Help please - VR120 IF images (NOT CELLULAR QUESTION)
 

Hi all
Got a question about the Yaesu VR-120.
It seems somewhat deaf on a few 477 Mhz freqs
I would like to try using the IF images (On some older Bearcats, like
my 200XLT, I use 498.9125 for 477.2125 due to intermod on the "real"
freq)
The IF's on this radio are 248.45 MHz, 15 MHZ, 450Khz according to the
manual.
BUT, I can't hear anything by either adding or subtracting the above
IF's to 477.2125
Is there something I am doing wrong, or does a triple conversion
receiver not work that way?
Any help appreciated!!!!

The reason that images are so well attenuated
on your VR-120 is not due to triple conversion,
per se.

The 1st IF is so high, that the image is very far
away (2 * 248.45 MHz) from the operating frequency.
Being this far away, the tuned circuits in the scanner's
front end attenuate the image.

Consider trying a different antenna.
The stock VR-120 antenna has a performance notch
near 159 MHz.
It may also have a notch at 477 MHz, which is 3 times 159 MHz
and that accounts for the problem you described near 477 MHz.

On Tue, 29 Jul 2003 22:13:00 +0000, Bruce Markowitz wrote:
Got a question about the Yaesu VR-120.
It seems somewhat deaf on a few 477 Mhz freqs
I would like to try using the IF images (On some older Bearcats, like
my 200XLT, I use 498.9125 for 477.2125 due to intermod on the "real"
freq)
The IF's on this radio are 248.45 MHz, 15 MHZ, 450Khz according to the
manual.
BUT, I can't hear anything by either adding or subtracting the above
IF's to 477.2125
Is there something I am doing wrong, or does a triple conversion
receiver not work that way?
Any help appreciated!!!!

--
================================================== =======================
Bob Parnass, AJ9S GNU/Linux User http://parnass.com

Thanks Bob
I have tried several antennas, including the Diamond, so it seems the
performance notch is in the radio, not the antenna
Of course, all the local stuff is around 477 Mhz (figures)
The station on 477.212. is very local, so no problem
But there is one on 478.3175 that should be strong (booms in on the
bearcats) and is dead on the Yaesu.
Oh well, guess there's no help for it

On Tue, 29 Jul 2003 20:18:12 -0500, Bob Parnass
wrote:

The reason that images are so well attenuated
on your VR-120 is not due to triple conversion,
per se.

The 1st IF is so high, that the image is very far
away (2 * 248.45 MHz) from the operating frequency.
Being this far away, the tuned circuits in the scanner's
front end attenuate the image.

Consider trying a different antenna.
The stock VR-120 antenna has a performance notch
near 159 MHz.
It may also have a notch at 477 MHz, which is 3 times 159 MHz
and that accounts for the problem you described near 477 MHz.

On Tue, 29 Jul 2003 22:13:00 +0000, Bruce Markowitz wrote:
Got a question about the Yaesu VR-120.
It seems somewhat deaf on a few 477 Mhz freqs
I would like to try using the IF images (On some older Bearcats, like
my 200XLT, I use 498.9125 for 477.2125 due to intermod on the "real"
freq)
The IF's on this radio are 248.45 MHz, 15 MHZ, 450Khz according to the
manual.
BUT, I can't hear anything by either adding or subtracting the above
IF's to 477.2125
Is there something I am doing wrong, or does a triple conversion
receiver not work that way?
Any help appreciated!!!!

--
================================================= ========================
Bob Parnass, AJ9S GNU/Linux User http://parnass.com

So where exactly would I look for the image? How much higher exactly, based
on the IF's I posted?
"Bob Parnass" wrote in message
.. .
The reason that images are so well attenuated
on your VR-120 is not due to triple conversion,
per se.

The 1st IF is so high, that the image is very far
away (2 * 248.45 MHz) from the operating frequency.
Being this far away, the tuned circuits in the scanner's
front end attenuate the image.

Consider trying a different antenna.
The stock VR-120 antenna has a performance notch
near 159 MHz.
It may also have a notch at 477 MHz, which is 3 times 159 MHz
and that accounts for the problem you described near 477 MHz.

On Tue, 29 Jul 2003 22:13:00 +0000, Bruce Markowitz wrote:
Got a question about the Yaesu VR-120.
It seems somewhat deaf on a few 477 Mhz freqs
I would like to try using the IF images (On some older Bearcats, like
my 200XLT, I use 498.9125 for 477.2125 due to intermod on the "real"
freq)
The IF's on this radio are 248.45 MHz, 15 MHZ, 450Khz according to the
manual.
BUT, I can't hear anything by either adding or subtracting the above
IF's to 477.2125
Is there something I am doing wrong, or does a triple conversion
receiver not work that way?
Any help appreciated!!!!

--
================================================== =======================
Bob Parnass, AJ9S GNU/Linux User http://parnass.com