Base antenna but which one for dx freeband.

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ch25
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Re: Base antenna but which one for dx freeband.

Post by ch25 »

How long coax do you need stanogs68? Up to 20m quality RG58 is just fine.
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Re: Base antenna but which one for dx freeband.

Post by MrWeetabix »

Like-for-like ish, then go for an Imax 2000. I have had several over the years and have one up as my main antenna.

Better performing than the A99, low visual impact and easy to install/tune. Only downside is they are £150ish new. 5/8th silver rod/venom type antenna will have good performance too, but not as durable in the winds.
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original45
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Re: Base antenna but which one for dx freeband.

Post by original45 »

Yup imax I had perused and did buy one however was unfortunately kaput. I can't see me spending 180£ for a imax when sirios are only about 100£ mark.
827 is looking better but will need the ring as it's going on side of house.
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Re: Base antenna but which one for dx freeband.

Post by The Collector »

If you do go for an Imax, check for any longitudinal splits in the fibreglass as there have been quite a few reports of this issue. An ebay trader was selling some as spares due to some coming back with the problem.

My own 1yr old £25? used ebay bargain turned out to have splits which I had to dremmel open and put fibreglass resin in to fix, or at some point it would have snapped...or at least, let loads of water in. I put a few pictures on here at the time regarding it.

Although I don't use the radio it's hooked up to, you'll recall at the time I had a 2s-point increase on RX using my Imax with a one-piece, 9ft tank-whip on top, over the signal using my old A99/Antron from the same idiot I have to listen to on ch19 when the radio is actually turned on.
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Re: Base antenna but which one for dx freeband.

Post by stanogs68 »

ch25 wrote: 08 May 2021, 01:32 How long coax do you need stanogs68? Up to 20m quality RG58 is just fine.
I need about 20 meters is that fine I have rg58 but this lad says get rg213 is that not right
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ch25
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Re: Base antenna but which one for dx freeband.

Post by ch25 »

You can even get 7/8" hardline, but it is nonsense for that length, power and frequency.
Cable loss difference would be 0.6dB vs 1.1dB - it means 1/6th of s unit.
If you want better coax get RF-7. Flexible and good quality.
Sample link: https://shopdelta.eu/coaxial-cable-rf-7 ... 16780.html
Get proper connectors if you decide to use RF-7

Also, I would suggest to use multiplication of 180° coax length to get proper SWR reading when you tune your antenna.
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Re: Base antenna but which one for dx freeband.

Post by stanogs68 »

ch25 wrote: 08 May 2021, 17:59 You can even get 7/8" hardline, but it is nonsense for that length, power and frequency.
Cable loss difference would be 0.6dB vs 1.1dB - it means 1/6th of s unit.
If you want better coax get RF-7. Flexible and good quality.
Sample link: https://shopdelta.eu/coaxial-cable-rf-7 ... 16780.html
Get proper connectors if you decide to use RF-7

Also, I would suggest to use multiplication of 180° coax length to get proper SWR reading when you tune your antenna.
I been meaning to ask this I have too much coax and it’s coiled up by my radio will that interfere and what is you final decision on coax I should get , I thank you for your help
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Re: Base antenna but which one for dx freeband.

Post by The Collector »

I don't think you should coil the excess up, especially not next to your radio anyway. Make yourself a balun thing right under the aerial which will take some of the slack up and may make your aerial act better at the same time.
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Re: Base antenna but which one for dx freeband.

Post by original45 »

So I think I'm narrowed down to choice of 3.
4000 ,827, and gainmaster.
I love the 827 build but concerned 're short
4000 it's bandwidth
Gainmaster it's reported breaking in wind.

Anyone feel they know the way from here ?

Am I going to notice difference between the 4000 and 827 in performance and what's the real difference in bandwidth in reality.I

They all appeal right now
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Re: Base antenna but which one for dx freeband.

Post by The Collector »

Can you guy the 4000 without it looking like a monstrosity and perhaps upsetting the neighbours?

The Lemm Super16 (AT-107) I mentioned is a 3/4 wave if it's height you're after...although they are about £165 gulp. Or they do an AT-92 5/8th wave that's very similar to a Sigma 2, although the legs on these will look worse looks-wise than a Vector 4000, especially the 107! :)
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Re: Base antenna but which one for dx freeband.

Post by original45 »

I won't be able to guy it I just keep looking at the physical length and think v4000,then strength of 827.

The rest just I need to look at again maybe.
Just don't want to get it wrong and not get the results
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Re: Base antenna but which one for dx freeband.

Post by stanogs68 »

ch25 wrote: 08 May 2021, 17:59 You can even get 7/8" hardline, but it is nonsense for that length, power and frequency.
Cable loss difference would be 0.6dB vs 1.1dB - it means 1/6th of s unit.
If you want better coax get RF-7. Flexible and good quality.
Sample link: https://shopdelta.eu/coaxial-cable-rf-7 ... 16780.html
Get proper connectors if you decide to use RF-7

Also, I would suggest to use multiplication of 180° coax length to get proper SWR reading when you tune your antenna.
Thank you
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Re: Base antenna but which one for dx freeband.

Post by wa10 »

Is the super 16 really a 3/4wave element or is it 5/8wave like my old lemm 5/8 ?
when you go longer than .64wave high angle lobes start to form, robbing energy from the low angles you want,

How it works :yawn: ,

When all antennas are mounted at the same tip height a good 1/2wave has a small advantage in low angle gain over longer antennas,

As you extend the radiator past 1/2wave you get out of phase radiation in the lower portion of radiator,

With a 5/8 wave radiator the lower 1/8wave is out of phase with the upper 1/2wave & detrimental to the wanted radiation from the upper 1/2wave,

That's why a good 1/2wave at the same tip height has a little more low angle gain than a 5/8wave,

5/8 is still an advantage because raising current maxima ( the most important thing ) up by 1/8wave increases low angle gain more than what the lower 1/8wave been out of phase takes away,

The tipping point is .64wave, any longer & what you gain with extra height is less than what you lose to hIgh angle lobes,

How can you get around the problem of out of phase radiation ?

You can raise current maxima higher than a 5/8wave & confine the out of phase radiation from the lower portion of radiator like a vector 4000,

You can split the radiator in two making an extended dipole like a Gain-Master,

You can split the radiator into sections with a phasing device/coil making it collinear.

Original45
The biggest mistake people make with their 5/8wave groundplanes is having them connected to a conductive mast or ground wire & not choking the coax at or near the feedpoint ;) .
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"An antenna with a poor ground using few radials cannot have a support mast grounded to the radial common point (at least it shouldn't if designed properly) There is no exception to this!
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Re: Base antenna but which one for dx freeband.

Post by original45 »

Thank you for a concise input. I have done nothing but read posts on net and watch vids trying to help me decide my next base antenna.
Strangely unexpectedly I found posts recommending to insulate the sirio 827 from the conductive mast.

I think your post also now gets me thinking ahead in so much one I have decided and bought the antenna what will the tips for that specific antenna and simple mods or protection people have found beneficial to its performance and longevity.

Waterproofing protecting from elements rust water ingress.
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Re: Base antenna but which one for dx freeband.

Post by wa10 »

Of SIRIO's so called 5/8 ground planes you picked the strongest / most wind resistant,

@ 19.5 & 20FT long respectively the 5/8 GPE and 2016 are both too short to be 5/8wave & the Tornado is far too flimsy & not DC grounded.

good luck
W8JI
"An antenna with a poor ground using few radials cannot have a support mast grounded to the radial common point (at least it shouldn't if designed properly) There is no exception to this!
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