Re: Station not coming together - the full post (sorry for repost, reply to this)
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@sco-inc.com sco@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
PVC
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. _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Quoting Jonny 290 jonny290@gmail.com:
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
Matt:
Sounds like a good idea. I was going to write to say that I have a similar set-up, with a Orbit 360 TV-type rotor only about 5 feet outside the window of the room I use as a shack. When it rotates, it is quite audible, and if I were trying to do work here I would find it distracting. If you undertake the above contraption, I would recommend putting the bushing on the side of the house first, before pounding the pipe in the ground :-)
A gain antenna really does make for a more forgiving setup. Be careful not to make the beams too long: you'll lose the high elevation and you'll go crazy tweaking your rotor. My 8 element 70cm does nicely with fixed elevation. I also recommend foregoing circular polarization in these antennas. See my discussion at: http://www.amsat.org/amsat/archive/amsat-bb/10day/msg56267.html (I can't seem to find a permanent link for archived messages.)
You were thinking of buying a downconverter for your HF rig. One further option for exploring satellite communications is the FT-817. These can be found second-hand quite cheaply on Ebay and other sources. I used a pair of them for some time on LEOs, and though a bit low on power, they allow you to walk outside and test your antennas in a handheld, short cable arrangement.
And for a satellite you might be able to work right now, check out AO-7 in mode A, every other day right now. (Consult http://www.planetemily.com/ao7/ao7log.php to see what mode is up today.) My 10m vertical fed by 30m of RG-8x can hear its telemetry, CW and some SSB. A loop around my shack might do even better. Last year, my HF antenna was a horizontal long wire, and I never did hear AO-7 because of the fragmented azimuthal pattern on 10m.
Since you seem to be interested in doing things yourself, you really would enjoy the Davidoff book I recommended earlier, not to mention the AMSAT Journal, whose quality is remarkably high and which is a perk of membership in AMSAT-NA.
73, Bruce VE9QRP
Yeah, I think the next paycheck's fun money is going to an AMSAT membership and a stack of 1/4" aluminum rod, heh!
I'm designing the beam on paper, and as per your suggestion, I'm attempting it with a single beam. So far, it looks great - folded dipole element, about 11db forward gain, exactly 50 ohms impedance, great bandwidth and at 30 degrees elevation, the horizon is 1.5db off peak response, and the -10db response on the upper side should be around 75 degrees.
I recall that satellites spend only an infinitesimal amount of time above 75 or 80 degrees elevation, and though it'd be ironic that I'd lose the satellite directly overhead, when it's at lowest path loss, I can deal with that for 30 seconds in one out every 20 passes I work, by my estimation.
If the single one works and I want to improve upon it, it'll be trivial to build another and phase them up.
Question:, for linear polarized antennas, am I going to see any benefit by orienting it any particular direction? I ask because I remember that horizontally polarized signals 'bend' a little bit more over the horizon, though admittedly this effect will be very small at 435 MHz; I also believe most man-made noise is vertically polarized, so I'm thinking that keeping it horizontal would be the best course of action.
Should I go Arrow-style and design a 3 element 2 meter beam at right angles to the 435 beam? If the more important 70cm antenna is horizontal, this would put the 2 meter beam vertical - and even though it'll be at a 30 degree elevation, that would give the uplink antenna a little bit of 'downtime' utility as an FM simplex antenna. That's a very minor issue, but I like to lay it all out as it zips through my head - due to my QTH constraints, antennas that can do 'double duty' are especially valuable to me.
I suppose I could just buy an Arrow....but that's the easy way out (not that those aren't great antennas!)
The Yaesu 817 is a great radio, but I am an irrational brand loyalist for some reason, and I can't help but be obsessed with Icom gear. My big decision is "435 downconverter or Icom 706mkiig" this spring. The downconverter would come about $700 earlier, but the 706 would give me the all-important all-mode 70cm receive as well as 70cm all mode transmit if I want to play with VO-52 or AO-7 in B, etc. My 735 is a hot radio and I believe it'd work very well with the downconverter and an ARR preamp, but the 706 is very tempting.
If the IC-703 had 70cm coverage, I'd have picked one up three months ago. It'd be perfect for this application - I wish they'd realize that and add it. They'd gain a lot of satellite operators with a rig you can snag for $450 or so - and it seems as though you can get by on 5 watts usually!
On the downconverter - mast mounting - good idea, bad idea? I see the upside of "28 mhz cable on RG213 = good", but the downside of "environmental factors/temperature on a crystal oscillator = bad." Thoughts? I'm confident that I can weatherproof, but I'm mainly concerned about the temperature changes.
Well, I think that's all for this evening - back to antenna building :)
73, Matt (or Jonny, whichever :) )
11db forward gain, exactly 50 ohms impedance, great bandwidth and at 30 degrees elevation, the horizon is 1.5db off peak response, and the -10db response on the upper side should be around 75 degrees.
BUT, LEO Satellites spend 30% of all in view time below 10 degrees. And less than 2% of their time above 60 deg. AND the satellite is 10 dB weaker on the horizon than it is above 45 deg. So you do not want to sacrifice anything at the horizon, and you could use a rubber duck above 45 deg.
So point your beam up 15 degrees. Don't waste any gain above 45 deg...
See my page: http://www.ew.usna.edu/~bruninga/rotator1.html
Bob, WB4APR
Very nice to read this material on the bb....brings back some of the excitement of building a first station.....
73 de Tim, K4SHF
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Jonny 290 Sent: Wednesday, March 07, 2007 7:16 PM To: AMSAT-BB@amsat.org Subject: [amsat-bb] Re: Station not coming together - the full post (sorryfor repost, reply to this)
Yeah, I think the next paycheck's fun money is going to an AMSAT membership and a stack of 1/4" aluminum rod, heh!
I'm designing the beam on paper, and as per your suggestion, I'm attempting it with a single beam. So far, it looks great - folded dipole element, about 11db forward gain, exactly 50 ohms impedance, great bandwidth and at 30 degrees elevation, the horizon is 1.5db off peak response, and the -10db response on the upper side should be around 75 degrees.
I recall that satellites spend only an infinitesimal amount of time above 75 or 80 degrees elevation, and though it'd be ironic that I'd lose the satellite directly overhead, when it's at lowest path loss, I can deal with that for 30 seconds in one out every 20 passes I work, by my estimation.
If the single one works and I want to improve upon it, it'll be trivial to build another and phase them up.
Question:, for linear polarized antennas, am I going to see any benefit by orienting it any particular direction? I ask because I remember that horizontally polarized signals 'bend' a little bit more over the horizon, though admittedly this effect will be very small at 435 MHz; I also believe most man-made noise is vertically polarized, so I'm thinking that keeping it horizontal would be the best course of action.
Should I go Arrow-style and design a 3 element 2 meter beam at right angles to the 435 beam? If the more important 70cm antenna is horizontal, this would put the 2 meter beam vertical - and even though it'll be at a 30 degree elevation, that would give the uplink antenna a little bit of 'downtime' utility as an FM simplex antenna. That's a very minor issue, but I like to lay it all out as it zips through my head - due to my QTH constraints, antennas that can do 'double duty' are especially valuable to me.
I suppose I could just buy an Arrow....but that's the easy way out (not that those aren't great antennas!)
The Yaesu 817 is a great radio, but I am an irrational brand loyalist for some reason, and I can't help but be obsessed with Icom gear. My big decision is "435 downconverter or Icom 706mkiig" this spring. The downconverter would come about $700 earlier, but the 706 would give me the all-important all-mode 70cm receive as well as 70cm all mode transmit if I want to play with VO-52 or AO-7 in B, etc. My 735 is a hot radio and I believe it'd work very well with the downconverter and an ARR preamp, but the 706 is very tempting.
If the IC-703 had 70cm coverage, I'd have picked one up three months ago. It'd be perfect for this application - I wish they'd realize that and add it. They'd gain a lot of satellite operators with a rig you can snag for $450 or so - and it seems as though you can get by on 5 watts usually!
On the downconverter - mast mounting - good idea, bad idea? I see the upside of "28 mhz cable on RG213 = good", but the downside of "environmental factors/temperature on a crystal oscillator = bad." Thoughts? I'm confident that I can weatherproof, but I'm mainly concerned about the temperature changes.
Well, I think that's all for this evening - back to antenna building :)
73, Matt (or Jonny, whichever :) ) _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Something else to consider is whether you are near a big city or not. I don't know if you mentioned it before so sorry if this is redundant in the other posts here but I found that noise associated with being near a large city effects my receive big time. I have to wait for high power times to work the LEO's on my HT setup which I don't need if I'm visiting a rural area. In fact when in a rural area, SO-50 power levels sound better than AO-51 on high power at home here. Just another factor to consider.
73 de Pat --- KA9SCF near Chicago Amsat #35741
participants (5)
-
Bruce Robertson -
Jonny 290 -
Patrick Green -
Robert Bruninga -
Tim Tapio