Poor Man's Spectrum Analyzer

[KA8WTK]

  A long time ago, or what seems like it, the fellow who made the Poor Man's Spectrum Analyzer used to come to Dayton and sell the boards and tuners to make the analyzer. I bought the stuff and made one. Back then it worked pretty good. Recently I dug it out after not using it for a long time. It doesn't seem to work so well now.
  Did anyone else build one of these? It is different than what they sell now, and of course, I can't find the documentation on the thing to help figure out what is wrong or try to align it.
  Do you have a copy of the docs you can scan?

Thanks,
           Bill KA8WTK

[K6IC]

Hi Bill,

In about 1980,  there was an article in QST for such a device.  It used a Cable box Varactor Tuner as the guts for the analyser.

A&A Engineering in CA did offer boards (naked) and even an encosure for this project.

This may well NOT be what you were referring to,  as I have never been to the Dayton Hamvention.

EDIT:  Here is one hit:
http://forums.qrz.com/archive/index.php/t-281690.html

Will try to find something on the Net ...   GL,  Vic

[WBear2GCR]

It would be interesting to see what it was...

...but you know you can do an awful lot with a Softrock type device and a cheap laptop or desktop as far as a display... not to mention as a receiver. They can be configured to run off the IF section of a receiver which is neat.

                 _-_-

[KA8WTK]

Hi Bear,
  I have 1 Softrock receiver and one Softrock IF board on the R-390 now. This predates the Softrocks by a bit, but it is still interesting to play with.

Bill

[Opcom]

There have been maybe three such projects in that time frame I know of. One used the TV tuner for 50-450MHz, and two others used a NE602 or something IC chip for 0-100Mhz?, I think. Both used an external scope, which made them very affordable.

Now this is a blast from the past. I copied the idea of the TV tuner one and made my own for sake of not enough $$, and although I ordered two of the tuners, did not use them. Instead, I decided to use a cable ready (full range VHF like the ones sold) U/V tuner from a scrap Sanyo Betamax VCR, a reed relay to select the IF from either tuner and apply it to a video detector from another VCR (yes the RBW is some 6MHz on mine..), and the instrument was built inside an old logic analyzer case having a 4" video monitor chassis as a display. My own goal was not to tie up an expensive scope, as they were in use at my TV/stereo/computer repair shop which is how I made my living then.

The picture of the analyzer is the lower left hand instrument. Complete with ugly control labels on an otherwise pretty build. I wonder if the wiring inside is still the rats nest I remember. This picture was my dining room workshop in the late 1980's, before I built the backyard one. There is never enough space for racks and test gear.

The tuning voltage amplifier and sweep generator and vertical deflection amplifier were all built on separate PCBs.

At first I used a stairstep to generate sweep, but it had a finite number of discrete steps, so I went to the monitor chassis using a sample of the yoke current as a swtooth analog signal generator and adjusted the sweep to 30Hz.

A choke of the proper inductance was substituted for the horizontal deflection winding of the yoke to permit normal HV generation for the CRT. The yoke was rotated 90 degrees so that the vertical yoke winding now draws a line across from right to left, and the H yoke winding became the V deflection winding. A STK0050 power amp was used to drive this as a current feedback amplifier.

The brighness was adjusted and left at a suitable level. Blanking remained provided by the CRT chassis.

The video signal was amplified and compensated to have an increasing response at higher frequencies. The sweep span and center position, 50-450/400-950 band selection, vetical gain, etc, are all adjusted by knobs on the front panel. I had a plastic shop make a black lexan panel for me that fit over the original panel of the instrument.

Outputs available are demodulated video and audio, either of which waveform may be displayed on the CRT, as well as a "descrambled" output, a nice feature added later after some experiments with the old analog cable TV as a signal source.

To tune a TV channel, one uses the span and centering 10-turn pots to zoom in on it, until the video signal is displayed. AFC is then turned on. A TV tuner function, and FM radio works too but its deviation is too wide 9coudl use a separate demod there) . The old analog cellphones were at one time tuneable, back when channels 70 and up had been given over to that service from analog TV.

Exploring so many signals was great fun. It took about a month to build it. It's on a shelf in the backyard lab these days.. The range starts at about 50Mhz, a bit high to work with HF. If I recall, the original tuned down to a much lower frequeny? Or was that another project? haha amazing.. before the internet.

How did it work? Good, as sensitive as a TV, not calibrated, no frequency display, no tracking generator, but pretty stable. Better properly called a spectrum monitor, rather than analyzer.

That website is still there. Perhaps the gentleman would let us have a print of the project, for old time sake.

[John K5PRO]

I may still have a paper copy of the PMSA article from one of the magazines (not QST) as well as the documentation. Will have to do some digging over the weekend.

[Pete, WA2CWA]

Info: http://www.science-workshop.com/
Horrible Article Scan: http://www.qsl.net/n9zia/spec/Poor_Mans_Spectrum_Analyzer.pdf
More info: http://wd4eui.com/Spectrum_Analyzer.html

[Opcom]

Info: http://www.science-workshop.com/
Horrible Article Scan: http://www.qsl.net/n9zia/spec/Poor_Mans_Spectrum_Analyzer.pdf
More info: http://wd4eui.com/Spectrum_Analyzer.html

The science workshop one is very nice, but complicated and not exactly for the 'poor', even if it is a huge savings. - I take it back, I have not looked at that page in years. It's much improved for value and ease. Now I want the kit.

The horrible article scan looks like something a poor man could make. Sabed that!

Mine's most like the WD4EUI one. I would like to know how he got to 1Mhz with a tuner that goes down to only 50Mhz. Maybe an up-converter and some very serious shielding? Despite their cheapness TV tuners are very refined instruments and can pick up very low sgnals.

Today, only the love of making such a thing would make it worthwhile. Monstrous old beasts can be had for very cheap.

[WQ9E]

I am pretty sure one of the TV tuner based analyzers appeared in 73 magazine in the middle 1980s.  I will take a look for it this weekend, I think I ran across the issue last year looking for other stuff.

[Pete, WA2CWA]

I quickly saw this link and thought it was the original "Poor Mans Spectrum Analyzer" that Bill was referring to.

Horrible Article Scan: http://www.qsl.net/n9zia/spec/Poor_Mans_Spectrum_Analyzer.pdf

I was incorrect. I believe the original article was in September 1986 issue of HAM RADIO magazine.. The stuff Bill is referring to being bought at Dayton is from the Science Workshop. I guess the real question is, what docs do you need? I remember the first year they sold them at Dayton. Started selling Friday morning; by Friday afternoon; they sold out. I think I bought a set of stuff from them in the second or third year.

[MikeKE0ZUinkcmo]

This is the block diagram from HR Mag.   



I wonder if there are converters today that are usable for this sort of project.

[Tom WA3KLR]

I remember the Poor Man's Spectrum Analyzer at Dayton one year way back.  It was a big hit.  I used to grab about every datasheet I could get my hands on at Dayton and file them away.  I just checked my S.A. file folder and I regret to say I have nothing on the Poor Man's S. A.

[KA8WTK]

Yes, the unit that was sold in Dayton back in the 90's by the Science Workshop is the one.
They sell a "book" with information on the newer boards they sell, but mine is too old.
What I really need is the alignment info. If no one has it, I'll figure it out eventually.

Bill

[Tom WA3KLR]

I did find a zerox of a simple spectrum analyzer article from rf design magazine January 1988 in my S. A. files.  Apparently this copy was presented to my father by a friend.  It's not a great copy.  There are notes in the top margin of page 3 on other articles including one mentioned above in another post.

*Edited 9:12 p.m.

Notes:
"For other simple spectrum analyzers see Ham Radio magazine Sept. 1986 page 82; March 1987 page 99; September 1987 page 49.  Also QST November 1985 page 23."

The copy of the article posted here has been deleted.  There is a new scan below of much higher quality from the original magazine.

[KA8WTK]

Thanks Tom. Between this and the other info offered, I think we can get it working again.

Bill

[Tom WA3KLR]

I was a charter subscriber to rf design. Attached is a new scan of the actual magazine pages from my archives:

[Opcom]

That's a great one there. Who still makes the NE602 or similar part in DIP? NXP had made an SA602, but it's not listed as a current item.

[Pete, WA2CWA]

I was pretty much a charter subscriber to rf design. Attached is a new scan of the actual magazine pages from my archives:

The author of the article is still around; lives in Florida now; use to be a Jersey boy, K2BLA.

[Pete, WA2CWA]

That's a great one there. Who still makes the NE602 or similar part in DIP? NXP had made an SA602, but it's not listed as a current item.

Lots of them on ebay. NTE list a NTE7164 as a replacement: http://www.nteinc.com/specs/7100to7199/pdf/nte7164.pdf
Who has stock: http://dilp.netcomponents.com/cgi-bin/nteinc.asp?partnumber1=NTE7164

Need a circuit for a NE602: https://www.google.com/search?q=ne602&hl=en&client=firefox-a&hs=J86&rls=org.mozilla:en-US:official&tbm=isch&tbo=u&source=univ&sa=X&ei=xjYoUbT3Hc-y0QGtr4DgDw&ved=0CD0QsAQ&biw=1649&bih=1033

[KF1Z]

That's a great one there. Who still makes the NE602 or similar part in DIP? NXP had made an SA602, but it's not listed as a current item.

Mouser still has plenty of stock.....


http://www.mouser.com/ProductDetail/NXP-Semiconductors/SA602AN-01112/?qs=sGAEpiMZZMvKM5ialpXrmhM37i8WNzJv

[KG0MN]

The ARRL's QRP Project Book has a number of circuits that use the NE602.