Month: February 2014
Part 1 of the freeze had me stuck in traffic for 12 hours, but Atlanta was better prepared for part 2. I noticed something odd with the flag on the front porch on Wednesday, so I called the missus out to take a photo. Our trusty stars and stripes no longer required a stiff breeze to keep it up at an angle!
So far, I haven’t had any luck making contact with the astronauts up in the ISS. I’m certain a better transceiver or a directional antenna would do the trick, but I’ve had none yet with simple quarter wave verticals yet. I’ve read some reports of other hams having success with that configuration, but none yet at this station.
Essentially, there’s 4 problems to tackle when making contact with an orbiting satellite:
1. You need to achieve line of sight with a moving object that is often eclipsed by the Earth. This will likely require steering a directional antenna system, and forces short contact windows. This typically requires satellite orbit prediction software and advance planning for good timing. I’ve attempted contact unsuccessfully a few times with the aid of those applications, but no dice.
2. While in process of contact, frequency shifts must be employed to counteract Doppler shifting of the orbital body’s signal through the procession of the contact. It’s only for about 10 KHz overall, and can easily be overcome by programming in the proper contact frequencies into the transceiver memory.
3. Distances at the leading and trailing edges of the time window have the craft at extremely long distances in comparison to overhead distances. Higher power transmitters, more sensitive receivers, or higher gain antennas will need to be employed for extended orbital contacts. I believe this is where the majority of my difficulties lie.
4. Astronauts are humans. They get busy, tired, need rest, and aren’t always available for radio contacts. I know they’ve got a lot of work to do up there, and it may simply be possible that my transmissions would have made it and they were not available to return contact. I don’t want to flatter myself here since I’m pretty sure my transceiver and antenna system were too weak to make it the distance.
I’m only interested in attempting voice operation in ITU region 2 since I live in North America, and I’m not equipped to operate packet radio presently. I programmed the following three FM voice channels into my list for my attempts:
- ISS 1: 145.805 MHz offset -1.32 MHz
- ISS 2: 145.800 MHz offset -1.31 MHz
- ISS 3: 145.795 MHz offset -1.30 MHz
There appears to be conflicting information available about which frequencies to use for contacts and how to compensate for the Doppler effect, and I suspect a fine grained VFO knob is the best answer for that. This is what I’ve attempted with no luck, so perhaps someone out there has some advice. I think I’ve got the research down properly, but the results haven’t been forthcoming.
Let’s wrap this up with some sources I’ve used for my research notes:
73 DE KK4TSJ QRT
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Made this 10 meter inverted vee dipole a couple of months ago. Each element is between 7.5′ and 7.75′ long. I cut it to length for resonance on 28.400 MHz for maximum quality operation on the USB (upper sideband) region of the 10 meter band available for technician operators. I used an Astatic PDC2 combination SWR and power meter I picked up off of Amazon for cheap. It’s designed for the unlicensed CB (Citizens Band) on 11 meter, but positive reviews from other hams indicating successful use on bands between 160 meters and 10 meters sealed the deal for me.
Unfortunately, all of my efforts to hang this antenna in a tree outside have proved fruitless. First, the weather got in the way, then a lack of the needed length of feedline did it in. I’m going to hold on to this since it has a good SWR for 10m, but I think I’m going to go with a vertical for operating that band. It seems that most of the hams out there operating on 10m are using shortened CB antennas, anyway!
73 DE KK4TSJ