EMRFD Message Archive 6755

Message Date From Subject
6755 2011-10-18 16:37:27 Bob Q Multiplier Revisited
Hi All -

A recent post - 6622 - touched on Q Multiplier circuit operation as did my much earlier post - 2350 et al. While my earlier query brought in several responses answering my questions, I've not seen similar responses to the newer post. Further, the questions raised in it are not unlike my earlier ones except that the Group responses to mine seem not applicable to it. I am puzzled anew by the newer post much like I was earlier. I've made some attempt to understand this newer quandry - without success. In this regard, I'm adding some discussion and test results to a new folder - "Q MULTIPLIER" - in the FILES section. I'm hoping this followup to 6622 will break loose some insight from the Group.

6756 2011-10-23 12:16:18 Bob Re: Q Multiplier Revisited
Hi All Again -

Since the effort described below, I have further exercised the subject circuit breadboard and found some on-board interaction (coupling effects) of the swept test signal source and the Q Multiplier portions of the assembly. This affected the amount of PEAK performance previously available but more dramatically affected the NULL function. I have since substituted a much better off-board sweep source and otherwise cleaned up the first breadboard assy. resulting in improved PEAK and NULL performance.

The improved performance is displayed in the Q MULTIPLIER folder (in Files) as photos QMult3 and QMult4. Comparison with the earlier posted photos clearly shows this performance improvement but even the improved behavior in NULL has some residue issues as noted in the photo. As previously indicated, I have no application for a Q Multiplier but rather a strong curiosity.

I know there is a huge amount of real talent in this Group so I'm a bit surprised and dissapointed at the lack of response to my hopes for some insight on how this circuit actually works. Interestingly, some possible explanation was recently posted
6757 2011-10-24 13:47:21 Wes Re: Q Multiplier Revisited
Hi Bob, and group,

I took a look at the Q multiplier problem and concluded that we have probably missed the boat by not having used the circuit in some of our rigs. In an attempt to generate some of that intuition that Bob sought, I did a SPICE analysis of the circuit. This is now posted in the files section as "q-multiplier SPICE analysis."

Many thanks Bob for tweaking us about this useful circuit.

73, Wes

6758 2011-10-25 07:01:33 d29602960 Re: Q Multiplier Revisited
Hi Bob and the group,

Not sure if this has been referenced here before but for anyone following the "Q-multiplier revisited" thread and/or interested in Q-multipliers then here is a link to a page which was recently referenced on the regenrx group Bob (K3NHI) mentioned. This page from James (KR1S) has pulled together a number of articles relating to Q-multipliers.


Though the articles cover mostly (though not exclusively) tube technology they give an insight into how Q-multipliers operate and how they may be applied to comms receivers.


Des (M0AYF)