|
I have three frequency counters. Two have oven standards. They are old and
purchased from ebay. They all disagreed about what frequency was what. They all
have 10 mhz frequency oscillators. I have tried calibrating them with WWV before
and been only moderately successful. Short wave receivers simply do not produce
audio below 100 hz. I needed to get much closer than that. What I had going was
three freq counters that might be as much as 45 hz off from each other on 10
mhz.
Then I had an inspiration. I realized that at the receiver detector, there is
nothing to limit frequency response. I got out my old DX160 receiver and a
schematic. I found the diode (D3) that did the detecting. I put a scope probe on
this. I then tuned in WWV. I put a little antenna on the BNC output of the
counters 10 mhz clock. Presto, I had a hetrodyne sine wave from the detector
that gave me the clock error. I moved the counter freq adjust up and down past
the null. I had to do this to be sure I was actually finding a null. I had to
slow down the scope horizontal sweep speed a whole lot to see the resulting sine
wave. I could actually see a 1 hz sine wave. I let the oven warm up for a half
an hour. I set it for a "perfect" null. You still cannot be perfect at this. I
had my scope on DC input. I could watch the error signal drift up and down as
much a 1 hz as the oven and crystal drifted. I then set the rest of counters to
my new standard.
BTW there was no sound of this mixed signal coming out of my DX160. It was just
too low to be reproduced.
This procedure is much cheaper than sending your counter into a lab to be
calibrated and finally I can trust the readings on my frequency counters. This
is pretty important when you are trying to receive and transmit SSB. A 30 hz
error is pretty apparent when you are listening to it. One of my counters was 45
hz off at 10 mhz! Yikes.
|
You can also do it the modern way, and measure the period of the 1pps
output of a GPS receiver.
(Assuming you don't want to go to the trouble of building/buying a GPSDO.)
|
Just for the sake of argument, what's the doppler shift between you and WWV?
With all your counters set to the same zero-beat, at least they all read the same frequency, all other things being equal, so any error is equal, at least on the time base.
73 Jim N6OTQ
From: amxcoder
To: TekScopes@...
Sent: Thursday, October 11, 2012 9:44 AM
Subject:
[TekScopes] How to calibrate a frequency counter (on the cheap)
I have three frequency counters. Two have oven standards. They are old and purchased from ebay. They all disagreed about what frequency was what. They all have 10 mhz frequency oscillators. I have tried calibrating them with WWV before and been only moderately successful. Short wave receivers simply do not produce audio below 100 hz. I needed to get much closer than that. What I had going was three freq counters that might be as much as 45 hz off from each other on 10 mhz. Then I had an inspiration. I realized that at the receiver detector, there is nothing to limit frequency response. I got out my old DX160 receiver and a schematic. I found the diode (D3) that did the detecting. I put a scope probe on this. I then tuned in WWV. I put a little antenna on the BNC output of the counters 10 mhz clock. Presto, I had a hetrodyne sine
wave from the detector that gave me the clock error. I moved the counter freq adjust up and down past the null. I had to do this to be sure I was actually finding a null. I had to slow down the scope horizontal sweep speed a whole lot to see the resulting sine wave. I could actually see a 1 hz sine wave. I let the oven warm up for a half an hour. I set it for a "perfect" null. You still cannot be perfect at this. I had my scope on DC input. I could watch the error signal drift up and down as much a 1 hz as the oven and crystal drifted. I then set the rest of counters to my new standard. BTW there was no sound of this mixed signal coming out of my DX160. It was just too low to be reproduced. This procedure is much cheaper than sending your counter into a lab to be calibrated and finally I can trust the readings on my frequency counters. This is pretty important when you are trying to receive and transmit
SSB. A 30 hz error is pretty apparent when you are listening to it. One of my counters was 45 hz off at 10 mhz! Yikes. ------------------------------------ Yahoo! Groups Links <*> To visit your group on the web, go to: ? ? <*> Your email settings: ? ? Individual Email | Traditional <*> To change settings online go to: ? ? ? ? (Yahoo! ID required) <*> To change settings via email: ? ? TekScopes-digest@... ? ? TekScopes-fullfeatured@...<*> To unsubscribe from this group, send an email to: ? ? TekScopes-unsubscribe@...<*> Your use of Yahoo! Groups is subject to: ? ?
|
> Just for the sake of argument, what's the doppler shift between you and WWV?
?
I don't think there is any Doppler shift associated with two points that aren't in motion realitive to each other. In the classic "sound of the train" example, you hear the shift if you are waiting at the crossing, but you wouldn't if you were on the train.
?
I have seen people with certain applications that worry about the latency (time of travel for the signal) in their reception of WWV, but I would think that would be trivial for this type of application.
? 73 de Jim W4JBM
http://www.hamuniverse.com/w4jbm/
"With a soldering iron in one hand, a schematic in the other, and a puzzled look on his face..."
?
|
A man with one counter always knows what frequency he is on ...a man
with two counters is never quite sure
:-)
Dave
NR1DX
ArtekManuals.com
On 10/11/2012 9:44 AM, amxcoder wrote:
?
I have three frequency counters. Two have oven standards.
They are old and
purchased from ebay. They all disagreed about what
frequency was what. They all
have 10 mhz frequency oscillators. I have tried
calibrating them with WWV before
and been only moderately successful. Short wave receivers
simply do not produce
audio below 100 hz. I needed to get much closer than that.
What I had going was
three freq counters that might be as much as 45 hz off
from each other on 10
mhz.
Then I had an inspiration. I realized that at the receiver
detector, there is
nothing to limit frequency response. I got out my old
DX160 receiver and a
schematic. I found the diode (D3) that did the detecting.
I put a scope probe on
this. I then tuned in WWV. I put a little antenna on the
BNC output of the
counters 10 mhz clock. Presto, I had a hetrodyne sine wave
from the detector
that gave me the clock error. I moved the counter freq
adjust up and down past
the null. I had to do this to be sure I was actually
finding a null. I had to
slow down the scope horizontal sweep speed a whole lot to
see the resulting sine
wave. I could actually see a 1 hz sine wave. I let the
oven warm up for a half
an hour. I set it for a "perfect" null. You still cannot
be perfect at this. I
had my scope on DC input. I could watch the error signal
drift up and down as
much a 1 hz as the oven and crystal drifted. I then set
the rest of counters to
my new standard.
BTW there was no sound of this mixed signal coming out of
my DX160. It was just
too low to be reproduced.
This procedure is much cheaper than sending your counter
into a lab to be
calibrated and finally I can trust the readings on my
frequency counters. This
is pretty important when you are trying to receive and
transmit SSB. A 30 hz
error is pretty apparent when you are listening to it. One
of my counters was 45
hz off at 10 mhz! Yikes.
--
Dave Henderson
Manuals@...
PO Box 175
Welch,MN 55089
651-269-4265
|
It's due to diurnal motion of the ionosphere, which relays the HF signal around the globe. See for example
For this reason WWVB (60 kHz carrier) was relied on for long-term stability before GPS. LF propagates along the ground, so the time delay is more stable.
toggle quoted message
Show quoted text
--- In TekScopes@..., Jim McClanahan <w4jbm@...> wrote:
I don't think there is any Doppler shift associated with two points that aren't
in motion realitive to each other.
"With a soldering iron in one hand, a schematic in the other, and a puzzled look
on his face..."
|
At 17:28 11-10-12, you wrote:
A man with one counter always knows what frequency he is on ...a man with two counters is never quite sure :-)
Correct, but there is a way. Tune WWV with, say, 1 kHz offset on a decent, stable SSB receiver (you may tune to 9999 kHz USB). Send the 1 kHz audio note from the receiver to a counter - it has not to be precise, only go to 1 part on 1000. Then feed the receiver with the 10 MHz signal you want to measure, and tune the crystal to get the same beat frequency. Repeat a few times, so you are sure that the radio does not drift. An antenna switch helps. It is easy to get +/- 1 Hz, and with some attention (and 10 s timebase) 0,1 Hz. 73 - Marco IK1ODO
|
Right on the button there Dave. When I had only one counter, I could assume it was on frequency. I was wrong to assume that, but it made me feel better. :-)
Michael
toggle quoted message
Show quoted text
--- In TekScopes@..., Artekmedia <manuals@...> wrote:
A man with one counter always knows what frequency he is on ...a man
with two counters is never quite sure :-)
Dave
NR1DX
ArtekManuals.com
On 10/11/2012 9:44 AM, amxcoder wrote:
I have three frequency counters. Two have oven standards. They are old and
purchased from ebay. They all disagreed about what frequency was what.
They all
have 10 mhz frequency oscillators. I have tried calibrating them with
WWV before
and been only moderately successful. Short wave receivers simply do
not produce
audio below 100 hz. I needed to get much closer than that. What I had
going was
three freq counters that might be as much as 45 hz off from each other
on 10
mhz.
Then I had an inspiration. I realized that at the receiver detector,
there is
nothing to limit frequency response. I got out my old DX160 receiver and a
schematic. I found the diode (D3) that did the detecting. I put a
scope probe on
this. I then tuned in WWV. I put a little antenna on the BNC output of the
counters 10 mhz clock. Presto, I had a hetrodyne sine wave from the
detector
that gave me the clock error. I moved the counter freq adjust up and
down past
the null. I had to do this to be sure I was actually finding a null. I
had to
slow down the scope horizontal sweep speed a whole lot to see the
resulting sine
wave. I could actually see a 1 hz sine wave. I let the oven warm up
for a half
an hour. I set it for a "perfect" null. You still cannot be perfect at
this. I
had my scope on DC input. I could watch the error signal drift up and
down as
much a 1 hz as the oven and crystal drifted. I then set the rest of
counters to
my new standard.
BTW there was no sound of this mixed signal coming out of my DX160. It
was just
too low to be reproduced.
This procedure is much cheaper than sending your counter into a lab to be
calibrated and finally I can trust the readings on my frequency
counters. This
is pretty important when you are trying to receive and transmit SSB. A
30 hz
error is pretty apparent when you are listening to it. One of my
counters was 45
hz off at 10 mhz! Yikes.
--
Dave Henderson
Manuals@...
www.Artekmanuals.com
PO Box 175
Welch,MN 55089
651-269-4265
|
I¡¯ve had some success coupling the counter¡¯s 10Mz. signal to the SW receiver¡¯s input (just a wire in close proximity ¨C minimum coupling to the counter to avoid pulling the oscillator). If you can get the counter¡¯s signal and the WWV signal reasonably close in amplitude, you should be able to tune the counter¡¯s trimmer to zero-beat with the WWV carrier. Is this what you¡¯re doing? When I tried it, I could hear the WWV signal fluctuate at the beat frequency well below a few Hertz. ? Chuck Lewis ?
toggle quoted message
Show quoted text
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of amxcoder
Sent: Thursday, October 11, 2012 9:44 AM
To: TekScopes@...
Subject: [TekScopes] How to calibrate a frequency counter (on the cheap)? ? I have three frequency counters. Two have oven standards. They are old and
purchased from ebay. They all disagreed about what frequency was what. They all
have 10 mhz frequency oscillators. I have tried calibrating them with WWV before
and been only moderately successful. Short wave receivers simply do not produce
audio below 100 hz. I needed to get much closer than that. What I had going was
three freq counters that might be as much as 45 hz off from each other on 10
mhz.
Then I had an inspiration. I realized that at the receiver detector, there is
nothing to limit frequency response. I got out my old DX160 receiver and a
schematic. I found the diode (D3) that did the detecting. I put a scope probe on
this. I then tuned in WWV. I put a little antenna on the BNC output of the
counters 10 mhz clock. Presto, I had a hetrodyne sine wave from the detector
that gave me the clock error. I moved the counter freq adjust up and down past
the null. I had to do this to be sure I was actually finding a null. I had to
slow down the scope horizontal sweep speed a whole lot to see the resulting sine
wave. I could actually see a 1 hz sine wave. I let the oven warm up for a half
an hour. I set it for a "perfect" null. You still cannot be perfect at this. I
had my scope on DC input. I could watch the error signal drift up and down as
much a 1 hz as the oven and crystal drifted. I then set the rest of counters to
my new standard.
BTW there was no sound of this mixed signal coming out of my DX160. It was just
too low to be reproduced.
This procedure is much cheaper than sending your counter into a lab to be
calibrated and finally I can trust the readings on my frequency counters. This
is pretty important when you are trying to receive and transmit SSB. A 30 hz
error is pretty apparent when you are listening to it. One of my counters was 45
hz off at 10 mhz! Yikes.
|
This method, while close enough for HF work, is not anywhere near as close as a GPSDO. With the prices of Trimble Thunderbolts in the $100 range, you really should consider getting one. I have two Trimbles, and two Truetime GPSDO's. I also found over on the
"evil empire" a box containing three phase-locked oscillators (72,5, 725 and 7,975 MHz) that require a 10 MHz reference. That gives me calibration points over a wide range. I have one Trimble that is used as the reference input (through an SRS FS710
Splitter) that feeds all 4 counters. The three phase-locked oscillators are fed from a HB GPSDO. A bit of over-kill, but I get anal about frequency measurement !! 73, Dick, W1KSZ
On Thu, Oct 11, 2012 at 9:02 AM, Chuck Lewis <clewis@...> wrote:
?
I¡¯ve had some success coupling the counter¡¯s 10Mz. signal to the SW receiver¡¯s input (just a wire in close proximity ¨C minimum coupling to the counter to avoid pulling the oscillator). If you can get the counter¡¯s signal and the WWV signal reasonably close in amplitude, you should be able to tune the counter¡¯s trimmer to zero-beat with the WWV carrier. Is this what you¡¯re doing? When I tried it, I could hear the WWV signal fluctuate at the beat frequency well below a few Hertz.
? Chuck Lewis ?
? ? I have three frequency counters. Two have oven standards. They are old and
purchased from ebay. They all disagreed about what frequency was what. They all
have 10 mhz frequency oscillators. I have tried calibrating them with WWV before
and been only moderately successful. Short wave receivers simply do not produce
audio below 100 hz. I needed to get much closer than that. What I had going was
three freq counters that might be as much as 45 hz off from each other on 10
mhz.
Then I had an inspiration. I realized that at the receiver detector, there is
nothing to limit frequency response. I got out my old DX160 receiver and a
schematic. I found the diode (D3) that did the detecting. I put a scope probe on
this. I then tuned in WWV. I put a little antenna on the BNC output of the
counters 10 mhz clock. Presto, I had a hetrodyne sine wave from the detector
that gave me the clock error. I moved the counter freq adjust up and down past
the null. I had to do this to be sure I was actually finding a null. I had to
slow down the scope horizontal sweep speed a whole lot to see the resulting sine
wave. I could actually see a 1 hz sine wave. I let the oven warm up for a half
an hour. I set it for a "perfect" null. You still cannot be perfect at this. I
had my scope on DC input. I could watch the error signal drift up and down as
much a 1 hz as the oven and crystal drifted. I then set the rest of counters to
my new standard.
BTW there was no sound of this mixed signal coming out of my DX160. It was just
too low to be reproduced.
This procedure is much cheaper than sending your counter into a lab to be
calibrated and finally I can trust the readings on my frequency counters. This
is pretty important when you are trying to receive and transmit SSB. A 30 hz
error is pretty apparent when you are listening to it. One of my counters was 45
hz off at 10 mhz! Yikes.
|
I just recently picked up a Racal Dana 1992 to rebuild which included the TCXO option and faced a similar dilemma. The 1992 is the only frequency counter I have with an external reference input and output. Eventually I will use a GPSDO with it to calibrate other instruments. There is no need to compare the 10 Mhz oscillator to WWV with the receiver set to produce a 0 Hz output. Instead use CW mode, with or without a narrow filter as you prefer, where the WWV carrier will show up at 600 Hz or whatever you have the receiver CW side tone set via the BFO. The actual value is not important. The oscillator output will show up as another tone close to the WWV tone and when the frequencies are matched, the output level will be constant. By ear I was able to get to within 1 Hz (1 Hz / 10 MHz = 0.1ppm) easily and 0.1 Hz (0.1 Hz / 10 Mhz = 0.01ppm) without too much effort. At low frequency differences, the match could be tracked on the S-meter. For best results the WWV and oscillator tones need to be roughly the same level so I used a step attenuator between the oscillator output and a handy 2M HT antenna. I needed about 12 dB of attenuation to get deep nulls when the frequencies were slightly off. I did not bother measuring the 600 Hz output with an oscilloscope but that would work also. On Thu, 11 Oct 2012 14:44:24 -0000, "amxcoder" <micoderup@...> wrote: I have three frequency counters. Two have oven standards. They are old and
purchased from ebay. They all disagreed about what frequency was what. They all
have 10 mhz frequency oscillators. I have tried calibrating them with WWV before
and been only moderately successful. Short wave receivers simply do not produce
audio below 100 hz. I needed to get much closer than that. What I had going was
three freq counters that might be as much as 45 hz off from each other on 10
mhz.
Then I had an inspiration. I realized that at the receiver detector, there is
nothing to limit frequency response. I got out my old DX160 receiver and a
schematic. I found the diode (D3) that did the detecting. I put a scope probe on
this. I then tuned in WWV. I put a little antenna on the BNC output of the
counters 10 mhz clock. Presto, I had a hetrodyne sine wave from the detector
that gave me the clock error. I moved the counter freq adjust up and down past
the null. I had to do this to be sure I was actually finding a null. I had to
slow down the scope horizontal sweep speed a whole lot to see the resulting sine
wave. I could actually see a 1 hz sine wave. I let the oven warm up for a half
an hour. I set it for a "perfect" null. You still cannot be perfect at this. I
had my scope on DC input. I could watch the error signal drift up and down as
much a 1 hz as the oven and crystal drifted. I then set the rest of counters to
my new standard.
BTW there was no sound of this mixed signal coming out of my DX160. It was just
too low to be reproduced.
This procedure is much cheaper than sending your counter into a lab to be
calibrated and finally I can trust the readings on my frequency counters. This
is pretty important when you are trying to receive and transmit SSB. A 30 hz
error is pretty apparent when you are listening to it. One of my counters was 45
hz off at 10 mhz! Yikes.
|
That is how I have done it. On modern receivers using CW instead of USB or LSB will produce a 600 or other tone. You could also just use USB or LSB and tune the receiver 600 Hz off frequency. On Thu, 11 Oct 2012 11:02:48 -0500, "Chuck Lewis" <clewis@...> wrote: I've had some success coupling the counter's 10Mz. signal to the SW
receiver's input (just a wire in close proximity - minimum coupling to the
counter to avoid pulling the oscillator). If you can get the counter's
signal and the WWV signal reasonably close in amplitude, you should be able
to tune the counter's trimmer to zero-beat with the WWV carrier. Is this
what you're doing? When I tried it, I could hear the WWV signal fluctuate at
the beat frequency well below a few Hertz.
Chuck Lewis
|
I only just recently acquired my first reciprocal and interpolating counter, a Racal-Dana 1992. Where can you find Thunderbolts for around $100? I suspect the big glut happened before I started looking and all of the ones I have seen are significantly higher. I may start off designing and building my own GPSDO. On Thu, 11 Oct 2012 09:41:24 -0700, Richard Solomon <dickw1ksz@...> wrote: This method, while close enough for HF work, is not anywhere near as close
as a GPSDO. With the prices of Trimble Thunderbolts in the $100 range, you
really should consider getting one.
I have two Trimbles, and two Truetime GPSDO's. I also found over on the
"evil empire" a box containing three phase-locked oscillators (72,5, 725
and
7,975 MHz) that require a 10 MHz reference. That gives me calibration
points over a wide range.
I have one Trimble that is used as the reference input (through an SRS
FS710
Splitter) that feeds all 4 counters.
The three phase-locked oscillators are fed from a HB GPSDO.
A bit of over-kill, but I get anal about frequency measurement !!
73, Dick, W1KSZ
|
About 2 years ago, I picked up a Rubidium oscillator on ebay for around $60. Put it in a box with power and convection ventilation. Picked up a Garmin miniature hockey puck sized GPS receiver for $59 (I think it was either direct or an Amazon purchase). Only problem is the Garmin put out a 1pps signal and I was not in the mood to get fancy with this.
I ran the 10MHz Rubidium into an HP 3336B and generated a much lower frequency at the output of the synthesizer. Both the lower frequency (can't recall, maybe 10kHz) and 1PPS were run into a scope, triggered on one and the timebase adjusted for a shorter and shorter interval as my adjustments of the Rubidium got closer.
After a few hours, I think I had it between 10^-9 and 10^-10 (an estimate by observing the rate of drift of the two).
At that point I called it a day and haven't checked since.
Den
toggle quoted message
Show quoted text
--- In TekScopes@..., "amxcoder" <micoderup@...> wrote:
I have three frequency counters. Two have oven standards. They are old and
purchased from ebay. They all disagreed about what frequency was what. They all
have 10 mhz frequency oscillators. I have tried calibrating them with WWV before
and been only moderately successful. Short wave receivers simply do not produce
audio below 100 hz. I needed to get much closer than that. What I had going was
three freq counters that might be as much as 45 hz off from each other on 10
mhz.
Then I had an inspiration. I realized that at the receiver detector, there is
nothing to limit frequency response. I got out my old DX160 receiver and a
schematic. I found the diode (D3) that did the detecting. I put a scope probe on
this. I then tuned in WWV. I put a little antenna on the BNC output of the
counters 10 mhz clock. Presto, I had a hetrodyne sine wave from the detector
that gave me the clock error. I moved the counter freq adjust up and down past
the null. I had to do this to be sure I was actually finding a null. I had to
slow down the scope horizontal sweep speed a whole lot to see the resulting sine
wave. I could actually see a 1 hz sine wave. I let the oven warm up for a half
an hour. I set it for a "perfect" null. You still cannot be perfect at this. I
had my scope on DC input. I could watch the error signal drift up and down as
much a 1 hz as the oven and crystal drifted. I then set the rest of counters to
my new standard.
BTW there was no sound of this mixed signal coming out of my DX160. It was just
too low to be reproduced.
This procedure is much cheaper than sending your counter into a lab to be
calibrated and finally I can trust the readings on my frequency counters. This
is pretty important when you are trying to receive and transmit SSB. A 30 hz
error is pretty apparent when you are listening to it. One of my counters was 45
hz off at 10 mhz! Yikes.
|
A couple of months ago I was also looking to use WWV to calibrate my Tek 2246. I will try your method as I also have a Realistic DX160 SW rcvr. I have been able to 'beat' a signal generator against the WWV carrier using the signal strength meter only. I had been able to get it within 1 in 10 million for a few seconds. The generator is an old EICO tube type that I could adjust just by adjusting the modulation level which would just slightly shift the carrier after setting the frequency knob. But it is just not that stable. That way you are not needing to rely on the AF freq response to hear the 'beat' Besides your ear can't hear it anyway. This method is described in my US Navy basic electronics book. Back when it was done this way.
If you have not yet done it, you can change some caps on that DX160 and increase its audio frequency response considerably. You will get the 100HZ out of the WWV signal then off the audio amplifier. Beside it will sound so much better when SWLing.
Nick
toggle quoted message
Show quoted text
--- In TekScopes@..., "amxcoder" <micoderup@...> wrote:
I have three frequency counters. Two have oven standards. They are old and
purchased from ebay. They all disagreed about what frequency was what. They all
have 10 mhz frequency oscillators. I have tried calibrating them with WWV before
and been only moderately successful. Short wave receivers simply do not produce
audio below 100 hz. I needed to get much closer than that. What I had going was
three freq counters that might be as much as 45 hz off from each other on 10
mhz.
Then I had an inspiration. I realized that at the receiver detector, there is
nothing to limit frequency response. I got out my old DX160 receiver and a
schematic. I found the diode (D3) that did the detecting. I put a scope probe on
this. I then tuned in WWV. I put a little antenna on the BNC output of the
counters 10 mhz clock. Presto, I had a hetrodyne sine wave from the detector
that gave me the clock error. I moved the counter freq adjust up and down past
the null. I had to do this to be sure I was actually finding a null. I had to
slow down the scope horizontal sweep speed a whole lot to see the resulting sine
wave. I could actually see a 1 hz sine wave. I let the oven warm up for a half
an hour. I set it for a "perfect" null. You still cannot be perfect at this. I
had my scope on DC input. I could watch the error signal drift up and down as
much a 1 hz as the oven and crystal drifted. I then set the rest of counters to
my new standard.
BTW there was no sound of this mixed signal coming out of my DX160. It was just
too low to be reproduced.
This procedure is much cheaper than sending your counter into a lab to be
calibrated and finally I can trust the readings on my frequency counters. This
is pretty important when you are trying to receive and transmit SSB. A 30 hz
error is pretty apparent when you are listening to it. One of my counters was 45
hz off at 10 mhz! Yikes.
|
(Freq1 + Freq2 / 2
Should better than the man with one unknown counter ;-]
toggle quoted message
Show quoted text
--- In TekScopes@..., Artekmedia <manuals@...> wrote:
A man with one counter always knows what frequency he is on ...a man
with two counters is never quite sure :-)
Dave
NR1DX
ArtekManuals.com
|
I do not have a synthesized frequency generator or time mark generator yet so for timebase calibration, I just use a function or pulse generator paired with a reciprocal frequency or universal counter. For analog oscilloscopes where sweep calibration will typically be 1 part in 200 (0.5% or 5000ppm) at best, any frequency counter will be a couple of orders of magnitude more accurate than needed. Using a synthesized generator or time mark generator will just take less time. On Sat, 13 Oct 2012 18:32:17 -0000, "nielsentelecom@..." <nielsentelecom@...> wrote: A couple of months ago I was also looking to use WWV to calibrate my Tek 2246. I will try your method as I also have a Realistic DX160 SW rcvr. I have been able to 'beat' a signal generator against the WWV carrier using the signal strength meter only. I had been able to get it within 1 in 10 million for a few seconds. The generator is an old EICO tube type that I could adjust just by adjusting the modulation level which would just slightly shift the carrier after setting the frequency knob. But it is just not that stable. That way you are not needing to rely on the AF freq response to hear the 'beat' Besides your ear can't hear it anyway. This method is described in my US Navy basic electronics book. Back when it was done this way.
If you have not yet done it, you can change some caps on that DX160 and increase its audio frequency response considerably. You will get the 100HZ out of the WWV signal then off the audio amplifier. Beside it will sound so much better when SWLing.
Nick
--- In TekScopes@..., "amxcoder" <micoderup@...> wrote:
I have three frequency counters. Two have oven standards. They are old and
purchased from ebay. They all disagreed about what frequency was what. They all
have 10 mhz frequency oscillators. I have tried calibrating them with WWV before
and been only moderately successful. Short wave receivers simply do not produce
audio below 100 hz. I needed to get much closer than that. What I had going was
three freq counters that might be as much as 45 hz off from each other on 10
mhz.
Then I had an inspiration. I realized that at the receiver detector, there is
nothing to limit frequency response. I got out my old DX160 receiver and a
schematic. I found the diode (D3) that did the detecting. I put a scope probe on
this. I then tuned in WWV. I put a little antenna on the BNC output of the
counters 10 mhz clock. Presto, I had a hetrodyne sine wave from the detector
that gave me the clock error. I moved the counter freq adjust up and down past
the null. I had to do this to be sure I was actually finding a null. I had to
slow down the scope horizontal sweep speed a whole lot to see the resulting sine
wave. I could actually see a 1 hz sine wave. I let the oven warm up for a half
an hour. I set it for a "perfect" null. You still cannot be perfect at this. I
had my scope on DC input. I could watch the error signal drift up and down as
much a 1 hz as the oven and crystal drifted. I then set the rest of counters to
my new standard.
BTW there was no sound of this mixed signal coming out of my DX160. It was just
too low to be reproduced.
This procedure is much cheaper than sending your counter into a lab to be
calibrated and finally I can trust the readings on my frequency counters. This
is pretty important when you are trying to receive and transmit SSB. A 30 hz
error is pretty apparent when you are listening to it. One of my counters was 45
hz off at 10 mhz! Yikes.
|
I have seen several "interesting" and inventive means of using WWV to calibrate a frequency counter, but I would warn that the use of HF signals is only suitable if the frequency is averaged over a long term, in terms of days or weeks. As somebody has said before WWVB is better within ground wave range. It has been suggested that a simple GPS receiver giving a 1pps output would be an alternative if your frequency counter has a time interval function (and enough digits) and you can adjust the counter standard so that the measured time interval is 1,000,000uSec or 1,000,000,000nSec or what ever your counter will do on its best resolution. Some simple GPS boards will give a 1 or 10MHz output when tracking satellites and may be purchased for a few pounds, euros or dollars on the evil wotsit place. The easy yet cheap way is to get something like a Trimble Thunderbolt which will allow you Standards Lab accuracy at quite a reasonable price. Geoff G8GNZ On 13 October 2012 20:32, nielsentelecom@... <nielsentelecom@...> wrote:
A couple of months ago I was also looking to use WWV to calibrate my Tek 2246. I will try your method as I also have a Realistic DX160 SW rcvr. I have been able to 'beat' a signal generator against the WWV carrier using the signal strength meter only. I had been able to get it within 1 in 10 million for a few seconds. The generator is an old EICO tube type that I could adjust just by adjusting the modulation level which would just slightly shift the carrier after setting the frequency knob. But it is just not that stable. That way you are not needing to rely on the AF freq response to hear the 'beat' Besides your ear can't hear it anyway. This method is described in my US Navy basic electronics book. Back when it was done this way.
If you have not yet done it, you can change some caps on that DX160 and increase its audio frequency response considerably. You will get the 100HZ out of the WWV signal then off the audio amplifier. Beside it will sound so much better when SWLing.
Nick
--- In TekScopes@..., "amxcoder" <micoderup@...> wrote:
I have three frequency counters. Two have oven standards. They are old and
purchased from ebay. They all disagreed about what frequency was what. They all
have 10 mhz frequency oscillators. I have tried calibrating them with WWV before
and been only moderately successful. Short wave receivers simply do not produce
audio below 100 hz. I needed to get much closer than that. What I had going was
three freq counters that might be as much as 45 hz off from each other on 10
mhz.
Then I had an inspiration. I realized that at the receiver detector, there is
nothing to limit frequency response. I got out my old DX160 receiver and a
schematic. I found the diode (D3) that did the detecting. I put a scope probe on
this. I then tuned in WWV. I put a little antenna on the BNC output of the
counters 10 mhz clock. Presto, I had a hetrodyne sine wave from the detector
that gave me the clock error. I moved the counter freq adjust up and down past
the null. I had to do this to be sure I was actually finding a null. I had to
slow down the scope horizontal sweep speed a whole lot to see the resulting sine
wave. I could actually see a 1 hz sine wave. I let the oven warm up for a half
an hour. I set it for a "perfect" null. You still cannot be perfect at this. I
had my scope on DC input. I could watch the error signal drift up and down as
much a 1 hz as the oven and crystal drifted. I then set the rest of counters to
my new standard.
BTW there was no sound of this mixed signal coming out of my DX160. It was just
too low to be reproduced.
This procedure is much cheaper than sending your counter into a lab to be
calibrated and finally I can trust the readings on my frequency counters. This
is pretty important when you are trying to receive and transmit SSB. A 30 hz
error is pretty apparent when you are listening to it. One of my counters was 45
hz off at 10 mhz! Yikes.
------------------------------------
Yahoo! Groups Links
-- ################################################# Geoff Blake, G8GNZ JO01fq: Chelmsford, Essex, UK <geoff@...> or <melecerties@...> Using Linux: Ubuntu 11.04 on Intel or Debian on UltraSparc and even on the NAS. Avoiding Micro$oft like the plague. #################################################
|
Geoff,
By the beat method at 10MHZ WWV using the S meter, if I get the needle to surge once (maximum) in 3 seconds, wouldn't that be an accuracy of 1 in 30,000,000? or 3x10^7 ? Because in one second 10,000,000 cycles had occurred and I was off by one in three seconds? I am not looking at drift over a long period of time. since for the calibration of my scope would is not that accurate by any means(when calibrating my scope.)
I would call that very accurate. no need for the averaging out across time.
Nick
toggle quoted message
Show quoted text
--- In TekScopes@..., Geoff Blake <geoff@...> wrote:
I have seen several "interesting" and inventive means of using WWV to
calibrate a frequency counter, but I would warn that the use of HF
signals is only suitable if the frequency is averaged over a long
term, in terms of days or weeks. As somebody has said before WWVB is
better within ground wave range.
It has been suggested that a simple GPS receiver giving a 1pps output
would be an alternative if your frequency counter has a time interval
function (and enough digits) and you can adjust the counter standard
so that the measured time interval is 1,000,000uSec or
1,000,000,000nSec or what ever your counter will do on its best
resolution.
Some simple GPS boards will give a 1 or 10MHz output when tracking
satellites and may be purchased for a few pounds, euros or dollars on
the evil wotsit place. The easy yet cheap way is to get something like
a Trimble Thunderbolt which will allow you Standards Lab accuracy at
quite a reasonable price.
Geoff G8GNZ
On 13 October 2012 20:32, nielsentelecom@...
<nielsentelecom@...> wrote:
A couple of months ago I was also looking to use WWV to calibrate my Tek 2246. I will try your method as I also have a Realistic DX160 SW rcvr. I have been able to 'beat' a signal generator against the WWV carrier using the signal strength meter only. I had been able to get it within 1 in 10 million for a few seconds. The generator is an old EICO tube type that I could adjust just by adjusting the modulation level which would just slightly shift the carrier after setting the frequency knob. But it is just not that stable. That way you are not needing to rely on the AF freq response to hear the 'beat' Besides your ear can't hear it anyway. This method is described in my US Navy basic electronics book. Back when it was done this way.
If you have not yet done it, you can change some caps on that DX160 and increase its audio frequency response considerably. You will get the 100HZ out of the WWV signal then off the audio amplifier. Beside it will sound so much better when SWLing.
Nick
--- In TekScopes@..., "amxcoder" <micoderup@> wrote:
I have three frequency counters. Two have oven standards. They are old and
purchased from ebay. They all disagreed about what frequency was what. They all
have 10 mhz frequency oscillators. I have tried calibrating them with WWV before
and been only moderately successful. Short wave receivers simply do not produce
audio below 100 hz. I needed to get much closer than that. What I had going was
three freq counters that might be as much as 45 hz off from each other on 10
mhz.
Then I had an inspiration. I realized that at the receiver detector, there is
nothing to limit frequency response. I got out my old DX160 receiver and a
schematic. I found the diode (D3) that did the detecting. I put a scope probe on
this. I then tuned in WWV. I put a little antenna on the BNC output of the
counters 10 mhz clock. Presto, I had a hetrodyne sine wave from the detector
that gave me the clock error. I moved the counter freq adjust up and down past
the null. I had to do this to be sure I was actually finding a null. I had to
slow down the scope horizontal sweep speed a whole lot to see the resulting sine
wave. I could actually see a 1 hz sine wave. I let the oven warm up for a half
an hour. I set it for a "perfect" null. You still cannot be perfect at this. I
had my scope on DC input. I could watch the error signal drift up and down as
much a 1 hz as the oven and crystal drifted. I then set the rest of counters to
my new standard.
BTW there was no sound of this mixed signal coming out of my DX160. It was just
too low to be reproduced.
This procedure is much cheaper than sending your counter into a lab to be
calibrated and finally I can trust the readings on my frequency counters. This
is pretty important when you are trying to receive and transmit SSB. A 30 hz
error is pretty apparent when you are listening to it. One of my counters was 45
hz off at 10 mhz! Yikes.
------------------------------------
Yahoo! Groups Links
--
#################################################
Geoff Blake, G8GNZ JO01fq: Chelmsford, Essex, UK
<geoff@...> or <melecerties@...>
Using Linux: Ubuntu 11.04 on Intel or Debian on UltraSparc
and even on the NAS. Avoiding Micro$oft like the plague.
#################################################
|
I have been able to ¡®beat¡¯
against WWV using the S meter.? When with a ¡®fast¡¯ AGC, and
the pass band is adjusted to ¡®center¡¯, you can see the S meter
slowly cycle as the frequency gets close to ¡®zero¡¯ beat.
?
This was on a Drake TR-7.
?
Joe
?
toggle quoted message
Show quoted text
-----Original Message-----
From: TekScopes@...
[mailto:TekScopes@...] On Behalf
Of nielsentelecom@...
Sent: Saturday, October 13, 2012
1:32 PM
To: TekScopes@...
Subject: [TekScopes] Re: How to
calibrate a frequency counter (on the cheap)
?
?
A couple of months ago I was also looking to use WWV to calibrate my Tek 2246.
I will try your method as I also have a Realistic DX160 SW rcvr. I have been
able to 'beat' a signal generator against the WWV carrier using the signal
strength meter only. I had been able to get it within 1 in 10 million for a few
seconds. The generator is an old EICO tube type that I could adjust just by
adjusting the modulation level which would just slightly shift the carrier
after setting the frequency knob. But it is just not that stable. That way you
are not needing to rely on the AF freq response to hear the 'beat' Besides your
ear can't hear it anyway. This method is described in my US Navy basic
electronics book. Back when it was done this way.
If you have not yet done it, you can change some caps on that DX160 and
increase its audio frequency response considerably. You will get the 100HZ out
of the WWV signal then off the audio amplifier. Beside it will sound so much
better when SWLing.
Nick
--- In TekScopes@...,
"amxcoder" wrote:
>
> I have three frequency counters. Two have oven standards. They are old and
> purchased from ebay. They all disagreed about what frequency was what.
They all
> have 10 mhz frequency oscillators. I have tried calibrating them with WWV
before
> and been only moderately successful. Short wave receivers simply do not
produce
> audio below 100 hz. I needed to get much closer than that. What I had
going was
> three freq counters that might be as much as 45 hz off from each other on
10
> mhz.
>
> Then I had an inspiration. I realized that at the receiver detector, there
is
> nothing to limit frequency response. I got out my old DX160 receiver and a
> schematic. I found the diode (D3) that did the detecting. I put a scope
probe on
> this. I then tuned in WWV. I put a little antenna on the BNC output of the
> counters 10 mhz clock. Presto, I had a hetrodyne sine wave from the
detector
> that gave me the clock error. I moved the counter freq adjust up and down
past
> the null. I had to do this to be sure I was actually finding a null. I had
to
> slow down the scope horizontal sweep speed a whole lot to see the
resulting sine
> wave. I could actually see a 1 hz sine wave. I let the oven warm up for a
half
> an hour. I set it for a "perfect" null. You still cannot be
perfect at this. I
> had my scope on DC input. I could watch the error signal drift up and down
as
> much a 1 hz as the oven and crystal drifted. I then set the rest of
counters to
> my new standard.
>
> BTW there was no sound of this mixed signal coming out of my DX160. It was
just
> too low to be reproduced.
>
> This procedure is much cheaper than sending your counter into a lab to be
> calibrated and finally I can trust the readings on my frequency counters.
This
> is pretty important when you are trying to receive and transmit SSB. A 30
hz
> error is pretty apparent when you are listening to it. One of my counters
was 45
> hz off at 10 mhz! Yikes.
>
|
Chuck Lewis
David Hess
