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Author Topic: MPD Digital RG8X cables? //check my setup?  (Read 2570 times)

Nathan Riddle

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MPD Digital RG8X cables? //check my setup?
« on: January 02, 2018, 02:55:13 pm »

MPD Digital rg8x-bnc-antenna-cable-12in RG-8X

Anyone used these / are they good?
I don't have tools to roll my own (yet).
RG8X seems better than buying RG58/9 even for shorter cables.

https://www.amazon.com/MPD-Digital-rg8x-bnc-antenna-cable-18in-MILSPEC-Connectors/dp/B00I9EHY0S/ref=sr_1_cc_4?s=aps&ie=UTF8&qid=1514921766&sr=1-4-catcorr&keywords=rg8x%2Bbnc&th=1

---

I want to use them as short interconnects for my distro -> passive splits since I have more receivers than distro outs.

[RF diversity fin] ->
[RF Distro 3x (+3dB) + 1 cascade(0dB)] -> [4x SLX receiver]
[RF Distro 1x (+3dB)] -> [2x1 split] -> [2 x SLX receiver]
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Dan Currie

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Re: MPD Digital RG8X cables? //check my setup?
« Reply #1 on: January 02, 2018, 05:26:23 pm »

MPD Digital rg8x-bnc-antenna-cable-12in RG-8X

Anyone used these / are they good?
I don't have tools to roll my own (yet).
RG8X seems better than buying RG58/9 even for shorter cables.

https://www.amazon.com/MPD-Digital-rg8x-bnc-antenna-cable-18in-MILSPEC-Connectors/dp/B00I9EHY0S/ref=sr_1_cc_4?s=aps&ie=UTF8&qid=1514921766&sr=1-4-catcorr&keywords=rg8x%2Bbnc&th=1

---

I want to use them as short interconnects for my distro -> passive splits since I have more receivers than distro outs.

[RF diversity fin] ->
[RF Distro 3x (+3dB) + 1 cascade(0dB)] -> [4x SLX receiver]
[RF Distro 1x (+3dB)] -> [2x1 split] -> [2 x SLX receiver]

I've had good experiences with MPD and wouldn't hesitate buying more of their cables.
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Henry Cohen

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Re: MPD Digital RG8X cables? //check my setup?
« Reply #2 on: January 02, 2018, 06:19:34 pm »

MPD Digital rg8x-bnc-antenna-cable-12in RG-8X

Anyone used these / are they good?
I don't have tools to roll my own (yet).
RG8X seems better than buying RG58/9 even for shorter cables.

https://www.amazon.com/MPD-Digital-rg8x-bnc-antenna-cable-18in-MILSPEC-Connectors/dp/B00I9EHY0S/ref=sr_1_cc_4?s=aps&ie=UTF8&qid=1514921766&sr=1-4-catcorr&keywords=rg8x%2Bbnc&th=1

---

I want to use them as short interconnects for my distro -> passive splits since I have more receivers than distro outs.

[RF diversity fin] ->
[RF Distro 3x (+3dB) + 1 cascade(0dB)] -> [4x SLX receiver]
[RF Distro 1x (+3dB)] -> [2x1 split] -> [2 x SLX receiver]

I didn't know cables could be digital  :o

I wouldn't classify a single braid shield construction as "low loss", but for short jumpers within a rack they'll be fine.
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Dan Currie

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Re: MPD Digital RG8X cables? //check my setup?
« Reply #3 on: January 02, 2018, 06:55:49 pm »

I didn't know cables could be digital  :o

I wouldn't classify a single braid shield construction as "low loss", but for short jumpers within a rack they'll be fine.

HA!!

Henry,
  I'm pretty sure in this case 'MPD Digital' is a proper noun.
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Nathan Riddle

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Re: MPD Digital RG8X cables? //check my setup?
« Reply #4 on: January 03, 2018, 02:19:09 pm »

Are they better than: Shure UA802 RG58C/U UHF coaxial cable 2ft?

I don't have tools (yet) to roll my own and LMR400 is probably too inflexible for short jumpers.

I'm inexperienced to building RF racks, and the builds I've learned off of were made out of 'crappy' cable (at least it seemed to me).
If I'm using them with passive splits I want the 'best' (within reason) cable.

I need to go read http://www.astronwireless.com/topic-archives.asp I believe.
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Russell Ault

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Re: MPD Digital RG8X cables? //check my setup?
« Reply #5 on: January 03, 2018, 06:13:52 pm »

Are they better than: Shure UA802 RG58C/U UHF coaxial cable 2ft?

Possibly, but it also might not matter much. Cable loss is typically quoted as a certain number of dB lost per 100' for a given frequency (the higher the frequency, the greater the loss).

While every cable is different, RG58 (and it's ilk) typically cause somewhere in the neighbourhood of 13 dB/100' of attenuation at 500 MHz. RG8X is more like ~9dB/100' at 500MHz, or about 4dB less attenuation per 100' at 500MHz.

4dB less attenuation sounds great, but let's consider it in the context of usage: 2' of RG58 (the Shure cable) will cause ~0.26dB of loss at 500MHz, while 18" of RG8X (the MPD cable) will cause ~0.14dB of loss at 500MHz, for a difference of only ~0.12dB which, in the grand scheme of things, isn't very much.

In my mind, for short intra-rack coax runs, the type of coax is less important than other considerations (quality of cable and connectors, durability of assembly, cost, etc.); even if you did something crazy and wired up your rack with RG316, by my math you'd still likely be looking at less than half a dB of attenuation per link from the cable.

-Russ
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Henry Cohen

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Re: MPD Digital RG8X cables? //check my setup?
« Reply #6 on: January 03, 2018, 10:18:34 pm »

In my mind, for short intra-rack coax runs, the type of coax is less important than other considerations (quality of cable and connectors, durability of assembly, cost, etc.); even if you did something crazy and wired up your rack with RG316, by my math you'd still likely be looking at less than half a dB of attenuation per link from the cable.

One reason for using low loss coax (braid over foil, double braid or corrugated shield) within a rack is for RFI immunity. Remember that a standard single braid shielded coax is not just lossy, meaning RF energy escapes, but that same porosity that let's RF energy out lets unwanted RF energy into the coax and can contribute to a number of maladies including IMD, gain stage saturation and receiver desense.

For a typical wireless mic receiver rack, low loss coax won't make a substantive difference, unless the rack is also loaded with a significantly "noisy" digital equipment, IEM transmitters with less than stellar shielding, or other potential RFI/EMI sources.
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Nathan Riddle

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Re: MPD Digital RG8X cables? //check my setup?
« Reply #7 on: January 04, 2018, 01:24:50 am »

Possibly, but it also might not matter much. Cable loss is typically quoted as a certain number of dB lost per 100' for a given frequency (the higher the frequency, the greater the loss).

While every cable is different, RG58 (and it's ilk) typically cause somewhere in the neighbourhood of 13 dB/100' of attenuation at 500 MHz. RG8X is more like ~9dB/100' at 500MHz, or about 4dB less attenuation per 100' at 500MHz.

4dB less attenuation sounds great, but let's consider it in the context of usage: 2' of RG58 (the Shure cable) will cause ~0.26dB of loss at 500MHz, while 18" of RG8X (the MPD cable) will cause ~0.14dB of loss at 500MHz, for a difference of only ~0.12dB which, in the grand scheme of things, isn't very much.

In my mind, for short intra-rack coax runs, the type of coax is less important than other considerations (quality of cable and connectors, durability of assembly, cost, etc.); even if you did something crazy and wired up your rack with RG316, by my math you'd still likely be looking at less than half a dB of attenuation per link from the cable.

-Russ

Thank you for giving me the 'damping factor' of sound for RF applications calculations/math. That definitely puts things in perspective :)

I found this site:
http://www.qsl.net/co8tw/Coax_Calculator.htm

And thoroughly enjoyed learning about the coax types and losses associated with them! I needed that so badly to get the light'bulb to go off in my head about RF.

The mud isn't as thick to see through now!
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Nathan Riddle

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Re: MPD Digital RG8X cables? //check my setup?
« Reply #8 on: January 04, 2018, 09:49:57 am »

What about something like this?

3.3dB @ 450MHz for 100ft according to spec sheet. $166

https://www.showmecables.com/by-category/cables/wifi-microwave/bnc-male-to-bnc-male-low-loss-400-ultraflex-coaxial-assembly

https://www.showmecables.com/media/specs/SMC-400UF-Wifi-Assemblies.pdf

Quote
LOW LOSS 400 ULTRAFLEX CABLE - 100FT BNC MALE TO BNC MALE
Designed to deliver high performance with minimal loss, Low Loss 400 UltraFlex  (LMR-400UF equivalent) assemblies are the standard for the wireless LAN industry.  With a durable Polyethylene jacket, these cables are suited for indoor and outdoor installations.

Features:

Connector 1: BNC Male
Connector 2: BNC Male
Cable Type: ShowMeCable Low Loss 400 UltraFlex (LMR-400UF Equivalent)
50 Ohm
Polyethylene (PE) Jacket suitable for Indoor or Outdoor Use
Stranded Center Conductor for Maximum Flexibility
Applications: Wi-Fi, Antenna Cables, Ham Radio, Patch Cables, Jumper Cables, WLL, GPS, WLAN, LMR, WISP, WiMax, SCADA, Mobile Antennas

I know it's probably one of those: buy once cry once kind of deals, but I don't have big tour budget to get the best, just what is needed/works.

Either this cable or RG8X for 150 with 8dB loss can't exactly afford RG8 (Belden 9913)@ 2.8 dB loss for $300.

---

Also, this is really for remote mounting of antenna from TX or RX, correct?

I'm still not completely convinced remote mounting the antenna (closer to stage) with associated cable loss is better than having antenna at FOH with less cable loss. Though I guess the logic here is that air losses is greater than coax losses.
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Brad Harris

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Re: MPD Digital RG8X cables? //check my setup?
« Reply #9 on: January 04, 2018, 10:51:40 am »

LMR-400 UF (basically what you quoted) Is what we use for the majority of our RF cables..... Well, what we purchase at least for between antennas and receivers/distros. 

We also use LMR-240, usually it is what most of the manufacturers/distributers are sending out now with large RF orders (or RG8). The few extra dB loss per run for the majority of our applications, it doesn't make a considerable difference between the two (<50ft).

However, for longer runs (100's of feet) LMR-400 is the way to go (or bigger, or fibre for 1000's of feet).

But do realize, that with the larger numbers (LMR-400), it is as thick as a 15A AC cable, and not nearly as flexible. You can fit a few hundred feet (probably a thousand+ feet) of coiled RG8 in the same space as 100ft of coiled LMR-400.


Get in the habit of doing path loss calculations over free space and cable. Find out what your receiver needs for signal strength and figure out what cable best suits your needs. If LMR-240 fits the bill, save some money and get that. But if you really need LMR-400, get the LMR-400.



BRad
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