[1000mp] Real S9

[Pete Smith]

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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