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Modulation meter
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cliffyk
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Joined: 28 Sep 2005
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Hello, my first posting here so please be gentle...

Apparently the US Government has just released a number of Boonton 8210 Modulation Meters into the surplus stream, as there seem to be 5-6 of them on eBay at any point in time. The are selling for $75 to $150 US and are rugged and accurate units--I got one for $90 US...

Make sure you get one with the "Option 01" which is substitution of the standard 15KHz low pass filter for a 30KHz filter, this will let you set the 19KHz pilot tone to 6.75KHz deviation. It is a great unit for the money, no affiliation with any of the sellers, just a satisfied customer.

It can display positive and negative peak, and average deviation; and has two ranges (each capable of displaying up to a 50% overload), 0-10KHz and 0-100KHz deviation--highly recommended and reasonable too!

I've got the instruction/calibration/service manual in a PDF file if anyone buys one of these and needs the manual (I contacted Boonton and they said they could not supply the manual, I asked if they considered it to be public domain material and they said "go for it").

Edit
2005-09-29; here's a photo of the meter in action...



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-cliff knight-
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Wed Sep 28, 2005 10:45 pm View user's profile Send private message Visit poster's website
cliffyk
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Joined: 28 Sep 2005
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Location: 87.9 to 107.9
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I got to read the operation and service manual this weekend--there's a jumper (soldered) on the AF board that permits the 750uS filter to be inserted before or after the display. Changing it from the default (before the display) configuration permits the unit to display total deviation including all frequency components of a stereo multiplex signal.

This jumper is on both the standard and "option 01" models, changing it would permit the standard model to display deviation for the 19KHz stereo pilot tone.

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Mon Oct 03, 2005 3:11 am View user's profile Send private message Visit poster's website
pcs
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Looks nice

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Mon Oct 03, 2005 10:01 am View user's profile Send private message Visit poster's website
cliffyk
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Joined: 28 Sep 2005
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Here's an update...

I finally got my Tek 496 back into the game, here's a shot of the Boonton's reading at the 2nd Bessel null (13.587 KHz input, see the insert)--as you can see the Boonton measurement is 75 KHz deviation right on the nose. I really hadn't expected that!

It is a peak reading meter though so if you get one don't worry about hitting 110-115 KHz on occasional peaks, and 90-100 KHz fairly regularly--you'll still be well within the 237 KHz PPL (it's "ballistics"aren't that fast).

The Boonton's show up on eBay rather often in the $100 US range, by modifying an internal jumper you can move the 750 uS filter to "after" the display and it will measure the deviation of the full stereo signal.



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