the article does a good job of explaining the circuit up to the Rf amplifier. Are you able to give me a brief overview of how the Rf amplifier, detector and pulse width descriminator work?Found this Heath Kit description in an old Electronics Australia Dec 1973.View attachment 257774View attachment 257775View attachment 257776View attachment 257777View attachment 257778
Thanks, that certainly helps.hi Al12,
Does this edited circuit help you understand the receiver section.?
Ask if you have a query.
E
thanks again, this helps out a bundle.Hi Al,
Is the frequency of the pulse determined when the magnet passes the pick up coil?
Or is there any component in this circuit that can increase the frequency?
L2 is a auto transformer winding, of the transformer, it is tuned to a resonant frequency of 200kHz, which is the frequency required by the transducer.
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Does the 200kHz tuned amplifier use a capacitor and the transformer as a bandpass filter to only allow a 200kHz pulse to reach the 2 stage amplifier?
Yes, T1 , is a transformer tuned for a 200kHz bandpass response, so that Q9 will provide a maximum gain signal gain for frequencies at ~200kHz.
So the two AC untuned amplifier stages will only further amplify the required 200kHz signal
The detector is basically a rectifier and smoothing capacitor, Rc,Ct & Dc, so the PWD input is a ‘DC’ pulse.
------------------
What is the function of the pulse width discriminator?
It designed to only allow through echo pulses with duration’s greater than a fixed period, basically cuts out ‘noise spike’ pulses that could trigger the neon.
This image is a LTspice simulation of a simplified section of the receiver, it may help you understand the receiver operation.
E
Note: the V(trx) trace, shows the initial transmit pulse at time 0.0mSec and simulated Echo pulse at ~4mSec
View attachment 260715
I'm still having a bit of trouble wrapping my head around the detector. what is the purpose of of rectifying the pulse at this point? How does T2 transform the DC pulse to almost 270v to power the neon lamp?Hi Al,
Is the frequency of the pulse determined when the magnet passes the pick up coil?
Or is there any component in this circuit that can increase the frequency?
L2 is a auto transformer winding, of the transformer, it is tuned to a resonant frequency of 200kHz, which is the frequency required by the transducer.
---------
Does the 200kHz tuned amplifier use a capacitor and the transformer as a bandpass filter to only allow a 200kHz pulse to reach the 2 stage amplifier?
Yes, T1 , is a transformer tuned for a 200kHz bandpass response, so that Q9 will provide a maximum gain signal gain for frequencies at ~200kHz.
So the two AC untuned amplifier stages will only further amplify the required 200kHz signal
The detector is basically a rectifier and smoothing capacitor, Rc,Ct & Dc, so the PWD input is a ‘DC’ pulse.
------------------
What is the function of the pulse width discriminator?
It designed to only allow through echo pulses with duration’s greater than a fixed period, basically cuts out ‘noise spike’ pulses that could trigger the neon.
This image is a LTspice simulation of a simplified section of the receiver, it may help you understand the receiver operation.
E
Note: the V(trx) trace, shows the initial transmit pulse at time 0.0mSec and simulated Echo pulse at ~4mSec
View attachment 260715
by Aaron Carman
by Duane Benson
by Duane Benson