Saturday, February 25, 2012

Multi Band Vertical 10-80 metres

Multi Band Vertical 10-80 metres

I'd thought I'd like to try a HF vertical

I've read about them, heard various reports on them, and read some more .... and then I thought I'd give one a try. It is a lot lighter than I'd thought it would be. Looks very impressive in a small suburban backyard. I used clothes hoist insulated nylon cord/rope for the three guy wires anchored via tent pegs. It went up quite easily - in a no breeze wind condition. When guyed, quite stable when the wind did blow and rain, too.

The mid-section.

Here you can see the 40 & 80 metre loading coils and capacitors. These are very tricky to tune. (3 to 5mm movement at a time!) The frequency spread is very narrow because of the high Q of this design and benefits from use of an antenna analyser in the alignment process. The wire is 5mm aluminium, the brackets made from 10mm aluminium and the nuts, bolts and washers are stainless steel. The piston capacitors are rated for 4kW! (Not that I would be using that level of RF power!)
Yes. I have a bit of an antenna farm, at times, too! (as can be seen in the background.) I enjoy experimenting and do take an active interest in my hobby.

40M coil and capacitor

Here's another view of how the top bit goes together.

Insulated mid-section

Yes. The mid-section is actually insulated. The flat aluminium bar clamps around this section for support. The 40 & 80M coils and capacitors connect to this "bar".

The 80M coil and capacitor.

This shows how the 80M bits.

The 80M capacitor clamp.

This shows the lower clamp for the 80M capacitor. You can also see the aluminium tube joiner in place. This is secured via 2 + 2 bolts with captive head nuts.

Ground level.

We can see the 75 ohm coax matching section fed to the base connection. The small coil acts as a dc grounded choke. (Also as a static leak!) You may also see a stainless steel bolt with nuts and washers, used for connecting radials, below the connector bracket. (Minimum of 4 per band, is recommended.)

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