What kind of VHF yagi design would be okay?
 

I'm wanting to build a receive VHF yagi covering the marine band, that is
from 156.025 - 162.05 Mhz (6 Mhz frequency range).

I want a design that maximises gain.

I would have thought that what I need is a wide-band yagi, but that's all,
not a very-wide band yagi.

Should I be using OWA design? Or what?

BTW, given the frequencies above, what is the yagi bandwith I'd require? I
mean, should I be building a yagi described as having a 6Mhz bandwith?

TIA.

"Richard" wrote in message
...
I'm wanting to build a receive VHF yagi covering the marine band, that is
from 156.025 - 162.05 Mhz (6 Mhz frequency range).

I want a design that maximises gain.

I would have thought that what I need is a wide-band yagi, but that's all,
not a very-wide band yagi.

Should I be using OWA design? Or what?

BTW, given the frequencies above, what is the yagi bandwith I'd require?
I
mean, should I be building a yagi described as having a 6Mhz bandwith?

TIA.


Futher: Some time ago I did download 4nec2, and obtained some yagi models. I
would have thought that all I have to do is scale one of these models and
then make corrections for the physical construction.

I managed to catogorise the models thus:

DJ6BV
OWA
SM5BSZ
VK3AAU
W6SA
Wideband Yagi (eg such 220-4eleYagi.nec) Not sue what this design is.
Wideband yagi W4NRL
Yagi (eg 220-3eleYagi.nec) Not sure what this design is.

One of these designs got to be wideband and maximised for gain I suppose.

On Fri, 18 Feb 2005 16:12:19 -0000, "Richard"
wrote:

Futher: Some time ago I did download 4nec2, and obtained some yagi models. I
would have thought that all I have to do is scale one of these models and
then make corrections for the physical construction.

Hi Richard,

If you do this literally so (even to element thickness). Some slop is
tolerable in going from one VHF frequency to another, but from HF to
VHF you need to scale closely.

One of these designs got to be wideband and maximised for gain I suppose.

4nec2 should resolve this - it is its purpose after all.

73's
Richard Clark, KB7QHC

On Fri, 18 Feb 2005 15:45:03 -0000, "Richard"
wrote:

I'm wanting to build a receive VHF yagi covering the marine band, that is
from 156.025 - 162.05 Mhz (6 Mhz frequency range).

I want a design that maximises gain.

I would have thought that what I need is a wide-band yagi, but that's all,
not a very-wide band yagi.

Should I be using OWA design? Or what?

BTW, given the frequencies above, what is the yagi bandwith I'd require? I
mean, should I be building a yagi described as having a 6Mhz bandwith?

TIA.


On the receive side, I don't think you need to worry too much. If you
create a yagi for the center frequency, you may find very little
difference on the ends of the spectrum you want to monitor.

The wider spaced the elements, the narrower the bandwidth. I don't
know how much, if any, you will notice a difference at the band edges
with that beam.

Good luck

--
73 for now
Buck
N4PGW

"Richard Clark" wrote in message
...
On Fri, 18 Feb 2005 16:12:19 -0000, "Richard"
wrote:

Futher: Some time ago I did download 4nec2, and obtained some yagi
models. I
would have thought that all I have to do is scale one of these models and
then make corrections for the physical construction.

Hi Richard,

If you do this literally so (even to element thickness). Some slop is
tolerable in going from one VHF frequency to another, but from HF to
VHF you need to scale closely.

One of these designs got to be wideband and maximised for gain I suppose.

4nec2 should resolve this - it is its purpose after all.

All the models I have are VHF ones.

Actually the bandwidth of the marine band, in terms of percentage is
6/159.025 = 3.78%. So, any beam ought to have a useble range of 3.78% at the
operating frequency. (I guess though that for any particular design it's
bandwith could be a producy of your personal SWR tolerance). I'm not even
sure if a yagi I need is just a regular one or a wideband type.

Anyway, I guess in truth, of those designs I mentioned, quite a few would be
satifactory. ie:

DJ6BV
OWA
SM5BSZ
VK3AAU
W6SA
Wideband Yagi (eg such 220-4eleYagi.nec) Not sue what this design is.
Wideband yagi W4NRL
Yagi (eg 220-3eleYagi.nec) Not sure what this design is.


I think perhaps I could probably go for any, (not sure about that) but folks
seem to rave about DL6BV designs and I think they may have a the requied
bandwith, but I'm guessing here, not being much of an antenna buff.

Richard

I dont have any *one* Yagi design to recommend for your 160 MHz
application. But, I sure do like playing with Yagis. I have a few
questions about your design plan for this antenna.
The gain from a 3 or 4 element Yagi isnt more than you could get from a
omniazimuth colinear array, and I suppose you will prefer vertical
polarizathion.

Jerry





"Richard" wrote in message
...

"Richard" wrote in message
...
I'm wanting to build a receive VHF yagi covering the marine band, that is
from 156.025 - 162.05 Mhz (6 Mhz frequency range).

I want a design that maximises gain.

I would have thought that what I need is a wide-band yagi, but that's
all,
not a very-wide band yagi.

Should I be using OWA design? Or what?

BTW, given the frequencies above, what is the yagi bandwith I'd require?
I
mean, should I be building a yagi described as having a 6Mhz bandwith?

TIA.


Futher: Some time ago I did download 4nec2, and obtained some yagi models.
I
would have thought that all I have to do is scale one of these models and
then make corrections for the physical construction.

I managed to catogorise the models thus:

DJ6BV
OWA
SM5BSZ
VK3AAU
W6SA
Wideband Yagi (eg such 220-4eleYagi.nec) Not sue what this design is.
Wideband yagi W4NRL
Yagi (eg 220-3eleYagi.nec) Not sure what this design is.

One of these designs got to be wideband and maximised for gain I suppose.

"Richard" wrote

I'm wanting to build a receive VHF yagi covering the marine band, that is
from 156.025 - 162.05 Mhz (6 Mhz frequency range).

I want a design that maximises gain.

I would have thought that what I need is a wide-band yagi, but that's all,
not a very-wide band yagi.

Should I be using OWA design? Or what?

BTW, given the frequencies above, what is the yagi bandwith I'd require?
I
mean, should I be building a yagi described as having a 6Mhz bandwith?

TIA.

Richard, if you live in an area plagued by pager-interference to the
marine-band, you may notice real improvement by a narrow-band yagi. I used
to use a wide-band yagi for marine but abandoned it due to its
impracticality in trying to cover 300 degrees of traffic from my station
location. Even so, with its large front to back separation and fairly narrow
directional gain, it did help reduce pager-interference.

73,
Jack Painter
Virginia Beach, Virginia

"Jerry Martes" wrote in message
news:FbsRd.2283$QQ3.1420@trnddc02...


Richard

I dont have any *one* Yagi design to recommend for your 160 MHz
application. But, I sure do like playing with Yagis. I have a few
questions about your design plan for this antenna.
The gain from a 3 or 4 element Yagi isnt more than you could get from a
omniazimuth colinear array, and I suppose you will prefer vertical
polarizathion.

Jerry


Actually maybe I'm barking up the wrong tree. Maybe a co-linear is the way
to go. I live about 70 miles from the sea, but maybe a good co-linear is as
good as a 4 element yagi. I can receive a marine station from my location,
and there is some marine traffic originating from canal boats about 30 miles
away.

"Richard" wrote in message
...

"Jerry Martes" wrote in message
news:FbsRd.2283$QQ3.1420@trnddc02...


Richard

I dont have any *one* Yagi design to recommend for your 160 MHz
application. But, I sure do like playing with Yagis. I have a few
questions about your design plan for this antenna.
The gain from a 3 or 4 element Yagi isnt more than you could get from a
omniazimuth colinear array, and I suppose you will prefer vertical
polarizathion.

Jerry


Actually maybe I'm barking up the wrong tree. Maybe a co-linear is the
way
to go. I live about 70 miles from the sea, but maybe a good co-linear is
as
good as a 4 element yagi. I can receive a marine station from my
location,
and there is some marine traffic originating from canal boats about 30
miles
away.

Richard

Since you have complete control of the performance specifications for
this is an antenna you can build almost any Yagi and try it. A 6 db
colinear array could be difficult by comparison
70 miles is quite a long didtance for that kind of communication. I hope
you are located well above sea level.

Jerry