Tuning the torroids for the "classic" filter board.

[kk7bco]

Hello,
I got a new "classic" band board, and put it together today. In the process of tuning, I have spent a lot of time googling with little help:

Manuel's video, and any other mention I have found, shows an example of what values to look for in a single band, without satisfying my confidence that I understand the correct process of defining the others.

What I gather is that I choose a target frequency (for maximum efficiency) for a given band: so with this new board L11 is the 10m coil, and I want to set that for the QRP calling frequency of 28.385MHz. To obtain this I had to add a wind taking it to 6t, giving me resonance on 28.5MHz. I then find the 2nd harmonic with this http://mustcalculate.com/electronics/ha ... hp?f=28.5M which gives me 57M, moving the windings together on L12 gives me 57.5M. The internal meter reports this as an efficiency of 48% at 0.95w. The way it was to begin with was 29.3M/58.4M, 71% and 2.2w.

Is this the correct procedure?

As Manuel mentioned in the video, the resonant peak is not clearly defined, as it is a slow curve, but the notch is quite easy to measure precisely.

Currently, after going through each band I have:

80m 3.8M/6.68M - 2.15W 71%
40m 7.4M/14.78M - 1.1w 62%
20m 14.4M/28.8M - 1.1w 53%
15m 21.8M/43.4M - 1w 54%
10m 28.5M/57.5M - 0.95w 48%

Power source is at 12v, I do not know how to measure current draw. I do not know how to read power with the oscilloscope. Power measured with my Daiwa CN-501H set to PEP is just under 1w at 28.365M, showing as 1.1w on the screen.

Any constructive help would be appreciated.

KK7BCO

[VA7RLX]

I will watch this thread with great interest. I too have a classic bands kit to build and am totally unclear about the tuning procedure. I need to read everything on this forum to find it perhaps?

[reytek79]

Hello friends, I'm in the same dilemma, I put together a classical band and I'm about to do the tuning. I have many doubts. I'm always keeping an eye on this topic.

[kk7bco]

Notes received from my post on the facebook group:

David:
You do not tune L11 for a frequency, you tune it for power and efficiency. The passband reading will be inaccurate on the Nanvna, so focus on second harmonic calculated by center of your operating frequency range per band.
Me:
I do this by checking internal power meter, then the frequency of the dip?
David:
Basic procedure: Power on the rig with the case bottom wall on to prevent short circuit. Change to the band you are tuning. Unplug the rig and separate RF board from main board. Plug in Nanovna sma cable with two pins at end as in Manuel's video. Center pin to 4th pin from center which is RF pin, and 3rd pin for ground and this should be on S11 of Nano vna. S21 goes to RF board sma connector
Activate Trace #1
Set Stimulus to a frequency range that includes your ideal 2nd harmonic notch. Example for 7mhz I want the center of band at 7.100mhz so set range to 13~16mhz.
Then you can spread the coils on L42 to lower the frequency notch and squeeze them to increase it. (I think this is correct but I might be backwards) If squeezing together is not working, add another coil, if spreading is not working take one away.
After getting notch to where you want it unplug nano vna and reassemble main board and case wall. Power up with 13.8V and check power output on CW, the rigs meter is accurate enough. Your goal is around 6W at 13.8V, 5W at 12V, and peak efficiency around 80%. Efficiency and power output will change as you move about the band, but play with it to see how it goes. Spread coils to increase power, squeeze to decrease. Most of the ones I have assembled the CW portion tends to have higher output power and lower efficiency than SSB portion which is where I tune the LPF to be centered.
Hope that helps.

Stephen:
If you don’t have access to a VNA or a spectrum Analyser tune a receiver to the second harmonic and adjust the toroid for minimal S Meter reading or volume. Set the receiver AGC off before you try this

Derek:
Manuel has a nice youtube video talking about it but there isnt really an "ideal" frequency. It depends mostly on your use case, if you plan to run CW vs Phone you might want to optimize the filters for one over the other.
I picked the middle of the phone bands and tuned at the 2nd hamonic.

[kk7bco]

Well, experimenting with these tips blew the PA on my 2nd board, so I may give up on the (tr)uSDX for a while. It is a little too frustrating.

[s57l]

If you want to save some output fets, use current limiter or usb power, not 12v, for experimenting.
I burned about 10 fdt86256 and even more bs170… but i did experiment a lot.
Class e is not the easiest thing to tune…
Fets are cheap, buy spares and do not be discouraged.
73 gl
Janko s57l

[reytek79]

If you want to save some output fets, use current limiter or usb power, not 12v, for experimenting.
I burned about 10 fdt86256 and even more bs170… but i did experiment a lot.
Class e is not the easiest thing to tune…
Fets are cheap, buy spares and do not be discouraged.
73 gl
Janko s57l

friend would have some step by step or video explaining the adjustment procedure safely so as not to burn the fdt86256?

[storyofyouandme]

HI H57L.Where and at what price did you buy your FDT86256. I also burned an FDT86256, which I think is the cause of poor heat dissipation. There are very cheap FDT86256 on the market, and I also doubt whether they are authentic.

[s57l]

friend would have some step by step or video explaining the adjustment procedure safely so as not to burn the fdt86256?

I think Manuel explained it very well in his many videos posted.
Perhaps start with low voltage, like usb power.
Gl!

[s57l]

HI H57L.Where and at what price did you buy your FDT86256. I also burned an FDT86256, which I think is the cause of poor heat dissipation. There are very cheap FDT86256 on the market, and I also doubt whether they are authentic.

I had them in stock, i bought it from reputable eu seller a while ago...
It is not a question of power dissipation, it is a question of tuning the filters.
It should basically stay cold to warm, if mosfet has something to dissipate, it will probably burn and the coils are not tuned correctly.