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Темы - R6LDD

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Технический раздел / ФНЧ
« : 23 Май 2019, 20:03:47 »
Коллеги, кто владеет, нужно ФНЧ со срезом 7 кгц посчитать. Выручайте.:)

Что за станция такая гремит на 82.5 кГц? Уровень дикий.

Андрей, поздравляю с днем Рождения!  Здоровья, благополучия тебе и семье!
Успехов в Радио! Всех благ!

ДВ антенны / Antennas for 136kHz by on7yd
« : 21 Февраль 2019, 22:45:24 »
Хороший линк. Раньше вроде не встречал.

Приветствую! Такой вопрос: надо жидкой канифоли, ест спирт, метиловый.
Для питья - это яд. Для канифоли можно, или пары это мелочи? Паранойю выключать надо?

Есть 20 шт. С5-35В-25 10 Ом. Как раз 2шт. по 100 Ом 250 Вт. в параллель = 50 Ом. Лучше чем лампа накаливания.
Вопрос по охлаждению. Думаю стоит посадить на медь 50х5 или нет?  На торцевых накладках крепежа прокладки из слюды
~ 1 мм. толщиной. И стоит ли слюду вообще ставить? Или только вентилятор на обдув?

Свободное общение / 136kHz CW QSO
« : 25 Ноябрь 2018, 22:44:13 »
Не знаю куда, пусть десь полежит.

KL7L 137kHz and 475kHz tuning aids - how to check your antenna is resonant (in phase) and its impedance is matched to 50 ohms; M0BMU scopematch
Интересно посмотреть.

Dear SLF friends,

A new step forward towards DC: Since yesterday 22:30 UTC i'm TXing a carrier at 80.005 Hz. That's the 3750 km band, where the far field begins at a distance of 598 km.

The antenna voltage is just 5 kV and i'm getting 1.2 mA antenna current, giving an ERP of  20 fW (2E-14 W).

The voltage is even higher than in my recent experiment on 270 Hz, anyway the S/N is lower, indicating that my RX lacks of sensitivity. Indeed this experiment helps to estimate the lack of sensitivity. Looks like i'm missing about 10 dB on that frequency. Anyway the signal is making the path of 3.5 km to my tree grabber, as usual shown at http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html. Not a big distance but still well beyond most garden fences!
The signal leaves a barely visible trace in the ZEVS window which is running at 3.8 mHz FFT bin witdh. Unfortunately ZEVS is off the air since a week or so. actually i wanted to transmit side by side with ZEVS, of course a bit deeper even.

>From a quiet period at night, i calculated the SNR of a 1 hour carrier period using vlfrx-tools: carrier S/N: 16.83 dB in 277.8 uHz, -18.73 dB in 1Hz

For the crazy homebrewers i'd like to share that website where i ordered the HV-transformer, http://www.hosin.de/Specials/HV-Trafo/hv-trafo.html A nightmare for all safety-fetishists! For the completeness it must be mentioned together with that page: http://kurts-werkstatt.de/hv-trafo.htm

73, Stefan

Well, today, i did a first step into the ITU radio band 2, SLF.

Since 21:00 UTC i'm transmitting on the INV-L on 270.01 Hz. The antenna current is just 2.5 mA. The ERP is about 6 pW.
Almost nothing but anyway a trace becomes visible now on my RX on the tree in 3.5 km distance (http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html)
Of course this is a near field experiment. There, on the 1110 km band, the far field begins at a distance of 177 km.

On the transmitter site i'm using the modified 5 kV mains transformer that was used to produce 5 kV at 970 Hz. Now there is a series capacitor of about 20 uF applied to the primary winding. Together with internal reactances this maximises the peak of the fundamental frequency of the output voltage.

The goal of this first experiment is just to put the foot into this part of the radio spectrum. And to do some pre-tests, trying to optimise filter and blanker settings for future tests.
In the end i'm planning to work on that frequency from the ground loop antenna, which is still in the near field, but anyway :-)

73, Stefan

Отдам плату синтезатора RN3AUS.Фрезерованная на станке.. Сам не осилю, а "сохатить" жалко.

Свободное общение / Наши зверушки.
« : 16 Октябрь 2018, 19:55:56 »
 У моей "маленькой Леди" - английская бульдожка, сегодня поменялся цвет глаз. Ровно 2 с половиной месяца.
И радостно, и немного грустно. Взгляд голубых щенячьих глаз не передать словами...
Знакомьтесь - леди Лада.:) На фото еще голубоглазая.:)

Как писал Сергей ADF хочется чего-то необычного.:) Попалось вот:

Залетела " пуля в голову".:)
QRB - 9м.:) Ключевание ручное - коряво.


Today i run a carrier transmission on 970.01 Hz. Start time was 08:05 UTC. The carrier run for 3 hours without an interruption. I got 1.9 A antenna current on my ground loop antenna, about 320 W DC input to the PA.
The signal was received on my 3-axis RX on the tree in JN49IK. The distance was, as usual, 55.6 km.

So far the results were disappointing. I expected a strong SNR (at least 10 dB in 424 uHz) from the new E field antenna which seems to perform very well in the complete ULF range. However the analysis of a two hour segment of the carrier showed an SNR of 6 dB, i.e. just noise. However, as i routinely calculated the SNR from the N-S loop i got a surprising SNR of 13.03 dB in 139.5 uHz.
At about 08:40 UTC the reception on the tree was disturbed by its own solar charger, just for a few seconds but that was enough to create a bright vertical line in the 424 uHz spectrogram showing the E field.

Anyway, i just analysed the full 3 hour segment, only from the N-S loop (which actually points rather to 30/210 deg) and got the following result (including processing command line):
vtread -T2018-09-29_08:05,+3h /raw | vtcat -p | vtmix -c0,1,0 | vtfilter -a th=6 -h lp,f=1500,poles=8 | vtblank -a27 -d0.0005 -t100 | vtmult -f970.01 | vtresample -r240 | vtresample -r1 | vtraw -oa | ebnaut -dp8K19A -r1 -c2 -v -f15 -f16 -M'***' -N3 -k20 -S24
carrier phase: -111.2
carrier Eb/N0: 1.9 dB
carrier S/N: 14.25 dB in 93.0 uHz, -26.07 dB in 1Hz, -60.05 dB in 2.5kHz

This is the first far field detection of a 970 Hz signal generated by amateurs on the 309 km band! A true milestone for me. Since more than a year it was my goal to cross that far field border on that band. :-) The efforts were immense.
The result is just preliminary. I want to tweak the parameters for a higher SNR and try to filter out the short QRM from the charger.

So now, why does the E field produce such bad results? At http://www.iup.uni-heidelberg.de/schaefer_vlf/ULF/ULFSLFELF.png you can see what it receives in the range of interest. The day/night QRN difference is higher than on the loops, so the loops seemed to be rather deaf. Does it maybe mean a steep reflexion on the ionosphere, so that the E field antenna doesn't see it, but the loops do?

Later i've done a DC measurement and got 1 A at 86.5 V, quite much this time. Maybe a bad contact somewhere. Will check that.

My 120 Ah LiFePo4 accu is fully recharged and i plan to do a new experiment on monday morning, 3 hours before my solar charger starts to work :-) The SNR seems to be promising, i plan to send a 5 character EbNaut message.

More results and a spectrum peak image will follow.

73, Stefan

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