Thinking Of Installing A Discone For My SDR Receivers

[Ubbe]

So if 12 or 16 disc and cone elements are needed on a low frequency Discone to equal solid sheet metal, the same amount will be needed for any Discone at any frequency.

Yes, if you disregard the thickness of the elements. At the lowest frequency, at the bottom of the cone and at the end of the disc, the relationsship between element thickness and space to the next element are bigger than at the top of the cone for the highest frequencies, where there are very little space between elements forming almost a solid cone and disc.

/Ubbe

 

[W5lz]

...thickness of the elements...
I fail to see any significance. What's your point?

 

[prcguy]

I think he is relating to the distance between the ends of the elements having less space between them, therefore being a smaller fraction of a wavelength when thick elements are used. This is probably true on a very small Discone and would have a lesser effect on a larger one.

...thickness of the elements...
I fail to see any significance. What's your point?

 

[Merovingian]

I am planning to go ahead and order a Diamond discone antenna and SIRIO SD 3000 N. My question now before I order is:

the Diamond D130NJ and the D3000N seem to be identical, yet one is $95 and the other is $150. Is there really any difference between the two?

 

[prcguy]

That's a gosh darn good question. I downloaded the assembly instruction sheets for each antenna and they look identical and have the exact same length elements. The 130 series mentions transmitting up to 900MHz where the 3000 says up to 1.2GHz.

???

I am planning to go ahead and order a Diamond discone antenna and SIRIO SD 3000 N. My question now before I order is:

the Diamond D130NJ and the D3000N seem to be identical, yet one is $95 and the other is $150. Is there really any difference between the two?

 

[Merovingian]

That's a gosh darn good question. I downloaded the assembly instruction sheets for each antenna and they look identical and have the exact same length elements. The 130 series mentions transmitting up to 900MHz where the 3000 says up to 1.2GHz.

???

I think I may go with the D130NJ. I don't care about transmitting. I can put the extra money toward something else.

Thanks

 

[prcguy]

If your going to use the Diamond as the lower frequency side of a two Discone system then it doesn't really matter, save the $$.

I think I may go with the D130NJ. I don't care about transmitting. I can put the extra money toward something else.

Thanks

 

[Merovingian]

If your going to use the Diamond as the lower frequency side of a two Discone system then it doesn't really matter, save the $$.

Yes. I'll be using the Diamond as the lower freq. antenna.

I put my orders in for the Diamond D130NJ and the SIRIO SD 3000 N a little while ago.

I still have a lot of other things to order before I can use the antennas. I've already ordered a number of aluminum pipes and cross-over clamps to support the antennas. Later when I have more money I will have to order the Wellbrook loop and the cables, connectors, cutting and crimping tools, then I'll need to see what I have to do with lightning protection. I'm thinking of getting some sort of small box to mount outside to run my cables through to ground them. I would think someone makes a grounding box or something.

 

[krokus]

Just in case it was a more obscure thing, like transmit power limit, gain, or construction materials, I looked again at the pages. They have the same specs, and both made of stainless steel. (The 130 is spec'd for transmitting 50 to 1300 MHz, where the 3000 only covers to 1200 MHz.)

Seems like a no-brainer, unless there is something we are all missing. (Element diameters, higher grade stainless, or something like that.)

Sent using Tapatalk

 

[Merovingian]

I received my Diamond D-130J today. I'm still waiting on the SIRIO SD 3000 N.

 

[Merovingian]

I received my SIRIO SD 3000 N today. Tomorrow the aluminum pipe I ordered to support the antennas should arrive. I will take a while longer before I will finally be able to try my new antennas.

 

[Merovingian]

I spent all afternoon on Christmas eve up on the roof installing my Loop, Sirio and Diamond D130J. I finally finished around 9pm. It took a long time before I had all of the pieces to the puzzle but I finally have a three antenna system for HF through UHF.

One problem I found is with the Diamond discone. I first hooked up the Sirio UHF to my SDR. As I pressed the SMA connector into the antenna input jack, signals appeared on the spectrum display and improved as I screwed the connector into the jack. I first checked the local FM frequencies and moved on up beyond 2GHz, just playing around.

When I connected the Diamond discone signals briefly appeared as I started to screw the SMA connector into the jack but disappeared immediately. I am getting no signals from the Diamond discone. There is one tiny spot the first turn or two of the SMA connector where I can get a signal but it is very touchy, I think the coax cable is acting as an antenna rather than the Diamond supplying the signal.

I have swapped 4 different LMR-100 pigtail N female to male SMA cables.
This morning I swapped the cable going from the lightning arrester to the SDR.
I also bypassed the lightning arrester all together, connecting the indoor cable directly to the cable coming from the antenna.

None of those changes made any difference, so that leaves the coax from the antenna or the antenna itself.

Tomorrow I am going to go back up on the roof and take down the diamond antenna, remove all of the connector waterproofing and temporarily connect another cable to it to see if that fixes the problem. If not the only thing left is the antenna itself.

Has anyone heard of these Diamond D-130J antennas doing something like this? Since this is my first, I don't have any other experience with this.

I received my Diamond D-130J today. I'm still waiting on the SIRIO SD 3000 N.

 

[jonwienke]

It's more likely the cable than the antenna itself. Did you check the cable before installing?

 

[Merovingian]

No, I was gun-ho with getting the antennas up I didn't check anything. I had the cables custom made from USA Coax, they were brand new, so I stupidly assumed that they would all be good. It didn't want to make up the cables myself to avoid this kind of problem. I wanted them done professionally so that I know they would be made "right".

It's more likely the cable than the antenna itself. Did you check the cable before installing?

 

[jonwienke]

If you get a piece of shrink wrap or similar stuck in the connector, that can bork the connection without the cable itself being bad.

 

[Merovingian]

I'll have to inspect the connectors on both ends more closely tomorrow to see if anything looks out of the ordinary.

If you get a piece of shrink wrap or similar stuck in the connector, that can bork the connection without the cable itself being bad.

 

[jonwienke]

I'll have to inspect the connectors on both ends more closely tomorrow to see if anything looks out of the ordinary.

Get one of these:

Amazon.com: KKmoon Vector Network Analyzer, Portable Handheld Vector Network Analyzer 50KHz-900MHz Digital Display Touching Screen Shortwave MF HF VHF UHF Antenna Analyzer Standing Wave: Electronics

Amazon.com: KKmoon Vector Network Analyzer, Portable Handheld Vector Network Analyzer 50KHz-900MHz Digital Display Touching Screen Shortwave MF HF VHF UHF Antenna Analyzer Standing Wave: Electronics

www.amazon.com

It will tell you if the cable is open or shorted, and show how much loss it has over a range of frequencies. You can do open/short tests from the inside end of the cable without going up on the roof.

 

[Merovingian]

Oh yes, I've been reading about those. There is supposed to be a version coming out very soon that goes up to 3GHz, I was planning to get one of those whenever it comes out. It would come in hand right now. It didn't know that it could tell me about my cable status. It would be nice if the 3GHz model was going to be available next week.

I suppose I could check the impedance with a multi meter in the meantime.

Get one of these:

Amazon.com: KKmoon Vector Network Analyzer, Portable Handheld Vector Network Analyzer 50KHz-900MHz Digital Display Touching Screen Shortwave MF HF VHF UHF Antenna Analyzer Standing Wave: Electronics

Amazon.com: KKmoon Vector Network Analyzer, Portable Handheld Vector Network Analyzer 50KHz-900MHz Digital Display Touching Screen Shortwave MF HF VHF UHF Antenna Analyzer Standing Wave: Electronics

www.amazon.com

It will tell you if the cable is open or shorted, and show how much loss it has over a range of frequencies. You can do open/short tests from the inside end of the cable without going up on the roof.

 

[jonwienke]

If the cable is open or shorted, you'll have an abnormally low return loss, and the Smith chart will be out of whack. You can test that from inside.

 

[Merovingian]

That would be much easier. I wish I had one of those now.

If the cable is open or shorted, you'll have an abnormally low return loss, and the Smith chart will be out of whack. You can test that from inside.