Hi Peter,
Thanks for replay!
See my comments inline below...
Yes, the lack of matching keeps the circuit simple but you pay the price
of less than the best achievable performance from this circuit. In the
real world you will need to measure and compare the results of both
matched and unmatched circuits to see the performance difference and
keep in mind that often what looks good on paper does not translate into
a large practical (real world) difference, ie; the improvement may not
be worth the added complexity.
Sure. I fully agree. Based on my own experiments I can just confirm: theory is sometimes very far from the practice :-)
[...] for the DBM to
be effective the diodes need to be switched hard on/off as quickly as
possible.
That's right!
It seems to me that it is probably easier to achieve this if
the DBM is being driven from a low impedance source which ensures
maximum current flow through the diodes.
Hmmm... are you sure?
There is no current flowing through the diode until we pass the diode voltage barrier (depending on the type of diode it is usually from 0,2V to 1V). So I think the voltage on the diode is much more important then the current in fast switching conditions.
Following your point (but I'm not convinces about that) the mixer should work even better having 200 ohms on each port (in opposition to 50 ohms) because we have higher voltage on the port much earlier for greater impedance. Is my understanding correct?
I'm not convinced about that and I think there is really no difference in mixing efficiency when we have any different impedance (on each port!) then 50 ohms. Do you have any materials (I mean experiments, measures etc.) which say that I'm wrong in that?
This link was posted by a member of our group in the past and compares
the performance of various DBM's. I was very happy to see that the
homemade 1N4148 DBM's performed so well against the commercial DBM's. Of
course you will have to be careful in how you build the homemade DBM,
match the diodes and be careful with the transformers but if you do a
good job the results can be quite good. See link below:
Thanks for this link!
I have to analyze it in details, but a brief look shows that 1N4148 can be really close to ADE-1 if you spend a lot of work on that (diode matching, well positioning etc.)
But that means, we can have really good results (or even better) without that pain - just by using ADE-1 single chip - so, less complexity, less pain, more repeatability, right? :-)
Regards,
Rafal SP3GO
