Home lab suggestions?

[Rich Grise]

HP5245L counter with various plug-ins.

Heck, get a 10 MHz crystal and _build_ a counter, for heaven's sakes!

Then, you can build a 10 MHz TRF receiver and calibrate your counter
to WWV.

Cheers!
Rich

 

[mc]

HP5245L counter with various plug-ins.

Heck, get a 10 MHz crystal and _build_ a counter, for heaven's sakes!

Then, you can build a 10 MHz TRF receiver and calibrate your counter
to WWV.

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.

 

[Jim]

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.


http://www.zianet.com/erg/





Jim Pennell

--

18:30 Pacific Time Zone
Aug 2 2006

International Time
01:30 UTC
03.08.2006

 

[Phil Hobbs]

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.

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

 

[Michael A. Terrell]

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.

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

 

[jure]

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

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.

 

[Brian]

So which of your favourite old instruments have I forgotten?

Cheers,

Phil

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.

 

[Ken Smith]

Then, you can build a 10 MHz TRF receiver and calibrate your counter
to WWV.

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.

 

[mc]

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.

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.

 

[Phil Hobbs]

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

 

[Nico Coesel]

Well, after raising two very fine daughters who both turned out to be
gifted in fuzzy subjects such as languages and history and bunk like
that, my son is showing signs of technical aptitude and interest.

Therefore, I'm putting together a lowish-budget home lab off ebay, with
an eye to doing some Jacob's ladders or Tesla coils or stuff like that
there, with maybe an electro-optical thing now and again, such as a
machine to detect deer and hit them with paintballs.

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?

 

[Rich Grise]

I wonder if by TRF he meant direct-conversion.

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

 

[[email protected]]

What sort of mechanical tools do you have?
A descent bench vice, pillar drill and assorted blunt drills

and a variac

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

 

[John Woodgate]

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

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

 

[Phil Hobbs]

Phil Hobbs wrote:




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

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

 

[Chris Jones]

Good point. Don't have enough of those things, especially no drill
press. I have a Panavise and hand drills, but that isn't the same.
Variacs I've been looking at, but I'm mostly going to be starting from
good-quality DC power, at least initially, so I can do the "gradual
smoke test" with the panel knobs.

Cheers,

Phil Hobbs

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

 

[Ken Smith]

I wonder if by TRF he meant direct-conversion.

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

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.

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.

 

[Michael A. Terrell]

[...]
Then, you can build a 10 MHz TRF receiver and calibrate your counter
to WWV.

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.

I wonder if by TRF he meant direct-conversion.

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

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.

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.

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

 

[Ken Smith]

[...]
Then, you can build a 10 MHz TRF receiver and calibrate your counter
to WWV.

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.

I wonder if by TRF he meant direct-conversion.

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

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.

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.

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

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.

 

[Michael A. Terrell]

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.

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

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.

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