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Sencore CB42 CB Analyzer calibration?

Eastside

Well-Known Member
Apr 29, 2011
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My CB42 rf generator is off freq a little....how do you get it on freq?
 
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I need a bnc to bnc cable to connect the cb42 to my freq counter.....lost the other one I had....
 
Off frequency

My CB42 rf generator is off freq a little....how do you get it on freq?

Borrow or rent a freshly calibrated frequency counter and use it as a transfer standard. Align the CB42 according to your service manual and be tight on the adjustments for frequency. If the specification is plus or minus 50 Hz tune it to less than 5 Hz of the center specification if you can. Some adjustments can get twitchy when you are real close to set point.

Good Luck,
Tallman
 
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Tallman gave some decent advise....
First you need to determine if the Sencor's counter is off or the generator is off frequency. Both can be. The counter adjustment is C604.

You really need a frequency standard. This is something that is a known standard and is always on frequency. If you have a shortwave reeiver then you have a standard. Just tune to 10.000 MHz to WWV coordinated Universal Time. You can use google or Youtube to learn how to zero beat your receiver against a counter to set up a frequency standard. I am not going to go into it in detail and re-invent the wheel since there is tons of info on the web about it. Once you have a known standard you can inject the signal from the generator into the external counter to check the gens output frequency.

There are a lot of things in the CB 42 to cause it to go off frequency. Specially the 5 volt rail. This rail needs to be at 5 volts. Not below or over. Strange things can happen when it is. Ripple on the 10 volt rail needs to be less the 30 mV so start there since the 5 volt rail is a by-product of the 10 volt rail.The power supply uses a 2N3055 as a 10 volt regulator and then a TIP 29 as a 5 volt regulator. The 10 volt regular must be set to 10 volts =/- 0.1 volt. Age and heat kills the power supply quite often.

Capacitors and solder joints are another big issue in the CB 42 due to age.

I did not see if where you said you had the manual or not but the info you need is in it along with calibration.You also need the 4 17x 23 fold out's.

Good luck
 
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Interesting picture of cb42

You know most frequency counters have a 10.000 MHz outlet on the back of the cabinet. I have a cheap frequency counter that has the 10.000 MHz outlet on the back. I opened it up just to inspect it since it was a eBay purchase. The 10 MHz is a top quality reference oscillator in a temperature controlled oven. I took it to a local calibration lab and had it all checked out. No adjustment was required since it met the manufacturer specifications.
I asked if there was any error in the read out and they said it was less than .5 Hz difference. (More warm up time?)
Close enough for any standard in my book.
If you use any item for a transfer standard you have to have calibrated twice as often as the items you calibrate. I guess that's a mil-spec thing.
I did a lot of calibration work in the military and it seemed like every eight weeks we took my station apart and down to the base calibration shop.

I have the B&K precision 1040 and the 2040 units(Calibrated) and like that setup. I'm still making cables to hook it all together.
 
Last edited:
You know most frequency counters have a 10.000 MHz outlet on the back of the cabinet. I have a cheap frequency counter that has the 10.000 MHz outlet on the back. I opened it up just to inspect it since it was a eBay purchase. The 10 MHz is a top quality reference oscillator in a temperature controlled oven.

Interestied in knowing what counter you have. I been looking myself for one wih a 10 mhz port. All my counters are a bit old. B7K 1801, Heathkit IM 2410. I have a Motorola Auto tune deviation/ frequency counter. Most of the time with commercial and Ham gear I use my IRF 1200s and my HP 8640B.

I have the B&K precision 1040 and the 2040 units(Calibrated) and like that setup. I'm still making cables to hook it all together.

Great setup for CB servicing. I have 3 2040's here in the shop.
 
You know most frequency counters have a 10.000 MHz outlet on the back of the cabinet. I have a cheap frequency counter that has the 10.000 MHz outlet on the back. I opened it up just to inspect it since it was a eBay purchase. The 10 MHz is a top quality reference oscillator in a temperature controlled oven. I took it to a local calibration lab and had it all checked out. No adjustment was required since it met the manufacturer specifications.
I asked if there was any error in the read out and they said it was less than .5 Hz difference. (More warm up time?)
Close enough for any standard in my book.
If you use any item for a transfer standard you have to have calibrated twice as often as the items you calibrate. I guess that's a mil-spec thing.
I did a lot of calibration work in the military and it seemed like every eight weeks we took my station apart and down to the base calibration shop.

I have the B&K precision 1040 and the 2040 units(Calibrated) and like that setup. I'm still making cables to hook it all together.

The cb42 came with most of its original test cables....the only one missing is the one I need....bnc to bnc.....so I can plug the cb42 rf generator into my bk 1801 freq counter.
 

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