[1000mp] MP Roofing Filter from INRAD -- hiss reduction needed?-YES!

Tue May 18 14:11:21 EDT 2004

I confirm that changing the pin diodes need also to adjust bias.
As an example I can say that when I changed in my old Cubic Astro 102BXA the
original (pin) diodes switching the band pass filters with HP 5082-3081 I
had an attenuation of the input signal ar the receiver. So I needed also to
change all the bias resistors at input and output of bandpass filters, using
lower value resistors to incrementate the bias milliamperes.
 Totally: 8 ham bands, 16 pin diodes, 16 resistors.
With the higher current (I think about 10 mA) the rx returned to usual
sensitivity.

About FT1000MP audio noise I confirm that without DSP there is hiss, and
usually I work cw without FT1000MP dsp. So I introduced  K9AN mod proposed
by W2VJN and these are my results:
(from a mine old e-mail)
IK4EWX:
Some days ago I finally tried the K9AN modification suggested to me by
George W2VJN (INRAD) long time ago.

-My FT1000MP, s.n. 7G....., had as C3015 capacitor on the audio board a
0.015 uf. I have soldered parallel a mylar cap 0,047uf (now total 0.062uf).

-I have measured MDS with my old but performing lab:
LOGIMETRICS 925-S125 rf signal generator
Alan high precision step attenuator 0-100db
HEWLETT PACKARD 3400A true rms audio voltmeter.

-Rig setting 14,200-cw-AGC off- 500hz filters
menu 9-1 setting 12.

MDS- minimum discernible signal measured:
before modification was -137dBm
after modification is        -141dBm

Really a 4dBm improvement in CW MDS with only a capacitor soldered is a big
improvement.

I also confirm that listening the 1000MP after the modification is a lot
more ears relaxing than before.

Many many thanks George W2VJN for the info  and the capacitor-hi!, and
thanks K9AN!

G.L.Cazzola - IK4EWX

----- Original Message ----- 
From: "D. J." <dalej2 at mac.com>
To: "All Things Pertaining To The 1000mp Series" <1000mp at mailman.qth.net>
Sent: Tuesday, May 18, 2004 7:43 PM
Subject: Re: [1000mp] MP Roofing Filter from INRAD -- hiss reduction needed?

> Hi Mike,
>
> Well, thankyou for the tips and about 7-7.  I just tried turning off
> 7-7, (off to 100-3100 Rx)  I cannot for the life of me tell a
> difference, must be my ears?  I did put my sound level meter on it and
> it also showed no difference.  So I am stumped, no kidding.  My radio
> was built in Feb 04 could it have some updates no one knows about?  I
> will keep checking and watching the postings for more information.  Yes
> that roofing filter idea of Georges is the best idea I've seen yet for
> improving these receivers.  I had a Mil-Spec 1030 some time ago which
> had a 8 khz roofing filter, and Collins 250 hz filte in the 455  IFr,
> it was a kool machine.
>
> I don't think you need to change those diodes.  I looked up the ones
> for switching rx bandpass filters and they are pins already.  I think
> when you change pin diodes the biasing may have to be changed also
> depending on the diode, maybe only one resistor.  Will you go to the
> HP's?  I bought a bunch one time from Newark.  Mouser most likely has
> them too.  I think they were -3080s, but not for sure.
>
> 73
> Dale, K9VUJ
>
>
> On May 18, 2004, at 12:54, Mike Schatzberg wrote:
>
> > Hello Dale:
> >
> > If you want to check the difference between the digital product
> > detector,
> > and the analog detector in the Mark V, it can be turned on and off in
> > menu
> > 7-7.  If you select off, you will be using the analog detector.  I
> > like to
> > use the 100-3100 setting, with the digital detector on SSB.  This
> > works very
> > well for weak stations, and seems to improve the signal to noise ratio.
> >
> > If the band conditions permit, and you want to improve the signal to
> > noise
> > ratio further, I like to use menu 5-0, and set it to the 8.2-455
> > position,
> > to remove the filter from the 2nd IF, and use only the 6.0 filter in
> > the 3rd
> > IF.  If you do the comparison between the two detectors as above, with
> > the
> > normal filter selection button lit, you will see a rather dramatic
> > difference.  I like to use this set up generally, as it also produces
> > the
> > best fidelity with stronger SSB stations.  If the QRM becomes a
> > problem, you
> > can either push the IDBT button, and superimpose the digital filters
> > over
> > the analog positions, or push the NAR1 filter selection, and have the
> > 2.4
> > khz filters cascaded in place the single 3rd IF filter.
> >
> > I also have noted that the best signal to noise ratio seems to come
> > with
> > about a negative 0.180 setting in menu 8-9, r-usbcar.  This also seems
> > to
> > improve the noise floor noticeably.
> >
> > Regardless, later this summer, following some other projects, and
> > despite
> > some criticism that it may not work well, I intend to change all the
> > switching diodes in both the preamps and front end.  I will finally
> > find out
> > what PIN diodes do, or don't do for the Mark V.
> >
> > As long as the new roofing filter is switchable, it certainly looks
> > like it
> > is a worthwhile change if you suffer from intermod issues.  Even out
> > here in
> > the country I have one or two signals I would like to see removed,
> > probably
> > from strong broadcast station mixes.  I also intend to enable the
> > antenna
> > tuner to work during receive when desired, to improve the Q of the
> > front
> > end.  I wonder what the reason is that Yaesu doesn't offer that
> > option, I
> > want to give it a try.
> >
> > Regards,
> >
> > Mike Schatzberg
> > WB2AJI
> > ----- Original Message -----
> > From: "D. J." <dalej2 at mac.com>
> > To: "All Things Pertaining To The 1000mp Series"
> > <1000mp at mailman.qth.net>
> > Sent: Tuesday, May 18, 2004 1:14 PM
> > Subject: Re: [1000mp] MP Roofing Filter from INRAD -- hiss reduction
> > needed?
> >
> >
> >> I just tried turning of the EDSP in menu 0-9 and I could tell no
> >> difference in receiver noise, the tone changed slightly but the output
> >> from the speaker did not, I had a sound level meter on the speaker.
> >> The antenna input was on a dummy load.  Am I doing it right?
> >>
> >> Also, could you provide details about disconnecting the manual notch,
> >> where did you do it?
> >>
> >> tnx
> >> Dale, K9VUJ
> >>
> >> On May 18, 2004, at 9:31, Harry Yingst wrote:
> >>
> >>> if you turn off the DSP in the Menus you should hear the hiss quite
> >>> well
> >>>
> >>>
> >>>
> >>>
> >>> --- Pete Smith <n4zr at contesting.com> wrote:
> >>>> At 10:25 AM 5/18/2004, you wrote:
> >>>>> Harry Yingst <ab2pn at yahoo.com>
> >>>>
> >>>>
> >>>> Sorry, Harry, I don't understand -- turning *what* off?
> >>>>
> >>>>
> >>>> 73, Pete N4ZR
> >>>> The World HF Contest Station Database
> >>>> was updated on April 26, 2004
> >>>> 2706 contest stations at
> >>>> www.pvrc.org/WCSD/WCSDsearch.htm
> >>>>
> >>>> _______________________________________________
> >>>> 1000mp mailing list
> >>>> 1000mp at mailman.qth.net
> >>>> http://mailman.qth.net/mailman/listinfo/1000mp
> >>>
> >>>
> >>> =====
> >>> Harry - AB2PN
> >>>
> >>> -
> >>>
> >>>
> >>>
> >>>
> >>> __________________________________
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> >>
> >> _______________________________________________
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> >
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