We have a SSTRAN AMT3000 transmitter for a backup transmitter but having difficulties with tuning and broadcast range.
We built the SSTRAN AMT transmitter and the base loaded antenna as described on thier web site. The transmitter works fine, sound quality, fidelity are good, however, tuning the transmitter with the base loaded antenna per the antenna instructions and with the multi-meter plugged into T1 & T2 the best reading we get is 6.5 volts DC. The instructions state that the voltage reading should be 13 volts DC for perfect tuning of the transmitter to the antenna. In this condition the broadcast range is only about 300 feet. (we’re looking for 1 mile plus)
Checked all the transistors for voltage against the circuit diagram and they did not seem to be off by much but we changed out all of them; 2N2222 , 2N3906 (Q1, Q2, Q3, Q4 & Q5) as well as fixed resistor 1k ohms (R31), still getting only 6.5 volts when tuning.
Would appreciate any thoughts on possible solutions to these problems.
Biff
I had the same experience when modifying a AMT3000 for a self-wound loading-coil/ antenna... we were not seeing the predicted 15 V when tuning the output.
The solution was to add a substantial ground.
Our installation is somewhat novel in that the transmitter is indoors.
Our antenna is a metal window frame with lengths of wire added vertically at the top and bottom of the window to reach 10-feet.
Our first attempt at ground was to run wire horizontally in two directions along the baseboard of the room. This was inadequate.
So we dropped a wire through an opening in the baseboard and clamped it to a stell I-beam in the basement that is inter-connected with electric-system ground and water-pipe ground, and the AMT3000 tuned according to the objective...15V.
Obviously this same situation would apply outdoors... at least a copper-clad ground rod, and more desirably copper radials in the ground would likely solve your case.
In addition to needing a good ground (radials) I found that tuning the antenna coil to resonance is very tricky due to the high Q of the antenna system. It took a lot of trial and error with the taps to find the right one.
Just a reminder that you have to change the transmitter circuit as detailed in the manual.
Neil
This is true: "...you have to change the transmitter circuit as detailed in the manual."
Some of the required changes are in the manual, and there is an additional white-paper available on the SSTran website giving further changes that the manual does not mention.
We should post a copy of this information on the ALPB Website in case the SSTran website is removed.
We have still not been informed why the SStran transmitters have been discontinued.
Thanks Carl and Neil,
I’ll work on improving the ground. Presently we have (1) 8’ coper jacketed ground rod but no Radials. Possible we can connect directly to the city water main (outside by the sidewalk). Also we’ll try playing with the TAPs to see if maybe we’re using the wrong one. The transmitter circuit has been modified per the white sheet but will reverify. Thanks again for the input.
Biff