Re: [Elecraft] Poor Man's Spectrum Analyzer
No trouble at all. I ordered the kit from Bruce Barlowe at The Science Workshop. http://www.science-workshop.com/ It's definitely not an Elecraft kit, you'll have to pick buy your own enclosure, power transformers, switches and front panel controls. The schematics are all hand drawn with no component values marked, but the parts list is complete. The assembly instructions are sparse, (install 16 resisters, install 14 capacitors, install 4 diodes, etc) but it will get the unit assembled. There is very little 'theory of operation' of the actual circuits, but the optional book offers lots of information on using the analyzer. On Tue, 11 Oct 2005 19:53:53 -0500, james [EMAIL PROTECTED] wrote: Matt just wounder have u had a hard time getting the parts for the spectrum analyzer was thinking about building one Sincerely harold n5tog ___ 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] Poor Man's Spectrum Analyzer
Matt You could consider making a 5 dB pad that also matchs from 50 to 75 ohms. 5 dB would not sacrifice too much sensitivity, and it would be very broadband, being nothing but three resisters. Good luck and 73 Bob N6WG -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Matt Osborn Sent: Sunday, October 09, 2005 7:43 PM To: elecraft@mailman.qth.net Subject: [Elecraft] Poor Man's Spectrum Analyzer The Poor Man's Spectrum Analyzer I'm building uses a varacter driven cable tuner as its front end. The cable tuner has an input impedance of 75 ohms. Most instruments have 50 ohm input impedance and my usage will be primarily with 50 ohm devices. Maybe it isn't worth worrying about, but I'm looking for a convenient way to convert from 75 ohm to 50 ohm input impedance. I've seen some writeups on building a 50 ohm to 75 ohm broadband unun, but the articles were incomplete (or my knowledge level is too low to recognize a complete article). The analyzer covers 5MHzto 500MHz. Does anybody have any advice? Leave it alone, build an unun, buy an unun, any other options? ___ 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] Poor Man's Spectrum Analyzer
On Sun, 09 Oct 2005 21:42:52 -0500, Matt Osborn [EMAIL PROTECTED] wrote: The Poor Man's Spectrum Analyzer I'm building uses a varacter driven cable tuner as its front end. The cable tuner has an input impedance of 75 ohms. Most instruments have 50 ohm input impedance and my usage will be primarily with 50 ohm devices. Thanks to all for the fine ideas and proposed solutions. Greg's suggestion of the Mini-Circuits ADT1.5-1 seems to be the exactly what I need. This is a _really_ great group! ___ 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] Poor Man's Spectrum Analyzer
The Poor Man's Spectrum Analyzer I'm building uses a varacter driven cable tuner as its front end. The cable tuner has an input impedance of 75 ohms. Most instruments have 50 ohm input impedance and my usage will be primarily with 50 ohm devices. Maybe it isn't worth worrying about, but I'm looking for a convenient way to convert from 75 ohm to 50 ohm input impedance. I've seen some writeups on building a 50 ohm to 75 ohm broadband unun, but the articles were incomplete (or my knowledge level is too low to recognize a complete article). The analyzer covers 5MHzto 500MHz. Does anybody have any advice? Leave it alone, build an unun, buy an unun, any other options? ___ 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] Poor Man's Spectrum Analyzer
Hi Matt, You can use two resistors to make the signal source think it is terminated in 50 ohms and make the SA think it is being driven from a 75 ohm source. I posted a diagram of the circuit here: http://w5big.home.comcast.net/50ohm_to_75ohm.gif The first resistor is 43.3 ohms in series with the input to the SA. The second resistor is 86.6 ohms to ground at the signal input. (87 ohms isn't a standard 5% value, but you could put two 43 ohms, 5% resistors in series). 1% metal film resistors are even better if you are getting into the UHF region. The leads should be as short as possible. With this arrangement, you have an easy-to-build wideband matching circuit without transformers. The loss is 4db which can be accounted for when you calibrate the SA. 73/ Bob - W5BIG - Original Message - From: Matt Osborn [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Sunday, October 09, 2005 9:42 PM Subject: [Elecraft] Poor Man's Spectrum Analyzer The Poor Man's Spectrum Analyzer I'm building uses a varacter driven cable tuner as its front end. The cable tuner has an input impedance of 75 ohms. Most instruments have 50 ohm input impedance and my usage will be primarily with 50 ohm devices. Maybe it isn't worth worrying about, but I'm looking for a convenient way to convert from 75 ohm to 50 ohm input impedance. I've seen some writeups on building a 50 ohm to 75 ohm broadband unun, but the articles were incomplete (or my knowledge level is too low to recognize a complete article). The analyzer covers 5MHzto 500MHz. ___ 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
