Re: Hey BMJ....



On Mon, 2 Nov 2009, BMJ wrote:

Me wrote:


Thanks for the info.

To keep it short: OK on below. Your Yagi should be good for more like 8-10 db gain. More like 40-50 watts ERP if you ask me.

You could be right.

Antenna tuners,
tuned manually, can be tricky if you don't know the tricks. Short advice: set both tuning capacitors to halfway from max/min. Then adjust transmitter output for about 4-5 watts (maybe you can't adjust that with your rig), then looking at _only_ reflected power, you rotate the step rotary switch throughout its entire range till you get minimum reflected power, even if it is a weak dip. Then go to the variable capacitors (either one) and adjust one or the other to see if you can get the reflected power down some more. Go for minimum, again. Then go to the other (second) variable capacitor and vary it up or down, again for minimum. Then go back to the first and vary it either clockwise or counterclockwise (remember which way you turn it), then go back to the second and vary that one again. If you can't get the reflected power to go down more, then go back to the first and rotate it _slightly_ in the _opposite_ direction from how you first varied it. Slightly means 3-7 degrees or so.

Once you get the hang of this "cycle", you'll wonder why it was so hard before you figured out this little trick. And, its funny that I've never seen this procedure described anywhere. And, in the beginning I struggled with it, too.

The homebrew Buddipole consists of a pair of telescoping whip antennas and some hand-wound coils, but no capacitors. All one has to do to tune it, in theory, is to adjust the length of the whips and use the appropriate coils.

The "capacitors" are the whips at the end. By making them longer or shorter you increase or decrease the capacitance and thus adjust resonant frequency.


But, you can always go out and buy an automatic tuner and play "spoiled brat" like all the other spoiled brat non-macho, quiche-eating dweeb-geeks.

One reason I consider using a tuner is that I could set up my antenna, tune it properly with my antenna analyzer one day, set it up again to the way I had it before another day and the SWR's gone to pot because a neighbour put something out on the balcony. All of the settings I had from before wouldn't be any good.

At least with a tuner, I might get some consistent settings, considering that in my neighbourhood, there are lots of things which could affect an antenna's performance. Personally, I'd rather tune it by hand without any other added hardware.

It should not affect tuning that much unless you get something very close to the antenna.


Don't worry too much about SWR. Anything up to 2:1 is really not hurting your rig or, significantly, your signal. A 3:1 SWR means you might be losing 25% of your power (depending on feedline length) which is something like 2 db and it would be difficult for anyone to really notice that without instruments. Bars on bar-graph indicators on FM transceivers are probably more like 4-5 db and I rarely hear any difference if guys up or down their power level, unless they are really "in the noise" to begin with.

I understand that part, but what drove me up the wall was when, despite following the designer's tuning instructions and building the antenna as close as possible to what he had, I couldn't get the SWR down below 5 on some bands.

Sounds like a problem.

I talked about it with another local ham who built one himself and he was similarly frustrated. A tuner, though it may be the easy way out, might overcome some of those problems. I got the idea from a newsgroup I subscribe to, so maybe the person who suggested it has some further comments about it.

Or, you didn't build it quite right.

On the other hand, I cobbled together a 2 m dipole using a set of rabbit ear antennas. I got the idea from an article in a ham magazine where the design called for some leftover whips from dead radios. Since I didn't have anything like that handy, I bought the rabbit ears from a nearby store and tried it out a few times without checking it with my antenna analyzer. I worked some local repeaters and checked in with a 2 m SSB net. It seems to work.

Keep it.


I made a contact, once, with a South African station on PSK-31 with about 15 watts output. But, then, you can do this on CW, too, if you are patient enough to learn code.

I'm CW qualified. Passed my exam over 3 years ago.

Fine.

Problem for me is that my CW code speed
just never gets much faster than 8-10 wpm then I start making errors and that's no fun.

I can copy at least 12 WPM and I'd like to push it towards 20.

I wish I could be there. At 12 wpm, I start missing about 10% of characters.

////////////

PSK-31 at least the computer figures it all out, and its
just keyboard to keyboard. I may get back into that, too. But, then there are other digital modes as well, but I don't want to try them all. don't forget, there are more straight CW ops than all the digital modes put together. I might also try old RTTY at some point, too.

I hear lots of it on 20 and 40 m.




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On Sun, 1 Nov 2009, BMJ wrote:

Me wrote:

Well, thanks for the fills. Yeah, they all peter out down the road, don't they?

Radiation takes its toll. When the two satellites collided above Siberia earlier this year, there was concern about how the debris might affect the OSCARs.

Way back some 20 years ago when they had 2 meter to 10 m
SSB, I got set up to make a few contacts (on SSB), had some 80 watts PEP out, into a 5 ele 2 meter beam, and alt-az rotors, and managed to get a few contacts, maybe a couple of QSL cards, then I got bored with it.

My FT-817 is a QRP rig with 5 W maximum output. With my Yagi, the signal PEP is probably double that.


It was a zoo back then, too (maybe still is today),

It still is a lot of the time. For example, during the last easterly pass of AO-27 for the day, I'm sometimes lucky if there's enough of a pause in the traffic for me to put out a call. SO-50, on the other hand, is often very quiet and I'm frequently talking to myself during a pass.

since what you do is
put out a carrier on 2 meters, swish it accross the bandpass while you listen on 10 meters for the beat note. Then, once you get that, you call CQ. Or, listen for other guys and then answer their CQs the same way.

I usually listen to hear when the background noise drops off, after which I put out a call, provided there isn't already traffic on the bird.


I have a home-made parabolic dish (six feet long, three feet wide) and it does work (on two meters) and I can use it for UHF TV, too. Gotta get back to that project, too.

I've got a Buddipole portable dipole that I started on two years ago but put away for a while because tuning it manually proved to be quite frustrating. Getting a consistent SWR on any given band for the respective lengths was quite maddening.

On one newsgroup I subscribe to, someone suggested using a portable automatic tuner to resolve that problem. In some ways, it defeats the purpose of the antenna design, but it's certainly less aggravating.


But, once I make a couple of contacts, then all the rest are about the same.

I rarely make any new contacts on the birds from my side of the building. I have to go outside and point my antenna towards the east but then I encounter the pileups.

Same with PSK-31 which I've done some of. Same-old-same-old.

I haven't tried digital yet. There's one local chap who I've heard on a repeater net once in a while who's had QSOs as far away as Russia on only 5 W in that mode.


Ragchewing, on the other hand, is one of my pet activities, however.

I've had some interesting QSOs over the birds. One station in Alaska is located near a volcano, so we got first-hand reports on its activities. During the summer, we got some commentary about the Los Angeles area forest fires, and I often compare weather conditions with someone in Montana.

Also, building stuff. Might never use it, but sure is fun to make, test, and show that it works.

Not a lot of that's done any more. I haven't got my Advanced certification yet, so I can't build any transmitting hardware.

Then, it ends up on the shelf (tsk, tsk).

///////////////////////////////

On Sun, 1 Nov 2009, BMJ wrote:

Me wrote:

I've been thinking more about trying satellites.

I looked at www.amsat.org and it looks like there are a few FM transponders, but maybe even fewer that are pretty good.

Looks like they are pushing AO-51.

That's the flagship bird. It's been in orbit for about 5 years but it's starting to show its age. The on-board software crashed a few times during the past few months which meant that it was out of service during those times.


What modes have you had experience with (i.e FM, SSB, etc)?

I've generally worked FM. It's nice and simple plus its wider signal bandwidth makes programming for Doppler changes easier as one doesn't need as many memories. Early in the spring, AO-51 operated with SSB up and FM down and I did manage to make one contact that way. I'll have to try again some time.

The SSB satellites I've heard people mentioning are AO-7 (an older one which, apparently, can be erratic at times), FO-29, and VO-52.


I might be able to do 2 meters FM uplink and 437 mHz downlink almost now (I guess I need a decent antenna for 437 which I don't have just now).

I use an Arrow dual-band Yagi:

http://arrowantennas.com/146-437.html

It's one that a lot of hams use and I'm quite satisfied with mine.


The live satellite tracking display is pretty neet; you can see the bird actually move accross your computer screen in real time.


Some more elaborate satellite stations have antennas which track the birds in a similar manner.



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