Posted in: Technique
Can someone advise if this transformer can be used for QRP transmitter modulation (in the collector circuit of the output transistor)?:
http://www.avelmak.sk/index.php?lm=865&pg=det&article=39831
I measured the parameters:
Primary: 147 mH, 60 ohm
Secondary: 270 uH, 0.6 ohm
In this transmitter:
http://blog.marxy.org/2008/09/80m-QRP-am-transmitter-first-contact.html
Thanks for the reply
Norbert
Thank you all for your willingness, I have already solved it, the transformer is okay, I just put a 6-ohm resistor in series with the secondary winding because 2 ohms
is too little for the lm386. It might hold up, these are quite resilient circuits.
I think you can't find a cheaper excitation transformer. I'm not advertising for anyone, you can get it in several shops.
Norbert
Hi Norbert, don't worry about the fact that no one has written you back, the vast majority can't even write back, and others don't even have a reasonable conversation with you until they see your call sign. It's great that you are engaged in tinkering and in the end you will find that you will have to "learn" most of the experience yourself, and that is also the most correct way. Keep doing it and don't be disgusted by the approach of some people.
Miro
I am not surprised that no one reacted.
If the author writes in the original, I quote:
I’ve built another version that is amplitude modulated using a 600 ohm telephone transformer.
then I don't understand why Norbert is forcefully putting something else there?!?
Maybe it would be good to improve the English or at least open a dictionary.
Otherwise, I don't care.
73, Vašek
Dear Vasek,
I do not quite get your point.
If I had a telephone transformer, do you think I would bother to ask people
for help?
Don't think so.
BTW, the transmitter works with the transformer I used though I am not quite sure if the performance will be satisfactory.
So we have now come full circle.
73 and take care of your English
Norbert
Hello Norbert,
I couldn't have written that answer better. People often have a clouded mind, they do not see and do not hear what they should. But what can be done.
I wish you a lot of fun with tinkering, but be careful with the regulations, especially nowadays. We never know who reads our posts HI.
Franta (OK2VFS)
Norbert,
for info - the telephone transformer is in every telephone modem, and since very few people use dial-up connections to the internet nowadays, it shouldn't be a problem to find some old modem.
BTW - you can buy a transformer in the Czech Republic, maybe even in Slovakia.
If the question was 'I need a phone transformer, help' I wouldn't doubt your English.
73, Vašek
I would try a regular output transformer from a radio. It can also be from a tube.
This is a classic case of an internet lone wolf. You need to join a group of either CB enthusiasts or radio amateurs, where you would learn much more than here on the internet. You need permission to use this device.
Hi, no, that transformer cannot be used, the ideal one for such use is a transformer with a ratio (turns ratio) of 1:3 to 1:5. Otherwise, even a QRP transmitter cannot officially operate AM, as it exceeds the allowed bandwidth of 2700Hz as stated in the licensing conditions. Although, I am convinced that, for example, 5 W AM would not bother anyone. HI HI 73 Miro OM3CU
That transmitter has less than 1 W (the current draw without modulation is about 40 mA at 13 V).
I put an RC low-pass filter in the modulator amplifier, so the bandwidth
the bandwidth should be OK, right?
I would really like to make my first connection with a device of my own design...
Noro, you need to realize that an AM transmitter has two sidebands and a carrier in the middle. The speech spectrum is from 300 Hz to about 2.4 to 3.1 kHz. This implies that if we consider up to 2.4 kHz, the carrier is +-0.3 to 2.4 kHz, so the total bandwidth is 4.8 kHz. But these are already the basics of technology that every interested party should master. Miro OM3CU
If I limit the frequency of the modulator amplifier to 1200 Hz, will that be okay? Total 2400. I think 1200 Hz is enough for speech. I just need to change the capacitance. The Australian who designed the transmitter writes that I am thinking too much about it and that I should just fire it up and that's it. Are the conditions in Australia stricter than here?
Building an SSB transmitter is not that simple. If someone has a simple schematic, I would be happy, even though I have put a lot of energy and time into the construction.