Bill - Sorry if I misunderstood, and, I probably did have you confused with someone else who usually gets on here not to contribute but just knock any suggestions offered down. I am in the process of relocating my laboratory within the house and just now set up my HP 8505A network analyzer with the 8501A normalizer and 8503A S-Parameter test set, so, I plan on making some more accurate measurements. I may use some minimal loss 75 to 50 ohm resistive matching networks as I am sure this being for HDTV is 75 ohms. However, like I said, I doubt that I will notice the difference for what I intend to use it for. Again I apologize for the misunderstanding and the fact that I had you confused with someone else. I sure as heck do not want to come across negative either. Regards - Mike
Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 -----Original Message----- From: Bill Hawkins [mailto:[EMAIL PROTECTED] Sent: Saturday, September 24, 2005 5:37 PM To: Mike Feher; 'Discussion of precise time and frequency measurement' Subject: RE: [time-nuts] Distribution Amp Sorry, Mike, email allows the reader to assume any context they wish. My post was born of curiosity about using a terminated transmission line with high-impedance receivers. There was nothing academic or esoteric about it. I use such a scheme for industrial process sensors with 32 drops on a line. You raised the topic, and I responded with a question about distribution. I don't know how you managed to read criticism into that. The relevant answer that I got from Robert Lutwak is that the high-Z receivers have to have isolated inputs in order to prevent them from putting unwanted signals on the line. Mike, I hope you have me confused with someone else, because I don't make negativism a habit. That's a poor way to live. Bill Hawkins -----Original Message----- From: Mike Feher [mailto:[EMAIL PROTECTED] Sent: Saturday, September 24, 2005 3:01 PM To: [EMAIL PROTECTED]; 'Discussion of precise time and frequency measurement' Subject: RE: [time-nuts] Distribution Amp Bill - This thing does have 18 outputs, so yes, I did mean one piece of equipment per one/each output. I do not know how that could have been misconstrued. Since I was talking about frequency the simultaneous fits as I indicated that a constant phase shift between outputs, to me is not relevant. If I was using it for a timing reference then I would be more cautious. I am well aware of mismatches occurring due to paralleling 50 ohm inputs or outputs. My post was not intended to bring out an academic and non relevant debate. I simply wanted to alert potential customers for a distribution amplifier to this one which seemed pretty cheap for what it does. Since it is for HDTV, I expect that all inputs and outputs are probably 75 ohms. That would explain the loss I was observing as I was using a 50 ohm instrument to measure the output power. I can live with the 1.5 to 1 VSWR at 10 MHz just fine. I wonder if you even looked at the URL, or did you just start your negativism out of habit. - Mike Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bill Hawkins Sent: Saturday, September 24, 2005 12:54 PM To: Discussion of precise time and frequency measurement Subject: RE: [time-nuts] Distribution Amp Mike Feher said, " It will be ideal to drive a bunch of test equipment simultaneously from the same source. " You mean one equipment per output, right? Paralleling 50 ohm inputs will result in the wrong termination resistance for a cable. This may not be a problem for a 10 MHz sine wave, as long as the direct coupled emitter follower can handle the load. I have used networks where the devices are high impedance. The cable sees 50 ohms at both ends. Some test equipment has an optional 50 ohm terminator, for use as a high impedance device. Suppose I have 3 frequency synthesizers that have optional terminators. Are there any ill effects, except phase shift, from putting them all on the standard's output, if only the end one is terminated? Has anyone tried the high impedance distribution scheme? Seems like "simultaneously" would be relative, unless the distribution cables are all of the same length. Bill Hawkins _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
