Balanced linked tuner turns ratio

[DMOD]

W4AMV, Phil, Chuck and all,

Ithink that should be better to make a test tuner with a dimensionally small but sufficient inductor (50uH+), a link coil with the right reactance for the frequency loading it with 120 Ohm resistor in series with 52uH inductance and check the possibilities.
I'll try first with 270pf caps in series with the load (120+600jx) to precancel the inductive reactance.
I'll also try without the caps and check if the OWL impedance can be handled by the parallel cap in co-operation with the inductor.
I'll also check the efficiency and measure the K factor.
It is true that my case is 'special' because of single band use and 3/8wl as total length of one leg of the dipole+OWL.
In case the results are dissapointing, I'll rethink about using the single band super efficient cap loaded dipole antenna.

Thank you all for simulations suggestions and possible solutions.
Stefano

Why not try a full size, unit-scale link coupled tuner with this circuit,
which uses a 2.5" Primary link coil OVER a 2" Secondary coil. These component values and sizes have been verified by simulation.

This Coaxial arrangement should provide the highest coupling coefficient.

See coil detail notes in lower left-hand corner.

This is essentially what you requested graphically in a previous post.

Phil-AC0OB

[aa5wg]

Wrong circuit design.  A variable capacitor needs to be added to the input inductor.  This will give you much more flexibility in tuning the antenna coupler, matching.

[AMLOVER]

For some reason I can't reply any more.

[AMLOVER]

That's good, I can post but I can't attach the photos of my just finished tuner. I'll try to find out what is wrong and come back with the photos.

[AMLOVER]

Just a test photo, nothing to do with this conversation.

[AMLOVER]

I found out the reason but I'll fix it tomorrow and I'll add the photos of what I have done till now.
Excuse me for the inconvinience.

[AMLOVER]

Phil, Joe, Steve, Chuck and all,

I fixed my problem with attachments. My photos archives were jpeg and I had to transform them to jpg.
I hope this time to get attached.
The main inductor is 34 turns 1/8'' spacing 3/8'' copper tube on a 5.5" pvc form and the link coil is 4 turns 3/8'' spacing 3/8'' copper tube on a 7'' form.
Due to dog house small dimensions I can't get any bigger. In any case I'll adjust OWL or antenna length to get the most efficient taping.
Plenty of taps for experimenting tunings.

[DMOD]

Phil, Joe, Steve, Chuck and all,

I fixed my problem with attachments. My photos archives were jpeg and I had to transform them to jpg.
I hope this time to get attached.
The main inductor is 34 turns 1/8'' spacing 3/8'' copper tube on a 5.5" pvc form and the link coil is 4 turns 3/8'' spacing 3/8'' copper tube on a 7'' form.
Due to dog house small dimensions I can't get any bigger. In any case I'll adjust OWL or antenna length to get the most efficient taping.
Plenty of taps for experimenting tunings.

When you say 5.5" and 7" forms, are those length dimensions?

If so what are the coil diameters?

Phil

[AMLOVER]

5.5'' and 7'' are the diameters from center to center of the 3/8'' tubes. The dimensions are 21.2'' for the 34 turns coil and 2.1'' for the 4 turns link coil.

[DMOD]

5.5'' and 7'' are the diameters from center to center of the 3/8'' tubes. The dimensions are 21.2'' for the 34 turns coil and 2.1'' for the 4 turns link coil.

Your 5.5" Dia. 34-turn Output coil has an inductance of 35uH and an XL of 415 ohms. About 220pF in parallel will tune it to 1.85MHz.

Your 7" Dia. 4-turn Input coil has an inductance of 3.5uH and an XL of 41 ohms or 9 ohms below the 50 ohm target.

[AMLOVER]

I think when there is a coupling between two coils, the inductance of the outer coil is increased because of the mutual conductance.
I will count it however when it is in its final place and I'll adjust, as possible, its inductance by squeezing the turns spacing.

[W4AMV]

I think when there is a coupling between two coils, the inductance of the outer coil is increased because of the mutual conductance.
I will count it however when it is in its final place and I'll adjust, as possible, its inductance by squeezing the turns spacing.

The design is based on the self inductance of primary and secondary. The mutual inductance is controlled by the coupling factor and so these items are chosen somewhat independent of each other. No issue, just put a tiny squeeze on the L if need be. Initial values might compromise best case return loss slightly.

[KC2ZFA]

possibly a naive question: all those designs here have low to very low L/C ratios, is that desirable ?

peter

[AMLOVER]

Hi Peter,

What values would you propose for L and C in a sircuit like the one in the attachment?
Single band use p.e 1850Khz, 50Ohm to 120+600jx impedance.

Stefano

[W4AMV]

The L/C ratio is driven by the complex line Zo with the antenna attached and the desired matching bandwidth, that is operating Q. A good treatment of the details is in the handbook, example the '63 treatment in the chapter on transmission lines. See copy of excerpt attached. There in Ch 13, the series and parallel balanced line tuning is addressed.

[DMOD]

I think when there is a coupling between two coils, the inductance of the outer coil is increased because of the mutual conductance.
I will count it however when it is in its final place and I'll adjust, as possible, its inductance by squeezing the turns spacing.

The design is based on the self inductance of primary and secondary. The mutual inductance is controlled by the coupling factor and so these items are chosen somewhat independent of each other. No issue, just put a tiny squeeze on the L if need be. Initial values might compromise best case return loss slightly.

In my calcs, the calculated coil inductances were for free coils by themselves.

If one is concerned with the Mutual Inductance, then
M ~ = (Ns X Np X Area)/length of coil.

M also is = k X SQRT(Ls X Lp)  where k is the coefficient of coupling.

If k ~= 0.9 for a coaxial set of coils, then M = 0.9 X SQRT(3.5uH X 35uH) = 0.9 X 11.1uH = 10uH.

[AMLOVER]

Even if it is a coaxial set up, the two coils have a distance of 3/4'' between them so K could be less then 0.9.

I used 4 turns for the link coil because this number was right in a previous linked tuner I made for an EFHW (4000Ohm +).

In that case I had the link coil (4 turns) around the cold side of the long inductor (44 turns). It worked perfectly without capacitor in series to ground.

In that case coupling was much better and K was for sure closer to 0.9. The long inductor was factory made and I managed a very tight coupling, may be less then 3/8''.

In any case if I'll count around 10uH when in place then with a var. cap and 1300pf in series to ground  I'll adjust it to the desire XLS.

[W4AMV]

Some more comments on this and to put this design approach in perspective.

Choosing Lp and Ls might be driven by the loaded
Q of the primary and secondary inductance. On the
50 ohm side, a Q of unity is realized at 1.8 MHz
with an inductive reactance of 50/(6.28*1.8 MHz)
or 4.4 uH, hence its value. On the balanced side
consider the magnitude of the Z termination, about
612 ohms, At a Q of unity, Ls would approach a
value of 54 uH. However, if the reactance of
600 ohms is tuned out at 1.8 MHz, the remaining
112 ohms is set by an inductance of 10 uH. A
range of 10-54 uH with suitable C to tune the reactance
is reasonable. It is the coupling factor, k, that
will significantly alter the final quality of the
match and the return loss. Recall in the earlier
designs of balanced matching tuner systems, a swinging
link was always touted as an ideal final adjustment.   

[W4AMV]

Should be 120 ohms, real, anyway still ~ 10 uH.

[aa5wg]

Alan - W4AMV, good material.


[/quote]

[KC2ZFA]

as the handbook text posted above says, as a first approximation use the LC values of the transmitter plate tank.

the 160M B&W balanced (for push-pull PA) coils are 94 uH and resonate at the bottom of 160 with 90 pF. The handbook recommendation is that the LC tuner tank resonates at 80% of the intended operating frequencies so max of 100-120 pF would be used in a parallel-feed balanced link tuner for 160 using the B&W hdvl or tvl coils depending on power. From what Stefanos is seeing at the input end of his ladder line he should use the parallel configuration.

and make the link variable to dispense with the capacitor on the link side.

[DMOD]

If Charles and Peter have some analysis and schematics they would like to submit, I am sure we could all benefit.

[W4AMV]

This is sort of a work in process. I found it interesting to look at the linked coupling transformer modeled as its "conductively coupled equivalent circuit". The results for a simple impedance matching system are interesting. More to follow while digging deeper.

[Tom WA3KLR]

I'm just diving into this thread. 1.4 picofarads at 160 meters; 60,000 Ohms? Doesn't look like a comma to me at 7:30 p.m. - tired.

[W4AMV]

Hi Tom... Yes sir... Keep in mind, there just numbers. Some notions are counter intuitive. Not necessarily practical.  However, it is the concepts and making sense of the mechanics so that practical and useful design paths are  obtained.