In article ,
says...
Pete KE9OA wrote:

When you turn up the RF gain control, you don't desense the radio, but you
do give the AGC loop more gain. Maybe this is what you meant.

Wouldn't that make it an IF GAIN control?

A while back I read a review by the ARRL of a transciver and they brought up
an interesting point. Modern receivers have enough gain to "hear" the
normal background noise, so beyond that it really does not matter.

In my environment the noise is so high that almost anything can hear it,
my R-5000 often hears S9 level background noise on 40m and nearby SW
bands. (5-10mHz).

Geoff.



Sometimes, the receiver is picking up it's own CPU hash, or display
hash. The early NRD-525's are somewhat bad on this. Later ones seem to
have partially solved it. Any hobby class radio with a fluorescent
display usually has audible hash someplace in it's tuning range.

My R5000 was hammered by the nearby country station on 1560. If you
couldn't hear images and spurs, there was a lot of hash below 7MHZ when
it was on (days only). It was hugely strong, traveling down the nearby
power lines. On most of my receivers, there would be an S-Meter reading
with no antenna connected at all. If I walked over to the receiver, it
would peg long before I touched the antenna connector. I built a couple
of AMBC killer filters from plans I found in a ham book, and it made a
huge difference. When the station redid it's grounds, after the owners
of neighboring houses started complaining that toasters, TV's, and
anything else that plugged in the wall was playing music at times.

That dropped the signal greatly here, I was able to remove the AM
killers on all my receivers except the R5000, it still had hash that
kept beat with the songs below 7MHZ, and on a few freqs I could hear the
audio in the background on AM stations.

BDK

In article , says...
S-UNIT DISCUSSIONS AT URL:

http://www.ac6v.com/sunit.htm

CL





Good page.

BDK

In article ,
"Pete KE9OA" wrote:

How do you figure that this is nonsense?

Well let's quote the the statement that I responded to OK?

In article , BDK
wrote: You can't even be sure identical
radios will have the same S-Meter readings, in most cases. The
reading is pretty meaningless, except to compare antennas, or if a
preselector is used, to adjust for max reading.

You already answered one exception to this blanket statement about
radios calibrated in an absolute scale.

Here is another exception, you can be reasonably sure that the same
model radio will have similar readings.

Typically, SWL radios would have their S-Meter calibrated at 14MHz,
so that S9 would equal 50uV. You are correct when you mention
S-Meters that are calibrated in dBm as being absolute, as long as the
system in in calibration for gain distribution, etc. Receivers that
have this function do provide for setting up the gain distribution.
Now, the mystery continues.................what exactly do you mean
by the following statement?

"The RF gain control just sets maximum sensitivity of the radio and
does not change the gain of the radio so by turning all the way down
you are at the radios published maximum sensitivity. As you turn it
up you are desensitizing the radio."

The above statement, in quotes, is a new one to me. Could be showing
my young 54 year old age. The RF gain control only sets the maximum
sensitivity of the radio when it is controlling the bias to the RF
stage in addition to the I.F. stages, and this usually isn't the
case, except for some of the older tubed equipment. Most RF gain
controls USUALLY only set the gain of the I.F. stage. This has
nothing to do with the sensitivity of the system, if we are talking
about noise figure (I realize that you didn't mention that, so I
won't put words in you mouth on this one). When you turn up the RF
gain control, you don't desense the radio, but you do give the AGC
loop more gain. Maybe this is what you meant.

Man, you are ancient.

No I pretty much meant what the user would experience using the radio.
Looking at the radio as a black box and not understanding how all the
circuits inside actually operate I described what would happen as the
RF gain control is operated with the AGC circuit on.

The perspective here is what to expect from the operation of the RF
gain control not unlike what to expect from the S-meter, which is the
subject of the thread.

--
Telamon
Ventura, California

In article ,
"Pete KE9OA" wrote:


"john" wrote in message
oups.com...

Telamon wrote:
In article ,
BDK wrote:

In article m,
says...

David wrote:
On Fri, 05 Jan 2007 02:17:32 GMT, Telamon
wrote:

In article
s.com,
"john" wrote:


An exception would be radios that have a signal strength meter in
dBm,
which is an absolute scale.

Millivolts?

actually the palstar and the drake scales are in Decibels, while the
kenwoods scale is in Db at the top and millivolts at the bottom. also
before anyone asks my rf gain is fully clockwise on both the drake
and
kenwood. the palstar doesn't have a rf gain control.



You can't even be sure identical radios will have the same S-Meter
readings, in most cases. The reading is pretty meaningless, except to
compare antennas, or if a preselector is used, to adjust for max
reading.

Nonsense.

so a stronger s-meter reading on one radio indicates the more sensitive
radio? in this case the kenwood?

No.

I would go with a big maybe.

--
Telamon
Ventura, California

In article ,
BDK wrote:

In article telamon_spamshield-2557A0.23063004012007
@newsclstr03.news.prodigy.net,
lid says...
In article .com,
"john" wrote:

Telamon wrote:
In article ,
BDK wrote:

In article m,
says...

David wrote:
On Fri, 05 Jan 2007 02:17:32 GMT, Telamon
wrote:

In article
s.com,
"john" wrote:


An exception would be radios that have a signal strength meter
in
dBm,
which is an absolute scale.

Millivolts?

actually the palstar and the drake scales are in Decibels, while
the
kenwoods scale is in Db at the top and millivolts at the bottom.
also
before anyone asks my rf gain is fully clockwise on both the drake
and
kenwood. the palstar doesn't have a rf gain control.



You can't even be sure identical radios will have the same S-Meter
readings, in most cases. The reading is pretty meaningless, except to
compare antennas, or if a preselector is used, to adjust for max
reading.

Nonsense.

--
Telamon
Ventura, California

so a stronger s-meter reading on one radio indicates the more sensitive
radio? in this case the kenwood?

It could. Like I posted earlier the readings would be comparable if the
radio has an absolute scale such as dBm instead of a relative scale.



And most SW and ham radios don't.

That's true...

--
Telamon
Ventura, California

In article ,
David wrote:

On Fri, 5 Jan 2007 10:51:03 +0000 (UTC), (Geoffrey
S. Mendelson) wrote:

Pete KE9OA wrote:

When you turn up the RF gain control, you don't desense the radio, but you
do give the AGC loop more gain. Maybe this is what you meant.

Wouldn't that make it an IF GAIN control?

A while back I read a review by the ARRL of a transciver and they brought up
an interesting point. Modern receivers have enough gain to "hear" the
normal background noise, so beyond that it really does not matter.

In my environment the noise is so high that almost anything can hear it,
my R-5000 often hears S9 level background noise on 40m and nearby SW
bands. (5-10mHz).

Geoff.
The RF gain control can be very handy for reducing noise to the point
where SSB voice comms sound extremely HiFi.

Putting the AGC on slow also helps for a similar reason.

--
Telamon
Ventura, California

In article telamon_spamshield-C9BF19.20290005012007
@newsclstr03.news.prodigy.net,
lid says...
In article ,
BDK wrote:

In article telamon_spamshield-F6523C.20501704012007
@newsclstr02.news.prodigy.com,
lid says...
In article ,
BDK wrote:

In article m,
says...

David wrote:
On Fri, 05 Jan 2007 02:17:32 GMT, Telamon
wrote:

In article .com,
"john" wrote:


An exception would be radios that have a signal strength meter in
dBm,
which is an absolute scale.

Millivolts?

actually the palstar and the drake scales are in Decibels, while the
kenwoods scale is in Db at the top and millivolts at the bottom. also
before anyone asks my rf gain is fully clockwise on both the drake and
kenwood. the palstar doesn't have a rf gain control.



You can't even be sure identical radios will have the same S-Meter
readings, in most cases. The reading is pretty meaningless, except to
compare antennas, or if a preselector is used, to adjust for max
reading.

Nonsense.



Wanna bet? In most cases, side by side, identical models have different
meter readings. Usually it's slight, but sometimes it's huge. My JRC
NRD-515 has a "tight" meter. SSB audio can be clearly heard with the
meter at the left peg. Another 515 I had here for interconnect repair
was just as sensitive as mine, but the same signal would read S-2 or 3.
Same thing has happened with Kenwood R5000's, R2000's, and JRC NRD-525s.
(The first ones had a "spastic" S-Meter, later ones were cured of this)

In "pro" radios it might be true, but in hobby receivers, it's not true
that S-meters have any real correlation with signal strength in
comparing one radio to another.

Oh come on. The same model with the same factory adjustment would have
the same reading or very close. It would be reasonable to see a small
variation but a "huge" difference would indicate a problem with one of
the radios.



Obviously, your and my idea of "tolerances" isn't what theirs is. A
whole lot of radios are aligned "just good enough", or they need
touching up due to aging after a really short time. Some just are not
right at all out of the box, and a slight adjustment works wonders. I've
seen huge differences between Icom R-71A's. Some, like the last one I
had were dead on freq, the PBT was aligned right, etc, but some I had
previously owned, and worked on weren't even close. Some of these were
brand new, and I was helping the owner install a filter or something.
when compared to a good one, it was obvious something was wrong.

Electronic Equipment Bank (EEB) sold a lot of alignments on brand new
radios, as the factories weren't doing a real good job of it. They would
turn on your brand new R71A, R5000, Yaesu FRG-8800, and let it cook for
a couple days, then align it.

Then there is the thing all the major brands of ham and SW equipment
have in common, the lack of ability to tighten screws. Most were just
snugged, and by the time the thing had ridden across the country in a
UPS or Fedex truck, gone through a few heat/cool cycles in the process,
they weren't even close to being tight anymore. Even after an EEB
alignment, the S-Meter's could still be off a little from one to the
next.


Then you have techs who forget to tighten screws in your $1000 receiver
before they ship it, and not only does the alignment get messed up, but
you are overjoyed that something wasn't broken. Yes, it happened to me
about 15 years ago. I sent my NRD-515 in for a minor problem, more an
annoyance than anything else. When it came back, it rattled, and two
screws holding the top PC board had fallen out, and the rest were so
loose they were about to fall out. I ended up checking around and
finding a good freq counter and realigned it myself. Close, but not 100%
right, I need to do it again. I also fixed the original problem that
they "couldn't duplicate". Odd, since it did it as soon as I turned it
on after I put the screws back in and tightened it all up.

The only real way to compare (without any equipment) two radios is to
hook them up to a coax switch and then to the same antenna, and switch
them back and forth to compare.

BDK

In article . com, rhf-
says...


On Jan 5, 10:10 am, BDK wrote:
In article ,
says...





Pete KE9OA wrote:

When you turn up the RF gain control, you don't desense the radio, but you
do give the AGC loop more gain. Maybe this is what you meant.

Wouldn't that make it an IF GAIN control?

A while back I read a review by the ARRL of a transciver and they brought up
an interesting point. Modern receivers have enough gain to "hear" the
normal background noise, so beyond that it really does not matter.

In my environment the noise is so high that almost anything can hear it,
my R-5000 often hears S9 level background noise on 40m and nearby SW
bands. (5-10mHz).

Geoff.Sometimes, the receiver is picking up it's own CPU hash, or display
hash. The early NRD-525's are somewhat bad on this. Later ones seem to
have partially solved it. Any hobby class radio with a fluorescent
display usually has audible hash someplace in it's tuning range.

My R5000 was hammered by the nearby country station on 1560. If you
couldn't hear images and spurs, there was a lot of hash below 7MHZ when
it was on (days only). It was hugely strong, traveling down the nearby
power lines. On most of my receivers, there would be an S-Meter reading
with no antenna connected at all. If I walked over to the receiver, it
would peg long before I touched the antenna connector. I built a couple
of AMBC killer filters from plans I found in a ham book, and it made a
huge difference. When the station redid it's grounds, after the owners
of neighboring houses started complaining that toasters, TV's, and
anything else that plugged in the wall was playing music at times.

That dropped the signal greatly here, I was able to remove the AM
killers on all my receivers except the R5000, it still had hash that
kept beat with the songs below 7MHZ, and on a few freqs I could hear the
audio in the background on AM stations.

BDK

BDK - This Receiver is so Sensitive
Why - It can hear itself !
Is not just Ad-Hype anymore ~ RHF
.

My first NRD-525 was fantastic at hearing itself with great dynamic
range, on 13 MHZ, I think it was. I did a mod that allowed me to turn
off the display to solve it. The one I have now is maybe 10% as bad as
the first one, and unless it's the middle of winter, with snow on the
ground, it's not really noticeable. One more reason to love those red
LEDS in the 515.

BDK

In article telamon_spamshield-A34E18.20182005012007
@newsclstr03.news.prodigy.net,
lid says...
In article ,
"Pete KE9OA" wrote:

How do you figure that this is nonsense?

Well let's quote the the statement that I responded to OK?

In article , BDK
wrote: You can't even be sure identical
radios will have the same S-Meter readings, in most cases. The
reading is pretty meaningless, except to compare antennas, or if a
preselector is used, to adjust for max reading.

You already answered one exception to this blanket statement about
radios calibrated in an absolute scale.

Here is another exception, you can be reasonably sure that the same
model radio will have similar readings.

You replied to two different people, the above was mine. I agree, in
theory, but it's not always true, as I explained in another post.
And yes, I'm ancient too.

BDK


Typically, SWL radios would have their S-Meter calibrated at 14MHz,
so that S9 would equal 50uV. You are correct when you mention
S-Meters that are calibrated in dBm as being absolute, as long as the
system in in calibration for gain distribution, etc. Receivers that
have this function do provide for setting up the gain distribution.
Now, the mystery continues.................what exactly do you mean
by the following statement?

"The RF gain control just sets maximum sensitivity of the radio and
does not change the gain of the radio so by turning all the way down
you are at the radios published maximum sensitivity. As you turn it
up you are desensitizing the radio."

The above statement, in quotes, is a new one to me. Could be showing
my young 54 year old age. The RF gain control only sets the maximum
sensitivity of the radio when it is controlling the bias to the RF
stage in addition to the I.F. stages, and this usually isn't the
case, except for some of the older tubed equipment. Most RF gain
controls USUALLY only set the gain of the I.F. stage. This has
nothing to do with the sensitivity of the system, if we are talking
about noise figure (I realize that you didn't mention that, so I
won't put words in you mouth on this one). When you turn up the RF
gain control, you don't desense the radio, but you do give the AGC
loop more gain. Maybe this is what you meant.

Man, you are ancient.

No I pretty much meant what the user would experience using the radio.
Looking at the radio as a black box and not understanding how all the
circuits inside actually operate I described what would happen as the
RF gain control is operated with the AGC circuit on.

The perspective here is what to expect from the operation of the RF
gain control not unlike what to expect from the S-meter, which is the
subject of the thread.

BDK ) writes:

In "pro" radios it might be true, but in hobby receivers, it's not true
that S-meters have any real correlation with signal strength in
comparing one radio to another.

Oh come on. The same model with the same factory adjustment would have
the same reading or very close. It would be reasonable to see a small
variation but a "huge" difference would indicate a problem with one of
the radios.



Obviously, your and my idea of "tolerances" isn't what theirs is. A
whole lot of radios are aligned "just good enough", or they need
touching up due to aging after a really short time.

But fundamental to all this talk about s-meters is that they never were
intended to be anything but a relative indicator. And once you have
that situation, there is little reason for the manufacturers to fuss
over them.

They are great to indicate at a glance that one station is stronger
than the other, and if you need to peak or null something they provide
a better indicator than your ears, and as I once saw suggested, they
are a great way to get a rough idea of whether your receiver is working
fine or not (just turn on the crystal calibrator when you first get the
receiver, and then record the s-meter readings on various bands. If those
start changing dramatically, then something is wrong, though it's no
indication of what might be weakening.).

Over the years, there's been lots of discussion of "how much is an
s-unit" and while some have tried to impose a value on it, there really
isn't anything to it.

Before there were actual meters attached to receivers, there were the
magic eye tubes, which had no scale at all. "You're about half open on
the magic eye tube..."

Want to give someone a better s-reading? Put up a bigger antenna, or
add a preamp ahead of the receiver. It will raise the meter reading,
but the signal as it arrives at your antenna hasn't changed one bit.


Before there were meters on receivers, there was the "RST"
system for rating signals. Readability/Signal Strength/Tone
that you'd transmit to the other guy to give an indication of
how his signal sounded at your receiver. It was all subjective,
but nevertheless likely helpful to some extent in the early days of
radio. Even today, some amateur radio contests require the exchange
of RST, though it's my impression that in those cases they
just send "59" or "599" (for code, the "T" relates to the tone of
the signal and doesn't apply to voice) to comply with the rules
and don't bother to actually send something that reflects the
state of the signal at their receiver.

From the 1961 ARRL Handbook, this is the how you are
supposed to interpret the Signal Strength code:
1 faint signal, barely perceptible
2 very weak signal
3 weak signal
4 fair signal
5 fairly good signal
6 good signal
7 moderately strong signal
8 strong signal
9 extremely strong signal

I can no longer remember if I read it outright years ago, or made an
assumption, but somewhere I got the impression that S-meters are
named after the RST system.

Given that, any attempt at defining an s-unit is retroactive, trying
to impose some absolute on something that has always been relative.

One of the silliest things I ever saw was a digital s-meter to attach
to CB sets. It was a 2-digit digital voltmeter, and you'd attach it
to the AGC line of your CB set (all s-meters are just voltmeters measuring
the voltage on the AGC line), and get flashy numbers. I can't recall
if it did anything to actual give the basic idea of s-units, or just
was a linear voltmeter. I'm sure it did sell well, because it was
the sort of gadgetry that would sell at the time, and the whole
concept of s-meters is so muddled that I'm sure the less technically
inclined would buy into the notion of digital s-meters.


Michael