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Circuit to extend frequency range of 8753 down to 20 Hz.

Question asked by drkirkby on Mar 5, 2015
This might interest some. 
QEX is a amateur radio publication published by the American Radio Relay League (ARRL) QEX is fairly technical in nature - much more so than QST, about which one Americal ham said to me a typical circuit was +"How to build a 12 V 1A power supply using a 7812"+ ! 

In the January/February 2015 issue of QEX there's an article with the title +A Low Frequency Adapter for your Vector Network Analyzer (VNA)+ by Jacques Audet, VE2AZX. Currently this is a sample article, so anyone can read it, but I thought I'd attach a copy anyway. 

In this design, the author takes the 10 MHz frequency reference out of an 8753D to drive the LO port of a couple of mixers.  As the frequency of the source from port 1 is changed from 10.00002 MHz to 15 MHz. so a tunable IF changes from 20 Hz to 5 MHz. That's fed into the DUT, then the output of the DUT is mixed back up to the range 10.00002 MHz to 15 MHz and fed into port 2 of the VNA. 

This only works in transmission S21. 

Does anyone know how many 8753's were sold? I can understand if its considered confidential information, but there sure are a lot of them around to this day, and I know there are tons of them used in commercial companies to this day - it is not just radio hams that own them. 

Some of you may know I sell low-cost VNA calibration kits. A reckon the number of people that buy them for 8753's must be 10x the number for the 8720, 8510, FieldFox & PNAs all added together. Of course, someone with the budget for a PNA is less likely to want a low-cost cal kit than someone with an 8753, although one customer rather surprising had a PNA-X.  But there's no doubt the 8753 was a successful range. I'm sure Joel must smile. 

Dave Kirkby, G8WRB.