Yeah, I agree. Unless there is something wrong with your existing coaxial cable, I doubt you'll notice any difference. LMR-400 is marginally better than name brand RG-8. I wouldn't waste money on it.
I think I said this in one of your earlier posts, but I think you have something wrong with your setup. Rather than throwing more money at it, take some time to find the issue and fix it.
This is for UHF/VHF only.
Current SWR: varies from about ~1.5 or 2.5:1, also goes up slightly with power increase so a sign something is off.
Yes, I think you need to trouble shoot this. It's unlikely your SWR should change with increasing power for your setup. Usually this means there's an intermittent connection somewhere, corrosion, poorly installed connectors (don't assume that because you bought it that it's good). I'd also question your SWR meter.
I'd pull everything down and go through it carefully. Visualize all the connections, look for any discoloration, corrosion, pitting, any signs of water. What I usually see is that someone misunderstands the importance of properly waterproofing coaxial connectors. A wrap of electrical tape is NOT waterproofing. Goop you squirt into the connector won't protect the coax/connector interface.
I'd also take a close look at the coaxial connectors on the cable. If the weight of the cable has been pulling on it, then it's really easy to pull things apart.
Look for any breaks in the jacket, anywhere water can get in.
Take your antenna off the mount, look for signs of water intrusion on the NMO mount. Make 100% sure the center tab/pogo is making contact with the center of the NMO mount. Make sure everything is good and tight, including any set screws that hold the whip in place. Ideally disassemble as much of the antenna as you can. All electrical connections need to be clean and shiny.
Current Setup:
Antenna: MFJ-1432 Mobile antenna, 2m/70cm, UHF/NMO, 5ft
Supposed gain from MFJ (I'm skeptical on this): 7/8 Wave 5.0dB Gain on 2m 5/8 Wave 7.6dB Gain on 70cm
Mount: Tram Stainless Steel So-239 to So-239 Antenna Mirror Mount (bolted to painters pole)
Ground plane kit: Harvest 1401 V/UHF Dual Band Ground Plane Converter Kit (likely not an exact match and causing some impedance miss match)
Feedline: 35' American made RG8U with UHF male on both ends
Manufactures line loss stats:
1.8dB @ 150MHz/1.22kW/65.4% E
3.3dB @ 450MHz/0.69kW/47.3% E
Two things that raise a little red flag...
MFJ. Not the highest quality stuff. Often you'll hear it referred to as "Mighty Fine Junk".
I've never been impressed with anything from Tram/Browning. I've disassembled some of their connections and they were sloppy, to say the least. I'd really take a close look at the connector.
Ground plane….
As long as it's at least 1/4 wave length long radials on your lowest frequency (about 20 inches) you should be OK. Ground radials do not need to be tuned. Car roof tops are not cut to tune mobile antennas….
I'm thinking of switching to the following:
Antenna: Diamond Original X50NA (considered the 10' model but likely just too large for our small place).
Slightly lower gain but I trust Diamond's stats more.
Mount: 2 u bolts, comes with the antenna
Ground plane kit: built into the antenna and likely much better matched.
Feedline: 35' Times Microwave LMR-400 Cable Assembly, N-Male To Pl-259 (Uhf Male) Connectors, 35 Feet Long
Manufactures line loss stats:
We sometimes have an issue with new technicians at work. When something isn't working right, they'll be in a rush to close out the ticket. They blindly start swapping out parts with no rhyme or reason. They'll keep doing this until it starts working. They assume the last part they swapped out was the issue, toss it in the trash and put all the other stuff back on the shelf. Being in a rush to get it fixed might make the customer happy, but it costs a lot of money and sometimes bad parts get put back into stock.
So, kind of off on a tangent there, but what I'm trying to say is that you'll save a lot of money AND learn a lot more if you find the cause(s) of the issue with your set up and fix those.
On the other hand, if you have $250.00 burning a hole in your wallet, then by all means, go for it. But figure out what you are going to do with all that old stuff that may or may not work. You can toss it all in the trash and be done, or if you are like many amateurs, you'll want to reuse it sometime. Then you'll go through all this heartburn again trying to figure out what the issue is.
My thoughts are, better manufacture antenna with pre-matched radials,
Higher quality lower loss coax with n connector for feedpoint ( I understand this is a lower loss at UHF frequencies and more weatherproof).
A better manufacture antenna might still have the same issue if the original antenna wasn't the cause of the problems. Have you confirmed 100% that your SWR meter isn't at fault? Are you using the SWR meter correctly, calibrating it each time you change power levels or frequency?
As said above, the difference between 35 feet of decent RG-8 and LMR-400 is going to be minimal. In fact, I'd go as far as to say that without good test equipment, you'll probably not be able to tell the difference. Your ears will not be able to hear a .5dB difference in loss. You might notice it on very distant stations that are received a bit clearer, but for most stuff, you won't know.
N connectors are superior to UHF, but again, there' s a few issues with your approach;
Waterproofing… Yeah, N connectors have some sealing designed into them. But
no one in the LMR industry would install an N connector outside without doing proper waterproofing. If you install an N connector and don't waterproof it properly, you'll very likely be going through all this in another year or 5. Had this happen at work. A contractor (also an amateur, he proudly made sure we were aware) installed some antennas. He did a crappy job. The LMR-600/connector was not installed correctly and his "waterproofing" consisted of a wrap of electrical tape. We caught it and fixed it before any damage was done. It was an N connector on LMR cable installed by a "professional". It failed.
Lower loss…. Again, like the coaxial cable, unlikely you'll hear the difference. More than the lower loss is that N connectors provide a proper 50Ω impedance through the connector. UHF connectors do not. This can become an issue at higher frequencies. 70cm band, unlikely you'll have an issue. There are a lot of UHF connectors used on UHF equipment and they work fine if they are installed correctly and properly waterproofed. Not an ideal connector, but I'd not blow money on replacing all your cable/antenna just to get the coveted N connectors. Changing connectors on their own isn't likely to fix the issue. Replacing poorly installed, damaged, pulled apart, or water/corrosion damaged connectors will fix things.
I'm guessing this would set me back about $250. Would it be a meaningful upgrade?
Again, I doubt it. Until you figure out what the issue is, you would just be spending money and not necessarily fixing anything.
Check your SWR meter with a known good one. Really. Don't trust any of your test equipment unless it's been properly checked out and calibrated.
Rule #1, don't assume anything is "good" just because it worked last time, is new, or someone else said it was OK. A lot of people have pulled their hair out over troubles like this only to learn later that their test equipment way lying to them. I've been there, and sometimes you get a gut instinct about this stuff.
Check your jumper cables between the SWR meter and the radio, don't assume they are good.
Check all your coaxial cable for damage, water intrusion, cuts, sharply bent, crushed, etc. Check all 35 feet of it, inch by inch.
Check your coaxial connectors for proper installation. If you have a multimeter, check for continuity from end to end for both the center conductor and the outer shield. Also make sure the outer shield isn't shorted to the center pin anywhere. When you are checking, wiggle the hell out of all the connectors while you are doing it to find any intermittent connections or shorts.
Check the antenna mount. Nothing from Tram/Browning impresses me. Check for corrosion and broken connectors. Use the multimeter to make sure it's good all the way through.
Check the ground radials. Make sure everything is clean and tight.
Check the NMO mount, make sure it's not wet, corroded, or damaged in anyway.
Check the antenna base. Make 100% sure the antenna base is making full contact with the NMO mount.
Check the antenna whip. Make sure it's not loose, not corroded, not damaged.
If you get through all that and find nothing wrong, the SWR meter checks out, continuity/short circuit tests are all OK, then you need to start looking at how close your antenna is to the building. Try taking the entire setup out into a wide open space. Set it up and test again. Nearby metal, even coated windows, window screens, rain gutters, down spouts, any number of things can interfere with the antennas.
I'd hate to see you waste $250 bucks and still have the issue.
