[amsat-bb] Advice for a portable ground station

Kevin M n4ufo at yahoo.com
Fri Jan 16 16:38:00 UTC 2015


Tom,
I work satellites with AZ-El yagis from home but I also have an Arrow II antenna... I've played around using it in different configurations and asked a lot of advice. I'm currently putting together a setup to take roving. Let me share what I've learned based on the premise that you said 'for the FM satellites', keeping in mind what's already been said... right now, there is only the one.

Does your dual band HT operate full duplex? if not, you would be better off with a couple of small, cheap handheld size HTs. And if your HT is full duplex, does it suffer from desense problems? Only way to know is to test and again, if there is any desense, better to use two HTs. (Weight alone, in my case, 2 smaller HTs is better!)  I have an Icom W32A and two Baofengs (UV-3R+ and UV5R)... I'm going with the two Baofengs because the version of W32A I have has desense issues. (And you CANNOT tell from the serial number on the W32A as published on the internet... mine has a serial number in the supposedly 'good' range.)
Tripod... while many first time sat ops see it as a near necessity, most (but not all) of the prolific roving sat ops I know just use their Arrow or Elk antennas hand held. Even to me, the antenna seemed heavy on my first pass or two, but after a few times, I guess I built a little muscle up, because it's not a problem any more. When you mount the antenna to a tripod it sort of 'ties you down'. It's not as easy to adjust position or orientation and you become tethered to the mount; you are stuck where you are, can't move to aim around a tree, etc. But if you do decide on a tripod, make sure it has the ability to tilt the mount 90 degrees. You really need to be able to 'twist' the antenna to change the UHF yagi's orientation from horizontal to vertical and back to match the satellite. Without that reception will be much more difficult.
2m amplifier... if you mean a receive preamp, wait until the new FM birds are launched, you will likely not need it. If you mean a transmit amplifier, I can't see the need. I transmit with an entire 2 watts and worked J79TX in Dominca standing on my porch... I think he was using 1 watt. Even with an amplifier on a busy bird, at best you would 'double' with someone, not over ride them. That's why you need full duplex capablity... if you can't hear yourself, then unkey... let the other guy go and wait for another turn. Otherwise, nobody makes a QSO and the doubling continues

70 cm preamp... it would definitely help. But just try to make it small and lightweight and mount to the handle of antenna; as close to the grip as possible to reduce the lever effect. It WILL increase the weight some, so you may just want to try without it first. See how you do and if you feel it is necessary. A lot of guys are working the bird without one.
Coax... as short as possible, as low loss as possible. W5PFG and I have both advised ops to cut off a couple feet from the cable of a home made antenna and it made all the difference on UHF receive. The numbers say it shouldn't matter that much, but real world experience says it does.
Diplexer... if you use two HTs, one is not necessary. Save the weight, the loss, the extra cables and the hassle. The diplexer designed for the ARROW that goes in the handle is what I would use anyway; light and out of the way. I plan to hook up my receive HT through it since the cable is short and i know it hears with it. I will have a second jumper to bypass the diplexer and run to the 2m yagi for TX.
Recording... Something most consider critical that you didn't mention; an audio recording device. Forget relying on a notepad... it just doesn't work. You will invariably miss writing a call down or can't read your own writing later. Some use their phone... I have used a digital recorder strapped to the back of my HT. But the best way and one I bought the cabling to do, is wire up a splitter to run direct audio to a set of headphones and the recorder. This may also require some 'padding down' to keep from over driving the recorder input... I got an 'attenuating cable' for this. And running full duplex, hooking the recorder to the downlink, I will hear the other stations AND I will hear what actually GOT HEARD of what I said... Not just want I spoke into the microphone.
Microphone/headset... another big consideration you didn't mention. Remembering that you only have two hands, will be moving around and may be in a noisy environment, combined with full duplex and the potential for feedback... earphones or a headset is pretty much a must. If you purchase a good headset, try to have it so that the PTT switch can be mounted conveniently... like on the Arrow handle where your thumb will be. Since my Baofeng HTs are not much larger than a hand mic, I am going to start off trying one hand holding the antenna, the other holding the TX HT and crossing over with the thumb and forefinger holding that HT to adjust the RX HT's frequency. (On the new birds which will be U/V, I will be adjusting the TX frequency of the HT in that hand, much easier.) Then the RX HT has a splitter going to the recorder and a set of headphones. If it doesn't work well enough on initial testing, an order for a headset (mic and earphones) will be in my future. =^)

Hope you benefit from the research I've been doing... lots to think about and consider. Tripod versus handheld is a big consideration and one not taken lightly, but as I said, there are lots of pics and videos of many popular roving sat ops waving their handheld yagis around. Also a number of pics of tripod mounted setups, too. All a case of personal preference but the point I am making is to not assume automatically that tripod mounted antennas are better. You will have to try it and see what works best for you.
 Looking forward to working you in a rare grid! =^D
73 es GL!
Kevin N4UFO

 


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