Home lab suggestions?

My HP counter (don't remember the model, probably older than yours) has a

10-MHz output. That, plus an NE602, plus my ham radio antenna, and not much else, makes a receiver to tune WWV and calibrate the counter to sub-1Hz precision. I seem to recall using a 10.7-MHz FM IF transformer as the input coil.

Well, here is a link to a "build yourself a Spectrum Analyzer" that might be useful. It would be a great project to build together as a learning tool and a useful piece of gear when finished.

Jim Pennell

--

18:30 Pacific Time Zone
Aug 2 2006

International Time
01:30 UTC
03.08.2006

Now _that_ is a fun idea--bootstrap city. If I run a long wire across my back yard, I can probably get several dB gain at 10 MHz, if I orient the lobes right (gotta find that strategically-placed tree). Have to find a good project that needs that much precision and is a kid magnet.

Radioscience is an obvious idea, but radio is _so_ retro nowadays.

Cheers,

Phil Hobbs

If its any older, its all tubes.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Phil,

and now that you have all the lab and the equipment, in case you need a few ideas, get the "Amateur Scientist" CD , with all the articles in the column from the Scientific American we all loved....

Jure Z.

Building some of it may be fun. I don't know what level your kid is at, but Elenco kits for powersupplies and such could be fun.

In article , Rich Grise wrote: [...]

It doesn't have to be a TRF. You can use any old receiver. You just have to offset the calibration point from 10MHz by lets say 1KHz.

When the counter indicates a 1KHz audio for a 10.001MHz generator measurement, the counter is calibrated.

--
--
kensmith@rahul.net   forging knowledge

I wonder if by TRF he meant direct-conversion.

Anyhow, you can also use a superhet, and you don't have to offset the calibraiton point. Tune your regular shortwave radio to WWV at 10 MHz and turn the frequency counter on. Feed a little of its 10 MHz output to the area of the radio. You'll hear a heterodyne. Adjust as near 0 Hz as you can get. When it gets below about 30 Hz you won't hear it; instead you'll see the S-meter bobbing up and down. Make it bob as slowly as possible.

We'll probably try phase-locking. Building a 10-MHz VCXO will be a good project--especially using a 2N3904 for a varactor. ;)

Cheers,

Phil Hobbs

How about a logic analyzer? I use my LA a few times per year, but everytime I have to use it, I find the money well spend ($66 + $450 shipping).

Besides, are you sure you want to have your kid play with high voltage?

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl

...

Probably - when I learned it, it meant "tuned radio frequency" - it's just a tuned circuit, maybe an RF amp, and a detector of some kind. I suggested it because it seems like a good beginner-level project - maybe because the first thing I ever made with a transistor was an AM radio. :-)

Cheers! Rich

Variac with voltage and current meters.

A great thing to have around a bench, is a portable Rubbermaid cart. You can work on stuff without shorting out things. You can dissable things without loosing parts. You can push the cart aside to work on other things. In some cases I also work on fluid systems, and the fluid will stay in the cart without getting on the floor. Did I mention transport.

greg

In message , dated Thu, 3 Aug 2006, Phil Hobbs writes

Nah! Varactors should be made with 6J7Gs.(;-)

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

Right, HV safety is important, but on the other hand a boy has to do some real stuff to grow up. Pyrotechnics, firearms, rotating machinery, and high voltage are good candidates--much safer than talking to strange women, say. It's no use growing up into a perfectly safe wimp.

I learned about high voltage the hard way when I was about 14--I was building a 1.5 kV power supply for a transmitter. I couldn't afford the transmitter parts, but the power supply I could build from cast-off TVs, so I did. It had a monster 750V CT transformer from an old Admiral

26-inch colour set, that must have weighed 50 pounds. It was a choke input bridge rectifier setup, because I only had one HV cap.

I was working on it in front of a window in the attic, which was the 3rd floor, above a verandah, holding the chassis in my left hand, when I accidentally touched the B+ output with my right index finger. I woke up across the room on the floor, but the supply went through the window pane, knocked two shingles out of the porch roof, and embedded itself in the lawn. I still have the scar on my finger--it's a good reminder of my mortality.

Cheers,

Phil Hobbs

BTW: Just picked up an irresistible bargain on a Tek 464 storage scope. I'm swearing off Ebay for a month.

PH

Variacs are fun for experimenting with motors, electromagnets, small coil guns, Jacob's ladder etc., make sure it has a circuit breaker or fuse that will protect the variac and make sure you have an earth leakage (or whatever you call them) breaker for the bench to cut it off if anyone gets a shock of the kind that one of those can detect (but it won't help for the Jacob's ladder).

Chris

I think he was using it for "Tuned RF". This was how tube radios were made before Armstrong came up with the superhet.

This requires that you have an S-meter. The offset frequency method doesn't. You can get a very accurate calibration that way. If your counter has a "period" mode, you can get many digits.

--
--
kensmith@rahul.net   forging knowledge

Use your scope in X/Y mode for a better indicator.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

With WWV as a reference this doesn't work very well. You need to narrow band filter the WWV to get rid of noise far from the carrier. This is most easily done by using an existing radio.

BTW: With a dual channel scope, you can trigger from one and observe the other in the usual Y vs T mode and get the same effect. You tune for the waveform not moving.

This is handy for adjusting 32786 oscillators without actually connecting the probe to them. You just hold the probe a small distance away and turn the vert. of the scope all the way up.

--
--
kensmith@rahul.net   forging knowledge

You phase lock the WWV signal to a 10 MHz TCXO to filter out the noise.

I had to zero the 10 MHz TCXOs to our in house, GPS derived 10 MHz frequency standard for the Microdyne RCB-2000 series receivers. I did it with a Tek 1465 four channel scope.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida