[Etbrown4]

I built my first SBGH from the random images on Google which often are not labeled. It works great. Here's the dwg. Redirect Notice

So don't know which version I built. One difference I recognize is the center spacing, my drawing called for 1.75". For long distances 65+ miles is this a good place to start. I see some at 4+", etc. Interested to learn the pros and cons of the different designs.

What is the correct gap on the vhf rods to the main antenna? My drawing looks like maybe1", but I think it could be as close as .25".

 

[audioguy_on_ca]

There are calculators/simulators online that will fairly accurately give you an idea of a design’s operational/reception. They’ll also let you manipulate the design to optimize it for yourself/your use case.


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[Etbrown4]

Appreciate the info...
Where do you find these design calculators?
With the 1.75" or 44mm gap, which GH version am I using?
What is the most common setback for the mesh reflector? I have mine at 4".
What is the most common gap between the main antenna and the vhf element?

 

[Xauto]

Etbrown4 THis looks like a gen1. the max gap that I have note of is 3.75 inchs or 95 mm. The reflector is from 3.75 to 4 "and the vhf top hat to main can be as small as 0.25" between.

 

[Red Knave]

Where do you find these design calculators?

This is a treasure trove of antenna design. ImageEvent- Share your events
More specifically the GH - ImageEvent- Share your events

 

[Etbrown4]

The info is helpful. Pretty sure the semingly professional drawing link i included in my first post shows a middle gap of 44mm or 1.75", and if someone drew or designed it wrong, somehow it works well at 65 miles on about 30 stations.

I think i saw someone with drawn gaps up to 6". Interested to learn the effect of the progressively larger gaps.

Will look at the sites mentioned.

 

[Yurii Pylypenko]

gap of 44mm or 1.75", and if someone drew or designed it wrong

the gap itself has no any influence.
but you connect some other elements (not shown on the drawing) between this gap and your cable - those elements introduce some impedance transformation.
So drawing of this [missing] part will influence SWR-matching of your setup.

In Norh America, popular choice is

http://imgur.com/yipcbmj

Symmetrical end is intended to be 300 Ohm transmission line. It is 300 Ohm only if not cut with knife

http://cdn.ecommercedns.uk/files/7/226987/9/8169219/e791f414b8abd10790125dc8ec128271.jpg

when you cut insulation and bend wires to the sides - it's not transmission line any more. They act as individual lumped inductances (positive +jX reactance). Usually this inductance is unwanted (antenna author usually optimize drawing to have best SWR, hence minimum reactance on antenna terminals. This [unwanted] inductance is proportional to length and in inverse ration with wire diameter. Thin and long wire have high [unwanted] inductance/reactance.

If you don't care about SWR - you don't lose much. SWR=3.5 is only 1.6 dB mismatch loss (SWR=2.5 is 0.88 dB loss, SWR=2 is 0.51 dB). Without precise metering equipment it is hard to tell that your antenna underperform 1 dB

 

[Etbrown4]

Looking deeper into GH it's clear that the Gh10n3 as modified by JED, Nikiml and Mr 300ohm is the state of the art, and so I'm starting to build one.

My understanding is that Nikiml 100% based his work on JED's drawings with no changes to JEDs dimensions. Hope that's right.

Looking at the seemingly well done 'consolidated' drawings by Unclesam and others, it seems that dimensions vary from JED's GH10, and Nikiml's drawing in post 72, Gh10n3. Perhaps I'm reading these incorrectly. Seems that we're at a disadvantage since the links to Nikiml's old site are broken.

For example Unclesam in post 877 seemingly shows the width of the highest horizontal portion of his top hat narod at 615mm. Nikiml shows it at 427mm.

Unclesam shows his a3 dimension on the top right of the active element at 176mm and JED states 190mm.

Likewise Unclesam shows the 45 degree active element dimension just below the centerline at 223mm whereas JED states 190mm, if I'm reading it correctly.

Interested to know on GH10ns, is there another good consolidated drawing, a new builder can refer to?

 

[audioguy_on_ca]

GH10 is a large antenna - are you that distant from what you’re looking to pick up/watch?


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[Etbrown4]

Yes, as I mentioned earlier my closest station is 65 miles, and I tried an early version of the GH. I'll proceed to build the Gh10ns for sure.

Because there seem to be a number of conflicting diagrams among some who have built the 10ns, hopefully some of those can weigh in on determination of the correct active element dimensions even though those seem clear on JEDs site.

Since Nikiml is seemingly no longer active, it seems that there are fewer people to ask about his well tested enhancements .

 

[audioguy_on_ca]

I built his GH0 and it worked surprisingly well for the stations 25mi in one direction and 20 opposite from them. And even the ones ~70degrees off axis from them were available most of the time, also 20mi away.
It’s all about height, so you’ll probably be best with a 50’ tower and proper guy wires


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[Etbrown4]

Do you have a consolidated drawing (Jed + Nikiml) you hopefully used for the GH10ns as that would help lots.

Otherwise how would you reconcile discrepancies like:
Unclesam in post 877 seemingly shows the width of the highest horizontal portion of his top hat narod at 615mm. Nikiml shows it at 427mm.

Unclesam shows his a3 dimension on the angled top right of the active element at 176mm and JED states 190mm, and more like it?

 

[audioguy_on_ca]

It was 8y ago, so no drawings. I wish nikiml still had his site up for you.


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[Etbrown4]

I agree with you.
I've seen Nikimls full name written out somewhere. Anyone remember, as maybe he could be somewhere on the www. Such a talented person obviously.

 

[Etbrown4]

I found Nikimls full name and a thorough google search yields nothing except an old link to a professor in Bulgaria.

Curious if Yurii or others with an engineering background know something on jeds drawings and could answer the following :

On Gh10 jed shows the angled segments of the active element as a3, a2, and a1, with a3 being the highest, a1 the lowest. Do you think jed intended that the next lower segment (just below the center point) is another a3, or would that be a1?

Engineers would know, and that lets the rest of us guess, so I imagine that lots of GH antennas might have been made incorrectly, and the builder never knew.

 

[hamiltonOTA2.0]

It was 8y ago, so no drawings. I wish nikiml still had his site up for you.

I made a copy of the website and nec_opt that can be downloaded in the modeling software post. There's also an online nec_viewer hosted on github by another forum member.

www.digitalhome.ca/threads/4nec2-other-antenna-design-modeling-software.83772/post-3142944

nikiml's Antenna pages - Nec Viewer

 

[audioguy_on_ca]

That’s fantastic! You rock!

What I’m waiting to see is someone plug their self-built antenna into their SDR dongle and stream reception results to the web…if they haven’t already and I just haven’t stumbled across it lol


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[hamiltonOTA2.0]

What I’m waiting to see is someone plug their self-built antenna into their SDR dongle and stream reception results to the web…if they haven’t already and I just haven’t stumbled across it lol

Did something like that as well Attic mounted GH8n3, testing notch filters I bought. Before the '36 repack, so OTA up to CH49 or was it 51? Don't remember.

Over in the amp/notch/bandpass/etc... thread
www.digitalhome.ca/threads/splitters-attenuators-filters-diplexers-other-signal-gear.42428/post-3088403

 

[Etbrown4]

Thanks to Hamilton OTA!

Most ordinary folks won't be able to handle modeling software, so I wonder if you or someone could kindly run it on the gh10ns and display the drawing with dimensions hopefully, in the forum as an image like Nikiml did in the Narods thread with post 72.

If a drawing can't be displayed, how about a jpeg or a pdf?

 

[hamiltonOTA2.0]

Is the Nec Viewer site display readable for you? You can hover over a line to see the length of something, or click on two points to find the distance or angle between two things. If you can built from that would be your best bet. You can download nikiml's archived site and browse the different antennas under the Non-modular GH*n3.

If you go to RabbitEars.Info and put in your rough location we can get an idea of what kind of gain you would need.