[time-nuts] Used Rb Operating Lifetime

gary lists at lazygranch.com
Mon Jan 2 02:35:13 UTC 2012


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<lists at lazygranch.com>  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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