Hi-Gain Vertical Half Wave Antenna

[radio-berlin]

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

[Banus_radio]

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

[Banus_radio]

Sorry I meant radio Berlin, not Britiania!

[Banus_radio]

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]

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]

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

[Banus_radio]

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

[Electronically]

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.

[Electronically]

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.


Sent from my iPhone using Tapatalk

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

[radionortheast]

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]

I have Nrg half wave

[MC Spanner]

I have Nrg half wave

Tec1. Thanks for posting the pic. I've still got a couple of questions about this antenna - I've built variations but I don't think Stephen's design can be improved upon much, especially the capacitor when running higher power.

Theoretically, I'm pretty clear on how it all works and on the general construction, but there are 3 parts I still have questions about. I've never seen a "real" NRG vertical close up! I'm asking from a construction point of view, rather than theoretical, as I'm thinking about how the thing will survive outside in the rain and also the lengths I'm going to have to go to to put the thing together.

First, the lower tube (counterpoise) which is the part that attaches to the mast. I don't think this is aluminium, as it appears quite dull and has the coax braid soldered to it. Anyone know what it's made from? Galvanised steel?

Second, the capacitor plates. The top one has a "strap" on it which attaches to the whip, and from pictures I've seen it looks like the strap and the plate on the "original" NRG are all one piece. This means the whole piece would have to be thin so that the strap can bend when the capacitor gap is adjusted. I suspect the top of the strap is screwed through the ring which goes around the bottom of the whip and has the top of the large inductor soldered to it, so it makes contact that way, but there's a chance it might be soldered (I can't see) which would make construction from aluminium difficult. The capacitor plates are quite shiny, so I'm guessing the top one at least isn't galvanised metal... any suggestions what it is? Tin plate would corrode in the weather surely... is it just thin aluminium perhaps?

Finally, the couple of pieces which have parts soldered to them - the ring which goes around the whip, around the outside of the plastic spacer. Looks like this contacts with the whip with 3 self tappers through the plastic pipe, but it's got the top of the inductor and (maybe) the capacitor "strap" soldered to it. So, what's it made from do you reckon? Tin plate?

Ditto the small piece of metal which has the coax inner soldered to it, where the 2 inductors join together.

Hope these questions make sense and someone can add something... I'll post what I come up with when I've done it.

[Electronically]

Hi mc spanner I've just noticed your post .the braided strap is soldered to the aluminum pole the other end is soldered to the plate .
The bottom ground clamping pole is just aluminum also .it's just not got the chrome paint on it .
And the plates used are just thin flex tin material there like a mirror but not as clear thought.and the ring parts I've no idea what your meaning with this .could you give a little detail to what part on antenna is it under the funnel or above ?

[Electronically]

Mc spanner I should have said the ground pole is wider in diameter .if your top radiator poles are are around 12 to 13mm diameter then I would suggest try get a ground pole about 14 or 15mm diameter bare in mind the plastic needs to fit in also before the top section is inserted to ground pole .so if ground pole is 15mm then plastic part has to be 14mm to slip in then your 13mm top section should all fit .the top section has two poles so make sure one end of the pole is 13mm the very top piece is 12mm to fit into to make the length then finally drill a hole screw it together .then it shouldnt come out .hope that helps .

[Electronically]

Again 15mm might just be a litte unwide try something about 22 to 25mm just like you would use as a dipole boom pole for your ground pole.then get a fitting of plastic that would be less than 22 to 25mm for inside of it for the attachments for above it to all fit inside the poke mind other end has to atleast be much less wider for your 13mm to fit in thought

[Electronically]

If your reactance is for around 200khz range then most probably could try 12k to get it spot on .in my experience I used a 9 mh coil also use your 65pf .

[Gigahertz]

Did anyone exactly get one on these build in the end?

Was thinking of using DK7ZB design with few adjustments to make similar antenna. Got a old 1/2wave CB antenna that I can hack to bits as the main structure and support.

https://www.qsl.net/dk7zb/6m/Vertical.htm

[Santiago]

looks like something I could attempt

[Santiago]

looks like something I could attempt

[mpx]

Would be great if these were available to buy again