[minima] Re: the double kiss
- From: farhanbox@xxxxxxxxx <farhanbox@xxxxxxxxx>
- To: joe@xxxxxxxxxx <joe@xxxxxxxxxx>, minima@xxxxxxxxxxxxx <minima@xxxxxxxxxxxxx>
- Date: Fri, 05 Sep 2014 08:36:49 -0700 (PDT)
joe,the shunt shorting will itself lead to mixing provided it is happening
for only half the cycle. during the other half, the ic end of the upper winding
is grounded. so the current will flow back from the port end into the ground in
the upper winding while the current from the mixer will flow into thr grounded
end of the lower winding. so, it works. er, so i think that it does.- f
------ Original message------From: Joe RocciDate: Fri, 5 Sep 2014 20:31To:
minima@xxxxxxxxxxxxx;Subject:[minima] Re: the double kissFarhan Look at the
schematic carefully. When 2A connects to 2B1, the lower half of the balun is
shorted to itself. I don't think this is what you intended, is it? The concept
schematic can work, bit I think there's something fishy in the actual
schematic. ----- Original Message ----- From: Ashhar Farhan To:
minima@xxxxxxxxxxxxx Sent: Friday, September 05, 2014 10:09 AM Subject:
[minima] Re: the double kiss
steve,
you are sharp! in spite of the flu!. but let's get to the nitty gritty. 1.
there are two pairs of complementary switches. so, u can either connect 6 and
11 to AC ground and 5 and 10 to the IF port or vice versa. it really doesn't
matter. 2. i had put the resistor of 470 ohms to load the Si570 output (it was
spikey as hell on my rigol 1052). now, it is squarer. i am not sure if this
was due to the cable length. I'd ideally mount the Si570 close to the mixer.
3. the 6 and 11 are not connected to the transformer! look again. i just
drew them on the 'wrong' side of the chip. in the interest of clarity, i think
i should move them to the left side of the chip. many a times, we get put off
by a circuit just because it is confusingly drawn. someone should write a
guide to 'drawing clear radio circuits'.
- f
On Fri, Sep 5, 2014 at 5:00 PM, Steve VK2SJA <vk2sja@xxxxxxxxxxx> wrote:
Hi Farhan,
Having trouble matching photo to circuit diagram. Suspect errors in
schematic. Looking at image I've got 6 & 11 tied together then to a 0.1uF
to what I make as being the IF port. But circuit diagram shows 6 & 11 on
the RF port side with the transmission line transformer. Do we have some
pin number errors? Or am I reading/seeing it wrong? (possible, suffering
the flu at the moment - so not thinking real clear).
RF port side of circuit seems to have a couple of non-symmetries that I
don't understand. But leaving that aside for the moment can you please
explain how does the phase reversal take place? I think I understand that
switching is to virtual ground reference of 2.5v established by voltage
dividers either side. But how does phase reversal take place? By all means
point me to the required reading in EMRFD etc-al... :-)
Also photo appears to have extra resistor on LO port direct to ground
before 0.1uF which us not in circuit - Yes?
73, Steve.
> joe, steve and comrades,
>
> i have thrown together yet another mixer after reading some more
> literature
> from w7zoi, joe's experiments and the second kiss mixer as well.
>
> so, here is what i did come up with. refer to the double_kiss.png
> attached.
> it simply a transformer with a DPDT switch on both sides of the primary.
> now, alternatively, one side connects to the input while the other side is
> grounded. so, all in all, the transformer's polarity is rapidly reversed.
>
> the advantage this has over the regular KISS mixer is that (a) it uses
> FST3253, hence, matching, biasing etc are already taken care of, (b)
> unlike
> the original KISS mixers, there is no 'unused' section of the transformer,
> hence, the LO isolation is very good.
>
> how is this different from Joe's mixer? this one uses a single
> transformer.
> it uses the FST3253 which can be hand soldered without resorting to SMD
> PCB. (see the picture).
>
> implementation details : there are a couple of resistors thrown in the
> provide biasing. they make the the circuit look more complicated that it
> really is. the output transformer is configured as a current balun rather
> than a voltage balun.
>
> performance:
> the performance is exceptiona. the losses are so low that the LPF, mixer
> and the crystal filter together are together less than -10db loss. The
> local oscillator leakage at the RF port is less than 5mv (except at 7 MHz
> where it is 10 mv). i couldn't measure the IIP3 properly as my dual
> generator isn't powerful enough. I suspect it is more than 20 dbm even
> with
> the crystal filter (reactive termination) at the IF port. i will need a
> stronger dual signal generator to accurately measure it (the IMD
> products
> are going into the noise grass).
>
> - f
>
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