Thursday, December 24, 2015

Simpleceiver ~ Part 23

Revisions to the Simpleceiver Detector

 
We are delighted to see that there are homebrewer's out there who are building this project and that is most gratifying. This gives me a sense that all of the time I spend developing circuits and maintaining this blog is having some impact and benefit to the greater ham community.
 
In an exchange of emails with Bob, K6GGO, who built the product detector with the intent of having an 8.0 MHz IF, he reported that he physically built the circuit and ran some test to characterize the performance. His conclusion was that the circuit performed nicely but was seeing an output response capability that extended beyond 100 kHz and in fact had seen a peak response closer to 200 kHz.
 
My response to Bob was that I had seen the same thing but simply ignored anything beyond 20 kHz as this was AUDIO and anything beyond that would never be heard by humans --maybe your dog would hear it? So in the interest of those who would have sleepless nights knowing that the output from their product detector could support  a frequency response output beyond the audio range, I did some further evaluations.
 
Using LT Spice it was a simple matter of making some trial runs to see the effect of changes. Basically I used the Direct Conversion Receiver to test the part change but the same change is made in the Product Detector circuit in he Superhet version.

I am happy to report there will be no output or peak response beyond the audio range and thus those who may suffer a sleepless night will have a peaceful rest. One component value change did the trick. L1 which is in the output filter network is changed from 1000 uHy to 100000 uHy. (For the old school guys like me that s 1 Milli Henry to 100 Milli Henry). I am delighted to report that 100 Milli Henry chokes may be acquired from Mouser  100MHy Choke The cost is a staggering 38 Cents.

 
 
 
 
There is much good in collaboration and having an openness to making changes. One part value change = peaceful sleep!
 
73's
Pete N6QW