New DPD OmniX vs old RS 20-176 -- Findings

[andy404ns]

I have been using a Radio Shack 20-176 for about 15 years now and wanted to try an upgrade. I purchased a DPD OmniX based in large part on reviews here and also to support a small business with quality customer service. I received the OmniX a few days ago and wanted to share my findings. First, the set up:

Both are mounted in my attic at the same height and roughly 5 feet apart from one another. Both are fed down to a Stridsberg Engineering 4 port multicoupler by 25 feet of LMR-400. The OmniX has a slight benefit as the connection to the LMR is N to N whereas the 20-176 has two different adapters on it. For testing purposes I compared using my older BCD996T jumped from the multicoupler. I then tried a separate test where I went straight into my SDS100 from the LMR (i.e. no multicoupler). With the BCD996T I was mostly comparing based on audio quality and signal bars. For the SDS I also included RSSI as a metric. I know that generally my comparisons are unscientific and there are myriad members here who could recommend a plethora of equipment to get true measurements but such is life.

My findings are that the 20-176 performed as well or slightly better than the OmniX in the VHF and UHF ranges. I was hard pressed to find a single channel where the OmniX was noticeably better than the 20-176. This was disappointing as the majority of agencies in my area are VHF and UHF.

In the 800 range, the OmniX was far better than the 20-176. I don't think that's very surprising given that the 20-176 was not advertised to perform in that range (at least not that I recall).

I had read in various posts that the OmniX does have some amount of directionality to it so I tried it in various orientations but it didn't change much.

TL;DR: I had pretty high hopes for the OmniX but thus far I am rather dejected. I'm curious to hear what other members here think. Is it possible that I've done something wrong with the installation? Does it require anything extra that I haven't thought of? If not then I suppose I have two final questions to consider:

1. Do I go ahead and order a Diamond Discone (D130NJ or D3000N - what is the difference??) and try that out?
2. Do I try to find a VHF/UHF dual band base antenna?

And I guess I should also proudly proclaim: Long Live Sputnik!

Thanks all for reading and posting any comments.

 

[bearcatrp]

I have the diamond D3000N and the mil Omni. I don’t see much difference. I put the discone back up since I have a receiver that goes up to 3 GHz.

 

[dave3825]

I had read that even tho the Omni is a omni-directional antenna, people rotated it to where it achieved a better signal, a sweet spot if you will.

Also read that some people have seen results improve just by raising it 5 feet or so. Generally the higher the better.

And as far as your testing, if you can, connect a jumper from the omni direct to the scanner and try rotating while watching a signal meter or rssi on the scanner.

 

[devicelab]

I have the diamond D3000N

Ditto. It's an excellent antenna. It may need a FM notch filter if you're in a city but it's definitely a worthy investment.

 

[Brales60]

I went from a Sirrio Discone to the Omni X. It's about 20' up. Big difference on my SDS200 I think. I get stuff from 27-800 no problems.

 

[andy404ns]

I have the diamond D3000N and the mil Omni. I don’t see much difference. I put the discone back up since I have a receiver that goes up to 3 GHz.

Ditto. It's an excellent antenna. It may need a FM notch filter if you're in a city but it's definitely a worthy investment.

I went from a Sirrio Discone to the Omni X. It's about 20' up. Big difference on my SDS200 I think. I get stuff from 27-800 no problems.

So now I have to decide if I want to spend another $180 just to see if the Diamond is a bit better than the other two. This hobby will be the death of me.

 

[andy404ns]

I had read that even tho the Omni is a omni-directional antenna, people rotated it to where it achieved a better signal, a sweet spot if you will.

Also read that some people have seen results improve just by raising it 5 feet or so. Generally the higher the better.

And as far as your testing, if you can, connect a jumper from the omni direct to the scanner and try rotating while watching a signal meter or rssi on the scanner.

Yeah I'll get up in the attic again tomorrow and do some directional testing. Ultimately I want to receive signals from all directions so it doesn't matter all that much.

I also recall reading a thread where someone suggested that the OmniX might perform better when installed at an angle versus perfectly vertical. I don't know how or why that would be the case but since I'll be up there anyway I might as well try it all.

 

[dave3825]

Ultimately I want to receive signals from all directions so it doesn't matter all that much.

That's all fine AND All BUT you may notice a better signal on a certain System's when rotated a certain way. I mean omni directional means as such but it seems that the antenna has a sweet spot which seems to defy the hole omni directional aspect.

 

[Brales60]

Yeah I'll get up in the attic again tomorrow and do some directional testing.

I have mine on a telescoping pole I made out of chain link fence posts that I lock at any height and rotate. I haven't noticed any difference at different heights or direction, but I honestly haven't payed that much attention because it just works when I turn it on.
I'm all about the money thing in this little hobby I picked up. I'll get into it a little heavier once I retire soon.

 

[332emdg]

TL;DR: I had pretty high hopes for the OmniX but thus far I am rather dejected. I'm curious to hear what other members here think.

FWIW, I've been using the OmniX for 7 years now without fail. One of the best built antennas out there. Sorry to read about your experience.

Dave, the owner of DPD Productions and the maker of your OmniX seems pretty humbled when he wrote this about the OmniX himself way back in 2008;

"The Omni is just a basic decent antenna, which will be the case with most antennas that don't stack multiple elements either vertically or horizontally. What helps over a single tuned antenna like a ground plane, is the fact that you have elements at various lengths, which makes it more resonant in various bands. So in that respect, the Omni will usually be better than an average ground plane because you can hit more resonance points.
Dave
www.DPDProductions.com
Antennas & Accessories for the RF Professional & Radio Hobbyist
DPD OmniX Multi Band Scanner Antenna
Dave
www.DPDProductions.com Antennas & Accessories for the RF Professional & Radio Hobbyist

 

[andy404ns]

FWIW, I've been using the OmniX for 7 years now without fail. One of the best built antennas out there. Sorry to read about your experience.

Dave, the owner of DPD Productions and the maker of your OmniX seems pretty humbled when he wrote this about the OmniX himself way back in 2008;

Yeah I read a lot of Dave's posts as I was doing research. His willingness to help out in this community was a big factor in why I went with the OmniX over the Diamond discone.

I also want to point out that when I ordered the OmniX I got an email from Dave within an hour saying that things were a bit backed up due to a lot of orders and that he was sorry that there would be a delay. He's clearly a stand up guy and I don't regret my purchase at all. In fact, I'll probably be using DPD for a mobile antenna when I'm ready to pick up that project.

I know this thread probably came off as negative for the OmniX but I think it's much more just pointing out how damn good the RS 20-176 is in the VHF/UHF bands. As of now I have switched over to the OmniX. Since it's pretty much equal to the 20-176 in VHF/UHF and also gives me far better performance in 800 there was no reason not to.

I might end up getting a Diamond as well because why not. I'll update here again if that happens.

 

[332emdg]

Yeah I read a lot of Dave's posts as I was doing research. His willingness to help out in this community was a big factor in why I went with the OmniX over the Diamond discone.

I also want to point out that when I ordered the OmniX I got an email from Dave within an hour saying that things were a bit backed up due to a lot of orders and that he was sorry that there would be a delay. He's clearly a stand up guy and I don't regret my purchase at all. In fact, I'll probably be using DPD for a mobile antenna when I'm ready to pick up that project.

I know this thread probably came off as negative for the OmniX but I think it's much more just pointing out how damn good the RS 20-176 is in the VHF/UHF bands. As of now I have switched over to the OmniX. Since it's pretty much equal to the 20-176 in VHF/UHF and also gives me far better performance in 800 there was no reason not to.

I might end up getting a Diamond as well because why not. I'll update here again if that happens.

The OmniX replaced a broken Scantenna ST2 that finally succumbed to one too many storms and bad weather. That thing was a beast. (RIP).

Funny you mentioned your interest in a mobile antenna project, this is actually one of the reasons I came across your recent post about the OmniX while I was doing some research for a new mobile antenna myself.

I just gave Dave my business, again, last week when I bought his Tri Band VHF/UHF Scanner Mobile Antenna. I am extremely pleased with it so far. I have the magnetic NMO mount sitting on top of my Back Rack headache rack with the cable routed up under the cab and through a plastic plug in the rear passenger floor area of my Ram 1500.

Cheers.

V/r

Todd

 

[andy404ns]

The OmniX replaced a broken Scantenna ST2 that finally succumbed to one too many storms and bad weather. That thing was a beast. (RIP).

Funny you mentioned your interest in a mobile antenna project, this is actually one of the reasons I came across your recent post about the OmniX while I was doing some research for a new mobile antenna myself.

I just gave Dave my business, again, last week when I bought his Tri Band VHF/UHF Scanner Mobile Antenna. I am extremely pleased with it so far. I have the magnetic NMO mount sitting on top of my Back Rack headache rack with the cable routed up under the cab and through a plastic plug in the rear passenger floor area of my Ram 1500.

Cheers.

V/r

Todd

Interestingly enough, I too had an ST2. It lived up in the skies with the 20-176. When I moved across the country I left it with my brother where to this day it resides in his garage. I need to pull that thing out and see if it's salvageable. Would be fun to do a comparison on all four of them.

The Tri Band VHF / UHF is exactly the one I was looking at from DPD. I was going to pose this question directly to Dave but I suppose I'll post it here:

The Tri Band VHF/UHF is 22 inches tall and shows gain of 3dBi VHF, 6dBi UHF. It is also tuned for 700-960
The Dual Band VHF/UHF is 28 inches tall and shows gain of 2.4dBd VHF, 5.5dBd

I actually missed the fact that one is labeled as dBi while the other is dBd and was pretty confused as to why the specifically tuned and taller antenna had less gain than the tri band. Based on 5 minutes of intense googling, it seems that the dBd measurement starts with an extra 2.5 dBi since a dipole antenna naturally has that gain versus an isotropic antenna that has no gain. I'm not 100% clear on why one of the antennas is listed in dBi while the other is dBd. I suspect it is as simple as the dual band is built on a dipole platform while the tri band isn't? The dual band has a wavelength measurement while the tri band has an SWR measurement.

Wild how much there is to learn in this hobby.

 

[prcguy]

Interestingly enough, I too had an ST2. It lived up in the skies with the 20-176. When I moved across the country I left it with my brother where to this day it resides in his garage. I need to pull that thing out and see if it's salvageable. Would be fun to do a comparison on all four of them.

The Tri Band VHF / UHF is exactly the one I was looking at from DPD. I was going to pose this question directly to Dave but I suppose I'll post it here:

The Tri Band VHF/UHF is 22 inches tall and shows gain of 3dBi VHF, 6dBi UHF. It is also tuned for 700-960
The Dual Band VHF/UHF is 28 inches tall and shows gain of 2.4dBd VHF, 5.5dBd

I actually missed the fact that one is labeled as dBi while the other is dBd and was pretty confused as to why the specifically tuned and taller antenna had less gain than the tri band. Based on 5 minutes of intense googling, it seems that the dBd measurement starts with an extra 2.5 dBi since a dipole antenna naturally has that gain versus an isotropic antenna that has no gain. I'm not 100% clear on why one of the antennas is listed in dBi while the other is dBd. I suspect it is as simple as the dual band is built on a dipole platform while the tri band isn't? The dual band has a wavelength measurement while the tri band has an SWR measurement.

Wild how much there is to learn in this hobby.

The difference between dBi and dBd antenna gain is 2.14dB. A perfect half wave dipole will have 2.14dB more gain than an a theoretical isotropic standard. A 1/4 wave monopole over infinite ground plane (think 1/4 wave whip on a large metal car roof) has less gain than a dipole and maybe around 1dB or so less because half the radiating part of the antenna is missing compared to a dipole.

With that said, how can a vehicle mounted 1/4 wave equivalent antenna on VHF like the DPD tri band show 3dBi of gain? Short answer is it cant. How can the 28" long DPD dual band show 2.4dBd gain at VHF and 5.5dBd gain at UHF??? Its impossible. If you change those figures to dBi its closer but still very questionable on how DPD is battling the laws of physics and winning. BTW the DPD tri band mobile antenna that runs $129.95 appears to be just a Browning or Taurus BR-137 tri band that can be had from Amazon, Walmart or the Antenna Farm for about $61 plus a mag mount for about $17. But I guess its nice that they are packaged together for you and available from one source.

 

[andy404ns]

The difference between dBi and dBd antenna gain is 2.14dB. A perfect half wave dipole will have 2.14dB more gain than an a theoretical isotropic standard. A 1/4 wave monopole over infinite ground plane (think 1/4 wave whip on a large metal car roof) has less gain than a dipole and maybe around 1dB or so less because half the radiating part of the antenna is missing compared to a dipole.

With that said, how can a vehicle mounted 1/4 wave equivalent antenna on VHF like the DPD tri band show 3dBi of gain? Short answer is it cant. How can the 28" long DPD dual band show 2.4dBd gain at VHF and 5.5dBd gain at UHF??? Its impossible. If you change those figures to dBi its closer but still very questionable on how DPD is battling the laws of physics and winning. BTW the DPD tri band mobile antenna that runs $129.95 appears to be just a Browning or Taurus BR-137 tri band that can be had from Amazon, Walmart or the Antenna Farm for about $61 plus a mag mount for about $17. But I guess its nice that they are packaged together for you and available from one source.

Thanks for that detailed info! I actually had a typo in my post. The VHF dual band is 38 inches, not 28 inches. Not sure if that matters or not as I still understand very little of what's being discussed

I think that the increased price is at least somewhat justified by the quality of the build, not necessarily the ability to pull in signals. That said I did pull up the BR-137 and it sure seems similar.

I'm studying for the technicians exam now so hopefully this stuff is covered but do you happen to have links to videos, articles, books, etc outlining antenna construction and the physics at play?

 

[vannossc]

I have the Omni X (non-mil) up about 33 feet. Connected to a Uniden SDS200 with 40' LMR-400UF. I can pull in all the UHF and VHF I ever looked for, no issue. 800mhz is excellent. Build quality is very good.

The air band tho...I wish it was a bit more sensitive as I have some trouble hearing (clearly) ground, tower, ATIS freqs from an airport just 12 miles away. It's AM I know but I thought it would still come in stronger. Of course, I couldn't hear any airport traffic before with my old antenna (some cheap nonamer) and RG-8X cable.

Love the Omni so much I ordered a 1090 ADS-B antenna. It seems Dave always posted he's busy and it will ll ship next week ( same thing he told me on these two). No prob - I'll wait.

 

[Brales60]

I have the Omni X (non-mil) up about 33 feet. Connected to a Uniden SDS200 with 40' LMR-400UF. I can pull in all the UHF and VHF I ever looked for, no issue. 800mhz is excellent. Build quality is very good.

The air band tho...I wish it was a bit more sensitive as I have some trouble hearing (clearly) ground, tower, ATIS freqs from an airport just 12 miles away. It's AM I know but I thought it would still come in stronger. Of course, I couldn't hear any airport traffic before with my old antenna (some cheap nonamer) and RG-8X cable.

Love the Omni so much I ordered a 1090 ADS-B antenna. It seems Dave always posted he's busy and it will ll ship next week ( same thing he told me on these two). No prob - I'll wait.

Funny about the air stuff, I was getting so much I killed because it was hogging up the scanner. Ground, tower and the jets.

 

[vannossc]

It's better but maybe my expectations were too high. Given the uncertain nature of the "directionality" of this antenna, I'm going to turn it 90 degrees this weekend and see what happens. Great antenna - love it. But curious if indeed it's "directional"...

 

[N9JIG]

Like a couple people I had (perhaps unrealistically) high expectations for the Omni-X when I bought it. It worked OK but compared to an ST-2 it replaced in my attic it was worse. I put the ST-2 back and stored the Omni-X. The Omni-X is very well built however and should last a long time outdoors.

I did try it in a couple orientations and there were a few differences that indicate that the lobes were asymmetrical. I wouldn't call it directional, but it did seem to favor broadside. That is to be expected of the design.

I am thinking of putting it outside on my homes roof and telling the HOA it is a TV antenna. There are TV antennas that have a similar appearance so I might get away with that.

 

[Brales60]

I am thinking of putting it outside on my homes roof and telling the HOA it is a TV antenna. There are TV antennas that have a similar appearance so I might get away with that.

Exactly what I did, no issues.