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Author Topic: IC-7610 Ragchewing & Review Requests Thread  (Read 3049 times)
VK3BL
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« Reply #15 on: December 11, 2017, 06:45:30 PM »

Most users simply do not know how to deal with this and blame the TX source rather than their own RX settings.  This is very relevant to the IC-7610, as was mentioned above, because it can easily overload and front end loading must be managed using RF gain and attenuator/pre-amp controls.  Probably why Icom felt it VERY necessary to include preselector filtering in the IC-7610.

Brian - K6BRN

I'd say so.  The preselector does a fantastic job as demonstrated in one of my videos; its pretty High-Q and you can easily see the roll off within 300kHz of spectrum on 40M.

It even changes the sound of static crashes, which is a good hint as to how out of band products can distort SDR signal quality.

I will say one thing though, the IC-7610 is noticeably harder to overload than the IC-7300; I have no doubt Sherwood Eng will find its 2kHz RMDR figure is over 100dB.
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J.D. Mitchell - VK3BL / XU7AGA - http://vk3bl.wordpress.com
W6RZ
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« Reply #16 on: December 11, 2017, 08:08:49 PM »

I will say one thing though, the IC-7610 is noticeably harder to overload than the IC-7300; I have no doubt Sherwood Eng will find its 2kHz RMDR figure is over 100dB.

You mean 3rd order IMD dynamic range, not reciprocal mixing dynamic range (RMDR). They are two different measurements. The Sherwood table is ranked by 3rd order IMD dynamic range.

The 2 kHz RMDR of the IC-7300 is 101 dB. The MDS of the IC-7300 is -133 dBm, so you need a -32 dBm signal to see 3 dB of noise floor increase. But on 40 meters, the atmospheric and man made noise floor is easily around -97 dBm (S1 on the S-meter).

Assuming a linear relationship of noise floor increase to power increase, it would take a  +4 dBm signal to hear phase noise above -97 dBm. But the IC-7300 ADC overloads (because it's at full scale) at -10 dBm. Therefore, you'll never hear reciprocal mixing noise on 40 meters, the ADC will overload long before that.
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VK3BL
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« Reply #17 on: December 12, 2017, 08:56:34 PM »

I will say one thing though, the IC-7610 is noticeably harder to overload than the IC-7300; I have no doubt Sherwood Eng will find its 2kHz RMDR figure is over 100dB.

You mean 3rd order IMD dynamic range, not reciprocal mixing dynamic range (RMDR). They are two different measurements. The Sherwood table is ranked by 3rd order IMD dynamic range.

The 2 kHz RMDR of the IC-7300 is 101 dB. The MDS of the IC-7300 is -133 dBm, so you need a -32 dBm signal to see 3 dB of noise floor increase. But on 40 meters, the atmospheric and man made noise floor is easily around -97 dBm (S1 on the S-meter).

Assuming a linear relationship of noise floor increase to power increase, it would take a  +4 dBm signal to hear phase noise above -97 dBm. But the IC-7300 ADC overloads (because it's at full scale) at -10 dBm. Therefore, you'll never hear reciprocal mixing noise on 40 meters, the ADC will overload long before that.

Yes, that is what I mean Smiley  Although the pre-selector won't be much help for close in stuff, it will certainly help out of band signal strong signal IMD.
« Last Edit: December 12, 2017, 08:59:01 PM by VK3BL » Logged

J.D. Mitchell - VK3BL / XU7AGA - http://vk3bl.wordpress.com
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