Homebrew 20m / 40m Vertical Antenna

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This is my homebrew vertical antenna for 40m and 20m.

Here we have a 10m (in length) fibre glass pole with 10 metres or 1.5mm pvc coated cable running up it.

The same for the 5m (in length) vertical..

Outer braid of coax is connected to an earth rod and 4 radials. Two 5m and Two 10m radials in length.

After recording this video I worked VA2PW in canada so I'm pretty chuffed my homebrew works ok!

This antenna seems to be resonant on 40m but swr on 20m is about 1.7 but using the internal ATU on my FT-450 brings this down.

I will be playing with the length of the 5m cable to try and make the 20m element more resonant.

73's for now...

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Category:

Science & Technology

Tags:

• homebrew
• 20m
• 40m
• hf
• vertical
• fibre
• glass
• fishing
• pole

[RIDDICKorigional]

Question? are your poles fibreglass - how do you know they do not contain carbon black as told this is very lossy for antennas i want buy pole but need make sure no carbon in it tnx.

[freakybwoy1]

@RIDDICKorigional Yes they are fibre glass and are not carbon fibre. I specifically chose which poles to buy. The 10m pole was purchased from ebay (in the UK) at a cost of £15 plus postage. The wire and other bits come to around a fiver.

[RIDDICKorigional]

You could also measure them as half wave antennas and just spiral wind the wire on to poles instead of running straight up just a thought :>)

[freakybwoy1]

@RIDDICKorigional Absolutely..! The great thing about Ham Radio is playing around with antennas. As long as you have a rough idea of how long it should be then you can simply play around. The "Ugly Balun" that you mention is something I thought of adding, but as the RF in the shack was minimal, and no TVI caused I havnt bothered yet. Its just to stop the common mode current, but I may add soon.

[Dreamlgider]

add more radials (read online about 120) will do the job on the ground.

OR you can try one or two 1/4 wave for each band raised above ground.

i tried raising the radials 10cm above ground in a simulation went from -5 or -6 to -1db maximum gain. from what i found online is that two 1/4 wl radials at 0.2wl above ground are about equal to 120 various radials on the ground.

73's de OY1R.

[RIDDICKorigional]

@freakybwoy1 best to coil it around pvc pipe one end to other also as if you simply coil the coax up and tape it together there is chance that the first and last coils will touch which will cancel it out :~) and not be effective like supposed to.

[RIDDICKorigional]

@freakybwoy1 just to mention you will benefit from an all band hf air core 1:1 choke balun or as they call it the UGLY BALUN at feedpoint to antenna - cut out any feeder radiation eliminating any inteference and ensuring antenna is doing all the radiating more power up the spout etc simply make coil between 18 to 21 feet of coax around pvc form pipe at antenna feedpoint or as close as - number of turns not important but length is 18 to 21 feet :>) this will maintain balance.

[RIDDICKorigional]

@freakybwoy1 Hi yes i was meaning with ATU but see you are using them to correct length without having use tuner no probs good show probably best way where did you purchase the poles for antennas pls just wondered tnx Dave.

[freakybwoy1]

But with this way, there is no need for an ATU for 20 or 40m :-)

With a little playing with wire lengths, I managed to get the SWR below 1.5 on both bands.

One other thing, as this is a ground mounted antenna, it is VERY important you have a GOOD earth system. (Basically its the other half of the antenna).

You can do this by using an Earth Rod (more than one maybe) and lots of wire radials. The radials dont need to be any particular length as they are ground mounted.

[freakybwoy1]

@RIDDICKorigional I believe it is to do with impedance where the antenna connects to the coax.

The lengths of antenna wire are typically measured so the impedance matches the coax (50 Ohm) or as close as we can get it.

With a half wave, a matching device would be needed to better match the impedance to 50 ohm. I suppose you could make a matching device (simple atu) that you just switch in an out of circuit when you want to use the other band.