[1000mp] Real S9
Pete Smith
pete.n4zr at gmail.com
Mon Mar 26 20:03:26 EST 2007
I don't disagree, but my point was that the only thing that I had changed
was my setting of the 9-1 menu. My roofing filter is one from the early
second buy, and my understanding is, as someone else said, that the later
roofing filter boards are considerably less lossy than the first couple of
batches. Hence I suspect that I have been running the IF gain too low ever
since I put it in. Only time will tell, but I can certainly testify that
band noise is higher than internal noise on all bands. If the receiver
noise doesn't mask signals that are above the band noise, why worry?
73, Pete N4ZR
At 11:17 AM 3/26/2007, you wrote:
>I have to agree with Chuck. The proper way, from a technical perspective,
>would be to optimize the receiver and then calibrate the "S"
>meter. Higher IF gain does not equal higher receive sensitivity. It
>might give the appearance of that due to the higher noise level and audio
>level, but at the expense of weak signal performance. My experience has
>been that in most cases the opposite is true. The lowest possible IF gain
>setting before actual sensitivity reduction, results in the highest
>signal to noise ratio. Internal noise is the sensitivity limiting factor
>in most receivers not lack of gain. I know that sounds crazy but it's
>true. In some receivers (not the FT-1000 series) I have actually measured
>the receive sensitivity to be the highest with the IF gain set to the
>lowest setting....problem is you run out of usable audio amp power to take
>advantage of it so it is a trade off.
>
>Pete I would be concerned about the health of your Roofing filter
>module....the reason the IF gain is reduced after the installation of the
>Roofing filter is to compensate for the gain associated with the active
>components on the Roofing filter card as I understand it. Installation of
>the roofing filter bumps up the gain in one stage and you adjust it back
>down in another with the software which is suppose to result in an
>improved S/N ratio and resulting receiver performance by redistributing
>the gain more evenly across the various stages of the receiver. A quieter
>receiver should be the result....and yes signals as registered on the "S"
>meter may be lower as well. But here is the payoff....you will most
>likely be able to detect a signal that won't even move the "S" meter off
>it's stop where with a higher internal noise level, from higher IF Gain
>settings or poorly distributed gain, you wouldn't be able to even hear
>that signal.
>
>This is all verifiable on the bench with a decent signal generator or
>probably with the XG-1, the step attenuator and a couple of good
>cables. A decent Analog RMS voltmeter is handy as well. (HP-3400 is great)
>
>Pete in your case I would pull the covers on the radio and lay it up on
>it's side and check the noise level and performance with the Roofing
>filter mod in and out of the radio...if you don't see a noticeable noise
>level increase with the installation of the Roofing filter and no IF gain
>setting changes it has a problem. Same goes for the Inrad IF Amp mod
>board if one is using it instead of the Roofing Filter mod.
>
>I have seen more than a couple of posts here about problems developing
>with the roofing filter board.
>
>Just some food for thought...
>
>Hope it helps...
>
>Cecil Acuff
>K5DL
>----- 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.
>>>>
>>>>______________________________________________________________
>>>>1000mp mailing list
>>>>Home: http://mailman.qth.net/mailman/listinfo/1000mp
>>>>Help: http://mailman.qth.net/mmfaq.html
>>>>Post: mailto:1000mp at mailman.qth.net
>>>>
>>>>
>>>>
>>>>--
>>>>No virus found in this incoming message.
>>>>Checked by AVG Free Edition.
>>>>Version: 7.5.446 / Virus Database: 268.18.18/733 - Release Date:
>>>>3/25/2007 11:07 AM
>>>
>>>______________________________________________________________
>>>1000mp mailing list
>>>Home: http://mailman.qth.net/mailman/listinfo/1000mp
>>>Help: http://mailman.qth.net/mmfaq.html
>>>Post: mailto:1000mp at mailman.qth.net
>>
>>______________________________________________________________
>>1000mp mailing list
>>Home: http://mailman.qth.net/mailman/listinfo/1000mp
>>Help: http://mailman.qth.net/mmfaq.html
>>Post: mailto:1000mp at mailman.qth.net
>
>
>______________________________________________________________
>1000mp mailing list
>Home: http://mailman.qth.net/mailman/listinfo/1000mp
>Help: http://mailman.qth.net/mmfaq.html
>Post: mailto:1000mp at mailman.qth.net
More information about the 1000mp
mailing list