|
|
Buck wrote: What he really wants is to illegally broadcast on the FM broadcast band. Look at the original post. 2/3 of his newsgroups are Pirate Radio. My Goodness! I would never break any FCC rules! How dare you accuse me. Even though you can use the Super J-pole up to 1500 watts or so, i would recommend not using more than 1 femtoWatt or so. Good for mowing the lawn with your walkman.... :) Slick |
wrote:
My Goodness! I would never break any FCC rules! How dare you accuse me. . . . No need for anyone to accuse you, it's all there on the Web: http://www.talkaboutradioshows.com/g...ages/7526.html Or try a google search of "dr slick" "pirate radio" Anyone interested in knowing a bit more about Garvin Yee, aka "Dr. Slick" can see: http://www.artwanted.com/webjump.cfm?artid=4990 Roy Lewallen, W7EL |
Roy Lewallen wrote: wrote: My Goodness! I would never break any FCC rules! How dare you accuse me. . . . No need for anyone to accuse you, it's all there on the Web: http://www.talkaboutradioshows.com/g...ages/7526.html Don't be silly Roy! I might sell 100 watt broadcast band transmitters, but i only encourage people to use them into 50 Ohm non-radiating dummy loads! Hehe! Makes a great bed-warmer! Or try a google search of "dr slick" "pirate radio" Anyone interested in knowing a bit more about Garvin Yee, aka "Dr. Slick" can see: http://www.artwanted.com/webjump.cfm?artid=4990 Thanks for the free plug! The art is for sale you know.... www.DrSlick.org Slick |
On 7 Feb 2005 21:27:32 -0800, wrote:
I couldn't find anything there that was similar to this: http://www.drslick.org/Temp1/yagiplot.jpg You can lead a horse to water, still can't get it damp. You'd have to look at the data sheet. All the commercial people are aware of this and it's accepted practice. What you missed is a 2 or 4bay dipole is a really nice antenna that can offer gain and pattern control. The usual use is a 4 bay vertically oriented with each of the 4 dipoles spaced 90 degrees around the mast for 5.6db omnidirectional gain. Now, if you want a directional pattern, such as cartioid then put all four on one side, also expect slightly higher gain as well. The commercial version are expensive but are known for their durability but, the good news is they can be built using copper pipe and will give the same perfomance. I might add, the gain numbers I gave are not theory, they are real numbers from proven designs. Ok, here are some links one how to build it.. http://www.repeater-builder.com/rbti...seddipole.html some good info here, the metal used is less desirable than CU pipe. The general design is proven. http://www.w4dex.com/kc4fwc/ant.htm Info on making a phasing harness, needed for a 4bay but not rocket science. http://dipole.w4zt.com/ look at the plumbers dipole page. This can be built as a 1/2/4/8 dipole array. The limit is 4 based mostly on size though I've seen one 8 dipole array and it's long(nearly 45ft!) but very effective. I might add if the mast pipe is made with 1" copper it can also serve as the supporing mast. This is a prefered design and offers good all grounded construction (lightining avoidance and static noise reduction). The two dipole array with both on one side of the mast is the same gain as the super jpole with two differences. the 4 bay will be longer but offers a real gain increase and slightly better pattern control. The gain increase for this type antenna is predictable, being 3DB for each time you double the elements. The single being 0 DBd, 2bays 3Dbd, and 4bays 6Dbd . Thereal world the practical antennas built as omnidirectional are really 0, 2.8 ,5.6dbd due to small but measureable losses in the cables. If the elements are lined up on one side the gain is higher (sme claim 9db) with a cartiod pattern. It's all copper and no required insulators and can be built more robustly. The pattern is predictable, less is left to chance. This type of antenna also works well against the side of a metal building (less tuning difficulties) though you will get a more directional pattern from the building shielding the opposing direction. These designs will you get away from theory and use practical designs. A repeater group I work with locally used the DBproducts 4bay and found it the best antenna they've put on the tower to date. It wasn't cheap and it was heavy. Experience at that site was anything less robust would barely stand a year before the SWR went to unacceptable. I've built the 4bay for UHF and it's a solid performer. The all copper design weathers very well, is very cheap to build and performs just as well as the commercial versions which are welded up from aluminum. I'm sure your getting results from the Jpole but, I can be certain from using them myself that your results are part luck and can easily be attributed to the added height (the 70+inches can really help) and placement more than the presumed gain. If you compare a yagi or dipole to a J-pole the radiating element must be the same height. Since the J-pole is really an end fed dipole it has a 38 inch advantage. For a yagi the centerpoint is the boom.. In direct comparisons the yagi you built would have to be minimally 3ft higher to compete on fair ground. J-poles in general do not like to be near (less than 1/2wave) metalic structures as it detunes them. Yagi behavour is also sensitive to metalic structures close to them. The Yo model is not complete enough for those cases. Allison KB1GMX |
wrote:
I challenge anyone else to use whatever Yagi Optimizers they have to come up with a 3 element design (to keep the size down) with a 180 degree front lobe, and with an 11dB F/B ratio, that has a greater than 4.5 dBi in the front lobe. Why would anyone want such an antenna? -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
On Tue, 08 Feb 2005 01:25:45 -0800, Roy Lewallen
You likely pegged it. Why anyone would use a yagi structure to get a pattern like that, it's not the forte` of that kind of design. That badly a detuned yagi would likely not perform as expected as well. I kinda figured that out between the hacked up beam and the almightly Jpole claims. Jpoles seem to be the holy grail of the pirates. Not to put down the Jpole but it's suffered more snakeoil and used car salesmanship than deserved. Oh well, if someone wanted to do it right at least the recipie is there even if Dr Slick doesn't fully appreciate it. Allison |
wrote:
Roy Lewallen wrote: wrote: My Goodness! I would never break any FCC rules! How dare you accuse me. . . . No need for anyone to accuse you, it's all there on the Web: http://www.talkaboutradioshows.com/g...ages/7526.html Don't be silly Roy! I might sell 100 watt broadcast band transmitters, but i only encourage people to use them into 50 Ohm non-radiating dummy loads! Hehe! Makes a great bed-warmer! This is an outright lie. On Ebay and at http://www.talkaboutradioshows.com/g...ages/7526.html you say: "...WHETHER 50 OHM DUMMY LOAD OR A PROPERLY TUNED ANTENNA..." An antenna is not in the category of "...non-radiating dummy loads!". John |
|
| All times are GMT +1. The time now is 04:43 PM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com