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

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On Thu, 04 Jan 2007 20:40:24 GMT, nobody@xxxxxxxxxxxx (Dave Houston) wrote
in message  <459d60f2.25084765@xxxxxxxxxxxxx>:

>"Jeff Volp" <JeffVolp@xxxxxxx> wrote:
>
>>"Marc_F_Hult" <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote in message
>>news:ghfqp257tr59qhe472qjbdenvksr4tkouj@xxxxxxxxxx
>>
>>> So a one-off X-10 RF signal strength sniffer/meter could indeed be
>>> constructed *without* programming for ~$15 or so (depending in part on
>>>what is already in your electronic junk box).
>>
>>While I agree a DIY version without a custom PCB or case can be put
>>together cheaply, I don't know of any electronic distributers that offer
>>free shipping.  That can become a significant factor when buying from
>>multiple sources.
>>
>>I had used a receiver some time ago that included an analog RSSI output
>>(received signal strength indicator).  That was useful to determine how
>>to dynamically configure the RF network for best performance.  The RSSI
>>output could be monitored by a VOM.  However, because of the pulsed
>>nature of X10 signals, some type of filter or peak detector may still be
>>needed.
>
>Jeff,
>
>Don't get misled. I've been using these receivers for several years,
>buying the RWS-374-2 direct from Wenshing in Taiwan until they raised
>their price beyond where it made sense. The Radiotronix receiver is made
>by another Taiwan company.
>
>     http://www.wenshing.com.tw/DATA/RF-MODULE/RWS-374-2.pdf
>
>The Wenshing datasheet has always labeled the two outputs "linear" and
>"digital". I see they have recently started silk-screening "RSSI", on the
>module itself, for the "linear" output but this is misleading as it
>requires further processing to use it as RSSI.
>
>In the absence of a signal, there's a continuous noise output on both the
>"linear" and "digital" pins so just measuring the voltage tells you
>nothing. When I tried a VOM yesterday, there was a negligible difference
>between signal and no signal which is why I then wrote that a PIC is
needed.
>
>A PIC is required to separate the wheat from the chaff.


Received Signal Strength Indicator "RSSI output is often a DC analog level"

http://www.maxim-ic.com/glossary/index.cfm/Ac/V/ID/252/Tm/RSSI

which sets an expectation consistent with the spec sheet I cited earlier
and is consistent with what Dave previously wrote in this newsgroup in
Message-ID: <42b57ce5.82022622@xxxxxxxxxxxxx> that:

	 "Also, the specific RF receiver I mentioned has a linear output
	 which can be used with an ADC input as an RSSI indicator.
	The RSSI of random noise will be low in comparison to a signal
	(as long as the signal is stronger than the random noise. You
	can use it as a rough Carrier Detect indicator."

but not with a plain reading of "there was a negligible difference between
signal and no signal" which is what Dave writes today.

But no matter ;-)

... Marc
Marc_F_Hult
www.ECOntrol.org