Author Topic: DIY RF EMC Biconic Antenna  (Read 3129 times)

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Offline Jay_Diddy_B

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Re: DIY RF EMC Biconic Antenna
« Reply #25 on: August 25, 2022, 07:08:20 pm »
Dazz1,

Did you know that the MIL461A std has all the drawings needed to build the antenna?

The document is attached to this message:

https://www.eevblog.com/forum/testgear/diy-biconical-antenna-30-300mhz/msg2257035/#msg2257035

There are some difference between your design and the drawings in the MIL standard:



The holes are at 30 degree angle.
The holes are not flat bottomed. The flat bottom will not change the antenna  performance. Only the diameter of the holes and the diameter of the rods have tight tolerances, but I think this is for mechanical not electrical reasons.

Your design has the holes at 90 degrees to the axis:



The antenna factor is also published in the MIL std:



If you build the antenna it should be very similar to the published antenna factors.

Regards,
Jay_Diddy_B
 

Offline coppercone2

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Re: DIY RF EMC Biconic Antenna
« Reply #26 on: August 29, 2022, 12:08:47 am »
I have been meaning to make that antenna you posted for a long time with aluminum  castings.
 

Online wilhe_jo

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Re: DIY RF EMC Biconic Antenna
« Reply #27 on: August 30, 2022, 07:26:35 am »
Maybe one should mention that the MIL standard is MIL-STD-461A. The newer editions miss these drawings. Btw: if someone has the original one (without the A), I'd be glad to have a look at it...

The biconical is IMHO not too good of a choice outside some chamber. You can find broad band TV Yagi antennas which work reasonably well for this purpose and allow for some tuning (front/back gain) to reduce some peaks at least for some 10-20dB.

However, if you have lots of Broadcast stations around, that's still a huge problem.

Btw, the 2 antenna calibration procedure is in mil-std as well...

73

[edit]
upps, the std-number was already mentioned... never mind :)
[/edit]
« Last Edit: August 30, 2022, 09:00:06 am by wilhe_jo »
 

Offline dazz1

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Re: DIY RF EMC Biconic Antenna
« Reply #28 on: September 05, 2022, 11:02:25 am »

...
The holes are at 30 degree angle.
The holes are not flat bottomed. The flat bottom will not change the antenna  performance. Only the diameter of the holes and the diameter of the rods have tight tolerances, but I think this is for mechanical not electrical reasons.

Your design has the holes at 90 degrees to the axis:
...

Regards,
Jay_Diddy_B

Hi
My design has 6 elements at 60 degree spacing.
The original Mil-Spec design used a lot of pipe fittings.  They would be expensive and plain ugly.  I believe that good engineering should look good.  It's an art.
Dazz

Why make something simple when you can make it really complicated AND get it to work?
 

Offline dazz1

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Re: DIY RF EMC Biconic Antenna
« Reply #29 on: September 05, 2022, 11:03:53 am »


Btw, the 2 antenna calibration procedure is in mil-std as well...



I never claimed that the two antenna calibration was my idea.  I only claim that I plan to use that method.
Dazz

Why make something simple when you can make it really complicated AND get it to work?
 

Offline dazz1

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Re: DIY RF EMC Biconic Antenna
« Reply #30 on: September 05, 2022, 11:13:03 am »
Hi
Manufacture of the bi-conic has hit a pause for a while.  I have wandered off the path.

I had a few options to configure my milling machine to make the top/bottom hats.  I chose to fit a table with angle adjustment.  When I fitted the table, I found that it clashed with the Digital Read Out encoder.   To fix that I needed to remove a gearbox cover.  When I did that I found 45 year old Soviet era grease.  Not a pretty sight.  So now I am stripping down the milling machine for deep maintenance to clean and re-lube. 

I also purchased a Philips PM3072 scope that doesn't work.  The power supply has a fault.  There may be more.

I will get back to the biconic.

« Last Edit: September 06, 2022, 02:04:20 am by dazz1 »
Dazz

Why make something simple when you can make it really complicated AND get it to work?
 
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Offline coppercone2

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Re: DIY RF EMC Biconic Antenna
« Reply #31 on: September 05, 2022, 05:15:30 pm »
lol thats how I feel about my equipment too, I found a dust bunny in a key and ended up taking a entire machine apart, washing it, and baking it. Thats electronics, but mechanical stuff too, like I end up taking crimp tools apart and shit like that because there is usually some crap with old grease, dirt, etc, in side. I hate that in my tool box. sometimes its a little risky and expensive when I screw up but its the right thing to do.  >:(

And I mean stuff like that is totally rational too because giant machines are hard to move and stuff like that, and you might find a cracked gear or whatever. And sometimes you have energy for a project but not for the maintenance work, and having something break down because of prior inaction is a deal breaker, especially if its something crazy thats deep in the bowels of a machine, talk about change of plot.
« Last Edit: September 05, 2022, 05:22:26 pm by coppercone2 »
 


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