View Single Post
  #10  
Old 08-22-2017, 02:56 PM
Tim R. Tim R. is offline
VideoKarma Member
 
Join Date: Mar 2011
Location: Portlandia
Posts: 112
Quote:
Originally Posted by dewdude View Post
I live about 5 miles from a NOAA station on 162.55mhz and, occasionally...I will get an image of it down around 21mhz.

If you've got really strong signals making in to your receiver...you can get stuff like this. It could be hetrodyning with a local oscillator...if you've got one in the radio running that high. In older radios it's usually 10mhz; my IC-725 transceiver from the late 80's has an IF running in the 70mhz range; but even then I don't often hear broadcast FM imaging.

You can also get hetrodyning from adjacent strong signals as well.
I live in an urban area, between 10-20 miles from most of the transmitters.

The radio is Philco's first model that received shortwave bands, from 1932. It uses a 450kc IF.


Quote:
Originally Posted by jr tech
Many older single conversion, single rf tuned radios are quite poor at rejecting "image" signals. They usually do not trap out higher frequency signals (there was no need in 1938 or so because the modern TV and FM bands did not exist).
These sets were "good enough" at the time, but that time is long gone.

Agree, if you want to do serious SW listening, get a decent modern radio.
I think you sum up the phenomenon nicely. The radio is a product of its time and as a result, some quirkiness should be expected.

For what it is, though, the set is an excellent performer. With a 50' antenna shortwave comes alive at night. I can pick up several dozen stations with little difficulty. Right now I have it tuned to WTWW, which actually has some decent programming.


Tim
Reply With Quote
Audiokarma