Racal Dana 8010B

[Refugee]

The user manuals for these are pretty hard to get and I would like to ask a few questions about the rear panel inputs/outputs. The handbooks are expensive
I was wondering if I could expect these functions to be connected as there are few optional extras fitted to it.
I understand what the gate does but i am not so sure about the scaled out as this might be part of an optional extra prescaler that is not fitted. I am also not sure what the marker does or even if it is an input or output.
I do not have a recorder or a remote.
Has anyone got a manual they could look in for me?
I could also do with a knob pointer. I think they are the type that can be separated from the knob.

DSCF5822C.jpeg (16.96 KiB) Viewed 3717 times

[Michael Watterson]

Gate can be for counter mode. Starts and stops the count.
There is probably a built in Pre-scaler or Prescaler option
Marker will be a reference squarewave out

[Refugee]

Core what a lot of queries about test equipment accuracy
I have for some time been on the lookout for an off air standard. As far as I can see these things receive the same signal the BBC use for the pips before the news on radio 4. A broken radio controlled clock would also be a candidate for making a home brew off air standard too.
A 10Mhz clock is divided down and phase locked to the pips themselves.
All you need to do is put the clock from the off air standard on one trace of a scope and the clock in the DFM on the other trace.
My Racal shown in the earlier post has a crystal oven in it so it is quite a posh one from the 1970s.

So back to the Marconi.
I took the cover off the oscillator and checked the resistors and as I predicted some of them are actually high and out of spec the wort of these being on the lower ranges.
The worst were the two 820K ones on the lowest range. These were reading over 1 meg.
I have not yet fitted the new ones due to a dinner call although I did get time to select them from stock parts.
With all the Qs and As about test equipment accuracy my big Fluke came into play in order to double check my every day DMM.
The access to replace the resistors is easy enough so it is not a lot of bother to sort out.

[Niall]

I have for some time been on the lookout for an off air standard.

So have I. I actually spotted a GPS based one on a club stand at Norbreck for a reasonable price, unfortunately someone else also saw it seconds before I did, and bought it. What's really annoying is I missed seeing it on my first round of the stalls.
The R4 based ones are a bit cheaper, but I wonder how long the source signal will last given the persistent rumors of closedown.

That said, whoever was the first owner of my big Racal counter specified all the options including the high stability reference and it still appears to be pretty accurate - used it to measure the LO frequency I was injecting into a receiver to pick up VOLMET and it was spot on.

[Cathovisor]

I have for some time been on the lookout for an off air standard. As far as I can see these things receive the same signal the BBC use for the pips before the news on radio 4. [...] A 10Mhz clock is divided down and phase locked to the pips themselves.

Errrr.... what?!

The off-air standard I have uses the carrier, not the pips! In my standard, there is an oven-controlled crystal that is compared to the carrier of Radio 4 LW. Radio 4 is received and then passed through a crystal filter to remove the modulation, the recovered carrier then being compared to the output of the crystal.

There are frequency standards on eBay - many of which are rubidium-based, and there are magazine projects too;
http://www.epemag3.com/proj/0415.html

[Refugee]

The frequency standard I used when I worked in a calibration shop locked on each pip and when the internal oscillator was slightly out the trace on the scope used to drift and then pull back with each pip.
It must have been a low cost unit and the reading had to be taken when the pips were heard through the little sounder.
I have looked at a radio spectrum site and there are time standards shown between the usual wavebands so there is a possibility of picking those up with a modified receiver of some kind.
An old FM if strip comes to mind.

[Cathovisor]

The frequency standard I used when I worked in a calibration shop locked on each pip and when the internal oscillator was slightly out the trace on the scope used to drift and then pull back with each pip.

You'll find pretty much anything off-air uses one of three sources:

Anthorn carrier (60KHz)
Droitwich carrier (198KHz)
GPS.

Mine's a Quartzlock 2A which uses Droitwich.

If making a home-brew, I'd be inclined to go for Anthorn as a reference as you an easily derive a 10KHz square-wave from its carrier to pull say, a 10MHz VCXO with. And a suitable TRF receiver would be a trivial matter to make....

Also, with note to the above - WWV at 10MHz?

[Terrykc]

In my standard, there is an oven-controlled crystal that is compared to the carrier of Radio 4 LW. Radio 4 is received and then passed through a crystal filter to remove the modulation, the recovered carrier then being compared to the output of the crystal.

Is that really necessary? I know that modulation will introduce phase changes in the carrier and there is (or used to be) a low level FSK data stream on the Droitwich carrier - although I can't remember what it was used for - but surely a PLL with a fairly long time loop time constant will average out all of these unwanted perturbations without the need for a crystal filter and ensure that the crystal oscillator remains locked to the mean carrier frequency which is, after all, what is wanted.

You'll find pretty much anything off-air uses one of three sources:

Anthorn carrier (60KHz)
Droitwich carrier (198KHz)
GPS.

... If making a home-brew, I'd be inclined to go for Anthorn as a reference as you an easily derive a 10KHz square-wave from its carrier to pull say, a 10MHz VCXO with. And a suitable TRF receiver would be a trivial matter to make....

But surely you wouldn't get an 10kHz square wave due to the carrier suppression on each second marker which contains the time, date and astronomical offset data?

I'd be inclined to detect the start of the second marker to trigger a 500mS delay so as to ignore all the data, then sample the 60kHz carrier to lock a local 60kHz oscillator.

[Cathovisor]

In my standard, there is an oven-controlled crystal that is compared to the carrier of Radio 4 LW. Radio 4 is received and then passed through a crystal filter to remove the modulation, the recovered carrier then being compared to the output of the crystal.

Is that really necessary? I know that modulation will introduce phase changes in the carrier and there is (or used to be) a low level FSK data stream on the Droitwich carrier - although I can't remember what it was used for - but surely a PLL with a fairly long time loop time constant will average out all of these unwanted perturbations without the need for a crystal filter and ensure that the crystal oscillator remains locked to the mean carrier frequency which is, after all, what is wanted.

Found this on the web:

The FSK carrier is/was used for Economy 7 switching.

<Goes off, looks at MSF carrier format>
Ah.

[Refugee]

I have just come up with a very quick fix for this job only that will be repeatable any time
The TF1101 covers 20hz to 200Khz putting 198Khz in my sights.
I will connect the counter under test to the TF1101 and switch on an AM radio tuned to R4 and tune the TF1101 for slowest beat with R4 and the counter should read the carrier frequency at 198Khz.
Job done.

[Terrykc]

<Goes off, looks at MSF carrier format>
Ah.

http://www.npl.co.uk/upload/pdf/MSF_Time_Date_Code.pdf

[Refugee]

Yes indeed it is a simple solution.
The number of digits on the counter will end up limiting the accuracy of my solution easily.
I will check both my counters this way later on when I have done all the household stuff.

[Refugee]

The Marconi is very stable and I see no problem with getting a 10 second beat.
I am not sure if I will get all the chores done before the end of the afternoon so it may have to wait until tomorrow.

[Cathovisor]

Some mdoern counters use reciprocal counting (swap the uknown and the gate) to give good resolution of low frequencies without excessive gate times.

First done in the late 60s, believe it or not - I have a Dawe mains frequency meter that does just this (in fact, I think Dawe patented it...).

[Refugee]

Surely would it not be better to count 500 cycles and shift the decimal point in order to get a resolution of 0.1hz and so on. That would be a gate time of 10 seconds.
How long is the gate time on the Dawe?

[Refugee]

I agree about the gate time.
There may well have been a way of deducting cycles above and below the clock count for the measured period before shifting the decimal point in order to display the result.
It is not very useful if you need to measure a wide range of frequencies though but all the same good for spot frequency measurement or indication.

[Refugee]

I had another look for a manual for the counter tonight with success this time. It is three huge PDFs.
I did post a thread here but not very many further posts. There were a few more on the other forum though and they led me astray and I posted lots of photos there.
It all gets even more confusing as the oven fitted shows a part number that is not listed in the manual.
730647 is fitted while the options are730551, 730578 and 730228 so I have no idea of the type apart from the fact that it feels warm when running.
http://www.vintage-radio.net/forum/show ... hp?t=89794
http://forum.radios-tv.co.uk/viewtopic.php?f=15&t=3439
Perhaps if a keen moderator wants to tidy up we could bump the original thread for the counter with all the extra replies about the counter here.

[Cathovisor]

Perhaps if a keen moderator wants to tidy up we could bump the original thread for the counter with all the extra replies about the counter here.

Done

[Cathovisor]

How on earth do you do calculate a reciprocal without a CPU or a decent size PROM to make a look-up table.[...]

It may also simplify things if you have a very restricted range of frequencies to cover, as in a mains frequency meter. That may take it into diode array territory.

That Dawe counter must have been expensive.

It doesn't look it - but here's the patent.
http://worldwide.espacenet.com/publicat ... &KC=A&ND=5

The display is three large end-viewed Nixies

[Refugee]

Cheers for the tidy up
The Daws unit appears to be pretty close to what I was expecting except for the counter being additive only with a count that starts below what is expected frequency stopping when the unknown frequency period is reached with the indicators wired as a user display only.
I have chosen a LW radio to do the radio4 beat test with while we have some fun checking out the crystal oven. It has to be on the web to fit in with the forum
It will be tomorrow now as there were a few household distractions today.

The original photos show the air filter that had turned to dust and the only other work was to replace a capacitor that felt warm to the touch and the new one still felt warm but somewhat less so.
Well with sheets of 74 series logic in there it did not startle me in any way.
I used a Wilco vacuum cleaner motor filter that is sadly now discontinued as a replacement for the dust.

[Cathovisor]

In presentation, it reminds me of a HP counter bought from a Radiophile event in Shifnal some twenty-plus years ago. There's something appealing about counters full of Nixie tubes... I also have an Advance timer/counter full of Nixies.

Day to day counter is a TTi PFM1300.

[Refugee]

Nixie tube kit is always nice and also well built.
I also have a little battery and mains LED with wall wart counter branded Optoelectronics INC that I bought new around 1980. I had to save up for it. The rechargeable batteries rotted long ago but thankfully they were mounted on long stand offs and did no damage.

[Cathovisor]

Nixie tube kit is always nice and also well built.

I think the reality was it was built at a time when the engineering considerations came first and the engineering department then said to the accountants "this is what it costs to make, now it's up to you to sell it." I have some early 1960s HP test equipment and the standard is utterly faultless.

It now seems to be the other way around

A well-known figure in the world of vintage television once said to me that sometimes it felt like Marconi were a metalworking company that occasionally fitted electronics to their products

[Refugee]

Marconi kit is well built too with those "picture frame" front panel castings to protect the knobs when the instrument is moved. They are heavy so a little knock would crack the knobs easily.
Modern stuff is so cheap as chips that you just replace it if it gets a little scratch on it.

[Refugee]

I have now done a calibration check on the crystal on both of my counters.
I plugged the counter into the sig gen and set it to 198Khz and switched on the oldest internet radio I could find and gently rocked the frequency control on the generator until I could hear it modulating the AGC at the difference between 198Khz and the indicated frequency on the counter.
It is spot on but still I did a triple check.
So with transistor lineups from three nations.
Internes radio Japan TR82 for Mullard and Pigmy for ATES (now part of SGS Thompson France).
All tests were consistent