Mar 22, 2009

Backyard 7 Mhz Vertical

For the sake of making contacts on the 'upper' Low Band I decided to do a quick & dirty GP set-up for 7Mhz.
The current 'Simple HF Multi band Vertical'(see previous blogs) had to go. There's no sunspots to expect in the next coming months, so no interest in the NCDXF beacon monitoring station currently. Even more because I have Hi-jacked the TRX (TS570SG) for the coming 6m season.

How to create a simple backyard GP

1. Make a full size radiator
Take a typical fibre glass fishing rod and any kind of conductive wire. Note: insulated wire intruduces a velocity factor of about 0.92 - 0.97, depending on the insulation type and thickness. Now start calculating the 0.25 wavelength, using the lowest frequency you want to be able to use; add another 5 % for adjustment.
Slightly spiral wind the wire around the rod and use electrical vinyl tape to fix it.

2. Install a ground rod
Just hammer(-drill) down any kind of 1-3m length copper pipe. It serves as a lightning rod and makes a good bonding point for the radials. Note:it is does not protect against a direct hit. When zapped by lightning it might avoid that all your shack-gear is toasted. There's lots of good websites on that subject so take proper care and be responsible.

3. Lay out some radials
Again; use whatever conducting wire you have available.
My backyard is 7 x 8 mtrs and the GP is mounted right at the corner. So no space available for 120 even spaced 'full size' (what is that crap?) radials. Just lay down whatever you can manage. I have 9 lengths between 4 and 8mtrs spread around the backyard. It covers 110 degrees around the GP. Why not 360 degrees? Simply because there is no space available.

4. Add a current balun.
Take a proper piece of ferrite (FT150A-K), put 8 windings no 16 AWG Thermaleze wire on it. Some 10-12 windings of thin teflon coax on a proper ferrite will be a good alternative too.
Use proper protection against moist.

4. Adjustment
Do the adjustment after you have layed out all radials. Adding more radials can alter the radiation resistance and shift the resonance frequency, certainly when you have only a few lying around like in my example. But my point was not to create a High-End antenna (what is that?), only to start being able to make contacts on another band.

How does it perform?
We have a full size vertical (3 out of 3 points), a ground rod + 9 short radials, covering only 110 degrees between north and south-west(1 out of 3 points) and a tiny backyard in a small village (2 out of 4 points). That makes 6 out of 10 points on the 5MW scale.
Within 24 hours I make numerous contacts to the USA and several to Asia. There are no radials in the direction of Asia, but I get through the pileups of BY and BV without severe drama involved. My operation is CW (only) and at a max. of 50W
Let's face it; ANY kind of antenna will allow you to make contacts. And depending how many effort you put into the process, you can master fine dx contacts at will.

Am I happy?
The antenna is up since February 6th and does perform as one might expect.
However, I kind to start disliking the band. Or today's hamradio operators behaviour to be more exact.
The art of rudeness and jamming from so many, makes me shutting of my TRX to often. If I would be able to put more effort into a directive high performing receiving antenna I might avoid them a bit. I also wish the dx-clusters would cease to exist. Tomorrow please..... ??

Anyway, time to return to my roots on the Low Bands: 160m !

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