[1000mp] Real S9

Mon Mar 26 10:49:34 EST 2007

Hello Clark:

Your posts are not coming thru the reflector.  Please resubscribe with your
current email address.  I have the settings to automatically accept your
subscription.

73,

Mike
W2AJI

Clark wrote:

Mike,

I think I figured out the problem with the reflector. I've been getting the
emails from the Yahoo group for several months so I thought I was an
official member of the group.  The problem was the email address I had
initially used was the forwarding address through arrl.net.   I have never
been able to see how to send a message from that address and didn't think it
was a problem. Well, now it is.

This morning I posted two new messages directly from the Yahoo group screen.
About an hour later, I changed my email address on mailman.  So, hopefully
the few posts I do henceforth will pass through ok.

Really appreciate your service to us hams, Mike.

73,

Clark

----- Original Message ----- 
From: "Mike Schatzberg" <cherokeehillfarm at earthlink.net>
To: "All about Yaesu 1000mp" <1000mp at mailman.qth.net>
Sent: Monday, March 26, 2007 9:34 AM
Subject: Re: [1000mp] Real S9

> Hello Chuck:
>
> What we were speaking of here is resetting the IF gain after the Inrad
> Roofing filter mod, not the IF Amp mod.
>
> Improved signal to noise ratio is achieved here due to the narrower first
IF
> filter and the few dB of net gain
> resulting from the surplus gain remaining after the filter insertion
losses
> are eliminated via the module amplifier.
> This is an additional advantage of the roofing filter mod, but not the
> primary objective.  The original design of
> the module amplifier was to be able to compensate for the losses of the
> narrower crystal filter.  Over time, the manufacturing
> process for the filter apparently became more refined, and the filter
> insertion losses deminished.  I wrote to Inrad myself
> suggesting that their instructions for installation might be modified to
> take advantage of this development.  They did
> indeed change their instructions after it became evident that newer
filters
> had lower losses.
>
> This change in the filters does more or less let the roofing filter mod
> parallel the performance of their earlier IF Amp mod.  Many people have
> swapped out the older mod for the newer roofing filter.
>
> I have worked here on the bench with the new filter installed, examining
> signal to noise ratio, noise floor with MDS, and the S meter calibration.
> While each radio is different due to component selection and overall set
up,
> my personal conclusion has been that the signal to noise ratio is
optimized
> generally within a decrease of 1 to 2 integers of the original factory
> settings, and that the S meter readings will not be significantly
> compromized for linearity within this range.
>
> While the S meter readings at S9 (50 uV input) may be correct for small
> reductions in IF gain settings, my measurements indicate that too low a
> setting will result in loss of linearity below S9.  You can then perform
the
> S meter calibration which is a two step process; first setting VR8006 for
a
> one dot deflection with a +11dBu input signal, and then setting VR8007 for
> S9 + 60 dB with a +100 dBu input signal.  Yaesu does not calibrate the
meter
> at S9, please see page 3-3 of the technical suppliment for this
information.
> Please note that the IPO lamp is off for these adjustments, meaning the
> preamp is operating.
>
> Regarding the accuracy of other receivers S meters, I would say that there
> are two issues at work here.  One source of error always seems to be
whether
> the S meter is calibrated with the preamp on or off, this makes for a 2 S
> unit change alone generally.  Secondly, some manufacturers really haven't
> adopted the Collins standard of S9 equal to 50 uV input, with one S unit
> being worth about 6 dB.  Their S meters are not only incongruent with this
> standard, but they are also non linear.
>
> You just might want to actually measure what you have created once you
have
> made a larger change to the IF gain to optimize signal to noise.  I will
not
> even venture to guess what might also change in terms of dynamic range and
> BDR with larger excursions from the original factory settings.
>
> Experience still says that downward adjustment of the gain in menu 9-1 by
> one to two units will produce acceptible results across the board.  You
will
> also see that the two receivers remain in approximate correlation at S9.
>
> 73 and Happy DXing,
>
> Mike
> W2AJI
>
>
>
>
>
>
>
> Chuck wrote:
>
> Hi, Mike,
>
> Oh, I have already installed the mod, and after that, the roofing filter.
> Both times I  followed the Inrad suggestions, lowering the 9-1 settings by
> 1-2 numbers (in my case, the roofing filter didn't change that amount of
> compensation);  and both times the resulting s-meter readings agreed
> generally with the sub-rcvr. However, I also used my ears and several weak
> sigs to establish what I sensed as the best weak-signal s/n ratio. This
also
> agreed (within 1 number) with the Inrad suggestions. The S-meter STILL
seems
> quite stingy (both main and sub) compared with other radios. My point is
> that, once I had done this, I satisfied myself that further messing with
the
> IF gain (which would not improve the S/N ratio, but only make all sigs
> louder, including the noise) would be a bad idea, and that I should live
> with a stingy meter. Either Yaesu's calibration is in error, or we all
have
> been misled by other radios' overly generous meters. The 50 uV generator
is
> a great way to give us all a consistent S-9 standard. But Pete's
suggestion
> to increase the IF gain until the s-meter reads S-9 at 50 uV just reverses
> all the good we got out of the IF mod. Remember, the reason for the mod
was
> to balance the gain distribution by reducing the 70 MHz IF and using the
> Inrad amp. to compensate upstream (I think I remember that correctly). I
> think it's erroneous to assess the RCVR's performance by looking at the
> S-meter. We all installed the mod to make the radio quieter (without
losing
> sensitivity). Just leave the IF alone, at it's best S/N gain and
RECALIBRATE
> ONLY THE METER using the 50uv generator as a standard! If I can find the
> meter calibration adjustment in the radio, I'll share it.
>
> Yes, if you're referring to the BHI noise reduction system, I've already
put
> that on my wish list!
>
> Chuck
>
>
> ----- Original Message ----- 
> From: "Pete Smith" <pete.n4zr at gmail.com>
> To: "All about Yaesu 1000mp" <1000mp at mailman.qth.net>
> Sent: Monday, March 26, 2007 7:19 AM
> Subject: Re: [1000mp] Real S9
>
>
> > Hi Chuck - well, my logic was that the only thing I had changed was the
IF
> > gain setting in menu 9-1, and the radio not only sounded a little dead,
> the
> > main RX definitely had less sensitivity  than the sub-RX.  Given that, I
> > felt that getting the S-meter back to reading more or less the same on
> both
> > with a 50 uV signal would indicate that I had restored the IF gain to
> > something like spec.  The XG-1 also has a 1 uV output, and Elecraft also
> > makes a highly accurate step attenuator kit if you want to go farther.
> >
> > 73, Pete N4ZR
> >
> > At 10:44 PM 3/25/2007, you wrote:
> > >Gee, Pete, I'm not trying to start a war here, but it seems to me that
> the
> > >gain distribution (affected by the I/F gain setting) should be set for
> > >max. S/N, not diddled with as a means to correct an S-meter
> > >mal-calibration. On the other hand, suggestions have been made that
> (after
> > >any Inrad mods, etc.) the I/F gain be adjusted until the main RCVR
> S-meter
> > >indicates the same as the Sub-RCVR reading. That would seem to be a way
> of
> > >returning the overall I/F gain to its factory setting. This seems fine
as
> > >long as one assumes that the sub-RCVR setting is consistent with the
best
> > >main RCVR S/N ratio: a bad assumption, IMHO.
> > >
> > >Why wouldn't it make more sense to (somehow) establish the best S/N
ratio
> > >by adjusting the I/F gain and THEN use the 50 uV standard to set the
> > >S-meter sensitivity? I've played a little with the I/F menu setting
using
> > >barely readable sigs to reach a (subjective) optimal setting. That
turned
> > >out to be fairly consistent with Inrad's suggested compensation when
> > >installing their I/F mod kit. My S-meter seems stingy, too, but it
seems
> a
> > >bad trade to give up weak signal performance (and lose the "hiss
> > >reduction" we paid for in the Inrad kit) just to get the S-meter right
> > >when there's probably a dedicated S-meter sensitivity adjustment
> somewhere.
> > >
> > >What am I missing here?
> > >
> > >73,
> > >Chuck, N4NM
> > >(Who's wishing he had one of those VG-1 kits, too :>)
> > >
> > >
> > >
> > >----- Original Message ----- From: "Pete Smith" <pete.n4zr at gmail.com>
> > >To: "All about Yaesu 1000mp" <1000mp at mailman.qth.net>
> > >Sent: Sunday, March 25, 2007 2:58 PM
> > >Subject: [1000mp] Real S9
> > >
> > >
> > >>I just finished building the Elecraft XG-1 signal generator.
> > >>
> > >>So why am I talking about it here?  Because It puts out a calibrated
50
> > >>uv on 7040.  After I built it, the first radio I hooked it to was my
> > >>TS-930. S9 right on the button.  Then I connected it to my Mark 5.
S6!
> > >>
> > >>I had thought for a long time that the Mk 5 sounded "dead" compared
with
> > >>the 930, but put it down to DSP, etc.
> > >>Not long after I got the MK5, I put in the Inrad IF mod, and then a
> > >>couple of years later I substituted the roofing filter.  The radio
also
> > >>has cascaded 400 Hz Inrad CW filters.  In the course of doing all
that,
> I
> > >>guess I had turned the IF gain down too far - anyway, using the XG-1,
I
> > >>was able to reset it to ~S9 at 50 uV - certainly sounds like the band
is
> > >>more open!
> > >>
> > >>I expect the VG-1 is going to prove very useful, anytime I want to
check
> > >>the performance of my antenna switching or bandpass filtering - and
for
> > >>$40, I can't imagine a cheaper way to do that.
> > >>
> > >>______________________________________________________________
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> > >>Help: http://mailman.qth.net/mmfaq.html
> > >>Post: mailto:1000mp at mailman.qth.net
> > >>
> > >>
> > >>
> > >>--
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> > >>Checked by AVG Free Edition.
> > >>Version: 7.5.446 / Virus Database: 268.18.18/733 - Release Date:
> > >>3/25/2007 11:07 AM
> > >
> > >______________________________________________________________
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