Re: X-10 RF meter (was Re: XTB II Review)

[nobody@xxxxxxxxxxxx (Dave Houston)]

"Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:

>"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
>news:459b1d21.9944265@xxxxxxxxxxxxxxxx
>> "Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:
>>
>> >>
>http://www.rfsolutions.co.uk/acatalog/RF_Signal_Strength_Meter.html
>> >
>> >Only 49 pounds for thre 315MHz units.  Not sure what that comes to in
>> >American money but I suspect it's outside my price range again.  I've
>found
>> >some used meters on Ebay for cheap (under $50) but with very little
>> >documentation it's hard to tell if they work in the proper frequency
>range.
>>
>> It might be possible to build one for under $15 but I'm not sure how it
>> might be affected by being handheld while searching for a transmitter.
>>
>> The RF receiver modules that I specified the BX24-AHT and roZetta have a
>> linear output pin which can be used as a signal strength indicator. You
>> would want an inefficient antenna, a battery and you might get buy with a
>> multimeter as the readout. More likely you would need a PIC and an LED or
>> some type of visual indicator.
>
>I googled some more and found this after plugging in the specs of the UK
>model you found:
>
>http://www.elecdesign.com/Articles/ArticleID/7573/7573.html
>
>"Priced at only $80, the portable RF Meter is a low-cost signal-strength
>measurement tool for designers of RF radio systems. Two models are available
>to detect signals at 315 MHz or 433.2 MHz. Radio-transmitter signal strength
>is indicated by a 10-digit LED display with a one-second peak hold function
>to simplify measurement readings. The unit operates from a 9-V flat battery,
>and it has low-battery indication and an auto-shutoff feature that activates
>after 60 seconds of no operation. RF sensitivity is -110 dBm. The IF
>bandwidth is 600 kHz. Housed in a 4.33- by 2.56- by 0.94-in. ABS enclosure,
>it operates from 0°C to 60°C."
>
>I can live with $80.  The only problem is the above turns out to be an older
>article.
>
>The vendor site:
>
>http://www.okwelectronics.com/products/radio/rfmeter.html
>
>Lists it currently at $114.  If this site that tested the output of various
>X-10 transmitters was right,
>
>http://billfernandez.com/bfd2/hobbies/home_automation/X10_xmit_strength.txt
>
>there's no guarantee that this meter will even be able to detect X-10
>transmissions at more than a few feet.  That may or not be enough to work as
>a stuck key finder.  I guess I'll keep looking - someone might have had a
>pallet load of them made in China and are selling them for less.  If I
>*knew* it would find stuck transmitters, I'd make the purchase but $114 for
>what could turn out to be totally useless gear is not an attractive
>prospect.
>
>Side note to Jeff: "nevermind!"  (-:

The key spec is "RF sensitivity" which is -110dBm (typical). Off the top of
my head, the small receiver modules I mentioned are -105dBm so the
sensitivity is OK. However, I suspect these are European made so they may
not be tunable to 310MHz. In the past, OKW has responded knowledgeably to
technical questions like this so you might ask them whether it might be
tuned to 310MHz.

I would put no faith in the results posted by Señor Fernandez. There are so
many uncontrolled variables that his tests are meaningless.

I will test whether the small superregenerative receivers will work with a
multimeter as readout. If so, it's a cheap way to fill what should be a
rather rare need. I have a handful of boards with coin cell battery holders
(Two CR2032 or BR2032) that might work for this.

http://davehouston.net
http://tech.groups.yahoo.com/group/roZetta/
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