
| | Posted on Wednesday, July 09, 2003 - 9:28 am: |
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Alpha1,
Drop me an e-mail when you get the chance.
Lon
Tech808
e-mailto:Tech808@copperelectronics.com |
Kirk
| | Posted on Wednesday, July 09, 2003 - 5:37 pm: |
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Jeff-
Tech 833 can give you better tech stuff than I can, but maybe to give you a little insight as far as a broadcast op (me) can tell you from the operations standpoint until he gets time to answer and add...the FCC has PLENTY of say about antenna gain and polar pattern a Broadcast Station can use.
We just finished up a new antenna install that handles Digital and Analog broadcast. We are on a close border to Canada (broadcast wise) and we had to be very selective on how much gain and what pattern we chose. We have an antenna that has to not go too far into Canada and at the same time, stay out of Detroit's region (that's in the particulars of our license). So picture a cardiod pattern (think of a vocal mic like a Shure SM-58 or the like), and that's what we have. We actually had to increase our power output to get the old coverage zone we used to have with our old stick, since this new one is more broad-banded. And we are regualted pretty tight as far as how much power goes out, as well as how much doesn't. We have high and low power tolerances we must stay within. Not to mention frequency (bandwidth) tightness. So...lots and LOTS of regs as far as that goes...and that's really just the start. Enter into EAS land [the old guys remember EBS] and there's another total set of rules that are really, really, tight!
MY Supervisor just told me that he could put anything in the UHF frequency into that antenna.....and then I said...."Hey, if I can get a 440 repeater....can we dump that in" to which he said..."sure...if you buy the combiner!"...which is waaaayyyy too much for me!
Sorry for rambling...hope this shed a little light on what you were asking Tech 833. Maybe he can pick up here.--- |
Tech833
| | Posted on Wednesday, July 09, 2003 - 9:49 pm: |
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Jeff,
A broadcast station isn't just regulated by the power output of the transmitter. The antenna pattern, gain, and other factors are included in the engineering and become part of the station license. If a station submits its license with a Jampro 3 bay full wave spaced CP antenna with a gain of X.X dB and a transmitter power output of XXXX watts and a tower height of XXX feet and from location X, then it all better add up to calculate the maximum ERP. You see, just as important as how much power, etc. a station runs is how much signal there is here and here and here.
Part of the engineering process is running maps that take into account all factors of the transmission system including gain, coax loss, connector losses, TPO, antenna V and H field patterns, null fill, beam tilt, etc. then couple that to the terrain (3 dimentional) etc. Using complex (and expensive) programs, we then have to state how much signal we will have within the areas of our coverage contours. If an antenna maker 'fudged' on their gain figures, circularity, pattern, etc., then our predicted field strengths would not be accurate. We could be subject to license revocation for falsifying the engineering. Not to mention, the consulting engineer would probably never work for a legitimate station again.
It's not as easy as we make it look! |
Kc0gxz
| | Posted on Thursday, July 10, 2003 - 12:15 am: |
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Tech833
WOW. That one sure made me dizzy.
Question...If the maker was to "fudge" on their gain figures by as little as a + or - 1/8 Db, who could possible know that? Let alone challenge it. And if that was to happen, WHO would challenge it?
Is it possible for you to "confirm" an antenna maker's gain claim BEFORE it is installed? If not, then it seems to me that you are at the mercy of the antenna manufacturing company and/or those who give you the specs on a particular antenna that you may already have in service.
Why should the radio station be held responsible if given bogas or even "unintentional" false gain specifications when they went "by-the-book" for this antenna installation as far as FCC Regs go? If anything, wouldn't it be more fair to run the antenna company through the FCCs ringer other than making the Broadcast station face possible fines, shut-down, and firing of a consultant engineer all because of "fudged" figures given by the maker?
And one more question (I find all of this facinating) if I may, please.
I am assuming that these Broadcast station antennas are omni-directional. Can they actually be designed to radiate more in one direction than another? Kirt made a statement that I found interesting and I quote, "We had to be very selective on how much gain and what pattern we chose. We have an antenna that can't go too far into Canada and at the same time, stay out of the Detroit region".
Or asked another way, does a potential Broadcast station know in advance what air/area coverage they will be allowed to have? If so, how is the wave pattern designed for that particular area and who is responsible for it's accuracy? I take it that all of this information goes into a computer long before the antenna is ever built.
I have far more questions for you but I know I shouldn't be tieing you up with all this stuff. There are probably just a few here that are interested in your line of work anyways and besides, this is suppose to be a Ham/CB forum.
Thank you and 73s
Jeff, kc0gxz.
PS: How do you engineers keep everything straight in your head? Don't things ever get a little fuzzy after awhile? |
Tech833
| | Posted on Thursday, July 10, 2003 - 8:23 pm: |
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Jeff,
First question is answered by saying it is important to buy your antenna from a reliable source. Also, particularly directional stations', antennas have to be approved by the FCC before you can use them.
That partially answers question two. Some stations are directional, and the pattern is designed by limitations in certain directions. For instance, look up KEJC FM. They have to protect KYA FM in SF which is their first adjacent. KEJC can only have so much signal in the direction of KYA FM's market. The patterns are carefully calculated, then a pattern designed which will keep the patterns from overlaping. Then, an antenna is designed and it MUST be proofed on the antenna test range by mounting it to either an exact support structure, or the actual support structure proposed to be used. The pattern must be verified before it can go up.
Most FM stations are omni. In this case, they are limited to ERP (Effective Radiated Power). Let's say a station gets licensed for 40,000 watts omni. They can run 40,000 watts into a 0 gain antenna or 4,000 watts into a 10 dB gain antenna to make their licensed ERP. Coverage is determined by terrain, height above average terrain, and ERP. Our imaginary station has to protect existing stations not only on their frequency, but around their frequency as well. This is determined with coverage maps and calculations. Our imaginary station might have to lower their ERP to accomodate others, or may have to change their proposed transmitter site location to make it 'fit'.
Check out v-soft software. That is what I use most. They sell the Longley-Rice study and shadow map software I use to design stuff.
Last question, how do we keep it straight? It is my work, my career, and thusly, my life. The same way the fry cook at McDonald's knows exactly how long to cook the fries and how much salt to put on them. Practice!
Also, you never stop learning. I attend many training sessions on various products and technologies to stay ahead of them. It is like never graduating from school. I should have had 3 PHD's by now. |
mikefromms
| | Posted on Sunday, September 14, 2003 - 5:34 pm: |
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Lots of guys around here now building these antennas. Talked to a guy about 20+ miles away on his homebrew dish antenna. It is directional and works. But it did not work as good as his Antron 99.
Mikefromms |
Bruce
| | Posted on Sunday, September 14, 2003 - 8:23 pm: |
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Mike.......
A 18INCH dish at 27 MHZ would radiate like a cantenna..... |
RCI 2990
| | Posted on Monday, September 15, 2003 - 2:40 pm: |
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Theres always someone that would see that antenna and be like "wow i have to have that looks like an awesome antenna!" and then would be dissapointed that it isnt what he wanted! Thats how these CB antenna makers work.
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Kc0gxz
| | Posted on Monday, September 15, 2003 - 3:21 pm: |
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Bruce
Lol. That was a good one Bruce. But true. I never thought of comparing it to a cantenna. Your answer just struck me funny.
73s.
Jeff. |
mikefromms
| | Posted on Monday, September 15, 2003 - 6:58 pm: |
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Bruce, I won't be building one. I have one of the finest groundplanes made in this Thunder 8 and it works as a beam. Seems to be a hobby catching on around here. To me, if it won't out do an antron (which is a fine antenna) why trouble yourself to build one? Someone is talking about building one with a 9 ft dish. That will be interesting.
mikefromms |
Bruce
| | Posted on Monday, September 15, 2003 - 7:30 pm: |
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Mike ????? thunder 8 hummmm do you have plans to build it e-mail me ..... |
Bruce
| | Posted on Monday, September 15, 2003 - 9:53 pm: |
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FOUND the thunder 8 ok .... i understand what that is... now as for a 9 foot dish FORGET IT it would have little or no gain |
mikefromms
| | Posted on Thursday, September 18, 2003 - 7:18 am: |
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Yeah, I wouldn't waste my time.
mikefromms |
Tech833
| | Posted on Saturday, November 22, 2003 - 11:15 am: |
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Mike,
Why don't you try building a curtain array? Then, you can also vary your takeoff angle at will. I believe it would be a worthwhile project for any antenna experimenter. |
Bluegrass
New member
Username: Bluegrass
Post Number: 7
Registered: 12-2004
| | Posted on Friday, December 03, 2004 - 1:33 pm: |
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hay if i were you i'de be careful this sounds like one of those scams like the mobile beam antenna or the antenna rejection kit(yes the rejection kit is just a scam)it does not work! any way a 17in dish antenna sounds too good to be true. |
Bruce
Senior Member
Username: Bruce
Post Number: 1836
Registered: 9-2003
| | Posted on Friday, December 03, 2004 - 9:51 pm: |
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Bluegrass
Its just nonsense treat it as such. |
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