EMRFD Message Archive 6074

Message Date From Subject
6074 2011-04-07 16:31:02 Chris Trask Split-Ring Mixer (was: high level mixers)


> I do not recall any EMRFD group member that has commented on assembled
> circuit and its performances.
> I have posted my report, to be taken as informative of my trials, in
> Files under I7SWX-Experim-Diode-HMode&SplitMixers. I hope other people
> will test your Split-Diode Mixer and see if the results are repeatable
> or can be better than my measurements.
> I Have done CL test from 1.75 to 220 MHz and a Dual Tone IMD measurement
> on 10MHz.
> My report shows your diagrams and my 2T simplifications. I could not do
> LO driving with square wave signal, only sinewave.
> I have copied the Spectrum analyzer screen copy of the 2T IMD measurement
> and Tables with Conversion losses at different bands.

Thank you for having gone to the trouble and effort to test the
split-ring mixer (SRM) independently. The 1N5711 diodes are comparable to
the BAT54S dual diode that I used, just lacking the matching. I'm
especially pleased to see that you have verified that the SRM does in fact
provide a much lower conversion loss that we normally see with passive diode
mixers in any form. I have ordered small quantities of the PMBD353,
PMBD354, and 1PS70SB84 for evaluation purposes. The PMBD devices have a
much higher quality factor and should provide a slight improvement in the
conversion loss, and their lower junction capacitances will improve the high
frequency cutoff.

I'm not sure if the 2-transformer approach alters the performance in any
way, but for now I'm going to stick with the 3-transformer approach as that
is what all my present data is for. I have found in the past, with my
feedback mixers, that combining two transformers as one can cause OIP2 and
OIP3 performance to deteriorate.

One small item: The modified design in your Fig. 6 was not an
"improved" version, but instead was a variation I used to detemine the
effects of lowering the LO source resistance seen by the diodes. I won't be
using that one again as it showed that a higher LO source resistance to
diode "on" resistance ratio gives better conversion loss.

Chris Trask
Senior Member IEEE
6076 2011-04-08 00:24:20 Gian Re: Split-Ring Mixer (was: high level mixers)
Hi Chris,

thanks for your comments.

I will follow your future results
6102 2011-04-13 06:00:24 Tom Re: Split-Ring Mixer PDF and Signal Hound
Hi Gian,

I noticed that in your PDF on `Experimenting with 2T Diodes H-Mode & Split Mixers' that you are using a Signal Hound <http://www.signalhound.com/> spectrum analyzer. I wonder if you would care to comment regarding its usefulness as a test instrument? The price seems right and I see they are on their second model.

Tom, ak2b
6125 2011-04-14 12:08:59 Gian Re: Split-Ring Mixer PDF and Signal Hound
6134 2011-04-15 06:22:58 Tom Re: Split-Ring Mixer PDF and Signal Hound
Hi Gian,

Thanks for your response. That's very nice of Signal Hound to replace your disappeared SA for free.
The idea of a small SA by itself is appealing. Even though some nice looking SA's appear on eBay every now and then, they are huge (not to mention, expensive) and you don't really know the condition of what your getting. I have a Tek scope that I got from eBay that works but the switches are so worn out from use that it has become intermittent. I picked up a Rigol 1052 last summer and I am very pleased with it.
Another recent thread here was discussing signal generators. I also have an HP8640B that I think is great but last year the power amplifier went out on it. Luckily I found someone on ebay that had one for a decent price and was able to fix mine. Just yesterday, Elecraft announced an interesting hand held programmable signal generator that covers 1.5 to 200Mhz <http://www.elecraft.com/elecraft_prod_list.htm#xg3> the manual is here http://www.elecraft.com/manual/XG3%20Owner%27s%20Manual%20Rev%20B.pdf. You can even sweep between two frequencies at programmable rates. This looks to be a good substitute when my HP gives up the ghost.

Again, thanks for responding. I need to do a little more thinking about the Signal Hound but I will be sure to menti