RE: [Elecraft] Oscilloscopes (WAS: spectrogram)
Poor John asked if he could use spectrogram as an oscilloscope, and that's morphed into recommendations to buy a 400 MHz scope! In my last job I was the video amplifier design guy, and in that role I designed video amplifiers to drive CRTs in high-resolution industrial computer displays. Over the years, resolution requirements constantly increased so the last generations of products had CRT cathode drive requirements on the order of 60Vp-p with 3nSec rise and fall times. As I recall, the last video amp I did was around 2.7nSec at 60 Volts drive. (now you know why CRT monitors can cause serious RFI ... shielding was one of the biggest challenges). My point is, I am familiar with and appreciate the need for fast oscilloscopes when the application requires it . My favorite was the 475 until we got 2465's, and I really liked the 2465. But I always felt the 2465 was more fragile than the old 465 - 475 series stuff, and the things that broke in the 2465's were always expens ive and proprietary. If you were going to buy one for home use, it might be easier to keep the older stuff going because they're tougher and fewer of the parts are made of unobtainium. But .. my REAL point here ... for home use for the average hobby user, we almost never really NEED a 400 MHz or even 250 MHz scope. My home scope for years was a Tek 455 with 50MHz bandwidth. I did design development work at home and fixed a zillion things with that scope and rarely found the 50 Mhz bandwidth a problem. For the less demanding hobbiest, it might NEVER be a problem. Of course you have to apply judgement and realize the limitations of the instrument, but that's ALWAYS the case with any measurement. People tend to think they have to always have the highest performance and anything less is inadequate (hence the internet surfers with 3.2GHz Pentium IV computers and a Gig of Ram to send e-mail) but if you hold off buying a scope because you can't afford the 250 MHz or 400 Mhz scope that you THINK you need ... be aware you can do 99% of your oscilloscope work with a decent 50Mhz scope. If you're designing fast logic or think you need to look at the carrier of a VHF transmitter, you need speed, but for fixin' radios, it's rare. Because of the gotta have the fastest mentality, the old 455's and such are real bargains, and will serve the average hobbiest well. Any scope is better than no scope. I can't imagine life without an oscilloscope in my basement. I have four ... including a 922 (15MHz??) that's my favorite for pick it up and go to help a friend fix something ... Just my humble opinion based on some years of experience ... Jim AB4CZ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Oscilloscopes (WAS: spectrogram)
By the way, one more comment on Tek scopes .. I loved the 475, REALLY loved the 2465, but I can barely tolerate Tek's DSOs... Maybe I'm just to dumb to use them, but I think the menu structures in most of the Tektronix digital scopes are non-intuitive and obtuse. If you want a really neat digital scope, look for a LeCroy. When I bought DSOs for my last company, I had HP, Tektronix, Philips, and LeCroy bring scopes in for me to play with. I refused to look at any of the user manuals. If I needed the manual to get basic use out of the scope, I didn't want the scope. The LeCroy won hands down for ease of use. I'd REALLY like to get a 350MHz or so LeCroy for home use! jim ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] Oscilloscopes (WAS: spectrogram)
Jim, AB4CZ gave you an excellent summary. If you think you'd like to use the 'scope for general bench work to look at waveforms, etc., on HF gear, then look for one with at least a 200 MHz bandwidth. Smaller bandwidth scopes are fine for a simple check on your transmitter waveform, but one of the greatest advantages to a scope is being able to see things you can't see otherwise - parasitics, the transition waveforms when keying, edges of clock signals, etc. While the fundamental frequency of the waveform may only be a few MHz, the frequency of the squiggles and other artifacts on the signal is much, much higher. For those applications a general 'rule of thumb' is to use a 'scope with at least 10 times the highest frequency you'll be interested in, the higher the better. If you try to observe signals on a narrower bandwidth oscilloscope, the higher-frequency information is simply lost. The displayed waveform will look much cleaner that it really is! For example, if you try to observe a 50 MHz square wave on a 50 MHz oscilloscope it'll show you a nice, clean sine wave, not a square wave. All of the higher-frequency information that makes the edges of the square wave sharp will be lost. To get a decent representation of the actual waveform you'd need at least a 500 MHz oscilloscope. At today's Hamfest prices, the price difference between a basic waveform monitor and a good general purpose scope is often small, and with the latter you have an instrument that will prove itself quite valuable over time if you enjoy tinkering with circuits on the bench. Ron AC7AC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Oscilloscopes (WAS: spectrogram)
Tektronix 475, baby! The 465 is OK, and the 485 a real 400MHz work of analog scope art I hope to own someday. Then if you're really serious you have a 7000-series mainframe and a lot of plugins hehe. A really good tutorial on scopes is Tektronix's The XYZ's Of Using A Scope which they used to give out, now you can download it from the net and the recent versions have a bunch of stupid stuff about their digital scopes - they tell such beautiful lies, stick to analog. 73 de Alex NS6Y. On Jan 23, 2006, at 7:06 PM, Ron D'Eau Claire wrote: Jim, AB4CZ gave you an excellent summary. If you think you'd like to use the 'scope for general bench work to look at waveforms, etc., on HF gear, then look for one with at least a 200 MHz bandwidth. ...If you try to observe signals on a narrower bandwidth oscilloscope, the higher-frequency information is simply lost. At today's Hamfest prices, the price difference between a basic waveform monitor and a good general purpose scope is often small, Ron AC7AC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Oscilloscopes (WAS: spectrogram)
Alex NS6Y wrote: Tektronix 475, baby! The 465 is OK, and the 485 a real 400MHz work of analog scope art I hope to own someday... -- Yep, Tek scopes are the most popular and they are very good. In the 1970's when I was running a television production studio we had to smuggle in our Tek waveform monitors because the facility was owned by Hewlett-Packard! Hewlett-Packard scopes are also EXCELLENT instruments though - at least their general-purpose lab scopes, which is what I was talking about here. When I was working in various labs I liked Tek scopes primarily because of their extreme flexibility, thanks to all of those expensive plug-ins G, and because they carefully kept the control layout much the same from model to model. Grab that big knob over there and it was always the time base control, no matter which Tek scope you were using. HP wasn't so consistent with their panel layouts and they don't have all the swappable plug-ins that Tek used. However, HP made its name as a lab instrument company for almost 40 years before they touched the computer business in the 1970's with world-class lab gear. One advantage of their 'scopes for the Ham today is that they are often a lot cheaper than the Tek scopes, feature for feature and per megacycle of bandwidth simple because the Tek scopes are so popular. I have an HP1740 sitting on my bench that was built in the 1970's. It's an analog scope, which I prefer, and it's still tickin' like the day it was built, almost 40 years later! Ron AC7AC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Oscilloscopes (WAS: spectrogram)
I have a 475 with the DM44 option, and a scad of different probes. It is on semi-permanent loan from my company (they have no need for it any longer). I have never used the DM44, but what looks interesting is that it will measure temperature in degrees C. I have the temperature probe and will get around to trying that out one of these days. I have never used an oscilloscope before about a couple of months ago, but I am trying to learn. The tutorial that Tek has on their website is pretty informative. Stan Rife W5EWA Ron D'Eau Claire wrote: Alex NS6Y wrote: Tektronix 475, baby! The 465 is OK, and the 485 a real 400MHz work of analog scope art I hope to own someday... -- Yep, Tek scopes are the most popular and they are very good. In the 1970's when I was running a television production studio we had to smuggle in our Tek waveform monitors because the facility was owned by Hewlett-Packard! Hewlett-Packard scopes are also EXCELLENT instruments though - at least their general-purpose lab scopes, which is what I was talking about here. When I was working in various labs I liked Tek scopes primarily because of their extreme flexibility, thanks to all of those expensive plug-ins G, and because they carefully kept the control layout much the same from model to model. Grab that big knob over there and it was always the time base control, no matter which Tek scope you were using. HP wasn't so consistent with their panel layouts and they don't have all the swappable plug-ins that Tek used. However, HP made its name as a lab instrument company for almost 40 years before they touched the computer business in the 1970's with world-class lab gear. One advantage of their 'scopes for the Ham today is that they are often a lot cheaper than the Tek scopes, feature for feature and per megacycle of bandwidth simple because the Tek scopes are so popular. I have an HP1740 sitting on my bench that was built in the 1970's. It's an analog scope, which I prefer, and it's still tickin' like the day it was built, almost 40 years later! Ron AC7AC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Oscilloscopes (WAS: spectrogram)
Hi Be careful buying older Tek scopes. Many of the repair parts are not available any more. You may get lucky and never need to repair one of these scopes but many of the parts were proprietary made custom for Tek or in the case of some of the IC's and CRT's were made only by Tek in there own fab. I worked for Tektronix for many years as a field maintenance instructor in the test and measurement division. My specialty was the 7000 series and the portable scopes among others. The reason the 7000 series is so cheap on Ebay is the problem of getting repair parts. The most common problem is with the cam switches and attenuators in both the 7000 and the 465 and 475 scopes. The 485 is even a generation earlier than the 465 or 475 so I would not ever consider one these scopes unless it had a good CRT, is in excellent condition and was virtually free. It also takes a real expert and some special equipment to properly tweak a 485 so it will meet specs. The 7000 series may be OK if you can buy two for a few hundred dollars. The second one for parts. I have a friend with a cal lab that has a warehouse full of broken 7000's that he uses for parts to keep the stuff he has under contract. Tek has a policy that they do not guarantee parts support seven years after a product is discontinued. The 465, 475 and most of the 7000 has exceeded that by two and the 485 by three However I personally own a 2465 and can highly recommend it. It is 400 Mhz four channel with both 1 meg ohm and 50 ohm inputs with dual timebase. This was the last of the really great analog scopes Tek made. This scope sold for over $5000 in the mid 80's and was worth every penny. I have seen them on Ebay for well under $1000 (I paid $800 for mine a couple of years ago) I know that is a lot of money to spend on a scope used for hobby work but a new scope with much less capability will cost as much or more. Ron Is correct on the bandwidth specification. Scopes are rated at 3 db down at the rated bandwidth. This means a 100 MHz scope can measure a one volt pk to pk 100 MHz sine wave at .707 volts and still be in spec. Also the probes are rated at a max bandwidth as well. If you use a 100 MHz probe on a 200 MHz scope then you will only have a 100 Mhz bandwidth at best Don Brown KD5NDB - Original Message - From: Alexandra Carter [EMAIL PROTECTED] To: Ron D'Eau Claire [EMAIL PROTECTED] Cc: elecraft@mailman.qth.net Sent: Monday, January 23, 2006 9:13 PM Subject: Re: [Elecraft] Oscilloscopes (WAS: spectrogram) Tektronix 475, baby! The 465 is OK, and the 485 a real 400MHz work of analog scope art I hope to own someday. Then if you're really serious you have a 7000-series mainframe and a lot of plugins hehe. A really good tutorial on scopes is Tektronix's The XYZ's Of Using A Scope which they used to give out, now you can download it from the net and the recent versions have a bunch of stupid stuff about their digital scopes - they tell such beautiful lies, stick to analog. 73 de Alex NS6Y. On Jan 23, 2006, at 7:06 PM, Ron D'Eau Claire wrote: Jim, AB4CZ gave you an excellent summary. If you think you'd like to use the 'scope for general bench work to look at waveforms, etc., on HF gear, then look for one with at least a 200 MHz bandwidth. ...If you try to observe signals on a narrower bandwidth oscilloscope, the higher-frequency information is simply lost. At today's Hamfest prices, the price difference between a basic waveform monitor and a good general purpose scope is often small, Ron AC7AC ___ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Oscilloscopes (WAS: spectrogram)
Hi In interesting piece of trivia. The DM44 sensor in the temperature probe is a 2n transistor. The circuit is similar to the temperature measuring circuit in the KPA100 used to monitor the heat sink temperature. Don Brown KD5NDB - Original Message - From: Stan Rife [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Monday, January 23, 2006 9:56 PM Subject: Re: [Elecraft] Oscilloscopes (WAS: spectrogram) I have a 475 with the DM44 option, and a scad of different probes. It is on semi-permanent loan from my company (they have no need for it any longer). I have never used the DM44, but what looks interesting is that it will measure temperature in degrees C. I have the temperature probe and will get around to trying that out one of these days. I have never used an oscilloscope before about a couple of months ago, but I am trying to learn. The tutorial that Tek has on their website is pretty informative. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Oscilloscopes (WAS: spectrogram)
Yes, but in actuality, you can very often pick up a good 465 or 475 for $100 or so, take it home, clean it up, and it will work for you for years. That's hard to beat. 73 de Alex NS6Y. On Jan 23, 2006, at 8:36 PM, Don Brown wrote: Hi Be careful buying older Tek scopes. Many of the repair parts are not available any more. You may get lucky and never need to repair one of these scopes but many of the parts were proprietary made custom for Tek or in the case of some of the IC's and CRT's were made only by Tek in there own fab. I worked for Tektronix for many years as a field maintenance instructor in the test and measurement division. My specialty was the 7000 series and the portable scopes among others. The reason the 7000 series is so cheap on Ebay is the problem of getting repair parts. The most common problem is with the cam switches and attenuators in both the 7000 and the 465 and 475 scopes. The 485 is even a generation earlier than the 465 or 475 so I would not ever consider one these scopes unless it had a good CRT, is in excellent condition and was virtually free. It also takes a real expert and some special equipment to properly tweak a 485 so it will meet specs. The 7000 series may be OK if you can buy two for a few hundred dollars. The second one for parts. I have a friend with a cal lab that has a warehouse full of broken 7000's that he uses for parts to keep the stuff he has under contract. Tek has a policy that they do not guarantee parts support seven years after a product is discontinued. The 465, 475 and most of the 7000 has exceeded that by two and the 485 by three However I personally own a 2465 and can highly recommend it. It is 400 Mhz four channel with both 1 meg ohm and 50 ohm inputs with dual timebase. This was the last of the really great analog scopes Tek made. This scope sold for over $5000 in the mid 80's and was worth every penny. I have seen them on Ebay for well under $1000 (I paid $800 for mine a couple of years ago) I know that is a lot of money to spend on a scope used for hobby work but a new scope with much less capability will cost as much or more. Ron Is correct on the bandwidth specification. Scopes are rated at 3 db down at the rated bandwidth. This means a 100 MHz scope can measure a one volt pk to pk 100 MHz sine wave at .707 volts and still be in spec. Also the probes are rated at a max bandwidth as well. If you use a 100 MHz probe on a 200 MHz scope then you will only have a 100 Mhz bandwidth at best Don Brown KD5NDB - Original Message - From: Alexandra Carter [EMAIL PROTECTED] To: Ron D'Eau Claire [EMAIL PROTECTED] Cc: elecraft@mailman.qth.net Sent: Monday, January 23, 2006 9:13 PM Subject: Re: [Elecraft] Oscilloscopes (WAS: spectrogram) Tektronix 475, baby! The 465 is OK, and the 485 a real 400MHz work of analog scope art I hope to own someday. Then if you're really serious you have a 7000-series mainframe and a lot of plugins hehe. A really good tutorial on scopes is Tektronix's The XYZ's Of Using A Scope which they used to give out, now you can download it from the net and the recent versions have a bunch of stupid stuff about their digital scopes - they tell such beautiful lies, stick to analog. 73 de Alex NS6Y. On Jan 23, 2006, at 7:06 PM, Ron D'Eau Claire wrote: Jim, AB4CZ gave you an excellent summary. If you think you'd like to use the 'scope for general bench work to look at waveforms, etc., on HF gear, then look for one with at least a 200 MHz bandwidth. ...If you try to observe signals on a narrower bandwidth oscilloscope, the higher-frequency information is simply lost. At today's Hamfest prices, the price difference between a basic waveform monitor and a good general purpose scope is often small, Ron AC7AC ___ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
