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 Post subject: HP 436 power meter
PostPosted: Jan Thu 12, 2017 3:54 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1064
Location: Tucson AZ
I've got the main unit, but need the cable and power head.

Question is whether it's worth investing in the power head and cable.

I bought one of these a while back and it's pretty accurate. Put it in this case with the freq counter.

http://www.ebay.com/itm/NEW-0-500Mhz-RF-Power-Meter-RF-power-Measurement-80-10-dBm-/262563218073?hash=item3d21fcc299:g:6Z0AAOSwZVlXo20g

All I am doing is occasional FM alignments.


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Last edited by xwarp on Jan Thu 12, 2017 4:09 am, edited 1 time in total.
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 Post subject: Re: HP 436 power meter
PostPosted: Jan Thu 12, 2017 4:07 am 
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Location: Annapolis, MD
How would that be used for FM alignment?

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 Post subject: Re: HP 436 power meter
PostPosted: Jan Thu 12, 2017 4:10 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Tucson AZ
When adjusting the output power for the IF and rf signals of the signal generator?


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 Post subject: Re: HP 436 power meter
PostPosted: Jan Thu 12, 2017 4:13 am 
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xwarp wrote:
When adjusting the output power for the IF and rf signals of the signal generator?

typically not necessary. Alignment is generally done using the lowest signal level that gives a usable output. In effect, the receiver is the power meter.

One benefit might be comparing different sets for sensitivity.

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 Post subject: Re: HP 436 power meter
PostPosted: Jan Thu 12, 2017 4:21 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1064
Location: Tucson AZ
While it may not be necessary, the question remains of whether the cost of a replacement power head and cable is worth it.


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 Post subject: Re: HP 436 power meter
PostPosted: Jan Thu 12, 2017 5:01 am 
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Joined: Jun Fri 19, 2009 6:34 pm
Posts: 7120
Location: Long Island
Figure anywhere from $75 to $100 for a cable that isn't beat and intermittent, and anywhere from $200 to $600 for a sensor that still works. Don't even consider a sensor that hasn't been tested by somebody who knows what they are doing, or doesn't come with a right-of-return. RF power meter sensors are easily damaged by feeding too much power into them and once that happens, repairs are not cost effective. You don't want to end up with somebody else's mistake! Damaged sensors may still appear to work when connected to a meter, but sensitivity and accuracy won't be where they should be.

As for use in FM receiver alignments, it seems rather pointless. A power meter has to operate on a known impedance (e.g. 50 ohms) to give useful readings; this impedance seldom occurs in FM radios of the entertainment variety. Also, there is usually a certain minimum level such as -50 dBm below which the sensor simply doesn't read, and that level may still be too high for direct connection to an RF or IF stage in a receiver. One can always measure a higher level and then pad it down, but it's not clear what is being accomplished.

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