| Author |
Message |
    
Bigbob
| | Posted on Saturday, January 18, 2003 - 7:56 pm: | 
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what is the true db gain of a four element quad antenna, signal engineering shows 14.6 db gain, jump in here bruce, thanks. Bigbob |
Taz
| | Posted on Saturday, January 18, 2003 - 10:08 pm: |
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well
thats about right I suppose |
bruce
| | Posted on Saturday, January 18, 2003 - 10:31 pm: |
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OK 14.6 DBI is ballpark thats 11 DBD a QUAD has 2.5 db over a beam so a 2 el quad will run as much as a 3 el beam or about 6 DBD add a elem on a quad and you should gain 2 db or so so 8 DBD and then there is if all goes well some gain by ground reflection bottm line 8-10 DBD is a real number or 11-13 DBI real world numbers. |
Crafter
| | Posted on Sunday, January 19, 2003 - 12:34 am: |
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Sounds good to me my moonraker is stated at 14.5 and the smaller pdl2 quad states 12.5 but what you got to look at is power multiplication factor the shorter the beam the wider it recieve longer is narrow. I've seen pdl's co-phased for 2db gain and for what it is a pdl 2 is a good little antenna I've had one and was never disappointed with it. I just recently sold it 2 weeks ago. I use the moonraker with a antron mounted in the middle for local talk with no noticeable affect on my dx talking. Hey bruce the moonraker works on 40m too. |
bullet151
| | Posted on Sunday, January 19, 2003 - 1:27 pm: |
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big bob,
i got to agree with bruce,
i come up with a bit over 10.5 dbd/12.7 dbi for a moonraker "converted" 4 element quad. with similar spacing and boom length of the moonraker4 original figures,using standard element lengths for reflector/driven/directors.
with a longer boom say at 20 foot as the one i build its around 11.4dbd/13.6dbi i dont like to figure ground gain as its not a contant figure you can count on from site to site.some company's add 2-5 db for ground effect gain but i see this as a tool to add to the confusion and hype of db gain issues.
if you go from a cubical shaped element (.86dbd)(120 ohms) to say the circular shaped element (1.13dbd)(135ohms) you could get 14.6dbd from a six element quad at 33 feet of boom. these are not maximum gain designs but offer high gain with good front to back ratio
witch we need here in the midwest because we get hit with signals from all directions at once at times.
the maximum gain from any of the many many shaped elements that can be used with quad steerable beem antennas is the intermediate design or the rectangle shape. though its hard to work with it offers 1.5dbd and a 50 or 75 ohm feed point depending on how you construct it. |
CM 3885
| | Posted on Sunday, January 19, 2003 - 3:38 pm: |
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I love my rakers and from were i am here in the Hoosier i can talk anywere i want to and not have any problems.. In fact i have 2 sets of rakers and i wont sell any of them.. The gain of 14 BD sound about right i think.. |
Znut
| | Posted on Sunday, January 19, 2003 - 6:20 pm: |
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My 2 element Quad with ROUND/CIRCULAR elements is soooo fun! It works great. Look here and related threads.
http://www.copperelectronics.com/discus4/messages/14/28569.html?
Znut
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bullet
| | Posted on Sunday, January 19, 2003 - 7:00 pm: |
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cm 3885
i agree i also like the moonraker beams as well!
although i think the gain figure 14.5 db is very generous must be in dbi counting ground effect.
i figured them to be closer to a real word figure of 9.6dbd / 11.8dbi. i assume the other 3 db is from ground gain.
besides the number mumbo jumbo these are great beams that ive had alot of fun with over the years
and have made alot of contacts with.
thier are some that have took down their moonraker beams to put up a quad. and some of those fellas turn around and put their moonrakers back up!(a couple that i have the utmost repect for) some say their too tight,and some say they dont talk to a yagi as well as another yagi will.
im not sure if its the design of the antenna the builder chose or its differant feed system or the lack of a good matching network or perhaps all the above.
i had one of this fellas 4 element quads it wasnt a bad performer but i didnt like some things on it and changed its spacings and element sizes and installed a balun at its feed point. it worked better after the rebuild, before its frontal lobe was squewed to the right and talked out the back almost as well as it did the front.
i will say this about the quads the bigger the tighter they are.the town im close to is 8 miles away. if i turn 30 deg off center of a fella in town using a barefoot radio he's gone! and can turn a 30+ signal to a quiver of the needle in the backside of my 6 elem quad. it gets old spinning this thing all the time to talk!
i run my stacked vertical array about all the time as its very user friendly and has a gain of 5-6dbd.(twice the tx power of a imax 2000) |
de
| | Posted on Sunday, January 19, 2003 - 10:12 pm: |
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The good and the bad....
The good side of a big gain beam is that your effective multiplication is better.
The bad side is that in order to do this you have to make your beam transmit its power into a much smaller field/angle. The result is that you hear less and less of signals from the side and the back as you focus more and more of your transmissions and listening dead ahead.
Hmmm, think a comparison between a common 3 element beam and a Lazer 500. The 3 element has less forward gain but it can hear a signal comming from its side. The Super Lazer 500 has a dang nice forward transmit and listen but just bout no ears on its side and from the back.
Signed
DE |
CM 3885
| | Posted on Sunday, January 19, 2003 - 10:12 pm: |
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I live close to the Ohio line and i can take my rakers and vlock out some guys that only live a few miles away. I know my beams are not as tight as say my astrobeams(now thats a TIGHT beam!)but on skip i love my rakers! |
Bigbob
| | Posted on Sunday, January 19, 2003 - 11:38 pm: |
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I've got a bell shaped rotor it says AR33 on it,I have 30' of 1.25" mast below it 10' of 1.25" conduit above it.I like quads for their static suppression during rain or snow.Signal engineering makes 2 4-element quads one has a 15' boom the other has a 17' boom,the longer one has 4db more side and back rejection and 2db more foward gain,all I want is a 3db improvement over a PDL2,is this possible with one of these quads?hopfully with the less expensive one.I plan on removing 5' to 9' of upper mast to reduce side thrust on the rotor,and possible fold up of upper mast in high wind.I mostly talk to stations 90 to 100 miles away,there are no locals any where on any freq.closer,so does this sound feasible? all I have is money for an antenna,no tower or new rotor. |
Bigbob
| | Posted on Monday, January 20, 2003 - 9:16 pm: |
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C'mon you guys,ever heard of an AR 33 rotor,PLEASE? |
Crafter
| | Posted on Monday, January 20, 2003 - 9:22 pm: |
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Yea, what the question? Its a good little bell rotor. hold 4 square feet I think. |
Bigbob
| | Posted on Tuesday, January 21, 2003 - 6:04 am: |
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Thanx. |
CM 3885
| | Posted on Tuesday, January 21, 2003 - 6:41 am: |
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I found some 10' and 12' sections of aluminum tubing at work and tomorrow im gonna take a moonraker hub into see if it is the right size... If it is ;-) .... Id like to build a moonraker 6 from all my parts someday. |
bullet
| | Posted on Tuesday, January 21, 2003 - 8:53 pm: |
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big bob,
you will see an improvement in rx/tx with those antennas over the pdlII. not saying its gonna mount up to a 3db gain over the pdl. it might, but you will like them better just the same.
i know when i took my 20foot 4 element down and
put up a 2 element quad i just built, in its place to give it a test run i seen a big differance in both rx and tx |
Bigbob
| | Posted on Thursday, January 23, 2003 - 8:33 pm: |
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Signal Engineering said they would give better than 3db over PDL2,and the regular white lightning is only 3.8 square feet perfect for my rotor.Will replace 10 feet of 1.25" thinwall conduit on top with 6 feet of 1.25" galvanized pipe,for a total height of 36 feet. |
bullet
| | Posted on Friday, January 24, 2003 - 3:34 am: |
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yah, got to remember that pdl is about 6 dbd and a 15 foot quad will be about 10dbd so id say there right.
good idea with the pipe, i work in a metal fab shop and i like to get sch 40 ss pipe or even 80 if its in stock. i like stainless over carbon steel as it does not rust away and become weak over the years and has more flex to it were mild steel tends to just bend.
galvanized pipe is good though id say ,ive never used it for mast pipe yet.i did make a gin pole out of some galv pipe.
later and goodluck with the lighting beam youll like it!
bullet |
Alsworld
| | Posted on Friday, January 24, 2003 - 8:16 pm: |
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Bigbob,
I will be listening hard to see how you like your results. I am very interested in some beams. What is the price? (e-mail is ok).
Alsworld |
CM 3885
| | Posted on Sunday, January 26, 2003 - 10:21 pm: |
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I used well pipe and never had any problems...
i got mine from Cardinal supply (a plumbing reatiler up here in Nothern Indiana) a few years ago. |
