Topband: 9V Topband?

[John Davies]

Greetings from Singapore. I have been toying with the idea of trying 160m for a few years now. My setup is a 270 foot doublet with 35 feet of open wire feeder to an SG-235 500 watt autotuner mounted on the roof of my apartment. The tuner is balanced with 30 feet RG213 coax wound on an 8 inch plastic pipe, then another 70 foot coax run to the shack. The tuner has been modified so that it can push out 600 watts true CW for a normal ragchew duty cycle without damage. My rig is a K2/100 with a homebrew 600 watt transistor linear. 

 

This has all worked fine from 80-10m and I have been quite successful on these bands. However, the SG-235 will not load on 160m due to a lack of L in the circuit (it needs at least 300 feet either side of the ladder line to affect a match).

 

I am planning to construct a remote controlled balanced tuner using 2 x 28 uH roller inductors and a 500pF vacuum capacitor in the near future to get me on 160m.

 

My receive antenna is a 20  foot diameter  horizontal loop mounted below the doublet, with a homebrew loop amplifier similar to the Wellbrook ALA 100.

 

I don't have space for a better loop - the area on the top of my apartment is quite small, but I have permission to string the big doublet across the roofs of the adjoining units.

 

Before I go down the homebrew remote tuner route, does anyone know a way I could get the SG-235 to perform on 160?

 

Also, is the effort worth it when you consider that the doublet is only 35 feet above the roof ( although both arms are 70 feet above ground in places where the apartment units are separated).

 

I know from experience on 80m that noise is a huge problem here. It was the main stumbling block for 9V1GO a few years ago when he was on topband.

 

Any thoughts and advice welcome.

 

73 de 

 

John / 9V1VV

 

 

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