RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

>  
> Did you test the db408 with both db404's harnessed and 
> working together?

No, I tested the upper and lower halves seprately.  I have some used DB408's
(not the dual version) that I'll try to sweep later.

Re: [Repeater-Builder] Decibel dipole array sweeps

[k5in]

Jeff,


I find this interesting, especially with regard to the db408.

Did you test the db408 with both db404's harnessed and working together?


Brian, k5in
  - Original Message - 
  From: Jeff DePolo 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Sunday, March 22, 2009 1:17 PM
  Subject: RE: [Repeater-Builder] Decibel dipole array sweeps



  For a parallel-fed (aka binary-fed, corporate-fed, etc.) antenna, if all of
  the elements are fed in-phase (i.e. the branches in the phasing harness are
  all the same length), as it typical with most dipole arrays, there won't be
  any uptilt/downtilt as you vary the transmitter frequency outside of the
  design range a bit. No matter what the frequency of the carrier is, it's
  always going to hit the elements in-phase, so there won't be any beamtilt. 

  This is constrast to an end-fed (series-fed) collinear, where you will get
  UPTILT if transmitting at a frequency ABOVE the antenna's design range, and
  DOWNTILT if transmitting at a frequency BELOW the antenna's design range.

  --- Jeff WN3A

  > -Original Message-
  > From: Repeater-Builder@yahoogroups.com 
  > [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Doug Bade
  > Sent: Sunday, March 22, 2009 4:10 PM
  > To: Repeater-Builder@yahoogroups.com
  > Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
  > 
  > Jeff;
  > This is very interesting findings especially in that using 
  > an antenna longer than your freq tends to exhibit down tilt... that 
  > 440 use of a 450 antenna seems to be working in the correct 
  > direction. I for one found it very interesting to read
  > 
  > It may be real interesting to see some of the amateur antennas tested 
  > too as multiband ones seem to rarely work very well on the upper 
  > bands compared to the lower bands of those I have seen
  > 
  > Doug
  > 
  > At 02:32 PM 3/22/2009, you wrote:
  > 
  > >I'm in the process of putting up a remote receiver for a 440 
  > ham repeater
  > >using a Decibel DB413 dipole array cut for 450-470 MHz. Since
  > >Decibel/Andrew stopped making the 440-450 MHz custom models, 
  > I've used the
  > >usual 450-470 split antennas for receive sites, and they've 
  > performed well.
  > >I swept the DB413, and it measured as I expected. While I had the
  > >Sitemaster out, I grabbed a few other Decibel dipole arrays 
  > out of the
  > >warehouse and swept them and prepared a little document. 
  > Since the topic of
  > >using commercial-band antennas on amateur frequencies comes 
  > up fairly often,
  > >I figured these measurements might be of some interest to 
  > list members.
  > >
  > >I tested these antennas with them mounted above ground 
  > level, and away from
  > >nearby objects, with the Sitemaster connected right to the 
  > pigtail so what
  > >you're seeing is the true return loss at the feedpoint. I'll 
  > continue to
  > >test more antennas (not just DB dipole arrays) over time and 
  > continue to add
  > >them to this document. I have gobs of sweeps of antennas, 
  > but unfortunately
  > >many of them were swept at the bottom end of heliax runs 
  > rather than right
  > >at the feedpoint. From now on I'll make it a point to sweep 
  > them on the
  > >ground this way.
  > >
  > >The antennas I tested in this first batch are:
  > >
  > >DB413, 450-470 MHz
  > >DB408D, 450-470 MHz
  > >DB411, 450-470 MHz
  > >DB411, 406-420 MHz
  > >
  > >Note that the DB408D is actually two DB404's on a common 
  > mast, each with its
  > >own pigtail/feedpoint, so there are separate plots for the 
  > upper antenna and
  > >lower antenna. Its performance wasn't what I expected. I 
  > have more of the
  > >same model of antenna, I'll try to test one of the others 
  > the next time.
  > >
  > >The document can be found here:
  > >
  > ><<http://www.broadsci.com/Antenna 
  > <http://www.broadsci.com/Antenna> 
  > >http://www.broadsci.com/Antenna <http://www.broadsci.com/Antenna> 
  > >Sweeps r1.pdf>
  > >
  > >If anyone finds this useful please let me know, so I know 
  > whether or not
  > >it's worth the time/effort to continue to test antennas and 
  > add them to the
  > >doc.
  > >
  > >--- Jeff WN3A
  > >
  > >
  > 
  > 
  > 
  > 
  > 
  > No virus found in this incoming message.
  > Checked by AVG - www.avg.com
  > Version: 8.0.238 / Virus Database: 270.11.3/1970 - Release 
  > Date: 03/21/09 17:58:00
  > 
  > 
  > 


  

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

> Hi Jeff, that's interesting data.
> 
> I was more curious whether or not you had any antennas easy to add to 
> the tests, or any locals nearby with different types of Sinclairs 
> around/available to add to the data while you "have the test range 
> setup", so to speak.
> 
> Not important enough to go hunting too hard for them though. The data 
> you shared on the DB antennas is very useful to a lot of folks, I'm 
> sure!

Off the top of my head, I have the following in storage that I can
eventually get around to sweeping.  Let me know which you're interested in
seeing.

Celwave PD1151 440-450 new

Celwave PD455 440-450 new

Celwave PD1151 450-460 used

Decibel DB420 450-470 new? and used

Decibel DB420 406-420 used

Decibel DB408 450-470 all used I think

Decibel DB420 440-450 new

Sinclair  5 dB fiberglass, marked 454.something, used

I don't think I have any Sinclair dipole arrays on the ground except for
VHF.  Lots of yagis, corner reflectors, and other directionals from
Sinclair, Celwave, Decibel, Antenex, Maxrad, Larsen, et al.  The yagis  with
adjustable feeds (gammas) probably aren't worth sweeping obviously.

I think that covers most of them for UHF anyway.

While we're on a related subject, has anyone tried any of the TX-RX (RFI)
dipole arrays?  I keep meaning to use one "on the next project" but haven't
gotten around to it yet.

--- Jeff WN3A

RE: [Repeater-Builder] Decibel dipole array sweeps

[Dave Gomberg]

At 09:01 3/23/2009, Mark wrote:
>Thanks, Bob.  Apparently you and I are in the same boat.  I have the full
>version of Acrobat 5 installed, and if I try to upgrade the reader only, it
>corrupts the entire installation.  And I'm too cheap to go out and 
>spend the $$$ for a new version.  ;-)

Mark, my morality about this is that if Adobe screws something up so that
I need a whole new version, I will buy it ANYWHERE I can (at the lowest
price).  I generally support getting real copies from vendors, but when the
vendor screws me, I return the favor




-- 
Dave Gomberg, San Francisco   NE5EE gomberg1 at wcf dot com
All addresses, phones, etc. at http://www.wcf.com/ham/info.html
- 

RE: [Repeater-Builder] Decibel dipole array sweeps

[Dave Gomberg]

At 09:01 3/23/2009, Mark wrote:
>Thanks, Bob.  Apparently you and I are in the same boat.  I have the full
>version of Acrobat 5 installed, and if I try to upgrade the reader only, it
>corrupts the entire installation.  And I'm too cheap to go out and 
>spend the $$$ for a new version.  ;-)

Mark, my morality about this is that if Adobe screws something up so that
I need a whole new version, I will buy it ANYWHERE I can (at the lowest
price).  I generally support getting real copies from vendors, but when the
vendor screws me, I return the favor




-- 
Dave Gomberg, San Francisco   NE5EE gomberg1 at wcf dot com
All addresses, phones, etc. at http://www.wcf.com/ham/info.html
- 

RE: [Repeater-Builder] Decibel dipole array sweeps

[Mark]

Thanks, Bob.  Apparently you and I are in the same boat.  I have the full
version of Acrobat 5 installed, and if I try to upgrade the reader only, it
corrupts the entire installation.

And I'm too cheap to go out and spend the $$$ for a new version.  ;-)

Thanks!
Mark -N9WYS

-Original Message-
From: Repeater-Builder@yahoogroups.com  On Behalf Of n...@no6b.com

At 3/22/2009 16:43, you wrote:
>I got to the page, but the file wouldn't open...
>
>Mark - N9WYS

It's likely you also have Acrobat (Reader) 5.0.

Rather than drag this sub-thread out, I remoted into another computer that
does have a current Adobe install & downconverted the PDF (attached).

Bob NO6B

Re: [Repeater-Builder] Decibel dipole array sweeps

[no6b]

At 3/23/2009 01:29, you wrote:

>On Mar 22, 2009, at 7:18 PM, n...@no6b.com wrote:
>
> > By now I've already managed to get the original PDF downconverted to
> > something everyone should be able to read.  Then again, unless
> > you're going
> > to print it HTML is the most universal format.
>
>Actually straight ASCII is the most "universal".  :-)

Not on this group, thanks to Yahoo stripping extra spaces from the text.

Bob NO6B

Re: [Repeater-Builder] Decibel dipole array sweeps

[Chuck Kelsey]

Check the antenna for VSWR at that frequency BEFORE it goes up. It's 
probably going to be borderline.


- Original Message - 

> On Sun, 22 Mar 2009, k5in wrote:
>> If I have a DB413 and I am going to use it on
>> 441.950 

Re: [Repeater-Builder] Decibel dipole array sweeps

[Nate Duehr]

On Mar 22, 2009, at 5:11 PM, Jeff DePolo wrote:

>
> I have a Sinclair 8-bay with half-wave element to mast spacing  
> stored in the
> Sitemaster, but it was swept from the far end of 600' of 1-5/8" with a
> topside TX-RX crossband coupler.  It's spec'ed for 406-512 MHz.  I  
> can't
> keep track of Sinclair's model numbers, it's probably a SD318- 
> HF2P2SNM,
> previously known as a SRL310C8NM*2-2.  I can send you the sweep  
> anyway if
> you want it.  It talks extremely well.
>
>   --- Jeff WN3A


Hi Jeff, that's interesting data.

I was more curious whether or not you had any antennas easy to add to  
the tests, or any locals nearby with different types of Sinclairs  
around/available to add to the data while you "have the test range  
setup", so to speak.

Not important enough to go hunting too hard for them though.  The data  
you shared on the DB antennas is very useful to a lot of folks, I'm  
sure!

I've always had good luck with Sinclairs, and they've always worked  
well, but I've never seen anything other than the manufacturer's  
published specs on them.  They do seem to work well, all of them.

We've used the 2-bay 1/4 wave spacing, the 4-bay 1/2 wave spacing, and  
the 8-bay 1/2-wave spacing models (a mix of VHF and UHF) on various  
repeaters.

The most surprising has been the performance of the "little" 2-bay 1/4  
wave spacing antenna on one particular site.

--
Nate Duehr, WY0X
n...@natetech.com

Re: [Repeater-Builder] Decibel dipole array sweeps

[Nate Duehr]

On Mar 22, 2009, at 7:18 PM, n...@no6b.com wrote:

> By now I've already managed to get the original PDF downconverted to
> something everyone should be able to read.  Then again, unless  
> you're going
> to print it HTML is the most universal format.

Actually straight ASCII is the most "universal".  :-)

/me puts on my computer curmudgeon voce... "Darn kids and their fancy  
graphics!"

   (GRIN!)

--
Nate Duehr, WY0X
n...@natetech.com

Re: [Repeater-Builder] Decibel dipole array sweeps

[Kris Kirby]

On Sun, 22 Mar 2009, k5in wrote:
> This is directed to you: If I have a DB413 and I am going to use it on 
> 441.950 you are saying there will be some down tilt in the pattern?
> 
> This doesn't bother me.  I am more curious than anything about this 
> antenna that is due to go up 140ft on a tower in a couple of months.

That's entirely dependent on the split the antenna was designed for. I'm 
sure there are others here who can hazard a better guess.

--
Kris Kirby, KE4AHR
Disinformation Analyst

Re: [Repeater-Builder] Decibel dipole array sweeps

[k5in]

Kris Kirby,

This is directed to you: If I have a DB413 and I am going to use it on 441.950 
you are saying there will be some down tilt in the pattern?

This doesn't bother me.  I am more curious than anything about this antenna 
that is due to go up 140ft on a tower in a couple of months.

Brian, k5in 
  - Original Message - 
  From: Kris Kirby 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Sunday, March 22, 2009 3:37 PM
  Subject: RE: [Repeater-Builder] Decibel dipole array sweeps


  On Sun, 22 Mar 2009 n...@no6b.com wrote:
  > Well, without a long explanation, I can't view files made for Acrobat 
  > 6 & later. No way around it unless I want to lose PDF authoring 
  > capability.

  Buy a Mac and image the Windows box and use it in a virtual machine. 
  Then you can author in PDFs and the Mac has a built-in PDF viewer and 
  Postscript conversion engine.

  Totally not the solution you were looking for. =)

  --
  Kris Kirby, KE4AHR
  Disinformation Analyst

  

RE: [Repeater-Builder] Decibel dipole array sweeps

[no6b]

At 3/22/2009 17:44, you wrote:

>Bob.  Always the trouble maker.
>
>Try this HTML version.  It was produced by Microsoft Word which has the most
>god-awful HTML generator on the planet IMHO.  I make no guarantees as to its
>readability.
>
>http://www.broadsci.com/AntennaSweepsR1.htm
>
> --- Jeff WN3A

Thanks Jeff; it actually looks quite good.

By now I've already managed to get the original PDF downconverted to 
something everyone should be able to read.  Then again, unless you're going 
to print it HTML is the most universal format.

Re: other PDF generators/readers: unfortunately they probably aren't 
options for me.  I need the ability to generate PDFs with tightly 
controlled parameters for work applications.  It's not likely the low-end 
PDF generators can handle those requirements.  And as I stated previously, 
Acrobat 5 doesn't "play nice" with other PDF readers.

Bob NO6B

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

Bob.  Always the trouble maker.

Try this HTML version.  It was produced by Microsoft Word which has the most
god-awful HTML generator on the planet IMHO.  I make no guarantees as to its
readability.

http://www.broadsci.com/AntennaSweepsR1.htm

--- Jeff WN3A



> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of n...@no6b.com
> Sent: Sunday, March 22, 2009 8:30 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: RE: [Repeater-Builder] Decibel dipole array sweeps
> 
> At 3/22/2009 16:23, you wrote:
> >Bob,
> >Paste the link into your location bar then remove the '%20' groups of
> >characters from the link. The result should look like this-
> 
> Not the problem. Acrobat 5 is as far as my home system 
> goes. Unfortunately the full version of Acrobat "overrides" 
> any Reader 
> installation. Not Windows' fault, but Adobe's.
> 
> I do have a 1 GHz PIII backup system I could put the new 
> reader on if I was 
> desperate, but not worth the trouble right now.
> 
> Bob NO6B

Re: [Repeater-Builder] Decibel dipole array sweeps

[Kevin Custer]

n...@no6b.com wrote:
> Not the problem.  Acrobat 5 is as far as my home system 
> goes.  Unfortunately the full version of Acrobat "overrides" any Reader 
> installation.  Not Windows' fault, but Adobe's.
>
> I do have a 1 GHz PIII backup system I could put the new reader on if I was 
> desperate, but not worth the trouble right now.


Or --  you could install Foxit reader.

Kevin

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

> > Free space doesn't have a ground. Can you disable ground altogether 
> > and see what the gain and pattern is?
> 
> Yes. It looks like what you'd expect a perfect antenna to look like.
> 
> > What does it give you for the gain of a single half-wave 
> dipole with 
> > no ground or support structure?
> 
> 2.16 dBi, as expected. -3dB comes at around 38.5 degrees, so 
> the total 
> -3dB beamwidth would be 77 degrees, vertical. 
> 
> With no ground (free space), the antenna (four stacked dipoles), 
> simulates at 8.6dBi, lobe at zero degrees, -3dB at 6.5 degrees, total 
> -3dB beamwidth is 13 degrees.

OK, that's more like it.  At a realistic antenna height (100 feet+, or
around 30 wavelengths at 2m), I would expect ground reflection effects to be
negligible, and that the major lobe would be on the horizon where it
belongs.  And, yes, with ground reflections, the elevation pattern WILL
change as you vary frequency, because the distance as measured in
*wavelengths* between the ground and antenna elements will obviously vary as
you shift frequency around.

Try running your previous models again with ground disabled, or at a high
height above ground, and see what you come up with.  Or, try offsetting your
antenna 1/4 wavelength (about 1.7 feet) vertically with respect to ground
and re-run your original models and you should see the beamtilt change
accordingly.

--- Jeff WN3A

RE: [Repeater-Builder] Decibel dipole array sweeps

[no6b]

At 3/22/2009 16:23, you wrote:
>Bob,
>Paste the link into your location bar then remove the '%20' groups of
>characters from the link. The result should look like this-

Not the problem.  Acrobat 5 is as far as my home system 
goes.  Unfortunately the full version of Acrobat "overrides" any Reader 
installation.  Not Windows' fault, but Adobe's.

I do have a 1 GHz PIII backup system I could put the new reader on if I was 
desperate, but not worth the trouble right now.

Bob NO6B

RE: [Repeater-Builder] Decibel dipole array sweeps

[Kris Kirby]

On Sun, 22 Mar 2009, Jeff DePolo wrote:
> Free space doesn't have a ground.  Can you disable ground altogether 
> and see what the gain and pattern is?

Yes. It looks like what you'd expect a perfect antenna to look like.

> What does it give you for the gain of a single half-wave dipole with 
> no ground or support structure?

2.16 dBi, as expected. -3dB comes at around 38.5 degrees, so the total 
-3dB beamwidth would be 77 degrees, vertical. 

With no ground (free space), the antenna (four stacked dipoles), 
simulates at 8.6dBi, lobe at zero degrees, -3dB at 6.5 degrees, total 
-3dB beamwidth is 13 degrees.

None of my computations so far have factored for antenna mounting 
structures; just one or four dipoles in space, over some ground.

> > MMANA-GAL (it's free, runs on Windows). I'd be happy to post 
> > the file if 
> > anyone wants to compare it.
> 
> Not familiar with it.  What code base is it based on?

MININEC-3.

--
Kris Kirby, KE4AHR
Disinformation Analyst

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

> On Sun, 22 Mar 2009, Jeff DePolo wrote:
> > Wait. You're saying that a center-fed dipole has a major 
> lobe that's 
> > not exactly perpendicular to the element? Something's amiss.
> 
> It's a theoretical antenna over a real ground. In free space, 
> the lobes 
> are closer to zero, but even over a perfect ground, there will be 
> interaction effects due to the waves bouncing off of the ground. 

Free space doesn't have a ground.  Can you disable ground altogether and see
what the gain and pattern is?
 
> > Something has to be wrong here. 12.44 dBi of net gain for a 4-bay? 
> > What is the element spacing? Or does that include azimuth 
> gain due to 
> > the mount pipe?
> 
> No losses. Element spacing is one wavelength at 145MHz. 

What does it give you for the gain of a single half-wave dipole with no
ground or support structure?

> MMANA-GAL (it's free, runs on Windows). I'd be happy to post 
> the file if 
> anyone wants to compare it.

Not familiar with it.  What code base is it based on?

--- Jeff

RE: [Repeater-Builder] Decibel dipole array sweeps

[Kris Kirby]

On Sun, 22 Mar 2009, Gary wrote:
> Bob,
> Paste the link into your location bar then remove the '%20' groups of
> characters from the link. The result should look like this-
> 
> http://www.broadsci.com/AntennSweepsR1.pdf

This works:

http://www.broadsci.com/AntennaSweepsR1.pdf

--
Kris Kirby, KE4AHR
Disinformation Analyst

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

I guess I could, but you'd also see the effect of the crossband coupler,
jumpers, and everything else in-line.  I figured I'd start afresh with all
new antennas tested at ground level. 

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey
> Sent: Sunday, March 22, 2009 7:18 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
> 
> Why not just include it with your article already posted? 
> Just add the notes 
> along with it.
> 
> Chuck
> WB2EDV
> 
> - Original Message - 
> From: "Jeff DePolo" mailto:jd0%40broadsci.com> >
> To:  <mailto:Repeater-Builder%40yahoogroups.com> >
> Sent: Sunday, March 22, 2009 7:11 PM
> Subject: RE: [Repeater-Builder] Decibel dipole array sweeps
> 
> >
> > I have a Sinclair 8-bay with half-wave element to mast 
> spacing stored in 
> > the
> > Sitemaster, but it was swept from the far end of 600' of 
> 1-5/8" with a
> > topside TX-RX crossband coupler. It's spec'ed for 406-512 
> MHz. I can't
> > keep track of Sinclair's model numbers, it's probably a 
> SD318-HF2P2SNM,
> > previously known as a SRL310C8NM*2-2. I can send you the 
> sweep anyway if
> > you want it. It talks extremely well.
> >
> > --- Jeff WN3A
> 
> 
> 
> 
> 
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.0.238 / Virus Database: 270.11.3/1970 - Release 
> Date: 03/21/09 17:58:00
> 
> 
> 

RE: [Repeater-Builder] Decibel dipole array sweeps

[Gary]

Bob,
Paste the link into your location bar then remove the '%20' groups of
characters from the link. The result should look like this-

http://www.broadsci.com/AntennSweepsR1.pdf

Gary
N6LRV

-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of n...@no6b.com
Sent: Sunday, March 22, 2009 3:29 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] Decibel dipole array sweeps

At 3/22/2009 13:01, you wrote:

>Boy, Yahoo really mangled the URL, even though I put it in angle brackets.
>Let's try re-naming the file without spaces, maybe that will work...
>
><http://www.broadsci.com/AntennaSweepsR1.pdf>
>
>Bob - the file opened fine for me, both locally and from the web site.  I'm
>using Acrobat 9.0.  The document info shows it's PDF version 1.5 for
Acrobat
>version 6.x or later.  I've had a few other cases where I couldn't open
>recently-produced PDF's sent to me by others using Acrobat 9; upgrading to
>the current version of Reader fixed it, even though the files should be
>compatible with Acrobat 6 or later.

Well, without a long explanation, I can't view files made for Acrobat 6 & 
later.  No way around it unless I want to lose PDF authoring capability.

Bob NO6B







Yahoo! Groups Links

RE: [Repeater-Builder] Decibel dipole array sweeps

[Kris Kirby]

On Sun, 22 Mar 2009, Jeff DePolo wrote:
> Wait.  You're saying that a center-fed dipole has a major lobe that's 
> not exactly perpendicular to the element?  Something's amiss.

It's a theoretical antenna over a real ground. In free space, the lobes 
are closer to zero, but even over a perfect ground, there will be 
interaction effects due to the waves bouncing off of the ground. 
 
> Something has to be wrong here.  12.44 dBi of net gain for a 4-bay?  
> What is the element spacing?  Or does that include azimuth gain due to 
> the mount pipe?

No losses. Element spacing is one wavelength at 145MHz. 
 
> > Center of lobe: +2.7 degrees
> 
> When you're saying the "center of lobe", do you mean the midpoint between
> the -3 dB points, or the point of maximum gain?

Point of maximum gain. According to the graph, it's inbetween the -3 dB 
points.

> By the way, what are you using to model it?

MMANA-GAL (it's free, runs on Windows). I'd be happy to post the file if 
anyone wants to compare it.

Also, I did build the antenna out of copper pipe, not aluminum.

--
Kris Kirby, KE4AHR
Disinformation Analyst

RE: [Repeater-Builder] Decibel dipole array sweeps

[Mark]

I got to the page, but the file wouldn't open...

Mark - N9WYS

-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Eric Lemmon
Sent: Sunday, March 22, 2009 5:25 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] Decibel dipole array sweeps

Mark,

It may be a browser issue.  I clicked on the link below, and the correct
page opened.  It works fine with XP Pro and IE7.  Go figure...

73, Eric Lemmon WB6FLY
 

-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Mark
Sent: Sunday, March 22, 2009 3:08 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] Decibel dipole array sweeps

Using the link Eric posted below, I got the same error message that Bob NO6B
got - "file damaged and could not be repaired"...

Mark - N9WYS

-Original Message-
From: Repeater-Builder@yahoogroups.com
<mailto:Repeater-Builder%40yahoogroups.com>  On Behalf Of Eric Lemmon

I got the same result. The link was parsed incorrectly. Try this:


73, Eric Lemmon WB6FLY







Yahoo! Groups Links



No virus found in this incoming message.
Checked by AVG - www.avg.com 
Version: 8.0.238 / Virus Database: 270.11.23/2016 - Release Date: 03/21/09
17:58:00

Re: [Repeater-Builder] Decibel dipole array sweeps

[Joe]

I've had arguments with tower crews about antennas that are too good 
when doing a system sweep.  They would proudly state that the install 
was really good because the Return Loss was 28 dB on a wide band 800Mhz 
antenna that was only suppose to be about 14-18dB RL at the antenna.  
Turned out to be a bad (lossy) connector many times.  Reinstalling the 
connector would fix it.  This is where the Distance to Fault sweep comes 
in handy.

73, Joe, K1ike


Jeff DePolo wrote:
> In general, the loss in the feedline will only make the return loss look
> better.  If you have an antenna with a 14 dB return loss at the frequency of
> interest at the feedpoint, and connect it to a feedline that has 2 dB of
> loss, the return loss will be 14dB + 2 x 2dB = 18 dB looking into the
> transmitter end of the coax. 

Re: [Repeater-Builder] Decibel dipole array sweeps

[Chuck Kelsey]

Why not just include it with your article already posted? Just add the notes 
along with it.

Chuck
WB2EDV



- Original Message - 
From: "Jeff DePolo" 
To: 
Sent: Sunday, March 22, 2009 7:11 PM
Subject: RE: [Repeater-Builder] Decibel dipole array sweeps


>
> I have a Sinclair 8-bay with half-wave element to mast spacing stored in 
> the
> Sitemaster, but it was swept from the far end of 600' of 1-5/8" with a
> topside TX-RX crossband coupler.  It's spec'ed for 406-512 MHz.  I can't
> keep track of Sinclair's model numbers, it's probably a SD318-HF2P2SNM,
> previously known as a SRL310C8NM*2-2.  I can send you the sweep anyway if
> you want it.  It talks extremely well.
>
> --- Jeff WN3A

Re: [Repeater-Builder] Decibel dipole array sweeps

[Joe]

Actually, years ago I did some really crude "antenna test range" tests 
on an antenna.  I brought it up on the roof on a 10 foot mast and 
monitored a repeater.  Then I tilted the pole back and forth towards the 
repeater to see if I could find the major lobe while watching the S 
meter on my HT.  It gave me an idea of the take-off angle of the antenna.

73, Joe, K1ike

Chuck Kelsey wrote:
> The group hereby accepts Joe's offer to construct an antenna test range to 
> conduct pattern testing. What a nice guy! LOL!!
>
> Chuck
> WB2EDV
>
>
> - Original Message - 
> From: "Joe" 
> To: 
> Sent: Sunday, March 22, 2009 4:22 PM
> Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
>
>
>   
>> Although, in some cases, the return loss (or VSWR) looks to be
>> acceptable I wonder what the take-off angle of radiation and radiation
>> pattern looks like at frequencies out of it's design range.
>>
>> 73, Joe, K1ike
>> 

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

I have a Sinclair 8-bay with half-wave element to mast spacing stored in the
Sitemaster, but it was swept from the far end of 600' of 1-5/8" with a
topside TX-RX crossband coupler.  It's spec'ed for 406-512 MHz.  I can't
keep track of Sinclair's model numbers, it's probably a SD318-HF2P2SNM,
previously known as a SRL310C8NM*2-2.  I can send you the sweep anyway if
you want it.  It talks extremely well.

--- Jeff WN3A


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Nate Duehr
> Sent: Sunday, March 22, 2009 6:52 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
> 
> 
> On Mar 22, 2009, at 12:32 PM, Jeff DePolo wrote:
> 
> > The antennas I tested in this first batch are:
> >
> > DB413, 450-470 MHz
> > DB408D, 450-470 MHz
> > DB411, 450-470 MHz
> > DB411, 406-420 MHz
> 
> By the way, I like it, Jeff!
> 
> Got any Sinclairs handy for a comparison between common brands?
> 
> --
> Nate Duehr, WY0X
> n...@natetech.com <mailto:nate%40natetech.com> 
> 
> 
> 
> 
> 
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.0.238 / Virus Database: 270.11.3/1970 - Release 
> Date: 03/21/09 17:58:00
> 
> 
> 

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

 
> I'm modeling a half-wave dipole with the bottom .25 wavelength (at 
> 145MHz) above zero, with five meters added from the bottom. This 
> antenna, five plus meters above ground, shows that when 
> transmitting at 
> 165MHz, the highest point of gain is a lower degree of elevation than 
> when transmitting at 120MHz. 

Wait.  You're saying that a center-fed dipole has a major lobe that's not
exactly perpendicular to the element?  Something's amiss.

 > I just ran a stacked dipole configuration, essentially a 
> DB-224 without 
> phasing harnesses or the losses associated thereof. This 
> antenna, with a 
> design resonance of 145MHz, exhibits a maximum gain (again, 
> mounted five 
> meters above ground at the bottom of the antenna [not the center of 
> radiation]) at 2.8 degrees above zero, with a gain of 12.44 dBi. 

Something has to be wrong here.  12.44 dBi of net gain for a 4-bay?  What is
the element spacing?  Or does that include azimuth gain due to the mount
pipe?

> Center of lobe: +2.7 degrees

When you're saying the "center of lobe", do you mean the midpoint between
the -3 dB points, or the point of maximum gain?

By the way, what are you using to model it?

--- Jeff WN3A

RE: [Repeater-Builder] Decibel dipole array sweeps

[no6b]

At 3/22/2009 15:37, you wrote:
>On Sun, 22 Mar 2009 n...@no6b.com wrote:
> > Well, without a long explanation, I can't view files made for Acrobat
> > 6 & later.  No way around it unless I want to lose PDF authoring
> > capability.
>
>Buy a Mac

Of all the possible solutions, that is probably the most expensive & least 
practical.

Bob NO6B

Re: [Repeater-Builder] Decibel dipole array sweeps

[Nate Duehr]

On Mar 22, 2009, at 12:32 PM, Jeff DePolo wrote:

> The antennas I tested in this first batch are:
>
> DB413, 450-470 MHz
> DB408D, 450-470 MHz
> DB411, 450-470 MHz
> DB411, 406-420 MHz


By the way, I like it, Jeff!

Got any Sinclairs handy for a comparison between common brands?

--
Nate Duehr, WY0X
n...@natetech.com

Re: [Repeater-Builder] Decibel dipole array sweeps

[Nate Duehr]

On Mar 22, 2009, at 3:29 PM, Jeff DePolo wrote:

>
> In general, the loss in the feedline will only make the return loss  
> look
> better.

This leads to situations on poorly built systems where an antenna has  
gone bad but the feedline is such poor quality, that the transmitter  
is still quite "happy" with what it is seeing at the other end of the  
lossy cable... but of course, with the antenna broken, it doesn't  
really radiate.

Measuring VSWR at the repeater end of things, sometimes just doesn't  
tell the whole story.

One of those things one can learn "the hard way" if you're not paying  
attention and measuring each portion of your antenna system as a  
baseline at installation...

--
Nate Duehr, WY0X
n...@natetech.com

RE: [Repeater-Builder] Decibel dipole array sweeps

[Kris Kirby]

On Sun, 22 Mar 2009, Jeff DePolo wrote:
> the elements are fed in-phase (i.e. the branches in the phasing 
> harness are all the same length), as it typical with most dipole 
> arrays, there won't be any uptilt/downtilt as you vary the transmitter 
> frequency outside of the design range a bit.  No matter what the 
> frequency of the carrier is, it's always going to hit the elements 
> in-phase, so there won't be any beamtilt.
> 
> This is constrast to an end-fed (series-fed) collinear, where you will 
> get UPTILT if transmitting at a frequency ABOVE the antenna's design 
> range, and DOWNTILT if transmitting at a frequency BELOW the antenna's 
> design range.

I'm modeling a half-wave dipole with the bottom .25 wavelength (at 
145MHz) above zero, with five meters added from the bottom. This 
antenna, five plus meters above ground, shows that when transmitting at 
165MHz, the highest point of gain is a lower degree of elevation than 
when transmitting at 120MHz. 

When you remove the sense of "ground" and use a free-space model, 
nothing changes, except SWR and impedance. 

I just ran a stacked dipole configuration, essentially a DB-224 without 
phasing harnesses or the losses associated thereof. This antenna, with a 
design resonance of 145MHz, exhibits a maximum gain (again, mounted five 
meters above ground at the bottom of the antenna [not the center of 
radiation]) at 2.8 degrees above zero, with a gain of 12.44 dBi. 

Frequency: 174MHz
Gain: 12.53 dBi
Center of lobe: +2.4 degrees

Frequency: 165MHz
Gain: 12.5 dBi
Center of lobe: +2.5 degrees

Frequency: 145MHz
Gain: 12.44 dBi
Center of lobe: +2.8 degrees

Frequency: 137MHz
Gain: 12.29 dBi
Center of lobe: +3.0 degrees 

Frequency: 120MHz
Gain: 11.69 dBi
Center of lobe: +3.4 degrees

This antenna has a *design* frequency of 145MHz. This analysis doesn't 
factor for SWR at a 50-ohm feedpoint as the SWR wildly varies. In this 
case, the antenna exhibits downtilt of the resulting lobe as a result of 
lowering the transmit frequency, and uptilt as a result of increasing 
the transmit frequency.

So I've proven the original poster's point. But moreover that it affects 
both collinear and dipole array antennas. 

Here's a comparison for the more likely scenario:

Design resonance: 165MHz
Gain: 12.59dBi
Center of lobe: +2.7 degrees

Frequency: 147MHz
Gain: 12.24dBi
Center of lobe: +3.0 degrees

Frequency: 145MHz
Gain: 12.15dBi
Center of lobe: +3.0 degrees

The results, I would say in practical terms, is that a DB-224 cut for 
165MHz isn't a bad thing. You'll experience some uptilt. But matching 
the antenna to a 50-ohm transmitter is another issue altogether.

I am researching antenna inversion (mounting the antenna upside-down) at 
the moment.

--
Kris Kirby, KE4AHR
Disinformation Analyst

Re: [Repeater-Builder] Decibel dipole array sweeps

[Chuck Kelsey]

OK, that makes sense. It would still be interesting to see if the loss 
theory holds true using a known quantity of feedline.

Chuck
WB2EDV



- Original Message - 
From: "Jeff DePolo" 
To: 
Sent: Sunday, March 22, 2009 5:29 PM
Subject: RE: [Repeater-Builder] Decibel dipole array sweeps


>
> In general, the loss in the feedline will only make the return loss look
> better.  If you have an antenna with a 14 dB return loss at the frequency 
> of
> interest at the feedpoint, and connect it to a feedline that has 2 dB of
> loss, the return loss will be 14dB + 2 x 2dB = 18 dB looking into the
> transmitter end of the coax.  Why do you add 2X the feedline loss? 
> Because
> you have feedline loss in the forward direction, heading toward the 
> antenna,
> where at the feedpoint there is a reflection, and the reflected power
> likewise is attenuated due to feedline loss on the way back down the line,
> hence twice the loss in decibels (or the square root of the power loss in
> linear terms).
>
> I connected the Sitemaster to the pigtail and stepped away a few feet,
> reaching up from below to hit the "Save Display" button.  Moving the
> Sitemaster around, even closer to the lowest element, had no measurable
> effect until it, or the pigtail, got within a couple of inches of the 
> lowest
> element, and even then the change was only slight (remember, there are 4 
> or
> 8 or however many elements, so even de-tuning one element slightly isn't 
> as
> significant as compared to if you just had one element).
>
> --- Jeff WN3A

RE: [Repeater-Builder] Decibel dipole array sweeps

[Kris Kirby]

On Sun, 22 Mar 2009 n...@no6b.com wrote:
> Well, without a long explanation, I can't view files made for Acrobat 
> 6 & later.  No way around it unless I want to lose PDF authoring 
> capability.

Buy a Mac and image the Windows box and use it in a virtual machine. 
Then you can author in PDFs and the Mac has a built-in PDF viewer and 
Postscript conversion engine.

Totally not the solution you were looking for. =)

--
Kris Kirby, KE4AHR
Disinformation Analyst

RE: [Repeater-Builder] Decibel dipole array sweeps

[no6b]

At 3/22/2009 13:01, you wrote:

>Boy, Yahoo really mangled the URL, even though I put it in angle brackets.
>Let's try re-naming the file without spaces, maybe that will work...
>
>
>
>Bob - the file opened fine for me, both locally and from the web site.  I'm
>using Acrobat 9.0.  The document info shows it's PDF version 1.5 for Acrobat
>version 6.x or later.  I've had a few other cases where I couldn't open
>recently-produced PDF's sent to me by others using Acrobat 9; upgrading to
>the current version of Reader fixed it, even though the files should be
>compatible with Acrobat 6 or later.

Well, without a long explanation, I can't view files made for Acrobat 6 & 
later.  No way around it unless I want to lose PDF authoring capability.

Bob NO6B

RE: [Repeater-Builder] Decibel dipole array sweeps

[Eric Lemmon]

Mark,

It may be a browser issue.  I clicked on the link below, and the correct
page opened.  It works fine with XP Pro and IE7.  Go figure...

73, Eric Lemmon WB6FLY
 

-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Mark
Sent: Sunday, March 22, 2009 3:08 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] Decibel dipole array sweeps

Using the link Eric posted below, I got the same error message that Bob NO6B
got - "file damaged and could not be repaired"...

Mark - N9WYS

-Original Message-
From: Repeater-Builder@yahoogroups.com
<mailto:Repeater-Builder%40yahoogroups.com>  On Behalf Of Eric Lemmon

I got the same result. The link was parsed incorrectly. Try this:


73, Eric Lemmon WB6FLY

RE: [Repeater-Builder] Decibel dipole array sweeps

[Mark]

Using the link Eric posted below, I got the same error message that Bob NO6B
got - "file damaged and could not be repaired"...

Mark - N9WYS

-Original Message-
From: Repeater-Builder@yahoogroups.com  On Behalf Of Eric Lemmon

I got the same result.  The link was parsed incorrectly.  Try this:


73, Eric Lemmon WB6FLY

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

In general, the loss in the feedline will only make the return loss look
better.  If you have an antenna with a 14 dB return loss at the frequency of
interest at the feedpoint, and connect it to a feedline that has 2 dB of
loss, the return loss will be 14dB + 2 x 2dB = 18 dB looking into the
transmitter end of the coax.  Why do you add 2X the feedline loss?  Because
you have feedline loss in the forward direction, heading toward the antenna,
where at the feedpoint there is a reflection, and the reflected power
likewise is attenuated due to feedline loss on the way back down the line,
hence twice the loss in decibels (or the square root of the power loss in
linear terms).

I connected the Sitemaster to the pigtail and stepped away a few feet,
reaching up from below to hit the "Save Display" button.  Moving the
Sitemaster around, even closer to the lowest element, had no measurable
effect until it, or the pigtail, got within a couple of inches of the lowest
element, and even then the change was only slight (remember, there are 4 or
8 or however many elements, so even de-tuning one element slightly isn't as
significant as compared to if you just had one element).

--- Jeff WN3A


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey
> Sent: Sunday, March 22, 2009 4:44 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
> 
> Jeff -
> 
> When you are testing next time, it might be interesting to 
> see results of a 
> sweep using some feedline attached to the antenna. I have to 
> wonder what 
> impact it may (or may not) have.
> 
> When you test with your instrument connected to the pigtail, are you 
> standing right there, or is the antenna completely in the clear?
> 
> Chuck
> WB2EDV
> 
> 
> 
> 
> 
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.0.238 / Virus Database: 270.11.3/1970 - Release 
> Date: 03/21/09 17:58:00
> 
> 
> 

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

It wouldn't suprise me if the VSWR wasn't terrible since you'd be operating
the antenna at an odd multiple of its original design frequency.  However,
the elevation pattern will likely be a mess.  In other words, it may look
just dandy on the Sitemaster, but under-perform by a whole lot out in the
far field.  

A 1/2 wavelength dipole has a free space pattern which has one major lobe at
90 degrees perpendicular to the element, so, with the dipole oriented
vertically, the major lobe sits right on the horizon.  A 3/2 wavelength
dipole, which is what you'd have if you took a dipole cut for VHF but used
it on UHF at 3X its design frequency, has two equal major lobes, one about
42 degrees above the horizon and one about 42 degrees below the horizon if
memory serves.  There is also a third, minor lobe at the horizon.  So,
unless you want to talk to worms or martians, the 3/2 wave dipole probably
isn't going to give you the elevation pattern you're looking for.  Of
course, when you stack multiple elements, the fields from each element
interact, so it's hard to say what it will really look like for a multi-bay
antenna without modeling it, but I wouldn't expect it to be pretty...

--- Jeff WN3A

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Doug Bade
> Sent: Sunday, March 22, 2009 4:37 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: RE: [Repeater-Builder] Decibel dipole array sweeps
> 
> Jeff;
> What is your thoughts on the radiation launch angle in this 
> case if beam tilt does not suffer/gain ???
> 
> I have a case in point of a wideband 406-470 uhf sinclair dipole 
> 310C4.. on VHF as the elements are larger than vhf needs ??? in other 
> words using it on both vhf and uhf assuming reasonable vswr
> 
> Doug
> 
> At 04:17 PM 3/22/2009, you wrote:
> 
> >For a parallel-fed (aka binary-fed, corporate-fed, etc.) 
> antenna, if all of
> >the elements are fed in-phase (i.e. the branches in the 
> phasing harness are
> >all the same length), as it typical with most dipole arrays, 
> there won't be
> >any uptilt/downtilt as you vary the transmitter frequency 
> outside of the
> >design range a bit. No matter what the frequency of the 
> carrier is, it's
> >always going to hit the elements in-phase, so there won't be 
> any beamtilt.
> >
> >This is constrast to an end-fed (series-fed) collinear, 
> where you will get
> >UPTILT if transmitting at a frequency ABOVE the antenna's 
> design range, and
> >DOWNTILT if transmitting at a frequency BELOW the antenna's 
> design range.
> >
> >--- Jeff WN3A
> >
> > > -Original Message-
> > > From: 
> > 
> <mailto:Repeater-Builder%40yahoogroups.com>repeater-buil...@ya
> hoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> 
> > > [mailto:Repeater-Builder@yahoogroups.com 
> <mailto:Repeater-Builder%40yahoogroups.com> ] On Behalf Of Doug Bade
> > > Sent: Sunday, March 22, 2009 4:10 PM
> > > To: 
> > 
> <mailto:Repeater-Builder%40yahoogroups.com>repeater-buil...@ya
> hoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> 
> > > Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
> > >
> > > Jeff;
> > > This is very interesting findings especially in that using
> > > an antenna longer than your freq tends to exhibit down 
> tilt... that
> > > 440 use of a 450 antenna seems to be working in the correct
> > > direction. I for one found it very interesting to read
> > >
> > > It may be real interesting to see some of the amateur 
> antennas tested
> > > too as multiband ones seem to rarely work very well on the upper
> > > bands compared to the lower bands of those I have seen
> > >
> > > Doug
> > >
> > > At 02:32 PM 3/22/2009, you wrote:
> > >
> > > >I'm in the process of putting up a remote receiver for a 440
> > > ham repeater
> > > >using a Decibel DB413 dipole array cut for 450-470 MHz. Since
> > > >Decibel/Andrew stopped making the 440-450 MHz custom models,
> > > I've used the
> > > >usual 450-470 split antennas for receive sites, and they've
> > > performed well.
> > > >I swept the DB413, and it measured as I expected. While I had the
> > > >Sitemaster out, I grabbed a few other Decibel dipole arrays
> > > out of the
> > > >warehouse and swept them and prepared a little document.
> > > Since the topic of
> > >

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

The link in Doug's email below still has spaces in it (%20 hex ASCII for
space character).  Use the revised name I sent out that doesn't have spaces
in it:

http://www.broadsci.com/AntennaSweepsR1.pdf

--- Jeff


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey
> Sent: Sunday, March 22, 2009 4:08 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
> 
> Page cannot be found using your "fixed" link.
> 
> Chuck
> WB2EDV
> 
> - Original Message - 
> From: "Doug Bade" mailto:kd8b%40thebades.net> >
> To:  <mailto:Repeater-Builder%40yahoogroups.com> >
> Sent: Sunday, March 22, 2009 3:54 PM
> Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
> 
> > The link is broken due to the space in the name...
> >
> > The actual url is
> > <http://www.broadsci.com/Antenna%20Sweeps%20r1.pdf 
> <http://www.broadsci.com/Antenna%20Sweeps%20r1.pdf> >
> >
> > Doug
> >
> > this may be a dup.. my outbound mail seems to be randomly getting 
> > delayed..
> 
> 
> 
> 
> 
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.0.238 / Virus Database: 270.11.3/1970 - Release 
> Date: 03/21/09 17:58:00
> 
> 
> 

RE: [Repeater-Builder] Decibel dipole array sweeps

[Gary]

An interesting project, I look forward to reading your report however your
link was incorrectly typed. Here is a corrected link;

<http://www.broadsci.com/AntennaSweepsr1.pdf>

Gary

 

-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Jeff DePolo
Sent: Sunday, March 22, 2009 11:33 AM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] Decibel dipole array sweeps

 

 

I'm in the process of putting up a remote receiver for a 440 ham repeater

using a Decibel DB413 dipole array cut for 450-470 MHz.  Since

Decibel/Andrew stopped making the 440-450 MHz custom models, I've used the

usual 450-470 split antennas for receive sites, and they've performed well.

I swept the DB413, and it measured as I expected.  While I had the

Sitemaster out, I grabbed a few other Decibel dipole arrays out of the

warehouse and swept them and prepared a little document.  Since the topic of

using commercial-band antennas on amateur frequencies comes up fairly often,

I figured these measurements might be of some interest to list members.  

 

I tested these antennas with them mounted above ground level, and away from

nearby objects, with the Sitemaster connected right to the pigtail so what

you're seeing is the true return loss at the feedpoint.  I'll continue to

test more antennas (not just DB dipole arrays) over time and continue to add

them to this document.  I have gobs of sweeps of antennas, but unfortunately

many of them were swept at the bottom end of heliax runs rather than right

at the feedpoint.  From now on I'll make it a point to sweep them on the

ground this way.

 

The antennas I tested in this first batch are:

 

DB413, 450-470 MHz

DB408D, 450-470 MHz

DB411, 450-470 MHz

DB411, 406-420 MHz

 

Note that the DB408D is actually two DB404's on a common mast, each with its

own pigtail/feedpoint, so there are separate plots for the upper antenna and

lower antenna.  Its performance wasn't what I expected.  I have more of the

same model of antenna, I'll try to test one of the others the next time.

 

The document can be found here:

 

<http://www.broadsci.com/Antenna Sweeps r1.pdf>

 

If anyone finds this useful please let me know, so I know whether or not

it's worth the time/effort to continue to test antennas and add them to the

doc.

 

--- Jeff WN3A

 

 

 



 

 

 

Yahoo! Groups Links

 

http://groups.yahoo.com/group/Repeater-Builder/

 

Individual Email | Traditional

 

http://groups.yahoo.com/group/Repeater-Builder/join

(Yahoo! ID required)

 

mailto:repeater-builder-dig...@yahoogroups.com 

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Re: [Repeater-Builder] Decibel dipole array sweeps

[Chuck Kelsey]

Jeff -

When you are testing next time, it might be interesting to see results of a 
sweep using some feedline attached to the antenna. I have to wonder what 
impact it may (or may not) have.

When you test with your instrument connected to the pigtail, are you 
standing right there, or is the antenna completely in the clear?

Chuck
WB2EDV

Re: [Repeater-Builder] Decibel dipole array sweeps

[Chuck Kelsey]

The group hereby accepts Joe's offer to construct an antenna test range to 
conduct pattern testing. What a nice guy! LOL!!

Chuck
WB2EDV


- Original Message - 
From: "Joe" 
To: 
Sent: Sunday, March 22, 2009 4:22 PM
Subject: Re: [Repeater-Builder] Decibel dipole array sweeps


> Although, in some cases, the return loss (or VSWR) looks to be
> acceptable I wonder what the take-off angle of radiation and radiation
> pattern looks like at frequencies out of it's design range.
>
> 73, Joe, K1ike

Re: [Repeater-Builder] Decibel dipole array sweeps

[Chuck Kelsey]

Jeff is correct. A corporate fed antenna will only start to loose a bit of 
gain when you go outside of the band. Obviously you go too far and the 
return loss goes sour.

Chuck
WB2EDV



- Original Message - 
From: "Jeff DePolo" 
To: 
Sent: Sunday, March 22, 2009 4:17 PM
Subject: RE: [Repeater-Builder] Decibel dipole array sweeps


>
> For a parallel-fed (aka binary-fed, corporate-fed, etc.) antenna, if all 
> of
> the elements are fed in-phase (i.e. the branches in the phasing harness 
> are
> all the same length), as it typical with most dipole arrays, there won't 
> be
> any uptilt/downtilt as you vary the transmitter frequency outside of the
> design range a bit.  No matter what the frequency of the carrier is, it's
> always going to hit the elements in-phase, so there won't be any beamtilt.
>
> This is constrast to an end-fed (series-fed) collinear, where you will get
> UPTILT if transmitting at a frequency ABOVE the antenna's design range, 
> and
> DOWNTILT if transmitting at a frequency BELOW the antenna's design range.
>
> --- Jeff WN3A
>

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

As I mentioned a few minutes ago, there won't be any change in the take-off
angle (beamtilt) for these parallel-fed dipole arrays.  However, as you go
lower in frequency, as we typically do when using a 450-470 antenna down in
the 440's, the elements are effectively spaced closer together (in terms of
wavelength) than they would be if we were operating at, say, 460 MHz.
Because of the reduction in the intra-bay spacing, there will be slightly
less peak gain on the horizon, and some variation in the minor lobes, but
the major lobe will still be centered on the horizon.

On-horizon gain tends to peak at a little under 1 wavelength for the
intra-bay spacing.  As you go above 1 wavelength, the elevation pattern
quickly starts to fall apart.  As you go under 1 wavelength, the peak gain
gradually starts to decrease as the major lobe gets fatter.  At
half-wavelength spacing (i.e. element tips almost touching each other), the
gain is on the order of roughly 2 dB below what it would be as compared to
the full-wavelength spacing case.  A spacing of around 0.9 wavelengths at
the highest-rated frequency is used for many VHF/UHF dipole arrays as a good
compromise.  Some dipole arrays with 4 or more bays have a little variation
between the element spacing too, which has the affect of altering the
sidelobes to help "fill" some of the nulls below the horizon, but that alone
won't create appreciable beamtilt of the major lobe.  Dipole arrays that ARE
designed for beamtilt have a phasing harness with unequal-length branches
that puts more progressively more delay in the branches to the lower
elements.

A long time ago I modeled a 4-bay VHF dipole array in NEC using the lengths
and spacings from a DB224 dipole array that was cut for 155 MHz.  Down at
146 MHz, the peak gain was only degraded about half a dB as compared to the
155 MHz case, and the main lobe got just a little fatter.

--- Jeff WN3A

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Joe
> Sent: Sunday, March 22, 2009 4:22 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
> 
> Although, in some cases, the return loss (or VSWR) looks to be 
> acceptable I wonder what the take-off angle of radiation and 
> radiation 
> pattern looks like at frequencies out of it's design range. 
> 
> 73, Joe, K1ike
> 
> Jeff DePolo wrote:
> > I tested these antennas with them mounted above ground 
> level, and away from
> > nearby objects, with the Sitemaster connected right to the 
> pigtail so what
> > you're seeing is the true return loss at the feedpoint.
> 
> 
> 
> 
> 
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.0.238 / Virus Database: 270.11.3/1970 - Release 
> Date: 03/21/09 17:58:00
> 
> 
> 

Re: [Repeater-Builder] Decibel dipole array sweeps

[Doug Bade]

The link is broken due to the space in the name...

The actual url is


Doug

this may be a dup.. my outbound mail seems to be randomly getting delayed..




At 03:31 PM 3/22/2009, you wrote:

>n...@no6b.com wrote:
> > At 3/22/2009 11:32, you wrote:
> >
> >> The document can be found here:
> >>
> >> 
> <http://www.broadsci.com/Antenna 
> Sweeps r1.pdf>
> >
> > I get a "The file is damaged & could not be repaired" error.
>
>And I get a 404 Page not found error.
>
>Paul
>

RE: [Repeater-Builder] Decibel dipole array sweeps

[Doug Bade]

Jeff;
 What is your thoughts on the radiation launch angle in this 
case if beam tilt does not suffer/gain ???

I have a case in point of a wideband 406-470 uhf sinclair dipole 
310C4.. on VHF as the elements are larger than vhf needs ??? in other 
words using it on both vhf and uhf assuming reasonable vswr

Doug




At 04:17 PM 3/22/2009, you wrote:


>For a parallel-fed (aka binary-fed, corporate-fed, etc.) antenna, if all of
>the elements are fed in-phase (i.e. the branches in the phasing harness are
>all the same length), as it typical with most dipole arrays, there won't be
>any uptilt/downtilt as you vary the transmitter frequency outside of the
>design range a bit. No matter what the frequency of the carrier is, it's
>always going to hit the elements in-phase, so there won't be any beamtilt.
>
>This is constrast to an end-fed (series-fed) collinear, where you will get
>UPTILT if transmitting at a frequency ABOVE the antenna's design range, and
>DOWNTILT if transmitting at a frequency BELOW the antenna's design range.
>
>--- Jeff WN3A
>
> > -Original Message-
> > From: 
> <mailto:Repeater-Builder%40yahoogroups.com>Repeater-Builder@yahoogroups.com
> > [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Doug Bade
> > Sent: Sunday, March 22, 2009 4:10 PM
> > To: 
> <mailto:Repeater-Builder%40yahoogroups.com>Repeater-Builder@yahoogroups.com
> > Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
> >
> > Jeff;
> > This is very interesting findings especially in that using
> > an antenna longer than your freq tends to exhibit down tilt... that
> > 440 use of a 450 antenna seems to be working in the correct
> > direction. I for one found it very interesting to read
> >
> > It may be real interesting to see some of the amateur antennas tested
> > too as multiband ones seem to rarely work very well on the upper
> > bands compared to the lower bands of those I have seen
> >
> > Doug
> >
> > At 02:32 PM 3/22/2009, you wrote:
> >
> > >I'm in the process of putting up a remote receiver for a 440
> > ham repeater
> > >using a Decibel DB413 dipole array cut for 450-470 MHz. Since
> > >Decibel/Andrew stopped making the 440-450 MHz custom models,
> > I've used the
> > >usual 450-470 split antennas for receive sites, and they've
> > performed well.
> > >I swept the DB413, and it measured as I expected. While I had the
> > >Sitemaster out, I grabbed a few other Decibel dipole arrays
> > out of the
> > >warehouse and swept them and prepared a little document.
> > Since the topic of
> > >using commercial-band antennas on amateur frequencies comes
> > up fairly often,
> > >I figured these measurements might be of some interest to
> > list members.
> > >
> > >I tested these antennas with them mounted above ground
> > level, and away from
> > >nearby objects, with the Sitemaster connected right to the
> > pigtail so what
> > >you're seeing is the true return loss at the feedpoint. I'll
> > continue to
> > >test more antennas (not just DB dipole arrays) over time and
> > continue to add
> > >them to this document. I have gobs of sweeps of antennas,
> > but unfortunately
> > >many of them were swept at the bottom end of heliax runs
> > rather than right
> > >at the feedpoint. From now on I'll make it a point to sweep
> > them on the
> > >ground this way.
> > >
> > >The antennas I tested in this first batch are:
> > >
> > >DB413, 450-470 MHz
> > >DB408D, 450-470 MHz
> > >DB411, 450-470 MHz
> > >DB411, 406-420 MHz
> > >
> > >Note that the DB408D is actually two DB404's on a common
> > mast, each with its
> > >own pigtail/feedpoint, so there are separate plots for the
> > upper antenna and
> > >lower antenna. Its performance wasn't what I expected. I
> > have more of the
> > >same model of antenna, I'll try to test one of the others
> > the next time.
> > >
> > >The document can be found here:
> > >
> > ><<<http://www.broadsci.com/Antenna>http://www.broadsci.com/Antenna
> > <http://www.broadsci.com/Antenna>
> > ><http://www.broadsci.com/Antenna>http://www.broadsci.com/Antenna 
> <http://www.broadsci.com/Antenna>
> > >Sweeps r1.pdf>
> > >
> > >If anyone finds this useful please let me know, so I know
> > whether or not
> > >it's worth the time/effort to continue to test antennas and
> > add them to the
> > >doc.
> > >
> > >--- Jeff WN3A
> > >
> > >
> >
> >
> >
> >
> >
> > No virus found in this incoming message.
> > Checked by AVG - www.avg.com
> > Version: 8.0.238 / Virus Database: 270.11.3/1970 - Release
> > Date: 03/21/09 17:58:00
> >
> >
> >
>
>

Re: [Repeater-Builder] Decibel dipole array sweeps

[Doug Bade]

Joe;

 The original posted file name had spaces in between Antenna, 
Sweeps, and r1 ...and some or all windows client email programs 
likley displayed as he sent it... Mine did but I spotted it as it 
showed as fractured hyperlink... Foxfire my have corrected it in your 
case. When I COPIED ( as in copy and paste) it into IE it inserted 
the %20's.. but if you launched it as a hyperlink directly it dropped 
everything after the first space... as being not part of the file 
name.. hence the broken links some found

Doug

At 04:16 PM 3/22/2009, you wrote:

>That's strange. I'm using Foxfire 3.0.7 and the original link was OK.
>
>Joe
>
>Doug Bade wrote:
> > The link is broken if you try to use it as it came through..
> > the space in the file name is the killer...
> > 
> <http://www.broadsci.com/Antenna%20Sweeps%20r1.pdf>

RE: [Repeater-Builder] Decibel dipole array sweeps

[Eric Lemmon]

I got the same result.  The link was parsed incorrectly.  Try this:


73, Eric Lemmon WB6FLY
 

-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of n...@no6b.com
Sent: Sunday, March 22, 2009 12:10 PM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Decibel dipole array sweeps

At 3/22/2009 11:32, you wrote:

>The document can be found here:
>
><http://www.broadsci.com/Antenna <http://www.broadsci.com/Antenna>  Sweeps
r1.pdf>

I get a "The file is damaged & could not be repaired" error.

Bob NO6B

Re: [Repeater-Builder] Decibel dipole array sweeps

[Joe]

Although, in some cases, the return loss (or VSWR) looks to be 
acceptable I wonder what the take-off angle of radiation and radiation 
pattern looks like at frequencies out of it's design range. 

73, Joe, K1ike


Jeff DePolo wrote:
> I tested these antennas with them mounted above ground level, and away from
> nearby objects, with the Sitemaster connected right to the pigtail so what
> you're seeing is the true return loss at the feedpoint.

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

For a parallel-fed (aka binary-fed, corporate-fed, etc.) antenna, if all of
the elements are fed in-phase (i.e. the branches in the phasing harness are
all the same length), as it typical with most dipole arrays, there won't be
any uptilt/downtilt as you vary the transmitter frequency outside of the
design range a bit.  No matter what the frequency of the carrier is, it's
always going to hit the elements in-phase, so there won't be any beamtilt.  

This is constrast to an end-fed (series-fed) collinear, where you will get
UPTILT if transmitting at a frequency ABOVE the antenna's design range, and
DOWNTILT if transmitting at a frequency BELOW the antenna's design range.

--- Jeff WN3A


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Doug Bade
> Sent: Sunday, March 22, 2009 4:10 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
> 
> Jeff;
> This is very interesting findings especially in that using 
> an antenna longer than your freq tends to exhibit down tilt... that 
> 440 use of a 450 antenna seems to be working in the correct 
> direction. I for one found it very interesting to read
> 
> It may be real interesting to see some of the amateur antennas tested 
> too as multiband ones seem to rarely work very well on the upper 
> bands compared to the lower bands of those I have seen
> 
> Doug
> 
> At 02:32 PM 3/22/2009, you wrote:
> 
> >I'm in the process of putting up a remote receiver for a 440 
> ham repeater
> >using a Decibel DB413 dipole array cut for 450-470 MHz. Since
> >Decibel/Andrew stopped making the 440-450 MHz custom models, 
> I've used the
> >usual 450-470 split antennas for receive sites, and they've 
> performed well.
> >I swept the DB413, and it measured as I expected. While I had the
> >Sitemaster out, I grabbed a few other Decibel dipole arrays 
> out of the
> >warehouse and swept them and prepared a little document. 
> Since the topic of
> >using commercial-band antennas on amateur frequencies comes 
> up fairly often,
> >I figured these measurements might be of some interest to 
> list members.
> >
> >I tested these antennas with them mounted above ground 
> level, and away from
> >nearby objects, with the Sitemaster connected right to the 
> pigtail so what
> >you're seeing is the true return loss at the feedpoint. I'll 
> continue to
> >test more antennas (not just DB dipole arrays) over time and 
> continue to add
> >them to this document. I have gobs of sweeps of antennas, 
> but unfortunately
> >many of them were swept at the bottom end of heliax runs 
> rather than right
> >at the feedpoint. From now on I'll make it a point to sweep 
> them on the
> >ground this way.
> >
> >The antennas I tested in this first batch are:
> >
> >DB413, 450-470 MHz
> >DB408D, 450-470 MHz
> >DB411, 450-470 MHz
> >DB411, 406-420 MHz
> >
> >Note that the DB408D is actually two DB404's on a common 
> mast, each with its
> >own pigtail/feedpoint, so there are separate plots for the 
> upper antenna and
> >lower antenna. Its performance wasn't what I expected. I 
> have more of the
> >same model of antenna, I'll try to test one of the others 
> the next time.
> >
> >The document can be found here:
> >
> ><<http://www.broadsci.com/Antenna 
> <http://www.broadsci.com/Antenna> 
> >http://www.broadsci.com/Antenna <http://www.broadsci.com/Antenna>  
> >Sweeps r1.pdf>
> >
> >If anyone finds this useful please let me know, so I know 
> whether or not
> >it's worth the time/effort to continue to test antennas and 
> add them to the
> >doc.
> >
> >--- Jeff WN3A
> >
> >
> 
> 
> 
> 
> 
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.0.238 / Virus Database: 270.11.3/1970 - Release 
> Date: 03/21/09 17:58:00
> 
> 
> 

Re: [Repeater-Builder] Decibel dipole array sweeps

[Joe]

That's strange.  I'm using Foxfire 3.0.7 and the original link was OK.

Joe

Doug Bade wrote:
> The link is broken if you try to use it as it came through..
> the space in the file name is the killer...
> 
>   

Re: [Repeater-Builder] Decibel dipole array sweeps

[Chuck Kelsey]

Page cannot be found using your "fixed" link.

Chuck
WB2EDV



- Original Message - 
From: "Doug Bade" 
To: 
Sent: Sunday, March 22, 2009 3:54 PM
Subject: Re: [Repeater-Builder] Decibel dipole array sweeps


> The link is broken due to the space in the name...
>
> The actual url is
> <http://www.broadsci.com/Antenna%20Sweeps%20r1.pdf>
>
> Doug
>
> this may be a dup.. my outbound mail seems to be randomly getting 
> delayed..

Re: [Repeater-Builder] Decibel dipole array sweeps

[Doug Bade]

Jeff;
 This is very interesting findings especially in that using 
an antenna longer than your freq tends to exhibit down tilt... that 
440 use of a 450 antenna seems to be working in the correct 
direction. I for one found it very interesting to read

It may be real interesting to see some of the amateur antennas tested 
too as multiband ones seem to rarely work very well on the upper 
bands compared to the lower bands of those I have seen

Doug


At 02:32 PM 3/22/2009, you wrote:


>I'm in the process of putting up a remote receiver for a 440 ham repeater
>using a Decibel DB413 dipole array cut for 450-470 MHz. Since
>Decibel/Andrew stopped making the 440-450 MHz custom models, I've used the
>usual 450-470 split antennas for receive sites, and they've performed well.
>I swept the DB413, and it measured as I expected. While I had the
>Sitemaster out, I grabbed a few other Decibel dipole arrays out of the
>warehouse and swept them and prepared a little document. Since the topic of
>using commercial-band antennas on amateur frequencies comes up fairly often,
>I figured these measurements might be of some interest to list members.
>
>I tested these antennas with them mounted above ground level, and away from
>nearby objects, with the Sitemaster connected right to the pigtail so what
>you're seeing is the true return loss at the feedpoint. I'll continue to
>test more antennas (not just DB dipole arrays) over time and continue to add
>them to this document. I have gobs of sweeps of antennas, but unfortunately
>many of them were swept at the bottom end of heliax runs rather than right
>at the feedpoint. From now on I'll make it a point to sweep them on the
>ground this way.
>
>The antennas I tested in this first batch are:
>
>DB413, 450-470 MHz
>DB408D, 450-470 MHz
>DB411, 450-470 MHz
>DB411, 406-420 MHz
>
>Note that the DB408D is actually two DB404's on a common mast, each with its
>own pigtail/feedpoint, so there are separate plots for the upper antenna and
>lower antenna. Its performance wasn't what I expected. I have more of the
>same model of antenna, I'll try to test one of the others the next time.
>
>The document can be found here:
>
><http://www.broadsci.com/Antenna 
>Sweeps r1.pdf>
>
>If anyone finds this useful please let me know, so I know whether or not
>it's worth the time/effort to continue to test antennas and add them to the
>doc.
>
>--- Jeff WN3A
>
>

RE: [Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

Boy, Yahoo really mangled the URL, even though I put it in angle brackets.
Let's try re-naming the file without spaces, maybe that will work...

<http://www.broadsci.com/AntennaSweepsR1.pdf>

Bob - the file opened fine for me, both locally and from the web site.  I'm
using Acrobat 9.0.  The document info shows it's PDF version 1.5 for Acrobat
version 6.x or later.  I've had a few other cases where I couldn't open
recently-produced PDF's sent to me by others using Acrobat 9; upgrading to
the current version of Reader fixed it, even though the files should be
compatible with Acrobat 6 or later.

--- Jeff WN3A


 

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Paul N1BUG
> Sent: Sunday, March 22, 2009 3:32 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Decibel dipole array sweeps
> 
> n...@no6b.com <mailto:no6b%40no6b.com>  wrote:
> > At 3/22/2009 11:32, you wrote:
> > 
> >> The document can be found here:
> >>
> >> <http://www.broadsci.com/Antenna 
> <http://www.broadsci.com/Antenna>  Sweeps r1.pdf>
> > 
> > I get a "The file is damaged & could not be repaired" error.
> 
> And I get a 404 Page not found error.
> 
> Paul
> 
> 
> 
> 
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.0.238 / Virus Database: 270.11.3/1970 - Release 
> Date: 03/21/09 17:58:00
> 
> 
> 

Re: [Repeater-Builder] Decibel dipole array sweeps

[Doug Bade]

The link is broken if you try to use it as it came through..
the space in the file name is the killer...


is the correct link

Doug


At 03:31 PM 3/22/2009, you wrote:

>n...@no6b.com wrote:
> > At 3/22/2009 11:32, you wrote:
> >
> >> The document can be found here:
> >>
> >> 
> <http://www.broadsci.com/Antenna 
> Sweeps r1.pdf>
> >
> > I get a "The file is damaged & could not be repaired" error.
>
>And I get a 404 Page not found error.
>
>Paul
>

Re: [Repeater-Builder] Decibel dipole array sweeps

[Paul N1BUG]

n...@no6b.com wrote:
> At 3/22/2009 11:32, you wrote:
> 
>> The document can be found here:
>>
>> 
> 
> I get a "The file is damaged & could not be repaired" error.

And I get a 404 Page not found error.

Paul

Re: [Repeater-Builder] Decibel dipole array sweeps

[no6b]

At 3/22/2009 11:32, you wrote:

>The document can be found here:
>
>

I get a "The file is damaged & could not be repaired" error.

Bob NO6B

[Repeater-Builder] Decibel dipole array sweeps

[Jeff DePolo]

I'm in the process of putting up a remote receiver for a 440 ham repeater
using a Decibel DB413 dipole array cut for 450-470 MHz.  Since
Decibel/Andrew stopped making the 440-450 MHz custom models, I've used the
usual 450-470 split antennas for receive sites, and they've performed well.
I swept the DB413, and it measured as I expected.  While I had the
Sitemaster out, I grabbed a few other Decibel dipole arrays out of the
warehouse and swept them and prepared a little document.  Since the topic of
using commercial-band antennas on amateur frequencies comes up fairly often,
I figured these measurements might be of some interest to list members.  

I tested these antennas with them mounted above ground level, and away from
nearby objects, with the Sitemaster connected right to the pigtail so what
you're seeing is the true return loss at the feedpoint.  I'll continue to
test more antennas (not just DB dipole arrays) over time and continue to add
them to this document.  I have gobs of sweeps of antennas, but unfortunately
many of them were swept at the bottom end of heliax runs rather than right
at the feedpoint.  From now on I'll make it a point to sweep them on the
ground this way.

The antennas I tested in this first batch are:

DB413, 450-470 MHz
DB408D, 450-470 MHz
DB411, 450-470 MHz
DB411, 406-420 MHz

Note that the DB408D is actually two DB404's on a common mast, each with its
own pigtail/feedpoint, so there are separate plots for the upper antenna and
lower antenna.  Its performance wasn't what I expected.  I have more of the
same model of antenna, I'll try to test one of the others the next time.

The document can be found here:



If anyone finds this useful please let me know, so I know whether or not
it's worth the time/effort to continue to test antennas and add them to the
doc.

--- Jeff WN3A