[GreenKeys] Northern Radio 152/2

[W2HX]

Hi friends,

A while ago, I picked up a NIB Northern Radio Dual Frequency Shift Tone Converter Type 152 Model 2 (basically a dual channel receive only TU).

http://www.w2hx.com/x/NorthernRadio/Type152Mod2/1.JPG
http://www.w2hx.com/x/NorthernRadio/Type152Mod2/2.JPG
http://www.w2hx.com/x/NorthernRadio/Type152Mod2/3.JPG
http://www.w2hx.com/x/NorthernRadio/Type152Mod2/9.JPG

It uses plug-ins for the frequency and shift (which I don't have). Today I was looking through the manual to read about these plug-ins and noticed something that was interesting.

There are about 22 possible filters listed. They show a center frequency and then a +/- shift. So for example, the first one is 425 cps with a shift of +/-42.5 cps.  The various plug-ins you could obtain show center frequencies listed include 425, 595, 765, 935, 1105, 1275, 1445, 1615, 1785, etc up to 3315 all with a shift of +/-42.5 cps.  Now clearly this is an 85 cps shift which I know was somewhat common for narrow shift stuff.

Similarly, they list 4 additional filters for center freqs of 1615, 2295, 2975, 3655 all with a shift of +/- 120 cps. This is a 240 cps shift. I have never heard of this shift. I would have expected 170 (2x85), maybe 850 (170x5) cps and also 425 (850/2).

Here's the question. Certainly the shift is important. But how important are these center frequencies? Couldn't I either detune the receiver in SSB to adjust the center freq of what I am listening to? Certainly there is a limit to this in order to keep the signal in the passband of the radio's IF as best as possible. Similarly, is there a way to use the BFO to shift the audio to match up to one of these center freqs? Maybe in CW mode with a 500 Hz or 1K or more filter?

And the bottom line. Assuming I can find my choice of these filters which is a real pipe dream, am I correct that the 240 shift really may not work for 170 shift? And this unit does not have the ability to key on just mark or space alone.

Ultimately I do have the circuit diagram for these filters. They all have the same diagram but just a change of components. I guess I might be able to make my own with my own shift once I understand it all better.

Anyway, just interesting. And I am interested in your thoughts on this.
73 Eugene W2HX




73 Eugene W2HX


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