I'm living in a wooded area and am trying to hit our club repeater
reliably. It's cloudy now so I'm and getting a bit of ducting but I
have a lot of trees, mostly poplars, in the direct path. I would have a
line of sight if not for the trees as I'm up enough in altitude. I can
cut the trees, they're mine, but finding the right ones is difficult and
i don't want to waste the whole grove.

I go from keying the repeater with no intelligible signal to not being
able to hit it. Today I actually have an S meter reading due to the
clouds. I am currently using a J-pole and will put up a Yagi soon but
wonder if NVIS would work on 2m? I have only seen references to it
being applied in HF.

'Captain' Kirk DeHaan
N6SXR

'Captain' Kirk DeHaan wrote:
I'm living in a wooded area and am trying to hit our club repeater
reliably. It's cloudy now so I'm and getting a bit of ducting but I
have a lot of trees, mostly poplars, in the direct path. I would have a
line of sight if not for the trees as I'm up enough in altitude. I can
cut the trees, they're mine, but finding the right ones is difficult and
i don't want to waste the whole grove.

Wait for winter and use a beam antenna to locate the tree(s) that need to be
trimmed.

If a 10 element beam won't "blast" through the trees in the summer, it should
get you down to a line of 1 or two trees that need to be cut.

A more radio oriented project would be to put a 6m or 10m input on the
repeater. 10m should groundwave over the trees anyway. It's easy enough to
test.

10m inputs are IMHO neat, at the top of the sunspot cycle, they give your
repeater worldwide input. At that point a 10m output would be good too, but
for now, it's not much of a problem.

Geoff.

--
Geoffrey S. Mendelson N3OWJ/4X1GM
It's amazing how many people have no clue what the word "contiguous" means. :-(

On 22 mayo, 20:04, 'Captain' Kirk DeHaan
wrote:
I'm living in a wooded area and am trying to hit our club repeater
reliably. *It's cloudy now so I'm and getting a bit of ducting but I
have a lot of trees, mostly poplars, in the direct path. *I would have a
line of sight if not for the trees as I'm up enough in altitude. *I can
cut the trees, they're mine, but finding the right ones is difficult and
i don't want to waste the whole grove.

I go from keying the repeater with no intelligible signal to not being
able to hit it. *Today I actually have an S meter reading due to the
clouds. I am currently using a J-pole and will put up a Yagi soon but
wonder if NVIS would work on 2m? *I have only seen references to it
being applied in HF.

'Captain' Kirk DeHaan
N6SXR

Hello,

The repeater antenna will probably have most of its radiation in the
horizontal plane and 145 MHz is far above the critical frequency, so
your rays will leave earth.

Did you monitor the signal for several time (also winter and rain) to
assess the real influence of the trees? Do you have any possibility to
move the J-pole to another place?

As you can open the repeater now and then, some 10 dB additional gain
will certainly help you to get above the FM-knee (assuming that you
can get the beam at same height as the J-pole. Nice thing is, it will
also improve reception.

With kind regards,

Wim
PA3DJS
www.tetech.nl
remove abc first in case of PM

On May 22, 11:04*am, 'Captain' Kirk DeHaan
wrote:
I'm living in a wooded area and am trying to hit our club repeater
reliably. *It's cloudy now so I'm and getting a bit of ducting but I
have a lot of trees, mostly poplars, in the direct path. *I would have a
line of sight if not for the trees as I'm up enough in altitude. *I can
cut the trees, they're mine, but finding the right ones is difficult and
i don't want to waste the whole grove.

I go from keying the repeater with no intelligible signal to not being
able to hit it. *Today I actually have an S meter reading due to the
clouds. I am currently using a J-pole and will put up a Yagi soon but
wonder if NVIS would work on 2m? *I have only seen references to it
being applied in HF.

'Captain' Kirk DeHaan
N6SXR

I can't see that NVIS has any VHF backers.

Can you exploit Google Maps, satellite view, to establish a precise
line bearing from your antenna to the repeater site? If you need even
more help than you get from your new yagi, then such a line bearing
will help identify your "trouble trees."

I had to do it for a new FD site a few years ago. We're in San Diego
and I wanted to work 2m into Los Angeles. First, I used a protractor
to determine LA was X-degrees True (whatever it was) from us; next, on
a close-up print of the FD site, I plotted that same line bearing from
the antenna site to obvious local landmarks which we then used on the
the ground for pointing the 2m beam.

This is not the only approach, but it got me what I needed.

"Sal"
(KD6VKW)

On 5/22/2011 1:04 PM, 'Captain' Kirk DeHaan wrote:
I'm living in a wooded area and am trying to hit our club repeater
reliably. It's cloudy now so I'm and getting a bit of ducting but I have
a lot of trees, mostly poplars, in the direct path. I would have a line
of sight if not for the trees as I'm up enough in altitude. I can cut
the trees, they're mine, but finding the right ones is difficult and i
don't want to waste the whole grove.

I go from keying the repeater with no intelligible signal to not being
able to hit it. Today I actually have an S meter reading due to the
clouds. I am currently using a J-pole and will put up a Yagi soon but
wonder if NVIS would work on 2m? I have only seen references to it being
applied in HF.

'Captain' Kirk DeHaan
N6SXR

Your yagi may fix your problem completely. Other things to consider:

* Try moving your existing antenna. Even a small movement may cure the
problem as you may have cancelling reflections at times. There is almost
always a "sweet spot" somewhere in the vicinity.

* Try tilting your antenna to 45 degrees and see if that helps. It might
improve reception due to the random polarization of the incoming signal
caused by the trees.

Note: do this on a day when the signal is either weak or non-existent.
You can always apologize for kerchunking. Or, use your S-meter if you
have one.

Cheers & Good Luck,
John
KD5YI

On 5/22/2011 1:04 PM, 'Captain' Kirk DeHaan wrote:
I'm living in a wooded area and am trying to hit our club repeater
reliably. It's cloudy now so I'm and getting a bit of ducting but I have
a lot of trees, mostly poplars, in the direct path. I would have a line
of sight if not for the trees as I'm up enough in altitude. I can cut
the trees, they're mine, but finding the right ones is difficult and i
don't want to waste the whole grove.

I go from keying the repeater with no intelligible signal to not being
able to hit it. Today I actually have an S meter reading due to the
clouds. I am currently using a J-pole and will put up a Yagi soon but
wonder if NVIS would work on 2m? I have only seen references to it being
applied in HF.

'Captain' Kirk DeHaan
N6SXR


Addendum: If you can add even a foot or two your antenna height, it may
make a world of difference.

Cheers,
John
KD5YI

On Sun, 22 May 2011 18:29:03 +0000 (UTC), Geoffrey S. Mendelson wrote:

10m inputs are IMHO neat, at the top of the sunspot cycle,
they give your repeater worldwide input.

s/input/QRM/

On Sun, 22 May 2011 11:04:10 -0700, 'Captain' Kirk DeHaan
wrote:

I'm living in a wooded area and am trying to hit our club repeater
reliably.

I live in a dense mostly redwood forest. Signals vary from full
quieting to not copyable. We also have two co-channel repeaters
sharing the frequency, that also vary radically in strength. I can
often point my 5 element 2m beam in a totally insane direction, and
improve the signal.

I go from keying the repeater with no intelligible signal to not being
able to hit it. Today I actually have an S meter reading due to the
clouds. I am currently using a J-pole and will put up a Yagi soon but
wonder if NVIS would work on 2m? I have only seen references to it
being applied in HF.

I just love technical posting with no numbers. It would be helpful if
you would offer a clue as to the distance you're trying to cover, what
manner of impervious to RF dirt is along the line of sight, antenna at
the repeater, power levels, etc. For extra credit, if you disclose
these plus your exact location, the repeater's exact location, and I
will contrive a Radio-Mobile path profile from you to the repeater.
That should give you a clue as to what challenges you are facing.
http://www.cplus.org/rmw/english1.html
It will look something like this:
http://802.11junk.com/jeffl/coverage/RST/RST-KCRA.jpg

As for a seat-of-the-pants guess as to a solution, I don't like J-pole
antennas. Actually, the antenna is fine, but the way most people
build, tune, and position them, is what I find disgusting. The lack
of any commercially manufactured J-pole antennas (other than the
American Legion J-poles) should offer a clue. Plenty of plans:
http://www.google.com/search?q=j-pole+antenna&hl=en&prmd=ivns&tbm=isch
but nothing from a commercial antenna manufactory.

In my never humble opinion, if you can barely talk to the repeater
with a J-pole, then a yagi will offer a substantial improvement. The
problem is how much gain is going to be needed to make it reliable. My
guess(tm) is that the J-pole has a gain of about 2.5dBi (opinions vary
on the gain), and that you'll need about 5dB more gain to get a decent
link. That means you'll need a yagi with about 7.5dBi of gain. That
can be done with a 5 element 2m yagi. Obviously, more gain is better
as is more altitude.

Good luck.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sun, 22 May 2011 17:55:16 -0500, John KD5YI
wrote:

* Try moving your existing antenna. Even a small movement may cure the
problem as you may have cancelling reflections at times. There is almost
always a "sweet spot" somewhere in the vicinity.

I beg to differ. I have about 30 years experience in dealing with
propogation through a dense redwood forest (Ben Lomond CA). The trees
in my area are about 120ft high. While moving the antenna around may
temporarily improve the signal quality by reducing frequency selective
fading, multipath, reflections, and just plain bad luck, they do not
tend to remain improved. Trees grow and move around. What works well
now, will probably not work well tomorrow.

I gave up on fixed antenna mounts for my rooftop verticals. (Well, I
have one mounted on a tripod, but that was before I realized what was
happening). Most of my verticals are mounted on 2x12 planks, held
down to the roof with sand bags, concrete blocks, and buckets full of
water. Every few months, I move the antennas around to see if I can
improve the signals to specific repeaters.

* Try tilting your antenna to 45 degrees and see if that helps. It might
improve reception due to the random polarization of the incoming signal
caused by the trees.

I beg to differ again. Tree trunks are mostly water and do an
impressive job of simulating a slot type polarization filter at 2m and
440Mhz frequencies. Leaves and branches will pass RF fairly well, but
not tree trunks. I've played with both polarizations, circular
polarization:
http://802.11junk.com/jeffl/circular-polarization/
and some diversity reception. Empirically, signals are about 6dB
stronger going through the trees vertically polarized, than
horizontal. The effect continues up to at least 2.4GHz. Above that,
at 5.7GHz, the signals seem to be going through the holes between the
leaves.

I must admit that I haven't actually tried 45 degrees on 2m or 440Mhz,
but I don't think it will help much. Still, it's an easy thing to
try.

Note: do this on a day when the signal is either weak or non-existent.
You can always apologize for kerchunking. Or, use your S-meter if you
have one.

Do it on a windy day, when the trees are moving around, so you can see
how much it will change.

Cheers & Good Luck,
John
KD5YI

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 5/22/2011 8:26 PM, Jeff Liebermann wrote:
On Sun, 22 May 2011 17:55:16 -0500, John
wrote:

* Try moving your existing antenna. Even a small movement may cure the
problem as you may have cancelling reflections at times. There is almost
always a "sweet spot" somewhere in the vicinity.

I beg to differ. I have about 30 years experience in dealing with
propogation through a dense redwood forest (Ben Lomond CA). The trees
in my area are about 120ft high. While moving the antenna around may
temporarily improve the signal quality by reducing frequency selective
fading, multipath, reflections, and just plain bad luck, they do not
tend to remain improved. Trees grow and move around. What works well
now, will probably not work well tomorrow.

You may be right, Jeff. But he may not have 120ft redwoods around and,
after all, this is a temporary fix until his yagi comes in.

I gave up on fixed antenna mounts for my rooftop verticals. (Well, I
have one mounted on a tripod, but that was before I realized what was
happening). Most of my verticals are mounted on 2x12 planks, held
down to the roof with sand bags, concrete blocks, and buckets full of
water. Every few months, I move the antennas around to see if I can
improve the signals to specific repeaters.

Good for you! Pat yourself on the back.

* Try tilting your antenna to 45 degrees and see if that helps. It might
improve reception due to the random polarization of the incoming signal
caused by the trees.

I beg to differ again. Tree trunks are mostly water and do an
impressive job of simulating a slot type polarization filter at 2m and
440Mhz frequencies. Leaves and branches will pass RF fairly well, but
not tree trunks. I've played with both polarizations, circular
polarization:
http://802.11junk.com/jeffl/circular-polarization/
and some diversity reception. Empirically, signals are about 6dB
stronger going through the trees vertically polarized, than
horizontal. The effect continues up to at least 2.4GHz. Above that,
at 5.7GHz, the signals seem to be going through the holes between the
leaves.

I must admit that I haven't actually tried 45 degrees on 2m or 440Mhz,
but I don't think it will help much. Still, it's an easy thing to
try.

You spent more words debunking the suggestion than admitting that you
don't really know whether it could help or not. Good move. And, by the
way, I have experience to the contrary at both 144 and 444 MHz. It all
depends on the location of the source and the receiver. At 2 meters,
some rotation of the antenna can sometimes be helpful. Note that we are
not concerned with GHz.

John