[R-390] Measuring tangential sensitivity

[David C. Hallam]

Mark,

Do I assume this method will also work on the Collins ham band receivers
that have an IF gain adjustment such as the 75S-3 series?

David
KC2JD/4
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Mark Huss
> Sent: Tuesday, March 13, 2007 8:56 AM
> To: Bill Hawkins
> Cc: r-390 at mailman.qth.net
> Subject: Re: [R-390] Measuring tangential sensitivity
>
>
> Bill, you are right. It's most common use is to test the Signal to noise
> ratio of video and wideband amplifiers and detectors. It is also used in
> Cable TV Amplifiers. And in Radio Telescopes. It is not often used in HF
> receivers because there is no way to really adjust the system noise
> floor in them. The R-390 and R-390A, with their IF Gain adjustment which
> not only adjusts the total receiver gain for matching purposes, but also
> has a large effect on the receiver noise floor, are exceptions to
> this rule.
> I first ran across this technique at Capitol Cable in Austin back around
> 1972. I was reintroduced to it again when being trained to repair
> R-390's in ASA School. And later when doing VHF/UHF and Satcom systems.
>
> Before you reject it out of hand, give it a shot. The only thing you are
> adjusting is the IF Gain pot. It is easy enough to adjust it back if you
> find it does not help your receivers noise floor.
>
> Bill Hawkins wrote:
> > Roy,
> >
> > Seems like I was off the mark. As is usual, one should do some
> > research before hitting the keyboard, unless one's intent is to
> > liven things up a bit.
> >
> > >From a blurb for Agilent wide range laboratory detectors:
> >
> > "Tangential sensitivity is the lowest input signal power level
> > for which the detector will have an 8 dB signal-to-noise ratio
> > at the output of a test video amplifier. Test amplifier gain
> > is not relevant because it applies to both signal and noise.
> > Agilent detectors are designed for optimal flatness and SWR."
> >
> > Since R-390s do not contain video detectors, I let the matter drop.
> >
> > Regards,
> > Bill Hawkins
> >
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