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I just replaced the 4 BS170 of the PA of my Hi Band QDX and I replaced the "conventional wound transformer for 12V" by a "WTST for 9V wounding", expecting an increase of output power. With the former transformer and BS170 I got only 1.5W on 10M band.

Now I have the following output power in a dummy load:

- 30M - 2.70W

- 20M - 3.50W

- 17M - 3.40W

- 15M - 1.2W

- 12M - 0.6W

- 10M - 1.6W

What toroids should I tune by spreading or tighening the coils?

- L2 or L6 or both?

- L3 or L8 or both?

- L4 or L10 or both?

The RF filter sweep shown by Putty gives:

- 30M minus14 from 10 to 12MHz then falling

- 20M minus15 at 14MHz? then minus23 at 15MHz

- 17M plus2 at 17.5MHz

- 15M plus6 at 21MHz

- 12M minus1 from 24 to 27MHz

- 10M plus4 from 27.5 to 31MHz

These results seem OK except for the 20M band. What should I do to the L12 toroid whin I built according to the manual to try to improve the 20M RF filter sweep and i the same time the 30M result?

About the 30M band, I just replaced in the "Band configuration" the 11M original settings by 30M settings with the same values as 20M (0 for both LPF and BPF numbers).

73 - Pierre - FK8IH?

?

The former output powers were taken using JS8Call software and show the power transmitted with JS8 mode.

I took the same measures using the "transmitter test" of Putty, clicking on "T" and read the following values:

- 30M - 2.7W

-20M - 3.7W

-17M - 3.8W

-15M - 1.5W

-12M - 1.5W

-10M - 4W

I should maybe finely tune the 15 and 12M bands and am satisfied witht he 10M result, which is important currently with the high solar activity. I have been heard on the East Coasts of Canada and USA on 10M with JS8 signals as recorded by pskreporter.info, around 9,000 miles, not bad for less than 4 Watt!

A last remark: replacing the 4 BS170 and removing the output transformer to rewind it was not an easy task for a 80 years old OM with bad eyesight and shaky hands but I definitely think the QDX very tiny board is well designed and manufactured and will accept abuse! This let me confident for my next build: either a Mid-band QMX or a QMX+, the latter being preferred.

73 - Pierre - FK8IH?

Pierre,?

? ? ?The BPF sweep problem on 20M on High band QDXs has been there for most people, and L12 changes to fix it haven't been established that I've seen. Doesn't seem to be much you can do about it, but make sure the audio level on that band is appropriate in WJST-X..and seems to still work pretty well on 20M for me.?

?

As far as power output, the middle set of toroids is for 15/17m... And I've found those to be a tradeoff...messing with them to increase power on 15m may mean a slight decrease on 17m.?

If you study the QDX manual and schematic, you can see which toroids affect which bands. There are 3 sets of LPFs, and they are assigned to different bands in the terminal application.?

?

-Nate

N8BTR

Nate,

Thanks for your answer. About the 20M band I already finely tuned the Audio gain (db) in Putty in order to get on each band a +30dB signal strength in JS8Call and for that I have set 30M to 76, 20M to 58, 17M to 58, 15M to 59, 12M to 71 and 10M to 71.

I will see if I can tweak L3 and L8 to get more power on 15M.

73 - Pierre - FK8IH

I read all the threads about the 20M band audio sweep and low output power problem. I tried to tune the LPF without any significant result and I stop doing these attempts to improve my QDX.
I just consider that the QDX has been some kind of prototype to build a new kind of radio and the problems encountered with its development have allowed Hans to design the QMX and QMX+, adding the lessons learnt from both QCX and QDX.?

I will in May build a QMX+ and I think that I will be right to tweak it perfectly because it can be done and I will have an awesome transceiver to add to my Hermes Lite 2.

73 - Pierre - FK8IH