5/8 wave vs Dipole

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alfaeire
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5/8 wave vs Dipole

Post by alfaeire » Tue Dec 20, 2016 10:09 am

Howdy all,
so for the last 3 years ive been using a 5/8 vertical wave pushing 50w, but we are upping our power and with it i was thinking of a new antenna setup.

If any of you remember, i was trying to construct a 300w tugi kit and i was having problems.. and i basically had no idea what i was doing. So, i sat back a read.. read and read some more.
Infact i left it alone for over a year while i did as much reading as i could.

The TX was rebuilt, has been tested on a high quality dummy load and is working well, the amp is heating up a bit so im looking into better cooling.

ive been toying with the idea of making my own antenna, just for the experience. but in the search Ive come across the following dipole on ebay.
https://goo.gl/acsb3J

Its only GBP 29.70..

Now im well aware, you get what you pay for.. so im looking to see what peoples opinions are.
Im also wondering if this particular dipole would work well stacked.. I know the benefits of stacking, Im just pointing back at the price and wondering would it fall apart after a few weeks.. hence me asking peoples opinions on the build.

our current antenna is a a****f 5/8th, at the time we bought it (2013), it was rated to 600w.

Any info would be grateful.

Regards.

nrgkits.nz
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Re: 5/8 wave vs Dipole

Post by nrgkits.nz » Tue Dec 20, 2016 1:30 pm

First of all don't buy anymore gear from a****eff, the guy Paul is a scumbag who has no idea about RF and ripped off Stephens designs.

Have a look at this thread:
viewtopic.php?f=11&t=231

I would suggest having a try at building the nrg half wave antenna.

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teckniqs
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Re: 5/8 wave vs Dipole

Post by teckniqs » Tue Dec 20, 2016 2:45 pm

The old Antiference Radio Rod dipoles are well priced on eBay and include mount, just stick to these if you need good quality bog standard dipole.

http://www.ebay.co.uk/sch/i.html?_from= ... od&_sop=15

Albert H
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Re: 5/8 wave vs Dipole

Post by Albert H » Tue Dec 20, 2016 3:28 pm

Remember - if you're using a dipole, it's a balanced aerial. If you just connect your coax to it you'll get at best a 1.5 : 1 match. You have to turn your unbalanced coax feeder into a balanced connection to connect to the antenna. The easiest way is to use a Pawsey stub (it's just an extra quarter-wave of coax and a little work), or you can use one of the more exotic feeding schemes like a gamma-match (more difficult to make).

The best basic aerial you can make for yourself is the NRG ½-wave (it's in another thread on here, complete with dimensions and assembly instructions). If you've been using a ⅝-wave, (especially one of those efforts), the ½-wave will be a revelation. Less of your expensive power will go straight up, and with (very) careful adjustment, you'll get a superb match, so that every Watt gets radiated in a sensible direction!

You could consider stacking dipoles - I find that a 4-stack is the practical minimum - but it's a very big aerial and needs a very carefully built and calibrated phasing harness to feed all the elements.

Other aerials to consider include the j-pole, the super-j and the ⅞-wave with groundplane.

If you want directional coverage, then you're looking at Yagis, but if you've been using an omni-directional aerial in the past, the above comments apply!
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

alfaeire
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Re: 5/8 wave vs Dipole

Post by alfaeire » Wed Dec 21, 2016 12:06 am

on a previous station we were using a NRG ½-wave..
I found that the plastic that was being used over the coils deteriorated with UV.
Whats the expected lifespan of one of these?

SOTS 87 7
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Re: 5/8 wave vs Dipole

Post by SOTS 87 7 » Wed Dec 21, 2016 9:19 pm

[

our current antenna is a a****f 5/8th, at the time we bought it (2013), it was rated to 600w.

Any info would be grateful.

Regards.[/quote]

We've had one of these antennas for about 3 or so years now, In my honest opinion the single dipole we had before was rather better than this. To me, it looks just like a cut down silver rod CB antenna with a hairpin gamma match attached to it, a bit of an afterthought.

MiXiN
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Re: 5/8 wave vs Dipole

Post by MiXiN » Wed Dec 21, 2016 11:52 pm

SOTS 87 7 wrote:[

our current antenna is a a****f 5/8th, at the time we bought it (2013), it was rated to 600w.

Any info would be grateful.

Regards.
We've had one of these antennas for about 3 or so years now, In my honest opinion the single dipole we had before was rather better than this. To me, it looks just like a cut down silver rod CB antenna with a hairpin gamma match attached to it, a bit of an afterthought.[/quote]
No surprises there.
He probably bought a load of them at £15 a piece, cut them down, then added an extra £100 on for good measure.

Albert H
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Re: 5/8 wave vs Dipole

Post by Albert H » Thu Dec 22, 2016 3:29 am

I've usually worked on the principle that the more metal you put in the air, the more signal you'll radiate. The ⅝-wave is pretty good when built and matched properly, and the ⅞-wave is even better, with a flatter radiation characteristic.

One useful thing to remember with groundplane aerials is that you can make the signal directly below the aerial very weak, which has fooled the authorities and confounded the rig thieves.

A further development of the basic groundplane aerials are the ones with more than a wavelength of radiator. A 15/8-wave aerial has an even flatter radiation angle, a really consistent match and almost nothing detectable below the groundplane. We put a few of these up in Eastern Europe on the few sites that needed omni-directional coverage, and used extended wire-mesh groundplane. We found that we got about 7dBd (we don't measure against the unrealistic "isotropic radiator" - that's just for desperate aerial manufacturers who need to inflate their dreadful gain figures!).

Constructors should also consider other types of aerial: http://213.114.137.49/antennas/6dbvhf0.htm is a great option. If built correctly, you can get about 6dBd and a vanishingly small VSWR. I used one of these on a station in northern England, and got really spectacular results. This was a significant upgrade on the poorly matched dipole they'd used before, and was a lot cheaper than buying a bigger rig!
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

alfaeire
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Re: 5/8 wave vs Dipole

Post by alfaeire » Thu Dec 22, 2016 12:54 pm

Image

A friend heard we were in the market for an antenna and has given us a little Xmas gift.

Label AKF1/N

It's gunna put a halt on me building an antenna, but Im gunna get stuck in early new year.

Sent from my Nexus 5 using Tapatalk

Frequent Lee
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Re: 5/8 wave vs Dipole

Post by Frequent Lee » Thu Dec 22, 2016 5:16 pm

The 5/8 Veronica/A****f are exactly what you said, a chopped down badly matched CB aerial. Worst ever, and hugely over priced. The new A****f monstrosity looks even worse. Paul Hollings is just a charlatan who ripped off Stephens designs, ruined them and ruined the reputation Stephen had spent years creating. I honestly don't know why people buy such overpriced shit.

SOTS 87 7
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Re: 5/8 wave vs Dipole

Post by SOTS 87 7 » Thu Dec 22, 2016 8:03 pm

Frequent Lee wrote:The 5/8 Veronica/A****f are exactly what you said, a chopped down badly matched CB aerial. Worst ever, and hugely over priced. The new A****f monstrosity looks even worse. Paul Hollings is just a charlatan who ripped off Stephens designs, ruined them and ruined the reputation Stephen had spent years creating. I honestly don't know why people buy such overpriced shit.
Totally agree.
I have a ''Veronica'' PLL9 exciter in which I have only connected up for testing purposes, utter poo! Thats all I can say. NRG stuff all the way, just far superior in simple terms, the Pro3 is a great (not so) little exciter.

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