Something for mstechca?

[Nigel Goodwin]

Just happened to come across this!, although it's HF amateur band, the principle still holds - it's a complete transceiver using the same transistor for both transmit and receive!.
**broken link removed**.

 

[mstechca]

My design does NOT use a crystal, and as soon as I can escape my receptionless room (which I have discovered IS the culprit), my receiver can pick up CTV (toronto), and CH (hamilton) TV stations. Both of these stations are in Ontario, Canada.

Thats interesting for a transceiver.

 

[audioguru]

Nigel,
I like the way that the circuit mutes the audio during transmitting by using the same diode used for AM detection.

MStechca,
Your "radio" manages to pickup the hundreds of thousands of watts of signal from CH-TV that is right next door?

:lol: :lol:

 

[Nigel Goodwin]

Nigel,
I like the way that the circuit mutes the audio during transmitting by using the same diode used for AM detection.

The use of the diode to turn off the amp is clever, but the diode isn't a detector, the detector is the transistor - on receive it's a direct conversion receiver (the transistor works as a mixer). An AM detector wouldn't be any use, as it's a CW transceiver, not an AM one.

 

[audioguru]

Where would the transceiver have a BFO connected to provide a tone during its receiving a blank carrier?

 

[mstechca]

MStechca,
Your "radio" manages to pickup the hundreds of thousands of watts of signal from CH-TV that is right next door?
:lol: :lol:

Did you read what I said I can receive?

my receiver can pick up CTV (toronto), and CH (hamilton) TV stations

 

[JimB]

Where would the transceiver have a BFO connected to provide a tone during its receiving a blank carrier?

The crystal oscillator is also the BFO.
A problem with such a simple scheme is that if the the other guy nets spot on to your frequency, you wont hear him. He would have to be a bit off your frequency to get a beat note.

An entertaining toy for a bit of fun and experimentation, but not a serious bit of kit. (A bit like a super-regen receiver really).

JimB

 

[audioguru]

The crystal oscillator is also the BFO.
A problem with such a simple scheme is that if the the other guy nets spot on to your frequency, you wont hear him. He would have to be a bit off your frequency to get a beat note.

The only time I used crystals was with a voice scrambler that used a MC1496 balanced modulator/multiplier IC and the communication link was radio. When I tried it with a 2nd scrambler with the same crystal frequency then the beat note was only about 1Hz. The oscillators weren't tuned. It produced an interesting effect: if somebody was between and was picked-up by both mics then their voice level increased then decreased slowly like they were walking towards then away from the mics. :lol:

 

[Nigel Goodwin]

Where would the transceiver have a BFO connected to provide a tone during its receiving a blank carrier?

The crystal oscillator is also the BFO.
A problem with such a simple scheme is that if the the other guy nets spot on to your frequency, you wont hear him. He would have to be a bit off your frequency to get a beat note.

That's the same with any CW transmitter, the note you hear is caused by the slight difference between the tuning at each end of the link - if you read the various articles about it, you will see that the adjustments alow the crystal to be 'pulled' about 1.5KHz.

An entertaining toy for a bit of fun and experimentation, but not a serious bit of kit. (A bit like a super-regen receiver really).

Hardly, it's a QRP transceiver, designed to be low power, but fully functional - but even so, communication is possible over huge distances. Unlike a super-regen, it's reliable and stable :lol:

The whole point of QRP is to see how far you can get on a small amount of power!.

 

[JimB]

Nigel

I am familair with all the concepts of QRP and direct conversion receivers.
My comments were directed at the circuit as shown.
There is no facility to pull the crystal, the selectivity in not defined by any particular filter, and the sensitivity will be fairly poor.

Yes it will work quite well within its limitations, but it does have limtations.

JimB

 

[Nigel Goodwin]

Nigel

I am familair with all the concepts of QRP and direct conversion receivers.
My comments were directed at the circuit as shown.
There is no facility to pull the crystal, the selectivity in not defined by any particular filter, and the sensitivity will be fairly poor.

Yes it will work quite well within its limitations, but it does have limtations.

Obviously it has limitations, but it's designed to be an easily built transceiver with a minimum parts count - what really makes it work is that it's CW. It's by far the most efficient method of communication, and makes simple effective circuits possible - pity I can't do morse! :lol:

 

[JimB]

pity I can't do morse! :lol:

I can!

JimB GM3ZMA

 

[Nigel Goodwin]

pity I can't do morse! :lol:

I can!

JimB GM3ZMA

Never got round to it!

G8MMV

 

[audioguru]

Dit, Dit, Dit, Daw, Daw Daw, Dit, Dit, Dit. Dit, Dit, Dit. Send Over Some Sandwiches! :lol:

I can't send them because you forgot to say where you are. Also, when I heard the 1st three letters I got busy alerting the fire department and didn't hear the 4th letter. :lol:

 

[akg]

MStechca,
Your "radio" manages to pickup the hundreds of thousands of watts of signal from CH-TV that is right next door?
:lol: :lol:

Did you read what I said I can receive?

my receiver can pick up CTV (toronto), and CH (hamilton) TV stations

yes he did hear .that's y he bolded some words
he is wondering of the sensitivity of the Rx :lol:

 

[mstechca]

CH-TV is about 2km away from me. I'm in West Hamilton, and CH-TV is in central Hamilton.

 

[audioguru]

You would be able to pickup the hundreds of thousands of watts at only 2km away with a kid's crystal radio.
Any ordinary radio or TV will pickup my 1/2W FM transmitter 2km away.
The difference in transmitted power is extrodinary.

For a TV transmitter with hundreds of thousands of watts of RF power, a range of only 2km is right next door.

 

[akg]

may be it is using AGC so that , if the RX is placed in the tv ant: itself , it won't saturate 8)

 

[Pommie]

Dit, Dit, Dit, Daw, Daw Daw, Dit, Dit, Dit. Dit, Dit, Dit. Send Over Some Sandwiches! :lol:

Has every one else realised that the little tune that is now associated with SMS messages is actually Morse for SMS - Dit, Dit, Dit, Daw Daw, Dit, Dit, Dit.

Mike.

 

[akg]

Dit, Dit, Dit, Daw, Daw Daw, Dit, Dit, Dit. Dit, Dit, Dit. Send Over Some Sandwiches! :lol:

Has every one else realised that the little tune that is now associated with SMS messages is actually Morse for SMS - Dit, Dit, Dit, Daw Daw, Dit, Dit, Dit.

Mike.

Isn't the SOS ??