Topband: Extreme directivity

[Raoul Coetzee]

>Extrapolate this to HF.
>Forgetting about the legality of the experiment for the moment, modulate
>that 432 carrier at 1.832MHz.  This gadget is going to throw a WHOPPING
spur
>on Topband.  You are going to hear that spur without-a-doubt.

When the 432 Mhz is modulated by the 1.8 Mhz thats what you will get , a
1.8mhz  modulated 432 carrier,plus the two sidebands (or more, depending if
the 1.8 mhz signal is also modulated) The  antennas will transmit this, very
much like a TV video signal is transmitted.
 On the receiver side you will have to detect the 1.8mhz signal again using
a 70cm radio,set  for whatever modulation mode you used in the first
place(FM, AM, SSB,).But there will not be a WHOPPING spur on 1.8 Mhz, only
the detected 1.8 mhz coming from your  broadband 70cm radio.Of course a
normal HAM 70cm radio wont work, unless you modify it to have an IF at least
as wide as the 1.8 signal you pass through.(not the normal 12.5 or 25 Khz)

I have been toying with this idea for a remote station, sending  20kHZ-30
KHZ of the 160m band on 70cm to my qth from a remote receiving site.


>The question is: will the modulation radiate well?
If you ask if the 1.8mhz signal will be received directly by a HF radio
tuned to 1.8Mhz, the answer is NO.

 Will the beam form or
not?
Yes, you will have a normal directional 432 beam pattern modulated by
1.8Mhz.

>Will the wave front propagate so as to conform to the 70cm antenna's
beam pattern?
Yes , the modulated signal will behave like any other 70cm signal provide
that the bandwidth of the antenna at 70cm is wide enough and 1.8 Mhz is no
problem at 70cm.
It will not propagate on 160m.
Regards,
Raoul, ZS1REC




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