A new ham’s guide to working the Oscars (on a budget)
By: Andy Fenstad (VE4RDO)
As a child of the 60’s, Space travel was a big part of my life. Apollo was in full swing, the Apollo 11 moon landing happened when I was 8, so space has always held a fascination for me.
I received my callsign in May 2010. Of course, every amateur operator wants to try all kinds of modes, but all that gear can be really expensive. So, like most new amateurs, I started with 2 meter. A dual-band HT and a ¼ wave, dual-band mag mount antenna and I was on the air.
While I enjoy local ragchews and nets, long distance communications is where its at for me. IRLP and Echolink are lots of fun, but (for me) VOIP is not quite the same as my antenna to theirs for long distance comms.
Back to that space thing. Of course, I had heard of the Oscar satellites, but knew virtually nothing about them. The internet comes to the rescue! I started reading, sites like Amsat (see ‘Resources’ at the end of the article) answered a lot of questions, but, I found later, not all of them.
I discovered that there are basically four satellites that are FM voice (the only mode I have, remember?). They are: AO-51, SO-67, HO-68, and AO-27. There are, of course, lots of other modes, but these were the only ones I could use.
So, I dutifully programmed my radio with the uplink and downlink frequencies for each. VHF uplink and UHF downlink in all of these cases. I also included them in my channel scan.
One day, I was driving down Regent Avenue, and suddenly, my radio was squawking with some guy with a callsign that started with an ‘N’! Holy smokes! That’s a guy on a satellite! Reacting quickly, I answered his call, and he responded! I was so excited, I have no idea to this day what his callsign was.
He also added a cryptic “Foxtrot November Three Four” after his callsign. “What the heck is he talking about”, I thought. I responded that I was in Winnipeg, Manitoba, Canada, and my first satellite QSO was over.
What just happened? Well, of course, the ‘FN34’ was his gridsquare (see resources) and Glen (VE4GWN) was kind enough to explain that to me. It appeared that the satellite (HO-68 in this case) was almost directly overhead, and the signal was strong enough for me to use it.
Over the next while, I heard the satellites on occasion (my work sometimes has me driving around a lot), but wasn’t able to make any contacts. After seeing some of the antennas and equipment some of the ‘big boys’ have, I figured I’d have to start buying stuff to make this happen.
At an Ares meeting, I was chatting with Kent (VE4KEH) and mentioned that I was having trouble and would have to shell out for some equipment. He asked how many frequencies I had programmed for each satellite. My answer was one (duh!). He said that because of Doppler shift, you really need FIVE sets of frequencies for each satellite. He also mentioned that Doppler seems to affect UHF more than VHF and that he started at 10Khz high on the receive frequency, 5Khz low on the transmit. He said that a small digital ‘memo recorder’ was a great idea when you are trying to adjust frequencies, key the radio, and hold that Arrow antenna all at the same time. That way, you could record the QSO and play it back later to get that callsign.
This caused the proverbial light to go on over my head. Everyone knows that satellites are moving very fast. When the satellite is coming towards you, transmitting away, all that forward speed has the effect of raising the frequency of its signal. The same thing happens to your signal on the way up, so you have to transmit at a lower frequency so your signal arrives at the ‘bird’ on the frequency it is listening to.
Conversely, when the bird is going away from you, the reverse happens, its transmitted signal arrives at your antenna at a lower frequency, and you have to transmit at a higher frequency, so your signal arrives on frequency. Of course, when its overhead, you use the ‘actual’ frequencies of the satellite.
The following is the list of frequencies I use for AO-51, which, strangely enough seems to be the satellite that my setup likes the best. 95% of my contacts are on AO-51 – your results may vary. AO-51 is listed as having a downlink frequency (down to Earth) of 435.300MHz and an uplink frequency (Earth to the bird) of 145.920MHz. Here is my five channels for AO-51:
Acquisition 1 (first look, just above the horizon) - Tx 145.915MHz Rx 435.310MHz
Acquisition 2 (higher, but still coming at us) - Tx 145.915MHz Rx 435.305MHz
Overhead - Tx 145.920MHz Rx 435.300MHz
Loss of Signal 1 (high, but going away) - Tx 145.925MHz Rx 435.295 MHz
Loss of Signal 2 (low, just about gone) - Tx 145.925MHz Rx 435.290 MHz
You’ll notice that the VHF doesn’t change as much as the UHF (remember what Kent said?). For other satellites, use similar frequency variations.
Now I have 20 channels for the four satellites, only three for the International Space Station (ISS) since both of its up and downlinks are VHF. The ISS is another story, you want to hear a pileup? Just listen on the ISS frequencies. Better yet, try to get a contact when you are pushing five watts and you are fighting guys with 200! But I’ll get in there some day!
Since I have programmed the 20 channels (back in early September 2010), my results have gotten WAY better. As I write this (December 13th), I have 26 QSO’s, 23 grids, 3 provinces, and 16 states.
[UPDATE: As of March 3, 2011, I have 54 QSO’s, comprising 37 grids, 22 states, 3 provinces and Inuvik, Nunavut!]
As I’m driving around, I will hear operators on a satellite. I pull over in an area that has a good look at the sky in all directions, turn the squelch down to zero, pull the recorder out of the glove compartment and start working. If I hear calls when I am on the first or second frequency, and they are nice and clear, I know it will probably be a good pass. If they are very weak or very staticky, or already on one of the last two frequencies, I may or may not get in.
Of course, it’s a crap shoot anyway – fighting the ‘big boys’ with five watts can be difficult.
As you listen, you will be able to tell when its time to switch to the next frequency. The signal will start to fade and garble, you click over to the next one, and everything is good again. After you listen a while, you will get the hang of it.
By the way, with a quarter wave like I have, don’t expect 59 signals. There WILL be static and signals can be weak. Even though the reports I get usually list my signal as 59, the best I’ve ever reported was a 37!
When you visit the Amsat site, there is a satellite prediction page (click on ‘Passes’). Pick a satellite, input your grid (Winnipeg is EN19), and tell it to predict the next 10 or 20 passes. Look for passes that show a ‘Maximum Elevation’ as high as possible. I have found that if it is less than 30 degrees above the horizon, its not worth trying. The radiation pattern of the ¼ wave is too high for that – again, your results may vary. Find a nice high pass, an open area, and give it a try!
Oh yeah, in my case, nighttime is not my friend. Not only do I not have any CONTACTS at night, I can’t even HEAR the things after dark! Maybe you will have better luck. The times I have found work best are just before dawn all the way to the late afternoon and into early evening (in summer). Dawn and daylight seem to work best.
So, if you’ve been able to follow my ramblings, you now know how to ‘work the birds’ on a budget. Let’s face it, a dual band HT, a $35 ¼ wave mag mount antenna, and a $35 digital voice recorder is not a big outlay of cash in this hobby. Especially when you probably already have the first two!
Catch you on the birds!
73
Andy
*****RESOURCES*****
AMSAT
AMSAT - The Radio Amateur Satellite Corporation
Satellite status:
AMSAT - Satellite Status
Pass Predictions:
AMSAT - AMSAT Online Satellite Pass Predictions
The Maidenhead Grid Square System:
Maidenhead Locator System - Wikipedia, the free encyclopedia
Find your Grid Square:
Find your QTH locator (or your grid square) with GoogleMaps
