Pete KE9OA wrote:
This can also occur in multiple conversion receivers, depending on the
ultimate rejection of the roofing filters.
In this case, image rejection has nothing to do with it. What is being
experienced are 3rd order IMD products. Do a Google search on 3rd order IMD
products in mixers, and it will become very clear.............

Pete

"dave" wrote in message
...
gccradioscience wrote:
If you live in a city area or some rural area with a real strong AM
station its likely it will be found on the longwave bands from 150 to
519 kHz (1050 kHz to 1419 kHz) the 900 kHz carrier image. Please
understand that this station is not a real longwave radio station.
Its a image from the broadcast station when the station is strong
enough to bleed on other longwave frequencies. The radios that I
have is the DX-380, DX-390, DX-392 and the yes the new Grundig G5.
It has do something with the dual conversion circuitry . I am
hoping that manufactuers, hobbyists, and technicians will use the 900
kHz formula to see other image stations to show that these AM stations
should not be on the LW bands.

Desired AM Station (kHz) - 900 kHz = Image Station

The images I am getting here locally in Virginia Beach, VA on LW is


150 kHz = 1050 kHz WVXX -AM
210 kHz = 1110 kHz WYRM-AM
330 kHz = 1230 kHz WJOI -AM
410 kHz = 1310 kHz WGH-AM
450 kHz = 1350 kHz WGPL -AM
500 kHz = 1400 kHz WPCE-AM

AM Band Images that are annoying

550 kHz = 1450 kHz
650 kHz = 1550 kHz

Adam E.






It's a single-conversion phenomenom usually. Two times the IF, + or - the
FOI.


Sir, I am a professional frequency coordinator and need no schooling on
3rd order IMD.

My trusty Philips AE-3805 (Sangean innards) has a big gap in coverage
(7300 kHz-9.500 kHz) that can largely be overcome by tuning 900 kHz
either side of the frequency of interest. 900 kHz is twice the IF.
This is the exact mathematical relationship described in the original
post. I suspect we are arguing over word usage, not the science.

A mixer simply produces a desired intermod product.

One of the few positives of a dual-conversion receiver is their ability
to keep the first image out of the downstream bandpass.