My Diamond D130NJ Antenna Assessment

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dcisive

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I know several folks here want to hear about my results thus far with the Diamond discone antenna I got and assembled today about as much as hearing about someones hemorrhoids but I still wanted to share the results thus far. It came with a 18ft RG8 cable with N on one end and BNC on the other. It didn't take long to put the discone together. I figured I'd scan the FULL database just to not miss anything as I've tested out before with the other antennas. This way I felt it would give me a good comparative idea how the antennas I've been experimenting compare.

Right from the get go I noted I'm now getting at least 8 channels from the Salt Lake Airport I wasn't getting at all before. The so called home made one by that Ebay guy Lowbander did better than the stock whips and rubber duckies, but that's all one can say there. This not only is bringing in more airport channels but they are 4-5 bars, highly intelligible and very low noise. I'm now getting 5 weather NOAA channels where before I got 1.

The 440-470mhz range is acting as if on steroids. The FRS channels for example, I was lucky to get even one of them. I'm not hearing local chatter from 4 of them, so I'm rather surprised. This in the 462mhz range.Also picked up a couple of HAM's which I've heard one or two of before, but the quality of the transmissions has gone from perhaps 3 to 5 bars and is nice and quiet. The lions share of my listening is in the 400-500mhz range and now all the Public Safety, Fire and Police in the greater Salt Lake Area are ALL coming in like they are parked across the street. There were several I became very familiar with that were rather noisy and didn't hear well no matter what I did or used. now they are clean 5 bars. I'm even hearing Ogden police department with a clean 3-4 bar signal (62 miles from me). The Davis Country stuff (about 40-45 miles) now sound local. Even the Park City (Summit County) broadcasts are super clean and noise free which rather surprised me. There are a ton of the LDS Church frequencies for their in house communications which are a bit dicey. Not anymore. 5 bars and noise free. The DMR is popping out all over the place in a simple search mode scan. I'd get one from time to time but NOT this regular. Needless to say being digital they are dead noise free.

I did a search in the 800mhz range and nearly all of the dozen or so broadcasts (mostly police related) were dead quiet as well so can't complain there. I'm also getting a number of 900mhz business channels I'd never heard before with at least 4-5 bars. I wasn't sure just how the discone would do up there but it's certainly working well. Tonight is THE night in this area to listen in. Tons of robberies, car chases, drug deals busted and loads of fun stuff to monitor. Going to make a pot of coffee and settle in for a hopefully nice noise free night ahead. Thanks in advance for tolerating my input on this. I just wanted ya'll to hear how this has been working out so far. So far so very good indeed. I rigged up a nice little stand for the radio so it's on easy line of sight with a competent Realistic speaker I've had for years mounted below. I'd share a pic but I don't believe there is a way to do that on this forum. Anyway....you all have fun...I know I will :)
 
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dcisive

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yeah you did. Dang was just listening to some Hams at 449mhz. Dead quiet 5 bars and lovin it. What a difference. Perhaps the best $95 I've spent yet ;-)
 

mmckenna

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I know several folks here want to hear about my results thus far with the Diamond discone antenna I got and assembled today about as much as hearing about someones hemorrhoids but I still wanted to share the results thus far.
Yeah, if we wanted to hear about hemorrhoids, we'd tune in on the amateur bands...

But seriously, thanks for posting that. It's a good follow up comparison to the other e-Bay antenna. Maybe this will save someone else some headaches.
 

dcisive

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yeah, in this case it most certainly was MUCH better for anyone to save their $50 and put it towards a much superior $95 antenna. I was greatly relieved that it wasn't by any means as overwhelmingly large since I have it nicely mounted on a vertically oriented microphone stand. It looks pretty nice actually. It came with a very nice dual mounting bracket that worked out great.
 

K1IWN

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Nice work, dcisive. You're onto something of good value to the community.

Thanks for the share and I look forward to more of this kind of discussion. [emoji1360]


Sent from my iPhone using Tapatalk
 

SOFA_KING

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VERY glad to hear you had success with the discone. I was afraid it wouldn't hear too well in your house, but even that couldn't stop it. :D

They're great antennas. My ham "high gain" base antennas don't do much better, if any, over my discone. Then again, hardline on the discone keeps signals strong, while LMR400 on the hammy antennas does have more loss.

Congrats! ...and enjoy!

Phil
 

ko6jw_2

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I have used discones for years and the D130NJ for three or four months. My only criticism of the Diamond is that it claims to be useful from 30 Mhz on up. It actually tunes up at about 50Mhz and thus could be tuned for use on 6 meters. However, if you want to listen here in California to the CHP on 42Mhz, forget it. I experimentally replaced the stock whip with a 48 inch whip and it tunes up a 42Mhz. What a difference.

I have made measurements of the antenna with an analyzer. The discone portion works starting at about 115Mhz on up. I can only test to 512Mhz, but it is below 2:1 through the entire range. The low band is NOT a discone, but a base loaded ground plane. Very narrow bandwidth - maybe 2Mhz at most.
The N connector makes a big difference at UHF frequencies. Running RG-8 with N connectors on both ends the UHF response in flat. Using an N to UHF connector combination has a bad effect on UHF SWR.

Before anyone brings this up: Yes, we know discones have no gain. I would rather have an unity gain antenna that has a flat response than a high gain antenna with limited bandwidth.

I transmit on 2 meters, 220 and 440 with good results.
 

SOFA_KING

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I put a 62 3/4" stainless steel whip (no coil) on top of my Diamond Discone. Great low band reception, and full 6m band Tx under 1.7:1. Love it! And I think my VHF high band reception improved as well. It's a 3/4 wave on high band, in addition to the receive capability of the disc. It just works great.

Phil
 

dcisive

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I haven't gotten my Ham license as yet. I've been playing with this stuff, even high end HF receivers over the last 48 years. I have a Ham neighbor that is leaning on me to join that club. I may weaken. Since I'm not transmitting on this discone that's not an issue. I guess a Unity Gain antenna has good merit in my area. All of the primary transmitters for the various things around here are conveniently placed on a number of the mountain tops where they proliferate. I'm pretty fortunate as even though I'm at the far south west corner of the Salt Lake Valley, I'm on a hillside far above the valley with a clear shot at ALL of those transmitter sites. Apparently this discone is taking good advantage of this. It is inside but facing a window with a clear shot of those sites, so perhaps that helps. The other antennas of all types that I've played with didn't bring this level of performance to the table. No doubt a Yagi would but I didn't want to deal with that in the house. It's kind of cosmic looking at that silver bad boy on the mic stand in the far corner of my room. Now I feel like I'm putting together a real "shack" like I had when I was in California. All I need now is to get that Ham license, a Icom 7300 and Kenwood TH-D74A and I'll be dangerous again. LOL. I have to sink $1100 into a new water heater and main water valve coming into the house along with a new RO water filtration upstairs for our drinking water. Oh well.....welcome to home ownership I guess. Nothing a few good sales in my business won't take care of. This stuff is sure a ton of fun that's for sure.
 

dcisive

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I mounted it on a microphone stand which was perfect for this application. The bracket on the antenna comes with is perfect for this. I left off the top whip and raised it up to the top of the ceiling which now is working even better. I don't monitor in the 25-50 range so no loss for me.
 

jonwienke

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Get that antenna outside above your roofline, and you'll see another dramatic jump in reception.
 

dcisive

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I'm probably already at an altitude that eliminates the NEED to get it outside. I'm easily monitoring tons of 800mhz and 900mhz stuff all day long and it's 5 bars strong with NO noise on the noise floor. So I'm good. I'm not going to be placing this outside regardless. No holes in the house and no need to. Besides, I enjoy looking at the thing ;-)
 

dcisive

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Here's a pic of my setup for those that are curious. As I mentioned it's working exceptionally well indeed. I'm hearing clean transmissions from Weber County over 60 miles away which I didn't even get at all before. I know it's weird but I actually enjoy looking at the antenna in the corner of the room. Oh well.
 

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Mike_G_D

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You don't need the loading coil on the top. It is purely for base loading the top "low band" section and is not needed for the pure discone part covering 110MHz on up. The whip and base loading coil are attached to make it a rough low band base loaded ground plane (with admittedly shortened ground plane radials).

I had a similar unit; it'll work fine above 110MHz or so as a discone without the whip and loading coil.
 
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