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Test instrument help? RF voltmeter Sadelco 7600




 
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Author Topic: Test instrument help? RF voltmeter Sadelco 7600  (Read 608 times)
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Patrick J. / KD5OEI
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« on: August 03, 2020, 10:03:12 PM »


This Sadelco 7600 signal level meter was given to me from an estate, and was labeled as working as of 7-20-2000. I know who did this and that they had also replaced the NiCd cells at the time.

The AC adapter is missing, I can't find any data on it, and the cells are of course dead now, or most likely ruined from storage.

It looks like it covers 54MHz to 800MHz? continuously in 4 bands. from TV CH 2-86 according to the dial.  (86?? -thought 83 was the top.)

I'm looking for the details on the AC adapter or even the manual so I can get it working, power it up,  and check my antenna signal strength on a couple of antennas I use to monitor interesting signals.

I know it's an AM board but I have no where else to ask about test equipment where people might have experience with this kind of thing.


* sadelco 7600 signal level meter.jpg (315.18 KB, 1600x1200 - viewed 86 times.)
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Radio Candelstein - Flagship Station of the NRK Radio Network.
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« Reply #1 on: August 04, 2020, 08:06:07 PM »

Keep in mind that itís a very narrow band field strength meter that is designed to measure a CW carrier or Video carrier of an NTSC television channel. It will not accurately measure an 8VSB digital broadcast channel.

As many Sadelcos as Iíve had over the years I donít recall the voltage of the charger. Itís been way too many years. My guess would be either 9V or 12V. Is the battery pack not marked? Most of those had tubular packs made up of cascaded batteries. You might be able to count them then multiply times 1.2.
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« Reply #2 on: August 04, 2020, 08:37:06 PM »

TEquipment lists the 7600/U battery pack as 11 x Sub-C nicads for a total of 13.2V. Most of the 7600 predecessors allowed you to substitute the battery pack with 12 AA batteries. I would try it with 12V. If it doesnít appear to be reading correctly then you can bump the voltage a bit.
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« Reply #3 on: August 04, 2020, 10:14:51 PM »

All the Sadelcos I had ran on 18 volts.  Four 9 volt batteries series parallel.  I may still have some info on these meters.  I'll try to find it and get back.  Even my Blonder Tongue field strength meter runs on 18 volts.

I used the meters to measure digital TV signals.  You can peak up your antenna direction using the meter.

Fred
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Patrick J. / KD5OEI
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« Reply #4 on: August 06, 2020, 09:49:54 AM »

All the Sadelcos I had ran on 18 volts.  Four 9 volt batteries series parallel.  I may still have some info on these meters.  I'll try to find it and get back.  Even my Blonder Tongue field strength meter runs on 18 volts.

I used the meters to measure digital TV signals.  You can peak up your antenna direction using the meter.

Fred

The battery pack, I forgot to mention it is 12 cells, if they are @1.2V then it would be 14.4V. It's 2 wires, so there's no thermistor. I can see it using a bit more since NiCd has a range up to what 1.25V or 1.3V max? It's not marked, it's just a board with the cells, wrapped up in nasty old electrical tape.

There is maybe what looks like a charging circuit with a transistor but I can't really tell. I just want to be careful.

Most likely I will want to use it with external power since I don't have the opportunity to do a lot of tests of this kind, and NiCd tend to go bad when left for months at a time.
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Radio Candelstein - Flagship Station of the NRK Radio Network.
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« Reply #5 on: August 06, 2020, 12:50:46 PM »

The meters have a regulator in them.  The circuits probably run on 12 volts.  The twin 9 volt batteries would last years and I used my meters nearly every day but for only short periods of time.  It was only when the batteries got weak that the meter would not measure accurately.  The meter should have a battery TEST.

I would try charging the NiCad pack with 15-18 volts, see if they hold a charge.

Fred
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« Reply #6 on: August 08, 2020, 12:42:12 AM »

Thanks much! I'll say how it went once I find a suitable AC adapter.
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