Hi to all,
Hi to all,
I am new in this forum. I am using a ATM3000-9K in Europe and would like to know how can I modify the ATM3000 to use it on the longwave band (if it is possible). Intended frequency : 207 kHz.
Thank you.
Denis
Denis,
It should be possible, though you may not get much range due to fact that antenna efficiency will probably not be very good. Is it permissible to operate a low power unlicenced transmitter in the longwave band in your country? You might want to check on this before proceeding.
I think it is possible to set the synthesizer to longwave frequencies (that will be a major determining factor). I will report back on this shortly. But you will also need to modify the values of the output stage collector choke and the output loading circuit in order to match to a longwave aerial. What type of aerial are you planning on using? This will be important to know in designing the output match.
This may be an interesting project for U.S. residents, since we have a narrow licence-free longwave band available here.
WEAK-AM
Classical Music and More!
Denis,
It should be possible, though you may not get much range due to fact that antenna efficiency will probably not be very good. Is it permissible to operate a low power unlicenced transmitter in the longwave band in your country? You might want to check on this before proceeding.
I think it is possible to set the synthesizer to longwave frequencies (that will be a major determining factor). I will report back on this shortly. But you will also need to modify the values of the output stage collector choke and the output loading circuit in order to match to a longwave aerial. What type of aerial are you planning on using? This will be important to know in designing the output match.
This may be an interesting project for U.S. residents, since we have a narrow licence-free longwave band available here.
WEAK-AM
Classical Music and More!
Thanks for the answer Weak AM.
I live in a remote area. The clossess house is at about 4 km. I am not specialy looking for range, just to be abble to use an old tubes radio that goes up to 1580 kHz, but at night, this upper range of the MW band is pretty crowded. On the other hand, I have good spots free all time on the LW band.
The antenna could be an external LC circuit like this one : http://www.imagenisp.ca/jsm/loop.html
Denis
Thanks for the answer Weak AM.
I live in a remote area. The clossess house is at about 4 km. I am not specialy looking for range, just to be abble to use an old tubes radio that goes up to 1580 kHz, but at night, this upper range of the MW band is pretty crowded. On the other hand, I have good spots free all time on the LW band.
The antenna could be an external LC circuit like this one : http://www.imagenisp.ca/jsm/loop.html
Denis
Denis,
Are you referring to the SSTRAN AMT-3000 unit? If so, it may be possible to modify it to operate in the VLF band if the PLL synthesizer will work at that low frequency. The feedback loop in PLLs is usually designed to operate at a certain frequency range and it may be necessary to modify this circuit for the lower frequency. The modulator and final amplifier contain no tuned circuits and it may be a matter of changing the output tuning/matching network. Perhaps you could run this by the manufacturer for his comments.
I don't know your particular circumstance, but here my AMT-3000 swamps all night time interference in my house and I have no problems at all in the regular AM band. Maybe, if you are having interference there is something wrong with your setup and it is not providing a strong enough signal.
Neil
Denis,
Are you referring to the SSTRAN AMT-3000 unit? If so, it may be possible to modify it to operate in the VLF band if the PLL synthesizer will work at that low frequency. The feedback loop in PLLs is usually designed to operate at a certain frequency range and it may be necessary to modify this circuit for the lower frequency. The modulator and final amplifier contain no tuned circuits and it may be a matter of changing the output tuning/matching network. Perhaps you could run this by the manufacturer for his comments.
I don't know your particular circumstance, but here my AMT-3000 swamps all night time interference in my house and I have no problems at all in the regular AM band. Maybe, if you are having interference there is something wrong with your setup and it is not providing a strong enough signal.
Neil
Hello Denis,
The formula for the SSTran synthesizer was covered here: http://part15.us/node/692
The European version uses a 3.6 MHz reference crystal. The formula is similar, except that the multiplier is 9 instead of 10:
Frequency in kHz = 9 * (S4_value + 1).
Since you want a frequency of 207 kHz, the S4 value should be 22. The binary equivalent of this is 10110. In the SSTran, the least significant digit corresponds to switch 1, and the most significant digit corresponds to switch 8 (of S4). Note that in the SSTran, a "1" is represented by "OFF" and a "0" is represented by "ON". Thus the switch settings on S4 would be as follows:
Switch 1: ON
Switch 2: OFF
Switch 3: OFF
Switch 4: ON
Switch 5: OFF
Switch 6: ON
Switch 7: ON
Switch 8: ON
Note that switches 6, 7, and 8 need to be set to the equivalent of "0" (ON). I hope this isn't too confusing.
I tried this with my unit, which uses a 4 MHz crystal and therefore tunes in 10 kHz steps, and it worked! However, the frequency came up at 230 kHz instead of 207, due to the X10 multiplier instead of X9. So the synthesizer part isn't too difficult to get working.
Unfortunately, you are not finished! You will probably need to increase the value of L8, in the collector circuit of Q5, to produce a high impedance at this lower operating frequency. In addition, you'll need to increase the inductance values of one or more of the output loading coils L4-L7 in order to get the output circuit to tune to resonance. Alternatively, you could short all of these out with the switches in S5 and use an external loading coil. This would probably be the best way to go.
Here in the U.S. we have a licence-free band from 160-190 kHz, so interested experimenters could give it a go. I don't think the range would be nearly as good as on the high end of the Medium Wave band, but it might be interesting to try.
WEAK-AM
Classical Music and More!
Hello Denis,
The formula for the SSTran synthesizer was covered here: http://part15.us/node/692
The European version uses a 3.6 MHz reference crystal. The formula is similar, except that the multiplier is 9 instead of 10:
Frequency in kHz = 9 * (S4_value + 1).
Since you want a frequency of 207 kHz, the S4 value should be 22. The binary equivalent of this is 10110. In the SSTran, the least significant digit corresponds to switch 1, and the most significant digit corresponds to switch 8 (of S4). Note that in the SSTran, a "1" is represented by "OFF" and a "0" is represented by "ON". Thus the switch settings on S4 would be as follows:
Switch 1: ON
Switch 2: OFF
Switch 3: OFF
Switch 4: ON
Switch 5: OFF
Switch 6: ON
Switch 7: ON
Switch 8: ON
Note that switches 6, 7, and 8 need to be set to the equivalent of "0" (ON). I hope this isn't too confusing.
I tried this with my unit, which uses a 4 MHz crystal and therefore tunes in 10 kHz steps, and it worked! However, the frequency came up at 230 kHz instead of 207, due to the X10 multiplier instead of X9. So the synthesizer part isn't too difficult to get working.
Unfortunately, you are not finished! You will probably need to increase the value of L8, in the collector circuit of Q5, to produce a high impedance at this lower operating frequency. In addition, you'll need to increase the inductance values of one or more of the output loading coils L4-L7 in order to get the output circuit to tune to resonance. Alternatively, you could short all of these out with the switches in S5 and use an external loading coil. This would probably be the best way to go.
Here in the U.S. we have a licence-free band from 160-190 kHz, so interested experimenters could give it a go. I don't think the range would be nearly as good as on the high end of the Medium Wave band, but it might be interesting to try.
WEAK-AM
Classical Music and More!
Just completed the kit and modified it for longwaves.
L4 and L7 were replaced by two 5000 microhenrys chockes.
The 3 meters supplied antenna is now 15 meters. The frequency choosen is 279 kHz. measured voltage at test points : 15.32 VDC with unmodulated carrier. No Hum and good warn sound.
As I built the kit in South America, I am using a fixed tuner (LW, MW & FM) so I was unabled to estimate the range. Also the 21 meters antenna runs horizontaly inside an apartment, but back in Europa, I will build an external vertical antenna of 20 meters.
Thanks to all for your comments.
What are you doing down there anyways? Best thing to do is stay in the 160 kHz to
190 kHz region for broadcasting. 144 kHz to 160 kHz is okay, since there is no GWEN broadcasting. I do longwave DXing as a hobby. I hope I can tune in.
Yes you can modify the "SSTRAN AMT3000-9k" for the European long-wave band with the standard European 9kHz channel spacing.
There are some minor modifications you need to do, and these are as follows :-
Capacitor 'C23' should be changed from 820p to 1000p. Capacitor 'C30' should be changed from 180p to 680p.
Inductors 'L4' should be changed from 56uH to 1000uH (1mH). 'L5' should be changed from 82uH to 2200uH (2.2mH). 'L6' should be changed from 180uH to 3300uH (3.3mH). 'L7' should be changed from 470uH to 4700uH (4.7mH). 'L8' should be changed from 1000uH to 4700uH (4.7mH).
The frequency changing DIP switches can be worked out by using the following formula :- The frequency in kHz divided by nine minus one, that will give you the Binary code number. Each DIP switch is given a number between 1 and 8 and the binary code number for each number switch is as follows :- 1=1, 2=2, 3=4, 4=8, 5=16, 6=32, 7=64, 8=128. All the switches that are not used for selecting your frequency must be ON.
So if (for example) you want to use the frequency of 189kHz, you must first work out the binary number by the formula :- 189 divided by 9 minus 1 this gives you the answer '20'. This means that DIP switches 3 and 5 must be switched OFF as their binary values are 4 and 16 making the required binary value of 20 when added together, but the other 6 switches must remain ON.
The ATU (DIP) switches must be selected by measuring the output voltage at the points provided in the normal way.
The 'Aerial' provided for 'MW' will not be very efficient on 'LW', but the radiator can be made slightly more efficient by adding a horizontal wire to the top with the vertical aerial connected to the centre. This is known as a "T" aerial and was very popular in days gone by for low frequency transmissions. Infact the UK 'Droitwich' Long-Wave tranmitter on 198kHz still uses this type of aerial.
The removal of resistor 'R18' will give a worthwhile rise in RF output.
I am currently using the original aerial supplied plus a horizontal wire, with the vertical wire connected to its centre, to form a "T" aerial, to make the vertical radiator aerial more efficient.
With the current setup and tuned to 225kHz with the internal ATU peaked and a high resistance digital voltmeter connected across test points 'T1' & 'T2' I am getting a DC reading of 61 volts ! This is almost double the voltage obtained when 'R18' (820 ohms) resistor was still in the circuit.