EMRFD Message Archive 8045
Message Date From Subject 8045 2013-01-05 18:29:17 Jerry Haigwood Winding a Balun Core for use with a diode ring mixer
I have a question about using a balun core (maybe a BN-43-302) for the
transformer of a diode ring mixer. When using a round core, the dots of the
schematic are always in phase with one another (all three dots are on the
same end of the schematic symbol and we call that Trifilar). Recently I saw
a schematic for a balun core and the dots were not all on the same end, in
fact there were no dots at all. If you can visualize, a single wire on the
left of the core and a twisted pair on the right of the core. The twisted
pair is center tapped by connecting the end of one winding with the
beginning of the second winding. The single wire on the input side (i.e.
either LO or RF) didn't seem to care. So, will this balun core transformer
work OK or do I have to make sure the two transformers are wound identical?
See the crude schematic below.
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-----8046 2013-01-05 21:31:00 Nick F Re: Winding a Balun Core for use with a diode ring mixer
It doesn't really matter if the mixer transformers are wound on a round core or a balun core. The two coils that are put in series have to be connected in such a way that the total inductance of them is larger (more than double) the inductance of a single coil. This is accomplished by winding all three windings with trifilar twisted wire and connecting the end of one coil (coil2) to the start of another coil (coil 3). For best results, the transformers have to be identical. I found out that inductance can be different when making transformers on same type of core, so it's best to make a few transfomers and then select two of them with closest inductances.
PS - probably my reply will appear8054 2013-01-06 16:33:37 Ashhar Farhan Re: Winding a Balun Core for use with a diode ring mixer
"it depends"
by keeping the secondary winding untwisted, you are essentially relegating
it to act like a conventional transformer. if you had a trifilar winding,
then all the three would have exhibited transmission line characteristics,
improving the usable frequency range of the transformer, lowering the
losses.
however, my understanding of the description may be wrong, but as i read
it, it appears that the technique is advocating primary and secondary on
different holes of the 'double barrel'. this will make them two separate
tranformers with some leakage between the two!
it is best that you use trifilar winding, counting a single pass through
both holes as one pass. i have routinely used these to make broadband
transformers that have worked well from 500 KHz to 150 MHz.
- farhan
8056 2013-01-06 18:38:55 Jerry Haigwood Re: Winding a Balun Core for use with a diode ring mixer
I am not talking about trifilar twisted wires. I am talking about one
bifilar coil and one single wire coil. If you lay the balun core on a desk
in front of you with the two holes pointing left and right, the twisted pair
wire is inserted from the right side and they are connected in series so
that you will have a center tap. The LO or RF input will be on the left
side of the balun core with a single wire winding. Diz, W8DIZ, the person
many of us buys toroid/balun cores from, uses this method. You can see the
transformer at:
http://www.kitsandparts.com/drm.php
Scroll down a page or two to see the transformer. I have never seen this
method used and I am curious as to how I would tell if the single wire
winding is kept in phase with the bifilar pair or if it is even required to
be in phase. I would like to use this method but I am somewhat concerned
about the phasing.
Jerry W5JH
"building something without experimenting is just solder practice"
8057 2013-01-06 18:39:13 Jerry Haigwood Re: Winding a Balun Core for use with a diode ring mixer
Take a look at:
http://www.kitsandparts.com/drm.php
Scroll down a bit and you can see the transformer. Does the two windings on
this transformer have to be in phase?
Jerry W5JH
"building something without experimenting is just solder practice"
8059 2013-01-06 20:21:04 John Kolb Re: Winding a Balun Core for use with a diode ring mixer
if you had 2 mixers and were building an I-Q receiver.
As pointed out elsewhere, trifilar windings give a wider bandwidth,
but the layout with one winding coming off the other side lays out
better sometimes. I've used this style building antenna splitters.
You can, however, assign phasing dots to the transformer. With
the bifilar winding on the right, put a dot on the upper right lead.
The dot for the single winding then goes on the lower left. If you
think of current flowing from the dot to the other end, it's flowing
clockwise in either winding.
I'm sure someone will correct me if my reasoning is wrong :)
John KK6IL
At 06:08 PM 1/6/2013, you wrote:
Hi Nicolae,
I am not talking about trifilar twisted wires. I am talking about one
bifilar coil and one single wire coil. If you lay the balun core on a desk
in front of you with the two holes pointing left and right, the twisted pair
wire is inserted from the right side and they are connected in series so
that you will have a center tap. The LO or RF input will be on the left
side of the balun core with a single wire winding. Diz, W8DIZ, the person
many of us buys toroid/balun cores from, uses this method. You can see the
transformer at:
http://www.kitsandparts.com/drm.php
Scroll down a page or two to see the transformer. I have never seen this
method used and I am curious as to how I would tell if the single wire
winding is kept in phase with the bifilar pair or if it is even required to
be in phase. I would like to use this method but I am somewhat concerned
about the phasing.
Jerry W5JH
"building something without experimenting is just solder practice"8068 2013-01-07 20:26:18 Jerry Haigwood Re: Winding a Balun Core for use with a diode ring mixer
Thank you! This was the info I was looking for. Also, it is nice to know the phasing as I sometimes build Norton amps and usually use a toroid to wind the feedback transformer. In the future, I will try a balun core and see if I can make an amp and not an oscillator. ;-) I once had a boss that told me, “amplifiers do and oscillators don’t - it is all in how you label them.” So, I guess the theory in that statement is to start out building an amp if you want an oscillator and vice-versus!
Jerry W5JH
"building something without experimenting is just solder practice"
8071 2013-01-07 20:26:19 Ashhar Farhan Re: Winding a Balun Core for use with a diode ring mixer
the windings that have a 'center-tap' must be properly in-phase. if you
look at the picture closely, you will notice the following:
a. on the right side, there are two windings, one is in green wire and the
other is red. both the windings are in parallel. the opposite ends of red
and green are connected together.
b. on the left side, there is a single winding.
the transformer in the picture don't use twisted wire at all. they are
conventional transformers. however, the windings on the diode side have to
be like those in the picture. the phase of winding on the input/output side
is non-critical.
often, i have used trifilar winding even on these 'double-barrel'. if you
see chris trask's paper on diode mixers (it is somewhere in the files
section of this group), you will see some clear illustrations of how the
windings are done.
- farhan
8081 2013-01-08 21:10:28 Jerry Haigwood Re: Winding a Balun Core for use with a diode ring mixer
I understand about the center tap, I was concerned about the single
wire and as you said, it doesn't seem to make a difference. Also, if you
read Diz's instructions, he recommends twisting the wire pair on the right
side 2-3 turns per inch. I have wound a lot of trifilar wires on a round
core but the balun core is a slightly different animal. Thanks for the
help.
Jerry W5JH
"building something without experimenting is just solder practice"