For a number of years, the Elecraft T1 mini-tuner has been tuning the long wire antennas up the maple tree in my small backyard. However, several reasons convinced me that it was time for a change:
- The switching between shack and portable use may have been taking a toll on the physique of the T1 and I would prefer to save it for travel and QRP portable operations only.
- When operating multiband, having to press the wake-up button for the T1 to be ready to retune partially defeats the purpose of having an auto-tuner, particularly inside the shack.
- I have been considering the possibility of re-acquiring the capacity to operate QRO (mainly for use in phone nets and for emergency communications) and operating at 50-100 Watts power would be outside the range of the T1.
Hence, I searched for a remote tuner that would not need to be awoken to retune and that would operate both on QRP and QRO power levels. I also favoured finding one that would not need TRX-specific connections: Hence, I honed on the LDG RT-100:
The LDG RT-100 is designed to operate remotely at QRP and QRO levels (0.1 – 100 Watts) and does not require waking-up. Also, it is powered via the coaxial cable, thus requiring only one singe cable to reach its remote location (the T1 required two cables: the coaxial plus the remote control cable). The RC-100 control box also contains another “Bias Tee” that injects DC power into the coaxial cable and the RT-100 unit has a similar circuit that separates the RF from the DC power
Only one precaution should be always observed with the RT-100: the shield of the coaxial should never be directly grounded, as this would cause a surge of power that would likely damage the “Bias Tee” in the RC-100.
The installation I chose is similar to the one I had for the T1 (with the exception of the RC-100 being between the meter and the tuner.
TRX –> Watt/SWR meter –> RC-100 –> RT-100 –> Antenna
I have installed the RT-100 in an inverted position with respect to what is recommended, but this is not a problem since the tuner remains indoors (between the house external and inner walls (i.e., a 2-foot coax starts the antenna leading through the external wall where it connects both with the cable going up the tree and the set of counterpoise 1/4 WL elevated counterpoise cables around the inside of the yard fence. Such a short coax at the base of the wire antenna does not seem to significantly affect its performance.
Without any balun, using the AM carrier signal at 0.5W (from the icom-703) the RT-100 readily tuned the 50+ Ft wire antenna currently up the tree to SWR values below 2.0:1 in all bands for which the antenna has a 1/4 WL elevated counterpoise wire. The only one it missed was the 160m band (for which the antenna lacks a suitable counterpoise).