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From: "Talbot Andrew" <ACTALBOT@dstl.gov.uk>
To: rsgb_lf_group@blacksheep.org
Subject: LF: RE: [Tech] Electronic Goniometer?
Date: Fri, 16 Nov 2001 08:37:46 -0000
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For the weighting elements why not use a binary switched attenuator.  At low
frequencies, FET switches onto a tapped constant impedance resistor ladder
will give you constant impedance and exact attenuation steps and will have
good strong signal handling capability
You can get the precise sin/cos values from a look up table.   Use a
processor (which could be as simple as a PIC) to make the look up from
sin/cos data stored in EEPROM based on input from your interface - voltage
from a potentiometer, rotary shaft encoder or whatever you like.

Andy  G4JNT


> -----Original Message-----
> From: Johan Bodin [mailto:sm6lkm.jbeab@swipnet.se]
> Sent: 2001-11-15 21:39
> To: rsgb_lf_group@blacksheep.org
> Subject: LF: [Tech] Electronic Goniometer?
> 
> 
> Dear LF group
> 
> Does anyone have an idea how to design an electronic goniometer?
> 
> Imagine a "black box" that is fed with two signals from a 
> pair of orthogonal
> (for example N/S and E/W) untuned loop antennas, let's call 
> them X and Y.
> The output from the box should ideally be X * cos(A) + Y * 
> sin(A) where A
> is a control signal which could be a simple DC voltage, a 
> digital control word
> or whatever.. Such a "black box" could be very useful for 
> direction finding
> without the need to rotate a loop physically.
> 
> When combined with an omnidirectional antenna and a phasing 
> circuit, the
> resulting cardioid pattern can also be used to null out 
> interference, just like
> a K9AY antenna does, but better - with steerable, instead of  
> fixed, null
> directions. My two loop / eight nulls (modified) K9AY is 
> doing a nice job
> but I miss the ability to put the null in ANY direction...
> 
> The "black box" could be a pair of attenuators with ability 
> to switch the phase
> 180 deg's. In its simplest form it could be just two 
> potentiometers and two
> switches (and phase reversal transformers). This would be OK 
> to manually
> null out interference but to make accurate D.F. measurements, precise
> sin/cos behaviour of the attenuators is required.
> 
> 
> Any ideas? (besides making a "physical" goniometer)
> 
> 73 de Johan SM6LKM
> 
> 
> 
> 


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