[Repeater-Builder] Re: Antenna Gain Specs
rick martin wrote: dBi Ringo Ranger and the use of dBi I like it to a subterranean isotropic radiator. I think a Heathkit cantenna radiates better. Let us not be too caustic, folks: I had occasion to slap one up for a 'quicky' packet station -- tuned with a tape-measure, ty-wrapped to a pipe, and raggidy coax (with two couplings), and decent weather .. in theory, the worst of EVERYTHING wrong. Turned out to be a monster performer. Still is -- 18 years later -- go figgure. g
Re: [Repeater-Builder] Re: Antenna Gain Specs
Well I have gone back to Decibel catalogue 23. Older books discarded. I am pretty sure that at one time the DB224 was rated at 4.5 dBd, and then later at 6 dBd., but this is from memory, I can't find an older catalogue. Regarding a clean and shiny antenna, we had a discussion at coffee. The preposition was that radio waves and light have many similarities, ie., wavelength, reflection, Fresnel behavior, and so forth. Using these similarities, a mirror reflects light, and a dark surface absorbs light, so, wouldn't a shiny antenna reflect incoming signals while a dark colored antenna absorbs signals? This may only apply to receiving antennas - hope I can get this idea to market before the April 1 edition of QST.. .. .. de nu5d
[Repeater-Builder] Re: Antenna Gain Specs
--- In Repeater-Builder@yahoogroups.com, Steve Bosshard \(NU5D\) [EMAIL PROTECTED] wrote: Well I have gone back to Decibel catalogue 23. Older books discarded. I am pretty sure that at one time the DB224 was rated at 4.5 dBd, and then later at 6 dBd., but this is from memory, I can't find an older catalogue. I have gone back to catalog 14 (early 70s I believe) and it is rated at 6/9dbd, same as today. Regarding a clean and shiny antenna, we had a discussion at coffee. The preposition was that radio waves and light have many similarities, ie., wavelength, reflection, Fresnel behavior, and so forth. Using these similarities, a mirror reflects light, and a dark surface absorbs light, so, wouldn't a shiny antenna reflect incoming signals while a dark colored antenna absorbs signals? This may only apply to receiving antennas - hope I can get this idea to market before the April 1 edition of QST.. .. .. de nu5d Compare a Telewave (black) and DB (shiny) :~) . If shiny turns out to be better, there may be a market out there for special aluminum burnishing steel wool. Laryn K8TVZ
RE: [Repeater-Builder] Re: Antenna Gain Specs
You guys are drinking way too much coffee. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Steve Bosshard (NU5D) Sent: Wednesday, February 21, 2007 12:40 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Antenna Gain Specs Well I have gone back to Decibel catalogue 23. Older books discarded. I am pretty sure that at one time the DB224 was rated at 4.5 dBd, and then later at 6 dBd., but this is from memory, I can't find an older catalogue. Regarding a clean and shiny antenna, we had a discussion at coffee. The preposition was that radio waves and light have many similarities, ie., wavelength, reflection, Fresnel behavior, and so forth. Using these similarities, a mirror reflects light, and a dark surface absorbs light, so, wouldn't a shiny antenna reflect incoming signals while a dark colored antenna absorbs signals? This may only apply to receiving antennas - hope I can get this idea to market before the April 1 edition of QST.. .. .. de nu5d Yahoo! Groups Links
[Repeater-Builder] Re: Antenna gain specs
Gary, Most of the commerical guys do have test ranges and some very detailed and well engineered. Most common below 1 GHz antennas were around long before computers like the PC were avialable and their technology, although sound and good, are old, go back into the 50s. Some of the broadcast guys are really getting serious. They have all kinds of ways of looking at antenna performance like just measuring the current distribution on the antenna elements to determine performance. A broadcast antenna must meet some FCC certification for performance/gain/pattern before it can be used because ERP is the standard for power. There has been lots of advancement in computer modeling and bet many not so good manufactures do use computer modeling as you said. 73, ron, n9ee/r It is also interesting to note that hardly any of the manufacturers of two way antennas actually have an antenna test range or have ever tested the antennas on a range. Most all the patterns that you see in the catalogs are computer generated. 73 Gary K4FMX
[Repeater-Builder] Re: Antenna gain specs
Mark, Right on the Diamond package is dbd, not dbi. However, I do not believe if in dbi. 73, ron, n9ee/r --- In Repeater-Builder@yahoogroups.com, N9WYS [EMAIL PROTECTED] wrote: I believe Diamond uses gain over **isotropic** (dBi) for their rating specs... which might account for the extra ~2.2dB. (If memory serves me the difference between dBi and dBd is about 2.2 - yes?) This is one reason to be careful about what the respective company is using for their comparison... gain vs Isotrpoic or gain vs Dipole. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Laryn Lohman Yup, Paul, you've caught on. Diamond must be good; very good. They've bent the laws of physics again. Diamond's 18 ft. long antenna has more gain than a DB Products, Sinclair, etc., which are actually slightly longer. 8.3db gain over what? I'm here to tell you, in my humble opinion, that the Diamond's actual gain over a dipole is closer to 6dbd. Laryn K8TVZ
Re: [Repeater-Builder] Re: Antenna gain specs
Paul Holm wrote: Reading the replies that mentioned gain specs, I can't help but think of our last ham club meeting. An older member persuaded the club to replace the VHF repeater antenna with a Diamond X500HNA rather than a DB-224 because the Diamond has 8.3 dB gain. And even worse is that the rest of the club was stupid enough to listen... I got a story about a club here and link receivers...I've got a box with 3 UHF HT90's in it, rocked up ready to go, that I got stuck with the bill on after they decided to put in ham-grade rx's instead. -- Jim Barbour WD8CHL
RE: [Repeater-Builder] Re: Antenna gain specs
Can you name any of the two way antenna manufacturers that do? 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Ron Wright, Skywarn Coodinator Sent: Tuesday, February 20, 2007 8:52 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Antenna gain specs Gary, Most of the commerical guys do have test ranges and some very detailed and well engineered. Most common below 1 GHz antennas were around long before computers like the PC were avialable and their technology, although sound and good, are old, go back into the 50s. Some of the broadcast guys are really getting serious. They have all kinds of ways of looking at antenna performance like just measuring the current distribution on the antenna elements to determine performance. A broadcast antenna must meet some FCC certification for performance/gain/pattern before it can be used because ERP is the standard for power. There has been lots of advancement in computer modeling and bet many not so good manufactures do use computer modeling as you said. 73, ron, n9ee/r It is also interesting to note that hardly any of the manufacturers of two way antennas actually have an antenna test range or have ever tested the antennas on a range. Most all the patterns that you see in the catalogs are computer generated. 73 Gary K4FMX Yahoo! Groups Links
Re: [Repeater-Builder] Re: Antenna gain specs
At 2/20/2007 07:11 AM, you wrote: Paul Holm wrote: Reading the replies that mentioned gain specs, I can't help but think of our last ham club meeting. An older member persuaded the club to replace the VHF repeater antenna with a Diamond X500HNA rather than a DB-224 because the Diamond has 8.3 dB gain. And even worse is that the rest of the club was stupid enough to listen... When it comes to gain, the Diamond probably really has 8.3 dBi. The real difference between the two antennas is pattern shape (DB224 has a cleaner pattern; the dual-band antennas have deeper nulls below the horizon), and of course the mechanical ruggedness of the DB224. Bob NO6B
[Repeater-Builder] Re: Antenna gain specs
When it comes to gain, the Diamond probably really has 8.3 dBi. That's probably true Bob. And the grapes to grapes comparison would suggest that a DB224 also has ~8.3dbi of gain. The real difference between the two antennas is pattern shape (DB224 has a cleaner pattern; the dual-band antennas have deeper nulls below the horizon), Can't argue there. and of course the mechanical ruggedness of the DB224. Bob NO6B For sure. Try top mounting one of the long, slender fiberglass sticks and you'll probably be replacing it sooner than you'd like. Side mounted and supported with at least one stay somewhere above halfway, it'll last a long time. Laryn K8TVZ
Re: [Repeater-Builder] Re: Antenna gain specs
What I don't understand is how at times the DB224 is rated at 4.5 dBd, then 6 dBd, and the DB304 (twice as much aluminum) rated at 6.1 dBd. over a span of 30 years...de nu5d
[Repeater-Builder] Re: Antenna gain specs
--- In Repeater-Builder@yahoogroups.com, Steven Samuel Bosshard \(NU5D\) [EMAIL PROTECTED] wrote: What I don't understand is how at times the DB224 is rated at 4.5 dBd, then 6 dBd, H that's a new one. Where/when and what frequency range have you seen the DB224 rated at 4.5dbd? and the DB304 (twice as much aluminum) rated at 6.1 dBd. over a span of 30 years...de nu5d Omnidirectional gain is achieved by vertically stacking more levels, if you will. Doing what they've done with the DB304 does not add more levels. So no more gain. To be honest, I'm not sure what the reason is for the double dipole arrangement. I suspect it electrically makes the mast disappear since each pair is symmetrical with the mast. Someone else I'm sure has a better explanation of this design. Laryn K8TVZ
Re: [Repeater-Builder] Re: Antenna gain specs
But don't mount it upside down. The base is not waterproof when inverted - I learned that the hard way! 73 - Jim W5ZIT -Original Message- From: [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Tue, 20 Feb 2007 3:19 PM Subject: [Repeater-Builder] Re: Antenna gain specs When it comes to gain, the Diamond probably really has 8.3 dBi. That's probably true Bob. And the grapes to grapes comparison would suggest that a DB224 also has ~8.3dbi of gain. The real difference between the two antennas is pattern shape (DB224 has a cleaner pattern; the dual-band antennas have deeper nulls below the horizon), Can't argue there. and of course the mechanical ruggedness of the DB224. Bob NO6B For sure. Try top mounting one of the long, slender fiberglass sticks and you'll probably be replacing it sooner than you'd like. Side mounted and supported with at least one stay somewhere above halfway, it'll last a long time. Laryn K8TVZ Check Out the new free AIM(R) Mail -- 2 GB of storage and industry-leading spam and email virus protection. =0
RE: [Repeater-Builder] Re: Antenna gain specs
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Laryn Lohman Sent: Tuesday, February 20, 2007 5:59 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Antenna gain specs --- In Repeater-Builder@yahoogroups.com, Steven Samuel Bosshard \(NU5D\) [EMAIL PROTECTED] wrote: What I don't understand is how at times the DB224 is rated at 4.5 dBd, then 6 dBd, H that's a new one. Where/when and what frequency range have you seen the DB224 rated at 4.5dbd? and the DB304 (twice as much aluminum) rated at 6.1 dBd. over a span of 30 years...de nu5d Omnidirectional gain is achieved by vertically stacking more levels, if you will. Doing what they've done with the DB304 does not add more levels. So no more gain. To be honest, I'm not sure what the reason is for the double dipole arrangement. I suspect it electrically makes the mast disappear since each pair is symmetrical with the mast. Someone else I'm sure has a better explanation of this design. Laryn K8TVZ When you look at the antenna patterns in the catalogs they look like nice smooth circles for the gain pattern. This is far from realistic as most antennas will have many many peaks and nulls in the pattern. What the diagram in the catalogs try to show is an average gain pattern. The addition of more elements on the same level in antennas such as the DB304 will fill in more of those peaks and nulls to make a better more consistent pattern. They can also be used to make the antenna more broad band. 73 Gary K4FMX
Re: [Repeater-Builder] Re: Antenna gain specs
I belive the double dipole (304) was supposed to have a more omni-directional pattern (the books show a 'normalized' pattern) - I will have to dig out some old DB Products catalogs, or call Lloyd Alcorn in Waco (he designed the 224 for DB before he and Kit Parsons and Larry Bush started Wacom Products) and get the info. Steve
Re: [Repeater-Builder] Re: Antenna gain specs
Reading the replies that mentioned gain specs, I can't help but think of our last ham club meeting. An older member persuaded the club to replace the VHF repeater antenna with a Diamond X500HNA rather than a DB-224 because the Diamond has 8.3 dB gain. - Original Message - From: Jim B. Sent: Monday, February 19, 2007 11:41 AM Subject: Re: [Repeater-Builder] Re: Antennas that work both in commercial and amateur As Laryn mentioned, the 10dB stationmasters are only available at UHF and above, because a 10dB version at 150Mhz (probably even 220) would be on the order of 40-50' long!
[Repeater-Builder] Re: Antenna gain specs
--- In Repeater-Builder@yahoogroups.com, Paul Holm [EMAIL PROTECTED] wrote: Reading the replies that mentioned gain specs, I can't help but think of our last ham club meeting. An older member persuaded the club to replace the VHF repeater antenna with a Diamond X500HNA rather than a DB-224 because the Diamond has 8.3 dB gain. Yup, Paul, you've caught on. Diamond must be good; very good. They've bent the laws of physics again. Diamond's 18 ft. long antenna has more gain than a DB Products, Sinclair, etc., which are actually slightly longer. 8.3db gain over what? I'm here to tell you, in my humble opinion, that the Diamond's actual gain over a dipole is closer to 6dbd. Laryn K8TVZ
RE: [Repeater-Builder] Re: Antenna gain specs
I believe Diamond uses gain over **isotropic** (dBi) for their rating specs... which might account for the extra ~2.2dB. (If memory serves me the difference between dBi and dBd is about 2.2 - yes?) This is one reason to be careful about what the respective company is using for their comparison... gain vs Isotrpoic or gain vs Dipole. Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Laryn Lohman Yup, Paul, you've caught on. Diamond must be good; very good. They've bent the laws of physics again. Diamond's 18 ft. long antenna has more gain than a DB Products, Sinclair, etc., which are actually slightly longer. 8.3db gain over what? I'm here to tell you, in my humble opinion, that the Diamond's actual gain over a dipole is closer to 6dbd. Laryn K8TVZ
RE: [Repeater-Builder] Re: Antenna gain specs
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Laryn Lohman Sent: Monday, February 19, 2007 8:27 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Antenna gain specs --- In Repeater-Builder@yahoogroups.com, Paul Holm [EMAIL PROTECTED] wrote: Reading the replies that mentioned gain specs, I can't help but think of our last ham club meeting. An older member persuaded the club to replace the VHF repeater antenna with a Diamond X500HNA rather than a DB-224 because the Diamond has 8.3 dB gain. Yup, Paul, you've caught on. Diamond must be good; very good. They've bent the laws of physics again. Diamond's 18 ft. long antenna has more gain than a DB Products, Sinclair, etc., which are actually slightly longer. 8.3db gain over what? I'm here to tell you, in my humble opinion, that the Diamond's actual gain over a dipole is closer to 6dbd. Laryn K8TVZ It is also interesting to note that hardly any of the manufacturers of two way antennas actually have an antenna test range or have ever tested the antennas on a range. Most all the patterns that you see in the catalogs are computer generated. 73 Gary K4FMX
Re: [Repeater-Builder] Re: Antenna gain specs
Sometimes if you just ask the question Relative to what! All manufactures don't base there Gain spec on Unity Gain of a Dipole, Some have there own Base Spec , and nobody knows what it is , I am always leery of companies that tend to always have the most of everything . The Company I worked for bought some Fiberglass antennas that were supposed to be 6 - DB Gain a 1/4 wave Mobil antenna would out perform them we ended up junking them . Had to drive 200 Miles one way and change out 16 Antenna . The antenna that worked best for us was a commercial copy of the ringo ranger 3/4 wave length on bottom 1/2 wave length on top with hair pin between.
Re: [Repeater-Builder] Re: Antenna gain specs
At 2/19/2007 17:27, you wrote: --- In Repeater-Builder@yahoogroups.com, Paul Holm [EMAIL PROTECTED] wrote: Reading the replies that mentioned gain specs, I can't help but think of our last ham club meeting. An older member persuaded the club to replace the VHF repeater antenna with a Diamond X500HNA rather than a DB-224 because the Diamond has 8.3 dB gain. Yup, Paul, you've caught on. Diamond must be good; very good. They've bent the laws of physics again. Diamond's 18 ft. long antenna has more gain than a DB Products, Sinclair, etc., which are actually slightly longer. 8.3db gain over what? I'm here to tell you, in my humble opinion, that the Diamond's actual gain over a dipole is closer to 6dbd. Correct, which is 8.1 dBi. Diamond Comet use dBi. Bob NO6B
RE: [Repeater-Builder] Re: Antenna gain specs
At 2/19/2007 17:51, you wrote: I believe Diamond uses gain over **isotropic** (dBi) for their rating specs... which might account for the extra ~2.2dB. (If memory serves me the difference between dBi and dBd is about 2.2 - yes?) 2.12 dB, to be exact. This is one reason to be careful about what the respective company is using for their comparison... gain vs Isotrpoic or gain vs Dipole. I just assume that unless specified, the gain is in dBi. For me to interpret a claimed gain as referenced to a dipole, it must be stated as dBd. Bob NO6B
