Hi-Gain Vertical Half Wave Antenna

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radio-berlin
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Re: Hi-Gain Vertical Half Wave Antenna

Post by radio-berlin » Mon Jan 16, 2017 12:42 pm

Just another little update for you

I tried the NRG tank circuit in 8mm winding using thicker wire 16awg.

I still didnt get a good match but was close. So at 11 turns on the hot side and 4 turns on the earthy side I managed to get a perfect match using a 2k resistor, Im usure what the feed impedance will be in the real world, im guessing around 5k as it will be mounted on a pole.
1053 tank.jpg
at 105.3 I was able to get swr at the lowest, then at 108 and 88 it was 1.02 ish

Tomorrow i will try this using copper pipe as 1/2 wave and see what results i get
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Banus_radio
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Re: Hi-Gain Vertical Half Wave Antenna

Post by Banus_radio » Wed Feb 01, 2017 2:57 pm

How did you get on with this Britiania ?
I couldn't build it, my swr was way high

Keep us posted, I'm very interested to see your results mate

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Re: Hi-Gain Vertical Half Wave Antenna

Post by Banus_radio » Wed Feb 01, 2017 2:58 pm

Sorry I meant radio Berlin, not Britiania!

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Re: Hi-Gain Vertical Half Wave Antenna

Post by Banus_radio » Thu Feb 02, 2017 10:40 am

I've built a jpole but can only get swr at 1.4
When I coil the coax it drops down to 1.2

Can anybody see any reason why I couldn't use a pawsey stub as an alternative to the coils ? The antenna is balanced I believe at the 1/4 section

Steve West
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Re: Hi-Gain Vertical Half Wave Antenna

Post by Steve West » Wed Feb 08, 2017 4:46 am

These are very good aerials. We did 50 miles on one from a mere 4th floor roof with one on a 20 foot pole using a 150 watt rig.
Sadly since the passing of Steve Moss they are no longer available, so I do hope someone can replicate them.

radio-berlin
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Re: Hi-Gain Vertical Half Wave Antenna

Post by radio-berlin » Wed Feb 08, 2017 9:14 pm

Hey mate

No sorry Ive not finished the NRG 1/2 wave yet, im very close.. ive been playing with the coils for each end of the band. Got a nice 1.5 on the meter but im not happy with that, it still needs some work.

In the meantime I made a small supply of Super J poles, they tuned up very nicely. I first made a normal J pole and i was able to achieve 50ohms on the nose, swr 1.0 X at 0, very tricky to get perfect though, it took me several hours trying lengths etc. If you are building remeber when you extend the 1/4 wave section you need to extend the 3/4 section 3 times the length of it. Its a 1/4 wave matching section end feeding a 1/2 wave section. I even went as far as moulding some fittings for it :-)
Once I had this spot on I then added another half wave section above and 1/2 wave matching section turning it into a Super J. This got tricky as the 1/2 wave length wasnt exactly the same as the bottom 1/2 wave length due to the aluminium being a lot thinner. eventually I got it spot on, I would say you couldnt do this without an aerial analyser, it would be very hard with just a swr meter.
Pics attached
super j.jpg
super j grass.jpg
image1.PNG
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Banus_radio
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Re: Hi-Gain Vertical Half Wave Antenna

Post by Banus_radio » Thu Feb 16, 2017 12:23 am

looks awesome mate. I think i spotted one of these earlier, not mentioning any frequencies. Im waiting on your half wave results, hurry up man

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Re: Hi-Gain Vertical Half Wave Antenna

Post by Electronically » Thu Aug 02, 2018 11:28 am

yup I agree with maximum the total length of 97mhz would be 148.5cm .so basically 148.5÷2 =74.25cm .join poles together would give you 148.5cm.

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Re: Hi-Gain Vertical Half Wave Antenna

Post by Electronically » Thu Aug 02, 2018 12:25 pm

Maximus wrote:
Mon Dec 26, 2016 6:54 pm
Banus_radio wrote:
Frequent Lee wrote:No, you can mount the aerial straight onto your scaffolding pole etc. The mounting pole goes to ground/shield of the coax so it's not a bad thing. Remember to put a lightening strike strip onto your pole too!
ok so im confused then.. because the excel spreadsheet has measurments for bottom pole. so if i mount this to my mast it will extend that length yes??
No it will not affect the antenna as it isn't a dipole. It's a tuned half wave vertical antenna. The only part that matters is the top radiating element.

Speaking of radiating elements, I've just measured mine and it's 147.5cm for 97.00mhz. The bottom pole measures 61cm.

The spacing between the radiating element and the ground pole is exactly 4cm.

When I repair the aerial and put the thing back together, then I'll take some detailed photos along with some measurements and post them here.


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hi maximum did you manage to get it all together again ?

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radionortheast
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Re: Hi-Gain Vertical Half Wave Antenna

Post by radionortheast » Wed Aug 15, 2018 1:51 pm

admit I wasn’t expecting this circuit to work since it involves coils and capacitor, I used 2 22 cms bits of wire, a 10pf capactor, it is showing simliar signal strenght readings to other aerials I make. Lowest swr I get is 1.6 around 89 mhz , using the capacitor think the band width is bound to be narrow, anything below 1.7 is usable with my low power transmitter.

I think this aerial might simliar to an aerial i’ve been experimenting with for a while, I posted a different thread about it viewtopic.php?f=11&t=2016

Tec1 87.5fm London
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Re: Hi-Gain Vertical Half Wave Antenna

Post by Tec1 87.5fm London » Wed Oct 10, 2018 11:10 pm

I have Nrg half wave
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