[OT again] Signal Strength

[X-post to uk.radio.amateur where it may be more on topic]

Hi,

still wildly off down the radio aerial route.

My neighbour was talking about improving his signal because he got a lot of
background hiss and bubble/crackle stuff on his FM.

Picked up a dipole for him, then went up into the loft to see what he had at
the moment.

It wasn't a Yagi it was a venerable YAGI!

Four elements before the one where the co-ax connects, and a big vertical
three element spread behind on the reflector.

Very old aerial (more green than silver) but if Yagis are high gain then
this must be capable of picking up a strong signal if it is working
correctly.

Laid across loft support beams (chest high and running about half the length
of the loft) and the elements are horizontal.

It is pointing more or less due west, where the signal should be coming
from.

The signal strength reading on his Hi-Fi tuner was showing 50-55dB.

So:

(1) Is this reading a reasonable one for a Yagi? What dB constitutes a good
strong signal?

(2) Could the aerial be too powerful - picking up all sorts of unwanted
noise as well?

(3) Could the age and high state of corrosion mean that it is largely
ineffective - perhaps needing stripping down and cleaning up to ensure
electrical continuity throughout the aerial?

I felt a bit like a Kia salesman suddenly realising he had been asked to
replace a Rolls Royce :-)

Cheers
Dave R

--

"David W.E. Roberts" wrote in message
...

The signal strength reading on his Hi-Fi tuner was showing 50-55dB.

Pretty meaningless, unless you know what the meter is calibrated against.
Assuming it is calibrated.

Many a quality communications receiver lacks a good S meter, so don't rely
on a HiFi one!

So:

(1) Is this reading a reasonable one for a Yagi? What dB constitutes a
good
strong signal?

See above.

(2) Could the aerial be too powerful - picking up all sorts of unwanted
noise as well?

No.

(3) Could the age and high state of corrosion mean that it is largely
ineffective - perhaps needing stripping down and cleaning up to ensure
electrical continuity throughout the aerial?

Possibly (even probably) the cause. Got to be worth a try. Don't worry
about the elements- just make sure the connections and cable are good. Has
the cable been damaged? Has it got water in it (I've seen water run out of
coax in the past!).

If you are in a strong signal area then indoors is OK for an antenna but
outdoors in more likely to succeed.

I felt a bit like a Kia salesman suddenly realising he had been asked to
replace a Rolls Royce :-)


Rolls Royces are OK, but I wouldn't want another one.

--
Brian Reay
www.g8osn.org.uk
www.amateurradiotraining.org.uk
FP#898

"Brian Reay" wrote in message
...
"David W.E. Roberts" wrote in message
...



Rolls Royces are OK, but I wouldn't want another one.


My sisters has been keyed about five times, so these days it stays in her
garage almost permanently.

Regards
tox

Sounds like a cable fault.
Put an ohm meter across the terminals at the bottom of the cable. It
should read about 2ohm, assuming that the aerial has a conventional
folded dipole. Disconnect the aerial and recheck. Reading should now be
infinity.
Simple logic will now tell you whether or not to replace the cable.
Bill

On Mon, 10 Jan 2005 17:28:15 -0000, "David W.E. Roberts"
wrote:

[X-post to uk.radio.amateur where it may be more on topic]

Hi,

still wildly off down the radio aerial route.

My neighbour was talking about improving his signal because he got a lot of
background hiss and bubble/crackle stuff on his FM.

Picked up a dipole for him, then went up into the loft to see what he had at
the moment.

It wasn't a Yagi it was a venerable YAGI!

Four elements before the one where the co-ax connects, and a big vertical
three element spread behind on the reflector.

Very old aerial (more green than silver) but if Yagis are high gain then
this must be capable of picking up a strong signal if it is working
correctly.

Laid across loft support beams (chest high and running about half the length
of the loft) and the elements are horizontal.

It is pointing more or less due west, where the signal should be coming
from.

The signal strength reading on his Hi-Fi tuner was showing 50-55dB.

So:

(1) Is this reading a reasonable one for a Yagi? What dB constitutes a good
strong signal?

(2) Could the aerial be too powerful - picking up all sorts of unwanted
noise as well?

(3) Could the age and high state of corrosion mean that it is largely
ineffective - perhaps needing stripping down and cleaning up to ensure
electrical continuity throughout the aerial?

I felt a bit like a Kia salesman suddenly realising he had been asked to
replace a Rolls Royce :-)

Cheers
Dave R

Old FM aerials are best replaced, mainly for the reason that most of
them have poor performance much above 102Mhz. A new dipole will give
more signal strength at higher frequencies than the biggest ancient FM
aerial. Old FM aerial = most aerials before 1990.

Marky P.

On Mon, 10 Jan 2005 17:28:15 -0000, "David W.E. Roberts" wrote:

The signal strength reading on his Hi-Fi tuner was showing 50-55dB.

Much more than adequate. My TV is 65dB which I call VERY good.

So:

(1) Is this reading a reasonable one for a Yagi? What dB constitutes a good
strong signal?

65dB !

(2) Could the aerial be too powerful - picking up all sorts of unwanted
noise as well?

No.

(3) Could the age and high state of corrosion mean that it is largely
ineffective - perhaps needing stripping down and cleaning up to ensure
electrical continuity throughout the aerial?

More than likely. Check the coax also for breaks, shorts, corrosion,
damp (unlikely with a loft installation), check connectors at the tuner
end as well; Belling-Lee plugs should be soldered onto the inner
conductor, not just as a push fit.


Jock.

--

"The graveyards are full of indispensable men."
- Charles de Gaulle (1890-1970)

On Mon, 10 Jan 2005 17:39:06 -0000, "Brian Reay"
wrote:

Rolls Royces are OK, but I wouldn't want another one.

Typical Brian. Poser!

(Shouldn't that be another two?)


Jock.

--

"The graveyards are full of indispensable men."
- Charles de Gaulle (1890-1970)

The signal strength reading on his Hi-Fi tuner was showing 50-55dB.


Much more than adequate. My TV is 65dB which I call VERY good.


So:

(1) Is this reading a reasonable one for a Yagi? What dB constitutes a
good
strong signal?



65dB !

dB is a ratio, not an amount. dB referred to what? 65dBuV is a
reasonable TV signal. 65dBmV is enough to feed a very large number of
flats.
As a matter of interest, some FM tuners claim that they will work OK on
10dBuV. The realistic lower level is probably more like 25dBuV if you
want to actually listen to the programme. A reasonable signal would be
about 55dbuV. 70dBuV is really solid, with good immunity to
interference.

Bill

The L.I.A.R. and his downright lying, perhaps?

"Brian Reay" wrote in message
...
Rolls Royces are OK, but I wouldn't want another one.

snip
Rolls Royces are OK, but I wouldn't want another one.


Brian, I cant fault you on your radio knowledge but try and tone down the
posing om

deBaser