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J Beam 14 element parabeam
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Brian Howie
Oct 26, 2018, 5:45:50 AM10/26/18
to
I'm looking for the dimensions of the J Beam 14 element parabeam.
http://mirror.thelifeofkenneth.com/lib/VHF_communications/1975/3-75.pdf
Page 173 . I want to examine the claim that the antenna has a 3 dB
advantage over a conventionally fed long yagi. I could reverse
engineer one from the boom length, but the original design parameters
would make this easier.
Brian GM4DIJ
--
Brian Howie
http://mirror.thelifeofkenneth.com/lib/VHF_communications/1975/3-75.pdf
Page 173 . I want to examine the claim that the antenna has a 3 dB
advantage over a conventionally fed long yagi. I could reverse
engineer one from the boom length, but the original design parameters
would make this easier.
Brian GM4DIJ
--
Brian Howie
Brian Howie
Oct 27, 2018, 3:24:03 PM10/27/18
to
In message <pr1av0$4ff$1...@gioia.aioe.org>, Jeff <je...@ukra.com> writes
>I would have thought that the claim of 3dB gain due to the slot feed
>would be easily confirmed by modelling using NEC and existing yagi
>files.
>
>Jeff
Yes I modelled my version of a 14 element parabeam and can only get
about 12dBd . A 14 ele conventional yagi with the same boom length has
slightly more gain . I'm not seeing the 3db advantage even with a 2
element version. Head scratching time.
One of the reasons I'm looking at this is our club enters the restricted
section of VHF NFD . We can't use stacked antennas, but we can use slot
fed antennas or quads. I was looking to see if I could get an extra 3dB
without doubling the boom length or having stacked parasitic elements as
per the conventional slot fed yagi.
Brian
--
Brian Howie
>would be easily confirmed by modelling using NEC and existing yagi
>files.
>
>Jeff
Yes I modelled my version of a 14 element parabeam and can only get
about 12dBd . A 14 ele conventional yagi with the same boom length has
slightly more gain . I'm not seeing the 3db advantage even with a 2
element version. Head scratching time.
One of the reasons I'm looking at this is our club enters the restricted
section of VHF NFD . We can't use stacked antennas, but we can use slot
fed antennas or quads. I was looking to see if I could get an extra 3dB
without doubling the boom length or having stacked parasitic elements as
per the conventional slot fed yagi.
Brian
--
Brian Howie
Brian Howie
Oct 28, 2018, 10:26:56 AM10/28/18
to
In message <pr48id$k09$1...@gioia.aioe.org>, Jeff <je...@ukra.com> writes
>A bit of digging on the internet has come up with these dimensions:
>
><http://www.rigpix.com/antennas/jaybeam_pbm142m_manual.pdf>
>
>When i get time I might try modeling it.
>
>Jeff
Thanks,
Just what I was looking for.
I tried changing a DK7ZB 9 ele to a slot feed plus dual reflector. Non
optimised it dropped 4dB. I reoptimised it and it came out 0.2dB lower.
I took out the first director and stuck it on the end and re-optimised
Th boom length is close to that of the 14 ele and the gain is 12.75dB
c.f. my attempt at a 14ele parabeam at 12.08dB
The J Beam antennas were designed to work over the whole 2m band and
the elements are close spaced. The super-gain yagis are wide spaced and
have a narrower band.
Brian
--
Brian Howie
>
><http://www.rigpix.com/antennas/jaybeam_pbm142m_manual.pdf>
>
>When i get time I might try modeling it.
>
>Jeff
Thanks,
Just what I was looking for.
I tried changing a DK7ZB 9 ele to a slot feed plus dual reflector. Non
optimised it dropped 4dB. I reoptimised it and it came out 0.2dB lower.
I took out the first director and stuck it on the end and re-optimised
Th boom length is close to that of the 14 ele and the gain is 12.75dB
c.f. my attempt at a 14ele parabeam at 12.08dB
The J Beam antennas were designed to work over the whole 2m band and
the elements are close spaced. The super-gain yagis are wide spaced and
have a narrower band.
Brian
--
Brian Howie
Brian Howie
Oct 28, 2018, 2:08:10 PM10/28/18
to
In message <8nv8TXb1...@b-howie.co.uk>, Brian Howie
<br...@b-howie.co.uk> writes
gain of 12.82dB , a long way short of the 15.2dB claimed. Impedance is
about 311ohm , so the 4:1 balun brings to down about 77ohm close to the
design 75ohm . F/b is 15.62db
Brian
--
Brian Howie
<br...@b-howie.co.uk> writes
>In message <pr48id$k09$1...@gioia.aioe.org>, Jeff <je...@ukra.com> writes
>>On 27/10/2018 20:15, Brian Howie wrote:
>>> In message <pr1av0$4ff$1...@gioia.aioe.org>, Jeff <je...@ukra.com> writes
>>>> On 26/10/2018 10:05, Brian Howie wrote:
>>>>> I'm looking for the dimensions of the J Beam 14 element parabeam.
>>>>>
>>>>> http://mirror.thelifeofkenneth.com/lib/VHF_communications/1975/3-75.pdf
>>>>> Page 173 . I want to examine the claim that the antenna has a 3
>>>>>dB advantage over a conventionally fed long yagi. I could reverse
>>>>>engineer one from the boom length, but the original design
>>>>>parameters would make this easier.
>>>>> Brian GM4DIJ
>>>>
>>>> I would have thought that the claim of 3dB gain due to the slot
>>>>feed would be easily confirmed by modelling using NEC and existing
>>>>yagi files.
>>>>
>>>> Jeff
>>> Yes I modelled my version of a 14 element parabeam and can only
>>>get about 12dBd . A 14 ele conventional yagi with the same boom
>>>length has slightly more gain . I'm not seeing the 3db advantage
>>>even with a 2 element version. Head scratching time.
>>> One of the reasons I'm looking at this is our club enters the
>>>restricted section of VHF NFD . We can't use stacked antennas, but we
>>>can use slot fed antennas or quads. I was looking to see if I could
>>>get an extra 3dB without doubling the boom length or having stacked
>>On 27/10/2018 20:15, Brian Howie wrote:
>>> In message <pr1av0$4ff$1...@gioia.aioe.org>, Jeff <je...@ukra.com> writes
>>>> On 26/10/2018 10:05, Brian Howie wrote:
>>>>> I'm looking for the dimensions of the J Beam 14 element parabeam.
>>>>>
>>>>> http://mirror.thelifeofkenneth.com/lib/VHF_communications/1975/3-75.pdf
>>>>> Page 173 . I want to examine the claim that the antenna has a 3
>>>>>dB advantage over a conventionally fed long yagi. I could reverse
>>>>>engineer one from the boom length, but the original design
>>>>>parameters would make this easier.
>>>>> Brian GM4DIJ
>>>>
>>>> I would have thought that the claim of 3dB gain due to the slot
>>>>feed would be easily confirmed by modelling using NEC and existing
>>>>yagi files.
>>>>
>>>> Jeff
>>> Yes I modelled my version of a 14 element parabeam and can only
>>>get about 12dBd . A 14 ele conventional yagi with the same boom
>>>length has slightly more gain . I'm not seeing the 3db advantage
>>>even with a 2 element version. Head scratching time.
>>> One of the reasons I'm looking at this is our club enters the
>>>restricted section of VHF NFD . We can't use stacked antennas, but we
>>>can use slot fed antennas or quads. I was looking to see if I could
>>>get an extra 3dB without doubling the boom length or having stacked
>>>elements as per the conventional slot fed yagi.
>>> Brian
>>
>>A bit of digging on the internet has come up with these dimensions:
>>
>><http://www.rigpix.com/antennas/jaybeam_pbm142m_manual.pdf>
>>
>>When i get time I might try modeling it.
>>
>>Jeff
>
>Thanks,
>
>Just what I was looking for.
>
>I tried changing a DK7ZB 9 ele to a slot feed plus dual reflector. Non
>optimised it dropped 4dB. I reoptimised it and it came out 0.2dB lower.
>I took out the first director and stuck it on the end and re-optimised
>Th boom length is close to that of the 14 ele and the gain is 12.75dB
>c.f. my attempt at a 14ele parabeam at 12.08dB
>
>The J Beam antennas were designed to work over the whole 2m band and
>the elements are close spaced. The super-gain yagis are wide spaced and
>have a narrower band.
>
>Brian
>
Using the dimensions in the link - as far as I can read them. I get a
>>> Brian
>>
>>A bit of digging on the internet has come up with these dimensions:
>>
>><http://www.rigpix.com/antennas/jaybeam_pbm142m_manual.pdf>
>>
>>When i get time I might try modeling it.
>>
>>Jeff
>
>Thanks,
>
>Just what I was looking for.
>
>I tried changing a DK7ZB 9 ele to a slot feed plus dual reflector. Non
>optimised it dropped 4dB. I reoptimised it and it came out 0.2dB lower.
>I took out the first director and stuck it on the end and re-optimised
>Th boom length is close to that of the 14 ele and the gain is 12.75dB
>c.f. my attempt at a 14ele parabeam at 12.08dB
>
>The J Beam antennas were designed to work over the whole 2m band and
>the elements are close spaced. The super-gain yagis are wide spaced and
>have a narrower band.
>
>Brian
>
gain of 12.82dB , a long way short of the 15.2dB claimed. Impedance is
about 311ohm , so the 4:1 balun brings to down about 77ohm close to the
design 75ohm . F/b is 15.62db
Brian
--
Brian Howie
Paul Cummins
Oct 28, 2018, 4:39:40 PM10/28/18
to
In article <QCln6hTe...@b-howie.co.uk>, br...@b-howie.co.uk (Brian
Most gain figures are dBi claims.
--
Paul Cummins - Always a NetHead
Wasting Bandwidth since 1981
Howie) wrote:
> Yes I modelled my version of a 14 element parabeam and can only
> get about 12dBd
Don't forget:
> Yes I modelled my version of a 14 element parabeam and can only
> get about 12dBd
Most gain figures are dBi claims.
--
Paul Cummins - Always a NetHead
Wasting Bandwidth since 1981
Brian Howie
Oct 29, 2018, 5:21:59 AM10/29/18
to
In message <memo.20181028...@paulcummins.gstgroup.co.uk>, Paul
Cummins <agree2...@spam.vlaad.co.uk> writes
Http://mirror.thelifeofkenneth.com/lib/VHF_communications/1975/3-75.pdf
J Beam made good antennas. Their 8 ele for 2m and the 4 ele for 4m were
entry level standard when I started in the early 70s. I still use the
8ele I got then now and again. The gain figures as modelled are close
to their claimed figures,
Brian
--
Brian Howie
Cummins <agree2...@spam.vlaad.co.uk> writes
>In article <QCln6hTe...@b-howie.co.uk>, br...@b-howie.co.uk (Brian
>Howie) wrote:
>
>> Yes I modelled my version of a 14 element parabeam and can only
>> get about 12dBd
>
>Don't forget:
>
>Most gain figures are dBi claims.
>
The article I quoted said 15.5dBd.
>Howie) wrote:
>
>> Yes I modelled my version of a 14 element parabeam and can only
>> get about 12dBd
>
>Don't forget:
>
>Most gain figures are dBi claims.
>
Http://mirror.thelifeofkenneth.com/lib/VHF_communications/1975/3-75.pdf
J Beam made good antennas. Their 8 ele for 2m and the 4 ele for 4m were
entry level standard when I started in the early 70s. I still use the
8ele I got then now and again. The gain figures as modelled are close
to their claimed figures,
Brian
--
Brian Howie
Brian Howie
Oct 29, 2018, 11:52:18 AM10/29/18
to
In message <pr705m$10m4$1...@gioia.aioe.org>, Jeff <je...@ukra.com> writes
>
>Some of the dimensions on that drawing are hard to interpret but using
>my best guess I get 14.8dBi, which is similar to your results.
>
>However, looking at the currents I seems to me as though I have not got
>the slot feed quite right, so I will have another play.
>
>It is also interesting that if you model just the slot feed it gives a
>gain of about 3.8dBi, which is a little low I think.
>
>Then if you add just the 2 reflector elements the gain goes up to
>7.5dBi, however, it would seem that as you add more directors that gain
>advantage disappears pretty much. Replacing just the slot radiator and
>directors with a conventional dipole and reflector gives a gain of
>14.4dBi, so only 0.4dB advantage from the slot feed.
>
>So I think something is not quite right at the moment.
>
>Jeff
>
I pasted your description into 4NEC2 and it seems to agree. The feed
impedance is different
I get 7.88 dBi for the slot + reflectors . I think the advantage for the
n over n slot fed yagi also reduces as n increases. Quads do something
similar.
I'd been hoping that adding a slot feed might have reduced the vertical
lobe on the NFD antennas and given us more gain , but it looks unlikely
, The antennas are 11 ele on 4m and 9 ele on 6m . N over N slot
versions would be impossible to put up.
This is the MMANA antenna description . I didn't have the vertical
support on the slot, but I added it in - not much difference.
*
144.1
***Wires***
24
0.0, -0.5, -0.365, 0.0, 0.5, -0.365, 0.005, -1
0.0, 0.5, 0.365, 0.0, -0.5, 0.365, 0.005, -1
0.44242, 0.34797, 0.0, 0.44242, -0.34797, 0.0,
0.005, -1
0.49523, -0.34797, -0.31561, 0.49523, 0.0,
-0.31561, 0.005, -1
0.44242, 0.34797, 0.0, 0.49523, 0.34797,
-0.31561, 0.005, -1
0.44242, -0.34797, 0.0, 0.49523, -0.34797,
-0.31561, 0.005, -1
0.51058, 0.34797, 0.31266, 0.51058, 0.0,
0.31266, 0.005, -1
0.44242, -0.34797, 0.0, 0.51058, -0.34797,
0.31266, 0.005, -1
0.44242, 0.34797, 0.0, 0.51058, 0.34797,
0.31266, 0.005, -1
0.74782, -0.4325, 0.0, 0.74782, 0.4325, 0.0,
0.005, -1
1.13082, -0.4325, 0.0, 1.13082, 0.4325, 0.0,
0.005, -1
1.51482, -0.4325, 0.0, 1.51482, 0.4325, 0.0,
0.005, -1
2.35382, -0.4325, 0.0, 2.35382, 0.4325, 0.0,
0.005, -1
1.89582, -0.4325, 0.0, 1.89582, 0.4325, 0.0,
0.005, -1
2.81382, -0.4325, 0.0, 2.81382, 0.4325, 0.0,
0.005, -1
3.27082, -0.4325, 0.0, 3.27082, 0.4325, 0.0,
0.005, -1
3.77582, -0.4325, 0.0, 3.77582, 0.4325, 0.0,
0.005, -1
4.28882, -0.4325, 0.0, 4.28882, 0.4325, 0.0,
0.005, -1
4.79382, -0.4325, 0.0, 4.79382, 0.4325, 0.0,
0.005, -1
5.34582, -0.4325, 0.0, 5.34582, 0.4325, 0.0,
0.005, -1
5.90582, -0.4325, 0.0, 5.90582, 0.4325, 0.0,
0.005, -1
0.51058, 0.0, 0.31266, 0.51058, -0.34797,
0.31266, 0.005, -1
0.49523, 0.0, -0.31561, 0.49523, 0.34797,
-0.31561, 0.005, -1
0.51058, 0.0, 0.31266, 0.49523, 0.0,
-0.31561, 0.005, -1
***Source***
1, 0
w3c, 0.0, 1.0
***Load***
0, 1
***Segmentation***
800, 80, 2.0, 2
***G/H/M/R/AzEl/X***
0, 0.0, 0, 300.0, 120, 60, 0.0
Brian
--
Brian Howie
>
>> Using the dimensions in the link - as far as I can read them. I get
>>a gain of 12.82dB , a long way short of the 15.2dB claimed. Impedance
>> Using the dimensions in the link - as far as I can read them. I get
>>a gain of 12.82dB , a long way short of the 15.2dB claimed. Impedance
>>about 311ohm , so the 4:1 balun brings to down about 77ohm close to
>>the design 75ohm . F/b is 15.62db
>> Brian
>
>Hi Brian
>>the design 75ohm . F/b is 15.62db
>> Brian
>
>
>Some of the dimensions on that drawing are hard to interpret but using
>my best guess I get 14.8dBi, which is similar to your results.
>
>However, looking at the currents I seems to me as though I have not got
>the slot feed quite right, so I will have another play.
>
>It is also interesting that if you model just the slot feed it gives a
>gain of about 3.8dBi, which is a little low I think.
>
>Then if you add just the 2 reflector elements the gain goes up to
>7.5dBi, however, it would seem that as you add more directors that gain
>advantage disappears pretty much. Replacing just the slot radiator and
>directors with a conventional dipole and reflector gives a gain of
>14.4dBi, so only 0.4dB advantage from the slot feed.
>
>So I think something is not quite right at the moment.
>
>Jeff
>
I pasted your description into 4NEC2 and it seems to agree. The feed
impedance is different
I get 7.88 dBi for the slot + reflectors . I think the advantage for the
n over n slot fed yagi also reduces as n increases. Quads do something
similar.
I'd been hoping that adding a slot feed might have reduced the vertical
lobe on the NFD antennas and given us more gain , but it looks unlikely
, The antennas are 11 ele on 4m and 9 ele on 6m . N over N slot
versions would be impossible to put up.
This is the MMANA antenna description . I didn't have the vertical
support on the slot, but I added it in - not much difference.
*
144.1
***Wires***
24
0.0, -0.5, -0.365, 0.0, 0.5, -0.365, 0.005, -1
0.0, 0.5, 0.365, 0.0, -0.5, 0.365, 0.005, -1
0.44242, 0.34797, 0.0, 0.44242, -0.34797, 0.0,
0.005, -1
0.49523, -0.34797, -0.31561, 0.49523, 0.0,
-0.31561, 0.005, -1
0.44242, 0.34797, 0.0, 0.49523, 0.34797,
-0.31561, 0.005, -1
0.44242, -0.34797, 0.0, 0.49523, -0.34797,
-0.31561, 0.005, -1
0.51058, 0.34797, 0.31266, 0.51058, 0.0,
0.31266, 0.005, -1
0.44242, -0.34797, 0.0, 0.51058, -0.34797,
0.31266, 0.005, -1
0.44242, 0.34797, 0.0, 0.51058, 0.34797,
0.31266, 0.005, -1
0.74782, -0.4325, 0.0, 0.74782, 0.4325, 0.0,
0.005, -1
1.13082, -0.4325, 0.0, 1.13082, 0.4325, 0.0,
0.005, -1
1.51482, -0.4325, 0.0, 1.51482, 0.4325, 0.0,
0.005, -1
2.35382, -0.4325, 0.0, 2.35382, 0.4325, 0.0,
0.005, -1
1.89582, -0.4325, 0.0, 1.89582, 0.4325, 0.0,
0.005, -1
2.81382, -0.4325, 0.0, 2.81382, 0.4325, 0.0,
0.005, -1
3.27082, -0.4325, 0.0, 3.27082, 0.4325, 0.0,
0.005, -1
3.77582, -0.4325, 0.0, 3.77582, 0.4325, 0.0,
0.005, -1
4.28882, -0.4325, 0.0, 4.28882, 0.4325, 0.0,
0.005, -1
4.79382, -0.4325, 0.0, 4.79382, 0.4325, 0.0,
0.005, -1
5.34582, -0.4325, 0.0, 5.34582, 0.4325, 0.0,
0.005, -1
5.90582, -0.4325, 0.0, 5.90582, 0.4325, 0.0,
0.005, -1
0.51058, 0.0, 0.31266, 0.51058, -0.34797,
0.31266, 0.005, -1
0.49523, 0.0, -0.31561, 0.49523, 0.34797,
-0.31561, 0.005, -1
0.51058, 0.0, 0.31266, 0.49523, 0.0,
-0.31561, 0.005, -1
***Source***
1, 0
w3c, 0.0, 1.0
***Load***
0, 1
***Segmentation***
800, 80, 2.0, 2
***G/H/M/R/AzEl/X***
0, 0.0, 0, 300.0, 120, 60, 0.0
Brian
--
Brian Howie
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