[amsat-bb] Re: Station not coming together - the full post (sorry for repost, reply to this)

Jonny 290 jonny290 at gmail.com
Wed Mar 7 15:06:34 PST 2007

Lying in bed last night, I realized my solution to the 'noisy rotator' issue
that's stopping me from putting up yagis.

Ground mounted rotator!

Pound a 1.25" steel pipe in the ground, bolt the rotator to that at knee
level, run the mast up.

Here's my thinking - 15 feet of PVC with a short yagi on top, mounted at 30
degrees elevation, give or take. At the 10 foot 'eave' level, I create some
sort of crude bearing using PVC that allows the pipe to spin, but not
wobble. Bolt that to the eaves and use it as the anchor point up top. The
pipe could down to just above ground level, where it's connected to the
rotator output.

I'm in a valley so winds never get higher than 40 mph gusts, and the PVC
should have plenty of 'give' to not mess up during a wind gust. I've got
stuff right nowon a 12 foot PVC mast that isn't even cemented together, and
it's tough.

This would allow me a steerable antenna without bothering my roommate. The
rotator noise should be almost inaudible when it's mounted down so low
(there won't be a window in the path to easily conduct noise) and if it's
still an issue, it'd only take an hour to build an MDF box  with a hole in
the top to cover, insulate and protect the rotator.

Think it'll work? :D

On 3/7/07, sco at sco-inc.com <sco at sco-inc.com> wrote:
> if your ultimate objective is P3E then try to hear your downlink on
> FO-29. If you can't then you won't be able to work P3E.
> At 03:06 AM 3/7/2007, you wrote:
> >OK, let's take a bite out of this.
> >
> >RE, the preamp: I agree that it is likely a weak point. I wanted to check
> it
> >out, though, and for $22 I couldn't go wrong. It'll still prove useful at
> >some point down the road.
> >
> >If one of the mast mount preamps are what the situation requires, I"m
> ready
> >to take that step.
> >
> >The eggbeater is actually designed with radials to 'pull' the signal
> towards
> >the horizon. It almost seems as though the radials may be working too
> well -
> >I've got moderate to great copy up to a few degrees, then it falls over
> >dead.  Due to my 'beater's design, it's trivial for me to replace the
> loops
> >and/or the radials without messing with the phasing harness or antenna
> >mount, so I can try an antenna that doesn't have a by-design null at high
> >elevations. I'd almost like to do this just as a lark, as it'd cost me a
> >grand total of  $7 to go buy another 10 foot piece of 1/4" fridge tubing.
> >
> >I can also experiment with putting the 435 eggbeater on a nonconductive
> >mast. Also a cheap experiment, couple of bucks for 15 feet of PVC. That
> >might get it up high enough with no metal above or near it, save for the
> >feedline.
> >
> >Here's my main issue with the TV rotator, and you'll think this is silly
> and
> >trivial, but it's a major sticking point, and why I've been going at this
> >with omni antennas so far. My main mast sits _directly_ outside my
> >roommate's window, due to overhead power line and tree location. It's the
> >only place where I can safely have a structure above 10 feet, that is
> less
> >than 75 'coax feet' from my shack window.
> >
> >I'm concerned that spinning the rotator at night will bother him. If the
> >mast is solidly mounted to the house just a few feet away, how much will
> one
> >of these inexpensive TV rotators conduct into the building? Could I cut
> that
> >down by putting some rubber between the mast and clamp, something of that
> >nature?
> >
> >The next step, and I'm ready to move to this point if I can address the
> >noise issue to my satisfaction, is to build a small cross yagi, 4 to 7
> >elements, and mount it at fixed elevation on a small TV rotator. I
> believe
> >that an antenna in this size range will prove a big advantage over the
> >omnis, should have a wide enough beamwidth such that I will get away with
> >fixed elevation, and should only have to crank the rotator every 60 to 90
> >seconds, except for the extremely high angle passes.
> >
> >If that works on receive, but I'm having uplink problems, I can put a 2
> or 3
> >element CP yagi for 2 meters on the same boom, which should let me hit
> most
> >of the satellites with 10-15 watts of power, max.
> >
> >I'm very eager and willing to design and play with antennas - love
> homebrew
> >in general, I just can't design a circuit to save my life - and know how
> to
> >model and build good quality antennas. I'm fairly certain that I can get
> >crafty enough to get around what restrictions this environment does have.
> >
> >So, here's what I'm looking at, I think.
> >
> >1: Mast mount preamp
> >2: Beam with rotator
> >3: Hamtronics downconverter (435.5 - 437.5 MHz, somebody tell me if I'm
> >getting the wrong frequency range choice - my HF radio stops at exactly
> >30.000.000 so I want to make sure I can hit the 437+ frequencies)
> >
> >The beam will require design and construction time (I don't believe in
> >buying antennas except in rare circumstances); I can throw green paper at
> >the preamp and get it out of the way, since store-bought is the best
> option
> >for that at this time. In addition, I don't want to have to install the
> beam
> >and rotator and preamp all at once; it'd be nice to have the preamp ready
> to
> >go by the time I put up the beam and rotator.
> >
> >I'll be honest, I'm generally an impatient person, and I'm busting my
> chops
> >and treating this station in a rent house as a challenge. I was serious
> >about hitting the Phase 3E sats when they go up, but I do _not_ expect to
> do
> >it at my current QTH.  If all comes together, I move into a house this
> fall,
> >at which I hopefully will have clear space and the ability to put up a
> >"real" antenna support. Once that happens, either a roof mount or small
> >tower, I'll build a long yagi array and get it under computer control.
> But
> >I'm not at that phase yet, and I want to get experienced at this level
> >before I think about trying to work the high orbit satellites.
> >
> >I actually grew up a ham in my early teen years back in the early 90's,
> and
> >remember poring endlessly over AO-13 articles. It seemed like the zenith
> of
> >technical accomplishment in our hobby. I came back to ham radio last year
> >and was disappointed to find that we had no high orbit satellites
> currently,
> >but the LEO satellite 'scene' seemed active and I figured I could get my
> >feet wet with them before I tackle the big ones when they go up.
> >_______________________________________________
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