See below;
On 4/23/06 at 4:58 PM Dr. David Kirkby wrote:
>Will Matney wrote:
>> All,
>>
>
>Hi,
>I tried mailing you off-list, but the message bounced with :
>
>Remote host said: 550 Email from your Email Service Provider is
>currently blocked by Verizon Online's anti-spam system.
>
Hmm, never had that problem before. That would be with the ISP as you say, not
on my end as the spam filter in my e-mail app just moves spam to the
wastebasket folder to be deleted.
>So it seems your ISP does not like my ISP!
>
>> I wanted to let everyone know I recently finished buying almost
>everything to set up a calibration lab for hams and others. The price of
>calibration is too high for anyone to stand,
>
>It's also debatable how many need acurately calibrated test equipment
>for amateur use. With the exception of frequency, I'm not sure what else
> needs to be accurately calibrated. Frequency is the one thing that is
>quite easy & cheap to do at home anyway.
>
You would be suprised. I primarily set this up for some guys on ebay who are
into selling used test equipment. Several have asked about calibration and
repair so I set it up.
>> so I decided to start this and offer prices that well all could afford.
>Right now, I will have the following equipment available to use by the end
>of next month;
>>
>> Fluke 760A volt/amp/ohm calibrator which was just calibrated by the
>military metcal lab.
>>
>> Calibration Standards DC-110BR precision voltage calibrator that shows
>the difference between the meter under test and the standard (differential
>test) allowing you to set the meter dead on with the standard.
>
>
>> ESI 230B Guarded Resistance Bridge which will be converted to a
>precision resistance standard of 1 Ohm - 12 Giga Ohm at 0.01% tolerance.
>>
>> A custom frequency standard which is under construction using a HP
>10544A high stability oven oscillator that was just checked for aging and
>calibrated with a cesium frequency standard. I will be building a custom
>rubidium standard within the next 2-3 months to go with it. Also, I am
>working on another OCXO standard using a Stanford Research Systems, low
>phase noise, 10 MHz oven oscillator.
>
>I don't feel a free-running OCXO is much of a frequency "standard" in
>this day and age. You would really need to lock that to a GPS or similar
>to consider it a worthwhile frequency standard in my opinion.
>
It will be good as gold for at least a year until I get my rubidium standard
finished. I also looked at those kits to build a GPS standard and may do one, I
don't know.
>There's quite a bit of data on oscillators like that (particularly HP
>10811A) on leapsecond.com. As you will see, they differ a lot even on
>the same model.
>
>It is not too hard to lock an OCXO to a GPS receiver. Either use
>something like the 'Brook Shera' design (originally in QST I think), or
>buy something like a Stanford PRS-10 rubidium and lock the rubidium to
>the GPS.
>
>And what do you mean by "just checked for aging"? Note aging rate
>changes if the oscillator is switched on/off, so people into frequency
>standards run them 24/7 with battery backup in case of mains failure.
>
Aging was checked for a week to make sure it didn't drift over at least that
time as some of the older ones begin to have that problem. That is what the cal
lab guy told me I bought it from. It has something to do with the oven I think,
not the crystal. The frequency was then checked and calibrated to their NIST
traceable cesium standard.
>> L and C standards are all I haven't started to purchase yet as there's
>not too many who have LCR meters to calibrate. I will eventually have
>these in the future. I am also looking at making some standards for L, C,
>and R to sell which will be a lot cheaper than the ones available. I have
>the supplies to buy the components from, it's just a matter of starting
>them.
>
>0.01% resistors are pretty cheap. I use them in projects some times when
>I want accuracy. Converting from pounds to USD, I reckon they are about
>$7. Not exactly expensive and quite within the range of a ham to own a
>few. Hence I somewhat doubt there is much point selling resistance
>standards.
>
The 0.01% is a guaranteed value of resistors and standards, Most standards
though are actually closer than that by a good size amount because they have
been calibrated against a NIST traceable standard. Most standard resistors were
hand wound at one time. General Radio and ESI both had resistor departments.
The 0.01% resistors off the shelf can vary up to that percentage. At 10k ohms,
that's +/- 100 ohms. A standard that has been calibrated is actually much
closer, within 1 to 5 ohms at 10k ohms from what I have seen (9995, etc. 0r
0.0005%). A 5-1/2 digit DMM will read that easily. Over 99.9k ohms, you need to
go on up to a 6-1/2 or 7-1/2 digits to see the smaller scale. A calibrated
standard though will hold the guaranteed value over the entire resistance it's
capable of. If you placed in series a bunch of off the shelf resistors together
at 0.01%, I doubt you could get that close.
>> If any are interested, please contact me off the list.
>>
>> Best,
>>
>> Will
>
>Good luck, but I somehow think you will have a hard time convincing
>others to pay for calibration, even if it quite cheap.
>
>
>
>
>
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Best,
Will
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