[1000mp] Fw: Inrad 1.8 Filters and Signal to Noise Problems

[Mike Schatzberg]

----- Original Message -----
From: "Mike Schatzberg" <wiremann@earthlink.net>
To: "Peter King" <va6no@shaw.ca>
Sent: Wednesday, February 13, 2002 11:29 AM
Subject: Re: Inrad 1.8 Filters and Signal to Noise Problems


> Thanks Peter....
>
> My Mark V calibrated at the old Collins standard of 50 microvolts equal to
S
> 9, on 10 meters...with the preamp set to the flat position....in the tuned
> position, 50 microvolts equals S 9 plus 10 db.....check your preamp menu,
> and try again on 10 and see what you get....it makes some difference..
>
> 73,
>
> Mike
> WB2AJI
> ----- Original Message -----
> From: "Peter King" <va6no@shaw.ca>
> To: "Mike Schatzberg" <wiremann@earthlink.net>
> Sent: Wednesday, February 13, 2002 10:43 AM
> Subject: Re: Inrad 1.8 Filters and Signal to Noise Problems
>
>
> > Hi, Mike:
> >
> > Thanks for the reply, Mike. I will be very interested to hear how you
> > make out with the Inrad filters. Are you going to put in the IF mods?
> > Either the Inrad one or the W8JI mod?
> >
> > OK on using your NIR filter in-line. well, I have a Timewave 599zx unit,
> > but, the Mk-V supposedly has NR, doesn't it? Do you use the built-in NR?
> > I guess not, not very useful, is it?
> >
> > About sending the rig back to Yaesu. Well, I wish you luck. What I'm
> > trying to do is to determine if my particular unit is defective. From
> > what you've said, and what I've read all over the 'Net, I think the
> > noise and readability problems are endemic to the radio. If you send
> > the rig back to Yaesu without a clear plan to alter the way it is set
> > up, then won't they just check out the rig in their standard way, and
> > you'll get back the same rig.
> >
> > I have test gear here that allows me to do MDS, BDR, and IMD tests on
> > the
> > rigs. I have all my records from working with the TS850's I used to
> > have,
> > and the Mk-V just does not compare very well. For example, for a single-
> > tone distortion check, the TS850 showed, for a sinal of S9+20dB, and AGC
> > on slow, a second-harmonic level of about -50dB relative to fundamental.
> > The Mk-V showed -22dB, under all test conditions. I then re-checked the
> > ARRL expanded test report on the Mk-V, and there it is, the Rx IMD test
> > shows the same thing.
> >
> > I reduced the IF gain (menu 9-1) initially from 12 to 9, to make the
> > S-meter make more sense. Out-of-the-box, S9 was 12 uV! With the RIF
> > gain number reduced to 9, S9 was about 40 uV, which is closer to what
> > I'm used to. But then I noticed that the distortion I am complaining
> > about is noticably worse with the RIF at 9, and found that the higher
> > I set the number, the lower the Rx distortion. There may be a clue here.
> >
> > I think I am going to get the service manual, if I can, so I can try to
> > understand the rig a bit better, but we may be facing a fundamental
> > design flaw (or, more than one). Here is a little "peeve" list of things
> > I don't like about the Mk-V.
> >
> >    Distortion of the received audio is higher than should be for a radio
> >    of this class. Listening to AM broadcast stations as an example, in
> >    either AM mode, results in an unacceptable level of distortion,
> >    especially if the AGC is on the "slow" position. Adjusting RF gain
> >    to S-meter indication just above that of the signal reduces the
> >    distortion, but one still experiences listener fatigue in just a few
> >    minutes.
> >
> >    S-meter readings below S-9 are useless. Just about any signal will
> >    move the meter to S-7. "Linear" S-meter operation seems to begin at
> >    about S-9.
> >
> >    When you switch on the EDSP Noise Reduction (NR), the audio level
> >    drops significantly. I see no reason why, in the DSP processing, the
> >    NR process can't be made to be gain-neutral.
> >
> >    There is a huge difference (like 20dB) in the ouput audio level when
> >    switching between SSB and AM. This results in getting blasted when
> >    you switch modes and forget to turn down the AF gain.
> >
> >    The readability of signals which are below about S-7, in the presence
> >    of any significant levels of noise becomes so poor as to be nearly
> >    useless, and no amount of IF filter selection, shift/width
> > adjusments,
> >    or IDBT will clear up the signals. I will say that the IDBT does
> >    seem to give me the "best" readability, but it ain't great.
> >
> >    In the absence of noise, on a quiet band, the rig seems to do very
> >    well with weak signals, as good as any other radio I have used.
> >
> >    I find the noise blanke (NB) to be ineffective. I have to set the
> >    menu 2-8 item to B13 before the NB has any effect, and then, incoming
> >    voice signals are so distorted as to be unreadable anyway.
> >
> > Well, I see I've ranted a bit, I apologize, Mike. Guess I'm frustrated.
> > This rig, with al the filters, cost me about 5K $CAD, and I didn't
> > expect to be so disappointed at this price level.
> >
> > Maybe we can start building a more generally-circulated "peeves" list?
> > It might provide (might, mind you) useful feedback for Yaesu in making
> > their rig adjustments, who kows.
> >
> > Anyway, best of luck with the filters, I've got my fingers crossed.
> >
> > cheers, and thanks again, Mike.
> >
> > ....73 de Peter (ve6epk)
> >
>