I just took possession of a Leader LSG-11 signal generator and have been tinkering to try and transmit a signal through an ipod/computer. No luck! I tuned my am radio to a quiet spot on the dial, tuned the signal generator to the same spot (I assume when the radio goes quietest is the point that the two are aligned?) and hooked up a headphone jack into the ipod the the left and right rca jacks into the ground and AF jacks of the generator. Being rca plugs I have to hold them in but I just get static. Generator is turned to 'Ext' and RF signal is highest. I am using a one metre lead in the RF output.

Tried for over an hour and looked up the net to see how other people are doing it but no, nothing!!! Anyone try this before?

I suspect it may have something to do with how I get the signal into the generator - do I cut the rca plugs?

Any suggestions are appreciated. P.S. I am new to all of this tech stuff but very keen to learn.

Regards
Angelo

There are issues here relating to broadcast transmissions & interference offsite to consider on the non electrical legality side.

The Leader is capable of external modulation, but there are issues relating to level of the signal, percent of modulation & impedance matching of iPod too the Leaders mixer tube to be addressed

Marc

The LSG11 is a fairly crude modulated oscillator using a 12BH7 twin triode for a Colpitts RF oscillator & cathode follower output, and a 6AR5 for modulation; either from an external input, or by making itself oscillate at audio frequencies with an LC circuit.
It was a common design used in many Japanese signal generators from the 60's & 70's. In fact, Dick Smith was still selling a later version (Model TE20) in the late 70's. I used to have one & an LSG11 - ok for aligning radio & TV sets and home transmitting, but nothing really serious. I offloaded them once I upgraded to Rhode & Schwarz SMS and the like.

1)It sounds like the RF part of the LSG11 is working if you can make the radio go quiet when tuned to your chosen frequency. I expect some 50 cycle hum in the background because this generator uses a half wave rectifier and low values of filter capacitor - mine certainly had it.
2)The most important point: Can you get the 400 or 1000 c/s audio tone? If not, something is amiss around the 6AR5 circuit.
3)Line level inputs from iPods etc will be sufficient enough to drive it. As there is 500K input impedance for the modulator, loading isn't an issue, but modulation level may be - the 250 odd millivolts line level won't drive a 6AR5 to the max, but it will give you something useful.

Your method of connecting the audio sounds a bit strange and if I'm interpreting it right, it won't work. You basically need to combine the L&R channels to form a mono signal which is then fed into modulation terminals.
It is not a good idea to simply connect L&R together as the output stages will try to fight each other; but rather use isolating resistors. Something around 10K will do for this application. Connect the active wire of each channel through a 10K resistor to the AF terminal, and the cable screen of both channels to the GND terminal.

Thanks Cool386 and sorry for the late replay. I used your method and it worked. The range was only about 2 feet but I was more interested in understanding how it worked. Regards.

2 feet is a short range, but I presume that was without any aerial connected to the RF output.

To increase the voltage there is always the option of trying a transistor audio transformer ( /s for stereo) with an impedence similar to that of the ipod, or in conjunction with the above resistor idea.

The issue I found with the TE-20 was that the HT was too low, it could have been doubled. It suffered distortion of the audio signal.

I could find little info on the valves data sheet, but that voltage placed the operating point right on the knee curve.

That would cause the negative & positive excursions of the wave to be amplified diferently.

Marc