On a sunny day (Sun, 07 Sep 2014 12:56:57 -0700) it happened Jeff Liebermann wrote in :
I think the main worry for me for high SWR is that the power gets reflected back to the transmitter's end stage, this can be destructive. My 27 MHz SWR meter has a visual and audible alarm for that situation, sometimes due to windload and corrosion you get bad contacts, well I had this several times. The alarm helps.
On a sunny day (Sun, 07 Sep 2014 12:05:00 -0700) it happened John Larkin wrote in :
Yes sure that works, now you need a housing for it too? The 1/12 wavelength trick is just inline with the cable, put some shrink tubing over it and you can hardly see it. I like simple :-)
Nice paper! Thanks.
George H.
That's okay, I understand your lack of ability in that area.
The Wikipedia article takes info from many sources. Can I interest you in a book written by Walter Maxwell entitled "Reflections III"? You would do yourself a big favor by reading and understanding it, rather than passing on hearsay from your past.
It is not what you forgot, it is what you are ignorant about.
In fact, Maxwell was with RCA and designed the antennas and feed systems for the early satellites. Funny you should mention that.
Again, do yourself a favor and read his book. In the meantime amuse yourself with the following...
The following is an ideal set-up for educational purposes...
You have a voltage source with 0 ohms impedance on the input of a half-wavelength piece of lossless transmission line of 50 ohms impedance. The load is 75+j0.
Yeah, I know. Not the real world. Neither is your estimate. Work that out and get back to us.
Ok, Jan, since you insist on matching...
Assuming you are using 50 ohm line everywhere, make a T in your transmission line 0.37 wavelengths from the 75 ohm antenna. Connect the
75 ohm antenna to one port of the T. On another port of the T, add an open piece of line 0.0357 wavelengths to shunt the line (an open stub). Use the last port to run the line your load.You can check this out using a Smith chart.
If you want this calculated for a different Zo, let me know. I'm happy to oblige.
There are several grades of bad but they are that bad. They're really horrible in unprotected areas (were they are commonly used). The cable companies and now my satellite company replace at least a few of them every time they visit. The only thing F connectors have going for them is that they're cheap.
You are charmed. As I've said, every time the cable company visits, they have to replace at least a few of them.
When they're new. A year from now...
I don't have an NEC deck for that antenna. However, it's a clone of the Channel Master 4221. Here's a quick plot of impedance, VSWR, and gain versus frequency from 200 to 1000 MHz. More detail when I have time. Notice that it's a 300 ohm antenna, and that the VSWR drops to about
1.2:1 at around 700 MHz and is fairly reasonable (for a receive only antenna) up to about 1GHz. Below 700 MHz, it's not so good, but to fix that would require larger "ears" on the bow tie elements.The challenge for today is "migrating" a customer XP laptop to their new Windoze 8.1 laptop. This should be easy, although experience suggests otherwise. I've allocated 1 day, which means it will probably take a week.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On a sunny day (Mon, 08 Sep 2014 11:23:07 -0500) it happened John S wrote in :
Sounds interesting. What also want to try is follow Mr Lieberman's idea, and next time I am in the shop buy some low -loss 75 Ohm, and use that The RG58 coax has a lot of loss per meter at 435 MHz, (33 dB / 100 m) but I had it. For the satellite LNB output I have some special 75 Ohm cable, but not enough for this. But ecoflex 10 (8.9 dB / 100 m) or aircom plus (8.4 db / 100 m) 50 Ohm would be cool too, with your setup. My cable comes from here, see the tables at the bottom of the page.
I think foam dielectricum is OK for indoors, outdoors it is hygroscopic. Aircom plus seems a very interesting cable with extreme low loss, and a different internal structure:
On a sunny day (Mon, 08 Sep 2014 10:07:04 -0700) it happened Jeff Liebermann wrote in :
I would not want MS win on my PC, I have some online interactive stuff that did not like Wine in XP mode, but somehow runs partly on wine in Vista mode, I am amazed. Even audio is working. It only crashed about 3 times so far, probably better than the original Vista ;-)
(wine is Linx MS windows emulator, you can conigure it to 'be' anything from win 98 to whatever is there now ('7?').
Why not allocate one hour, then it should be finished in a day?
--sp
Vista gets a lot of bad press but mainly from those who don't know anything about it first hand. I used a Vista laptop for over 4 years running all manner of engineering tools and other programs. To run the USB programmer for FPGAs I had to turn off UAC and had very little trouble with it after that... other than it only having 3 GB of RAM which was not very compatible with newer versions of the browsers. Oh yeah, I also turned off the Aero thing which was all user "puff".
Eventually the hardware died, but I can't blame that on Vista.
I remember when every version of Windows came out after 3.0 and there were always complaints about them. EVERYONE complained loudly about XP when it came out wanting to stick with Win98 or ME or 2K. But it was actually a step forward just as every version since has been. The main difference between Vista and XP that gives people trouble is that Vista has the same protections as XP, but turns on more by default. So if you don't like them you need to turn them off.
-- Rick
Because of inversely diminishing returns on optimism. The greater the optimism, the greater the eventual disaster. Were I to estimate only one hour, it will certainly take the entire month.
That recently happened to me. I setup a Lenovo Yoga 2 Pro laptop for a customer:
95% of the migration went smoothly and were done in about 3 days[1]. What could possibly go wrong?In all, the purchase, "migration", testing, delivery, and subsequent show-n-tell burned about 60+ hrs of my time. I was only able to bill for about 12 hrs due to the customer insisting on a fixed "not to exceed" estimate. I won't make that mistake again.
Todays challenge looks to be much the same thing. Fortunately, there's no AOL. Unfortunately, the machine is full of ancient MSDOS programs which are probably going to need DOSbox to function: If you don't hear from me for a week or so, you can guess why.
[1] I had some help with Windoze 8.1 which doubled the time required.-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Lenovo? Crap!!! My current machine is a Lenovo and there is not much about it I like. The keyboard is *very* sensitive and double enters, even triple enters constantly. They remapped the function keys to special purpose laptop keys like volume up and down. Now I have to hit the function button to get the normal F key functions and can't use it with Cntl and Shift. There is a BIOS flash to fix this, but I am very leery of flashing the BIOS because the laptop is bricked if you don't do it right.
The list goes on with the sleep mode not working well and other issues. I wish I had never bought it. Then on top of all that I bought it from Fry's bundled with a laptop bag which is too small for it and they won't replace it with one that fits!
-- Rick
Lenovo keyboards, like many others, seem to vary widely. No one ships Model-Ms with their boxes anymore. I certainly don't mind the remap of the function keys to the laptop controls. It beats the alternatives (BTW, Dell does the same). Other than its low-res screen, I rather like this Thinkpad X230T. If this were older, I'd probably buy a Yoga-2. I might buy one for my wife, anyhow.
It sounds like you have a hardware problem. Not sure who's bundle it is but I'd never make any large purchase from Fry's.
What do you mean it beats the alternatives? You mean remapping beats leaving the keys as F1 through F12 function keys that are used every day vs. changing them to laptop specific keys that are used once in a blue moon if I can even remember what they are? Like I said, the shifted and cntl version of the F1 - F12 keys are no longer available. To change the address mode of a spread sheet reference I have to manually edit the damn dollar signs.
Wanna buy my Ideapad Z710? 16 GB memory and full HD resolution. Of course the problem is that switching laptops - even from a crappy one - is a major PITA. I still don't have all the functionality installed that I had on my old unit.
Tell me about it.
-- Rick
I believe we may have a difference of opinion here. Like all computer vendors, there are good models, and total disasters. Lenovo is no exception and have their share of losers. I do my homework, read the user reviews, play with the laptop for a while, and do not hesitate to return anything that looks like it's going to be a problem. All I can say is that I've had fewer problems with Lenovo laptops (and desktops) than with other brands.
All the low profile keyboards are like that. Todays adventure in laptops was a Toshiba something "ultrabook" with one of those thin keyboards. I have trouble typing on them and do my best to avoid using one. If want to do some real typing, I use an external keyboard. For hunt-n-peck, I guess they're ok. For what it's worth, they do solve the problem of making the laptop very thin, which seems to be a big selling point.
Oddly, that was the result of listening to their complaining customers. Many customers complained that they were "confused" by having to hold the Fn key in order to change a control function. So, Lenovo made it easier for them, and successfully pissed off the other users, who use the function keys more often than the volume, brightness, etc. I'm sure the next model will make it a BIOS setup selectable option.
I did two BIOS updates today (Toshiba laptop and an HP something desktop). No fatalities or disasters. I did make sure that the laptop battery was charged, and that the desktop was running on a UPS. I think it's been 15 years since I last bricked a computah with a BIOS upgrade. Most have a recovery jumper just in case something goes wrong. The only one I recall that was unrecoverable was when HP issued a BIOS update that scribbled on both the BIOS and the recover program in one shot. That one went back to HP under warranty. UEFI BIOS upgrades have added a new level of complexity to a previously simple process, but it's survivable.
More:
BIOS issue again. For example:
There's a real problem. You bought it from Fry's. Not much I can suggest except to not do that again. As for the bag, get a sewing machine.
Do the BIOS update but only after you copy current work and important files to another machine so that you can continue functioning if something goes wrong, goes wrong, goes wrong, goes wrong...
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Do live in FLorida or sommething ? Somewhere near an ocean ? That salty air might be the cause of it because up here in like Ohio, we don't have to re place them much. Talking ten years, maybe, but you sound like it is not ten years between every time. I mean "every time" usually does not mean ten ye ars.
Well maybe for buying a new fridge or stove...
This is easy to say, but the sum total of issues with this model shows a disregard for usability and quality in a product. That is not something that is independent of a company's core values.
I can't see where this laptop is any thinner than my last one. It is certainly not going to win any awards for small size, it has a 17 inch screen! Why would anyone buying a 17 inch laptop be looking for a thinner case at the expense of usability? Again, very poor judgement on the part of Lenovo.
So no one is confused by having to hold down the Fn key to use the keys as they were intended originally and expected to be used in many apps? In fact, making it impossible to use in some apps! Yes, very clearly they listen to their customers, they just can't think...
2 for 2, great. When you get to 1000 for 1000 let me know. Care to flash mine... with a guarantee?Yeah if it was a desktop I would consider it. They tend to be forgiving. You can't even get to the coin battery in laptops without opening the case. I never fully opened my Toshiba case because I was too concerned that I wouldn't get the cables back together. I guess it is not so hard, but until I understand all the issues, I'm not touching that sort of thing.
How did Fry's make it a crappy machine? No one takes laptops back other than Costco and they aren't very inexpensive.
I don't have another machine I can use for work. I have an old XP era desktop that would be far too painful to use for nearly anything. I'll keep it the way it is for now.
-- Rick
what can go wrong? it's not like a power cut between erasing and writing the BIOS ould cause a problem.
-- umop apisdn --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
On a sunny day (Mon, 08 Sep 2014 14:50:03 -0400) it happened rickman wrote in :
Sort of justified. I ran MS win 3.1 on top of DR DOS (Digital research DOS) So you had a real command line, and a lot of games worked. When MS went to 98 they integrated the GUI, my games no longer worked. I think this was done just to kill DR DOS. So it was for sure not an improvement. Luckily in those days I got hold of a CD with Linux (SLS Linux, 1998, still have it on floppies), and it came with gcc, a free compiler, it was 100% stable, it had no memory limitations, and was open source, Xserver worked, was networked too, quite different from Trumpet Winsock on 3.1, Linus had great networking. There were not many applications at that time, so I wrote most if what I needed myself.
Yes I burned that disk. Never regretted that for one moment.
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