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eHam Forums => Satellites => Topic started by: K9SJB on March 07, 2013, 08:12:41 AM



Title: A question of trees
Post by: K9SJB on March 07, 2013, 08:12:41 AM
Hello all, I've a postage stamp size city lot that is pretty much filled with oak trees.  I would say that I have about 60% of the sky.  To the north trees would block until at an elevation of about 45 degrees, to the south, east and west it's hit and miss but usable.  Cant put a tower up so I'll be cobbling something together to get my yagi up to about 20 feet.  Dang city full of trees.  I know the trees will cause some reception problems with satellite communication.  I'm wondering if there are others that have a bunch of trees on their lot and what sort of reception they are getting?  All comments welcome and no the trees have to stay according to the XYL.

Thanks
Steve K9SJB


Title: RE: A question of trees
Post by: W5PFG on March 07, 2013, 09:06:53 AM
Hi Steve,

My property is surrounded by 80' tall pine trees.   My place is open and clear, but anywhere towards the horizon I have trees to contend with.  I do not have a tower at this time, though I am in the process to put up one soon.  Even then, I won't be clearing the pines.

The mode J downlinks (UHF) are a little trickier than mode B (VHF) downlinks.  This means you need a good antenna, good coax (9913, LMR-400), and a possibly receive preamplifier.  That being said, I often work the mode J birds (FO-29, SO-50) with just an Arrow going directly into my radio with a feed of LMR-240 Ultraflex.   

Your mileage may vary.  I would not rule out satellite operation just because you are on a lot surrounded by trees.  One of my friends has a gigantic magnolia tree practically on top of his satellite array and he works all the birds.

Again, I cannot stress the importance of a good feed line and antenna.

Since you mentioned you cannot put up a tower, I don't see a problem with a piece of chain link fence top rail attached to your soffit with a bracket.  A modest array (maybe a 10 element UHF and a 5-6 element VHF) should suffice.  They don't necessarily need to be circularly polarized, either.  With LEO satellites it's not as big of a deal.


Title: RE: A question of trees
Post by: K9SJB on March 07, 2013, 11:34:40 AM
Thanks for the advice.  I'm leaning toward a couple of antennas from Pete @ Gulf Alpha.  Most everything that I researched point to his as being very good for my small budget.  Yes, I know, he might take awhile to get them to me but I've got time.  Ground is frozen, 12 inches of snow and 30 degrees.  Will be awhile before I can cobble together a support system for them.

Thanks again

73's
Steve K9SJB


Title: RE: A question of trees
Post by: W5PFG on March 07, 2013, 12:23:58 PM
I purchased Gulf Alphas.  See http://www.w5pfg.us/2013/01/gulf-alpha-circular-polarized-vhf-5x5.html
Delivery time for my order tested my patience but in the end "good things come to those who wait."

Don't rule out using linear yagi's though.  It will save you a boat load of money.  Especially if you want to go with fixed elevation instead of full azimuth-elevation rotors. 


Title: RE: A question of trees
Post by: K9SJB on March 07, 2013, 12:46:51 PM
I'm actually on the fence with circular polarized or regular linear yagis.  I don't have a whole lot of space so the antenna need to be on the short side, 72" or less.  Gain will be a factor for me with the trees, want the best performance that I can get for the money.  I plan on have az only, no el, at least for the moment.  Can't afford an az/el rotor and would have to really rig something up to make one work with a makes shift tower.  I'm going to position at 45 degrees.  I assume you have or are using circular and linear and your performance is not impacted?  What about doppler and linear, does that not come into play?  As you can tell, I'm new to satellites.  Thanks.


Title: RE: A question of trees
Post by: KA1VF on March 17, 2013, 12:51:28 PM
My QTH is on a small city lot in an old neighborhood, so we have lots of trees (old and new).
A few years ago I tried working the FM birds with my mini dual HT when they were overhead.
I could full quiet SO-50 and AO-27 with 140 milliwatts and the factory rubberduck antenna.
My rig was the "Standard" model# C508A, and my secret to success was to stand on the round
metal manhole cover (city sewerage) that's in the middle of the road in front of my house.

        73,
            Bob
   


Title: RE: A question of trees
Post by: KO4MA on March 17, 2013, 01:55:32 PM
I'm going to position at 45 degrees. 

I wouldn't point them up so high, more like 15 degrees. You need the gain at the horizon more than overhead when the satellite is closest.


Title: RE: A question of trees
Post by: KQ6EA on March 17, 2013, 07:39:32 PM
I've been using Liner antennas for the entire time I've been on satellites. I have an M2 2M7, and a 420-450-11, and have no problems making contacts down to a couple of degrees at our Field Day site which has a 360* clear horizon.

Doppler is Doppler, and antenna polarization has no effect.

Jim


Title: RE: A question of trees
Post by: W1VT on March 18, 2013, 11:37:59 AM
Trees negate the usefulness of UHF/microwave preamps.  Ideally, your UHF beam would be looking at cold sky (10 Kelvin), not a 300 Kelvin tree!

On 436 you could run more power to get your transmit signal through a tree--on 10GHz you need a discussion with your wife and a chain saw.

Zack W1VT


Title: RE: A question of trees
Post by: K9SJB on April 15, 2013, 11:43:15 AM
Thanks all for comment.  BTW, my trees run cold especially this year and I suspect the neighbors would call the police if I were standing in the middle of the road.  Then again they all seem to know that I'm a bit off....... I've decided on a linear yagi for the moment and for the most part have all my hardware together.  Going to use my TS-711 for the 2M part and my FT-897 for the 70cm part.  Also a mobile that I can throw into the mix if need be.  I've been doing a lot of research on coax.  Times-400 seems to be the way to go.  Would all y'all concur?  Is there a better, comparable coax that's under $1.50 a foot?  I can always build a couple of preamps if needed I suppose.  Always looking for someone elses 2 cents worth.

Thanks and 73's
Steve K9SJB


Title: RE: A question of trees
Post by: KQ6EA on April 15, 2013, 12:12:32 PM
Davis RF sells "Bury Flex" that's close to the attenuation ratings of LMR-400, and much easier to work with.

I just bought some RG-8 size coax from DX Engineering, and it's also very good.

The ultimate is Andrew Heliax, but that's way over $1.50/ft!


Title: RE: A question of trees
Post by: K9SJB on April 16, 2013, 09:01:37 AM
Thanks for the suggestion of Bury Flex, I had wondered about that.  If it's easy to work with then I'm all over it.  That I think is the final piece to the puzzle.


Title: RE: A question of trees
Post by: KQ6EA on April 16, 2013, 09:18:44 AM
I've been using it for years, and it holds up extremely well. I had a 50' run of it across the roof of the apartment building I used to live in, and when I moved into my house, I checked it after I took it down.

The dirt just wiped right off the polyethylene jacket, and the loss was the same as when I first installed it.

And the poly jacket makes it a bit slipperier when installating, so it's easier to pull.

http://www.davisrf.com/buryflex.php