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Author Topic: 195 vs 58 cable?  (Read 4046 times)
KE2KB
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Posts: 127




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« on: February 12, 2013, 05:10:39 PM »

Hi;
I want to replace a length of RG58 BNC cable I am using to connect my HT to the LMR400 cable coming down from my Ringo Ranger.
I like the RG58 for its flexibility, but I am sure that the particular cable I am using is not of high quality, so I am looking to replace it.
What I really need is a 10ft cable with type N female at one end (to mate with the type N male on the LMR400 cable) and SMA male plug at the other to attach to my VX-150 radio.
I found just that combination in a "195 series" cable, but am concerned about the flexibility of the 195 compared to the 58 cable. I don't want anything that will be too stiff.

Thanks for your help.

Frank
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AB0RE
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« Reply #1 on: February 12, 2013, 10:38:59 PM »

I thought "195 series" and rg-58 were the same thing (195 refers to the outer diameter of the coax, .195", which should be the same as RG-58).  I think LMR-195, LMR-240, etc, are just Times Microwave trademarked names.  For flexibility the big thing to look for is whether the center conductor is stranded or solid.  Stranded is a bit more lossy, but at a mere 10' you are not going to notice a fraction of a dB difference.
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AA4HA
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« Reply #2 on: February 13, 2013, 05:26:39 AM »

It might just be easier to get an N-Male to SMA-Male cable (195 or 240 are both great) and to use an N-F to N-F barrel adapter to connect the two cables.

The '195 would be easier on the SMA connector so you are not mechanically stressing the connection to the radio.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
KE2KB
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Posts: 127




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« Reply #3 on: February 13, 2013, 08:01:39 AM »

Hey guys; Thanks for your advice/info on this.
Now I find that I have more problems with my feed line. For one thing, the N female to PL-259 adapters I am using are no good. The pin on the N male (which came attached to the LMR400 cable assy I purchased when I bought the Ringo antenna) is significantly smaller (in diameter) than the socket pin on the adapter, thus these do not make a good connection. I was not aware that there are different diameter N pins, but either that is the case, or the adapters I purchased are junk.
What I probably should do is replace all connectors with N, eliminating all of the PL-259. From what I have been reading, N are far superior to UHF for even 144-148Mhz use.
If I do that, then I need to replace the SO-239 connectors on the ICE 302 arrestor with N type.
It's either that, or replace the N plugs on the LMR400 with PL-259's, which I have plenty of; but PL-259 will not take advantage of the inner shield of the LMR400 cable.

I don't know what the diameter of the center pin on my LMR400 is, as I do not have a caliper. Maybe it's worth the cost to buy one now. I have some other uses for a caliper anyway.

I would really love to replace the Ringo Ranger ARX-2B with a better antenna which would work for 2m and 70cm, but the whole reason I chose the ringo is that it does not require radials (although this one did come with them - I am not using at the time) due to installation issues.
So if I get another antenna, and it will most likely have radials, I will have to figure out how I am going to get it up past the peak of the roof from the attic window (I don't have a ladder, so I installed the antenna outside the attic window on a set of wall mounts and 10ft of 1" EMT). If I did use the radials for the Ringo, they would be below the roof eave, thus would hit the side of the house, not clearing the peak of the roof. Another 10ft of EMT would do the trick, but then I've got physics working against me in that I won't be able to hold the assembly while raising it.

I'll have to look at and study the whole system before I make any changes.

Anyone know how much loss the UHF adapters cause? If I'm looking at tenths of a db, then I won't worry about changing that part, but if it's even 1db then it will be worth changing the connectors and cable.

Frank
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K1CJS
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« Reply #4 on: February 14, 2013, 07:53:41 AM »

Belden manufactured RG58 cable with a stranded center conductor--it sounds like that is what you may be looking for.  I don't know if they still do, but it's worth a look.

Added--  Don't worry about the loss factor of the UHF connectors, it's negligible at 2 meter frequencies and isn't much worse at 70 cm frequencies.  Also, N connectors are better than UHF at both 2 mtr. and 70 cm. frequencies, but they're not far superior--unless you're talking about being weatherproof.  When you get up into the frequencies higher than 70 cm, then N type are far superior to UHF connectors.
« Last Edit: February 14, 2013, 08:02:03 AM by K1CJS » Logged
AA4HA
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« Reply #5 on: February 14, 2013, 02:47:07 PM »

At VHF and lower the advantages of N connectors in regards to impedance or insertion loss fall dramatically. At that point the PL/SO connectors become a better choice even just from the cost perspective. I still lean in favor of the N connector but from the weather-resistance of the native connector.

Of course I would never leave any sort of coaxial connector PL/SO, N-family(N,TNC,BNC) or any of the other "families" in an untaped/booted state in the raw outdoors.

For jumper/throw cables <10' your losses are just going to be so minimal at fractions of a dB unless you get into the really "tiny" stuff, greater than UHF or very low-grade cables that have miserable shielding or were pre-damaged by age or moisture.

When you go up in frequency (>UHF) then you "really" pay a penalty for different cable types. Above a few GHz you start seeing dB losses that can and will make a difference in how a radio link performs. I was doing some commercial Wi-Max system design where we were putting in more than 90 runs of 100' coax at 3.65 GHz with transmitters at 23 dBm and the differences between LMR-240 and LDF4-50 were quite significant, to the point where it would of cost tens of thousands of dollars more for additional repeater sites because of the link budget losses. It is knowing when those trade-offs become significant and what your performance expectations are that will tilt a design one way or another.

Even in those systems I was using a 3' chunk of LMR-240 as a jumper from the lightning protector to the radio just because of the flexibility and bend radius (N to TNC connection).
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
WB6BYU
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Posts: 13288




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« Reply #6 on: February 14, 2013, 03:23:22 PM »

Quote from: KE2KB

...The pin on the N male (which came attached to the LMR400 cable assy I purchased when I bought the Ringo antenna) is significantly smaller (in diameter) than the socket pin on the adapter, thus these do not make a good connection. I was not aware that there are different diameter N pins...



Type N connectors come in both 50 ohm and 75 ohm "flavors".  You might have a
75 ohm plug in a 50 ohm system.
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KE2KB
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Posts: 127




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« Reply #7 on: February 15, 2013, 05:11:32 AM »

Thanks guys;
WB6BYU; you may have hit on something. I was reading that a smaller diameter center conductor in a feed line will result in a higher impedance of a coaxial cable, so if the same law is applied to the connector, it might be that I have an LMR400 cable with 75 ohm type N connectors. I'll have to check out the specs.
That said, I went ahead and replaced the N connectors with UHF (PL-259) type. I did this mainly because the connector at one end of the LMR400 came off at one point, and I had improvised by drilling several holes through the sleeve and soldering it to the braid, similar to how the PL-259 connectors are attached. It seemed to work, but I still didn't like the fact that the pins in the N male were too small for the N to UHF adapters I was using, so I replaced both connectors. I haven't noticed any difference in reception on 2m, but perhaps I am getting a bit more energy to the antenna. Still; checking the SWR before the fix, it was really flat at 1.2:1 (measured at the radio). I figured that if there was a problem with one of the connectors, the SWR would not be flat across 2m.

As for the RG58 cable I am using, it's labeled "RG58AU Cable". There is no brand. I don't like that. I think it's a cheap one I had bought for use with my old Ethernet at 10/100 Mbits. I've got 50ft of Belden RG58A/U cable available. All I need is two UG88 BNC connectors to build a good cable. I don't think I'll bother with going directly from the PL-259 on the LMR400 to the SMA on the radio, as trying to assemble that cable would be more difficult and probably not result in better performance than keeping the UHF adapters in place and running the BNC to BNC cable. That way, I can also use the cable for the FT-530. Now to find a pair of the UG88. If I don't have them, I'll have to order them. Too bad we don't have any electronic parts stores around anymore. Sure; there's Radio Shack, but the only BNC plugs they will sell me are the solderless ones, which I will not use.

Frank
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WB0UPD
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« Reply #8 on: February 15, 2013, 06:50:33 AM »

Agreeing on Radio Shack. They seem to want to be Walmart not electronics.
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KE2KB
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Posts: 127




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« Reply #9 on: February 15, 2013, 10:48:03 AM »

I use Digi-Key and Mouser for parts. Last time I ordered anything from either, Digi-Key has a $25 minimum order, while Mouser has none. Shipping is usually the biggest deterrent to ordering small parts online.
I'm looking at some Philmore brand UG88 type connectors that should fit the RG58A/U cable. Nice thing about Ebay is you can usually find free shipping.

Frank KE2KB
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AB0RE
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Posts: 293




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« Reply #10 on: February 17, 2013, 09:06:50 PM »

I use Digi-Key and Mouser for parts. Last time I ordered anything from either, Digi-Key has a $25 minimum order, while Mouser has none. Shipping is usually the biggest deterrent to ordering small parts online.
I'm looking at some Philmore brand UG88 type connectors that should fit the RG58A/U cable. Nice thing about Ebay is you can usually find free shipping.

Frank KE2KB

You got it backwards - Digikey has no minimum order and VERY reasonable shipping costs.  Mouser has a minimum order requirement.

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