This is just a tweak of the older two antenna scheme. Basically it gets
rid of the bidirectional nature of the two antenna version.
http://www.homingin.com/newdopant.html
Signals that are heavily modulated such as trunking control channels
don't work well with such schemes. [That part of the experiment I have
tried. No problem though with voice modulation.]
My understanding is they use the identical radio scheme feed into a
scope XY via demod taps. I haven't tried this since I don't have two
identical radios that can be synched. I'm eventually going to hack some
cheap scanners, just as the Pro-2035, and simply feed one scanner with
the mixers from the other. This would not maintain frequency accuracy,
but it would make the XY display possible.
My assumptions is you get a 45 degree line when the antennas are equal
distance to the transmitter.
This is like a radio interferometer, though perhaps not in the strict
sense. An interferometer, using an analogy to optics, would be mixing
the received spectrum prior to any detection.
The AR-One-C is set up for this type of DFing.
http://www.aorusa.com/receivers/ar-one.html
On 1/1/2012 6:19 PM, David wrote:
I think even my old Icom 706 would work that way. It has the high
stability option installed. From what I remember from the service
manual, every mixer has its local oscillator frequency locked to the
master oscillator through either a PLL or DDS which makes passband
shifting via the IF frequencies very easy. Since all of the local
oscillators except for the first one have very little range and are
relatively low frequency, the frequency synthesis was not too
expensive to do.
I suspect a Roanoke style direction finder with multiple radios would
work fine without locking the receiver oscillators but that requires a
carrier for FM demodulation.
On Sun, 01 Jan 2012 17:55:35 -0800, gary<[email protected]> wrote:
This is an interesting observation regarding the Icom radio that can be
run from one master reference. I would assume any radio which has a high
accuracy option has this feature. Looking at the block diagram of the
R-8500, this appears to be an option. For the R-7100, it looks like it
uses one oscillator for some operating modes. There is a 1GHz mixer on
the front end that can be switched in and out. That mixer is not derived
from the master.
The only reason I mention this is there are directing finding schemes
based on identical receivers but separate antennas.
The traditional diode mixer before the radio DF scheme doesn't work well
on digital signals.
Some of the more recent high end radios from AOR have this one master
oscillator scheme.
On 1/1/2012 4:14 PM, Magnus Danielson wrote:
So, they essentially did what I did with the heat gun, heat it up
properly. This technique was not "invented" by me, I in turn had picked
it from Gerald Molenkamp VK3GJM for the FRS-C:
http://www.vk3um.com/Rubidium%20Standard.html
Cheers,
Magnus
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