52 dB any good?
 

"Chris Isbell" wrote in message
...
On Fri, 28 Apr 2006 06:32:16 +0100, Stewart Pinkerton
wrote:

The trouble here of course is that Keith is obsessed with
measurements. What really matters is how the signal *sounds*! Is it
clean, with no multipath distortion and no noticeable hiss? Then you
have enough signal strength. :-)

Yes, up to a point.

I noticed a matterable improvement going from an adequate to a very
good aerial signal. This observation was not validated using a
double-blind level matched test, so it may be a consequence of the
effort expended optimising the aerial, or possibly down to reducing
multipath. ;-)

It would be interesting to hear from those who know about RF whether
there might be an engineering basis for this observation.

--
Chris Isbell
Southampton, UK

An "adequate" signal presumably is one that produces a pleasing result, that
is, an adequate S/N ratio and low impulsive interference due to the receiver
going well into limiting. With a "very good" signal, the S/N ration will
reach the receiver's maximum, which could be 10-15dB better than previously
achieved with an "adequate" signal. Also, the receiver will be much further
into limiting, and consequently impulsive interference will be reduced
further still. These will produce a feeling that the reception is a lot
better than before, as noise will be considerably lower, and the reception
will feel more "stable" due to lower impulsive interference. If you had
carried out measurements before and after, you could have quantified these
impressions, but nevertheless, there is a sound engineering reason for the
improvements you noticed subjectively.

S.

52 dB any good?
 

In article , Serge Auckland
wrote:

"Chris Isbell" wrote in message
...


I noticed a matterable improvement going from an adequate to a very
good aerial signal. This observation was not validated using a
double-blind level matched test, so it may be a consequence of the
effort expended optimising the aerial, or possibly down to reducing
multipath. ;-)

If the 'optimised' antenna has a more directional pattern, then I'd assume
that a reduction in multipath might be a reason for a change. A higher
signal level may reduce the tuner's sensitivity to multipath.


It would be interesting to hear from those who know about RF whether
there might be an engineering basis for this observation.

-- Chris Isbell Southampton, UK

An "adequate" signal presumably is one that produces a pleasing result,
that is, an adequate S/N ratio and low impulsive interference due to
the receiver going well into limiting. With a "very good" signal, the
S/N ration will reach the receiver's maximum, which could be 10-15dB
better than previously achieved with an "adequate" signal. Also, the
receiver will be much further into limiting, and consequently impulsive
interference will be reduced further still.

I'd agree with the above. In addition, you might find that the precise
shape of the bandwidth filtering and discriminator curve alter as the
signal level rises. Hence the level of distortion may alter.

No idea if any of the above *did* occur and were the reason(s) for what you
report, though. :-)

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

52 dB any good?
 

"Stewart Pinkerton" wrote in message
...
On Thu, 27 Apr 2006 17:49:12 +0100, Chris Isbell
wrote:

On Thu, 27 Apr 2006 13:44:00 +0100, "Serge Auckland"
wrote:

If the signal strength is -52dBm into 75 ohms, then that's a voltage
level
of 687uV which is a bit low.

My Sony ST-S311 tuner gives the signal strength in dBf, which I
believe is relative to one femtowatt (10E-15W). If my calculations are
correct, then 52dBf would equate to 109uV, which is not very good at
all.

The OP's manual should hopefully define the measurement units used.

The trouble here of course is that Keith is obsessed with
measurements. What really matters is how the signal *sounds*! Is it
clean, with no multipath distortion and no noticeable hiss? Then you
have enough signal strength. :-)



You couldn't be more wrong - I almost *never* measure anything and only go
'by ear' in the final analysis. The only reason I asked is that I discovered
if you hold the Mode switch (Stereo/Mono) down for a few seconds it displays
the 'signal strength' and, no, before anybody points it out - I don't
trust/believe it is necessarily anything like accurate or meaningful.

The tuner sounds fine, the numbers are academic (it only reads 50 dB this
morning)....

52 dB any good?
 

"Oddjob" wrote in message
...
"Keith G" wrote in message
...

My new/old Technics tuner advises me my FM signal strength is 52 dB - is
that good, bad or just plain ugly, given the palaver with the aerial
installation a while back?


Keith, I don't believe that Technics ever made a decent FM tuner!

I would say that Kenwood, Pioneer, Sansui and Yamaha are all better
bets...



I have the Technics and a Denon now - they sound the same to me.

I doubt I could discern differences between the makes...??

52 dB any good?
 

On Sat, 29 Apr 2006 12:00:16 +0100, "Keith G"
wrote:

The tuner sounds fine, the numbers are academic (it only reads 50 dB this
morning)....

I thought it was marginal on R3?

52 dB any good?
 

In article , Keith G
writes

My new/old Technics tuner advises me my FM signal strength is 52 dB - is
that good, bad or just plain ugly, given the palaver with the aerial
installation a while back?


That type of signal meter is "intended" only for a relative use not absolute
as such. Course it could be calibrated against a "known" but they very rarely
are accurate.

That said assuming that the BBC have use an ommni pattern at Peterbourgh and
that pattern isn't quite ommni as they will be using either dipole arrays on
each side of the mast face, or as the following example shows Spearheads on a
triangular mast!.


http://tx.mb21.co.uk/gallery/wrotham/mixedpol.asp

But lets assume that they are still using the same output power 20 kW per
service so at Keithy towers thats predicted to be a level of 68.7 dB/uV per
metre or -45.7 dBm which would be more than adequate for stereo reception
assuming that the mean aerial TX aerial height is 145 MAGL and that Keith's RX
aerial is say 8 MAGL which is a "line of sight" path!, and assuming that he's
finally got a four element and assuming that is on the correct bearing and
that the downlead is of CT 100 or similar then yep, thats fine.

So no problemo. Just enjoy the musicke:))

--
Tony Sayer