Unveiling the Truth: Measuring Coax Cable Loss for Ham Radio Beginners
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- Опубліковано 16 гру 2023
- Coax cable loss refers to the reduction in signal strength as it travels through the cable. By measuring this loss, we can determine the efficiency of our antenna systems and make necessary adjustments. Coaxial cable loss is a critical factor to consider in any ham radio setup. Understanding how to measure it ensures optimal signal transmission, reception, and overall performance. With the information shared here, you'll be able to identify and address deteriorating signal quality, troubleshoot connection issues, and fine-tune your radio system for peak operational efficiency. In this video, we perform a loss test on some coaxial cable with the NanoVNA using what is called an S21 Gain measurement.
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Everyone is always worried about how much of their output power is reaching the antenna and that is not what people should worry about. Its the tiny power that your antenna is sending back to your rig. Every db counts on weak signals and the difference between making a contact or not in many cases. You can always increase the transmitter power via amps to make up for any coax loss, but the other station may not.
As a general rule, put in the best coax cable you can afford. Its the most important part of your station setup.
Finally someone showing people how to test there coax rather than just pushing M&P claiming its the best!! Your the best Ape!! 👍👍👍
lol, thank you and glad you liked the video 👍
Excellent. Really makes you think twice about what coax to use in a vehicle for 2m and 70cm. Length is going to be short but the losses can be pretty high. Thanks!
Yeah, for sure. Thanks for watching 👍
Iv'e just upgraded from rg58 tp M&P HyperFlex 13 coax. Its very expensive but i wont need to upgrade for a long time, and the fittings are built like tanks.
I’m running some M&P and you are correct, the connections are beefy 👍
Good stuff. I appreciate you sharing the various tests you can run on your equipment with both the NanoVNA and the TinySA.
Thanks 45, I like doing them 👍
As I’ve said in the past I always learn something from your videos, thanks for the demonstration and for sharing
Hey Bob. Glad they are helpful 👍
Thanks for the S21 tutorial with the NanaVNA! Good sutff! Merry Christmas Ape!
Hey SF, merry Christmas 🎄
I need to buy a device that measures my exponential cash loss with this hobby!😕
Thnx Mr Ape.😊
lol 🍻
Thanks for the info, Ape! Merry Christmas to you and yours!
Same to ya 👍🎄
Thanks for the breakdown Ape.
Thanks for watching Paul 👍
Nice work Ape, pretty interesting.
Thanks Chuck 👍
Thanks, Ape 👍
Thanks for watching 👍
Good job professor!
FEP!
Coiling up the cable will only give you common mode inductance. Differential mode (what we use to get our wigglies to the antenna) is not affected by the coiling of the cable. Rest of the video is great, and this test is why I do the "through" calibration.
Fair point about CMC, thanks for the comment!
@@TheSmokinApe So, keeping that incorrect claim in the video perpetuates a myth. We have enough myths that hams believe.
Your videos are always excellent Ape.
Here I was thinking you only watched because I am cute
@@TheSmokinApe 🤣🤣🤣 well you found me out.
@@LifeAtTerminalVelocity I knew it! By the way, glad you like the videos bro 🍻
👍Thank you sir.
No prob, thanks for watching!
Thank you for explanations realy great !
Thanks vI, glad you liked it 👍
Good Video
Thanks Thump!
Great video Ape. I also use nano vna saver as the device screen tends to become unresponsive when using it outside in the cold.
I use it mostly because of my bad eyes, lol. Thanks for watching Mr Mud 👍
Great Video Ape. Even if you subtract the losses (which add up) of the connectors, it's obvious that you should select a different coax, or obvious how to choose the right coax for your application.
Thanks James. When you combine losses from bother components like transformers and tuners you see it adds up quick 👍
Great video Ape. Some hams don't even think about cable loss vrs frequency. You have to look at the system as a whole. 73
Hey Jeff. You are right, between tuners, coax and transformers the losses can add up quick 👍
Good vid Ape! I'm a General Class ticket but I'm big into Storm Spotting and chasing so I can justify LMR-400..But for HF I have no trouble running RG-8X...Merry Christmas bro!
Merry Christmas BA. Don't tell anyone but my main HF coax run is 8X 👍
Add another Chapter to TheSmokinApe Book of Ham Learning. Thanks
lol, thanks Bob 🍻
I use RG-316 for my POTA activations. 25’ of ABR with the choke beads on one end which for my vertical I put at the antenna end and EFHW at the radio end since I use the shield as a counterpoise. If I need a longer run I use a 50’ piece of RG-316. The losses are fairly negligible at HF frequencies. Because of that I gladly take the losses over the advantage of the small coax package. I’ve taken a variety of different coax types and lengths and haven’t really noticed any differences. Thanks for the video.
Hey Trucking, I am the same way... I'll take the loss hit just for the easy cable 👍
Thoroughly enjoyed that, Ape. You made a point about the coil of coax having impedance. Based on what I know, this is not a problem at all for this test since the impedance is against currents travelling on the outside of the braid only (choke) and won't impede RF travelling on the surface of the inner conductor. The coil should not affect the measurement at all. Do you agree? Alex, 2E0LUP
You are correct Alex, I would agree. Thanks for watching and for the comment 👍
@@TheSmokinApe Ok, there you have two viewers who noticed the mis-statement. Let's get that corrected. What say?
Another good video. I picked up some rg-213 for pota but just been too busy to try it. So what cable(s) are you running at your base?
I have a few feeds, mostly RG8x and some flavor of M&P.
I get the video was how to use the H4 ( you didn't show any menu settings ). The manufacturer spec sheet will tell you where that coax runs best as well.
Yes, you can use the manufacture spec if you have it and you didn't get gas station coax. Thanks for the comment Mark.
Great video Ape. Its definitely eye opening when you just think -1db from a 100 watt transceiver is going to be 80 watts out, and 1db isn't bad.
LOL, you are correct.
Yep.. Greetings...
Nano-H4 is very nice for less than 100 dollars.
Possilbe to mention Reflection losses due to coax as well !
Hey BLE, you are correct these VNAs can give you visibility into what’s actually going on in your circuit 👍
It’s very eye opening to put a wattmeter and dummy load at the end of the coax. I do however think the hype is overrated unless possibly you have to run the pre amp all the time.
Yes, the wattmeter and DL is a good test for sure 👍
Not just for beginners, a good reminder for everyone. 👍
Fair point Doug, thanks for watching 👍
Very cool. I knew this could be done with the NanoVNA but wasn't sure how. I'm curious what the loss differences are between a longer and short run of cable. I started using RG316 this year for POTA with the CaHR Mercury linked dipole and the N9SAB OCFD, since it puts much less strain on the mast for these antennas. I've got one cable that is around 20-25 feet and another that is around 30-33 feet, which was so I could put the antenna up higher. I'll have to check out what the difference is sometime. Thanks!
Hey Mike. You’re correct the longer the cable the more attenuation. I’m willing to loss some watts to have the smaller cable 👍
Most coax loss specs are calculated @ 100ft (but check carefully, some are at other lengths, including meters). A 25ft. cable would be 1/4 of that, 33ft. would be 1/3. A good reason to keep your cables as short as practical.
Thanks for another informative video Ape. I need to check your list to see if you have covered the subject of using coax lengths of half a wave length of the frequency band you are going to use. I've heard for and against on the merits of this... would welcome your opinion. 🤔 73 G0ACE
Hey Ace, glad you liked the video. So using a havewave or multiple there of if the frequency is a best pratice but its not something I have done a video on. I could add it to the list but be warrned, it's a long ass list.
@@TheSmokinApeThanks Ape, I realise it's a contentious subject too!
loss figures are available for most coax cables (db per 100 feet), useful for those who don't have a nano vna. either way one can soon work out which cable to use for the length and frequency to be used. 70cm in a car, RG58 is ok it only needs 10-15 feet. 10M with the antenna down at the end of your paddock, RG213 at least.
Hey not, I would agree with most of that. That said many folks reach out to me for help with their stations and don’t know what type of coax they have or they have a generic rg-58 or rg-8x and do not have a manufacturer data sheet. Thanks for the comment 👍
Will the loss at 440 with only 7 feet of that cable be as significant ? My K-400 lip mount came with that cable for use with a dual band antenna. Great Video !!!
I wouldn’t worry about 7’ this cable was about 35’ 👍
At 7 feet, it would be around 1.45 dB loss for 70CM, and 0.73 dB for 2M.
Including Rg-6 75 ohm Foam double shield would've been interesting as it's relatively Cheaper & has Less less loss than Rg-8....The 75 ohm coax has surprisingly less significant Mismatch loss & Vswr issues than you'd think for the cost...
I know a few folks who use it, I haven’t yet 👍
Can you do a video on gow to measure the length of a cable... Or where a break is?
I can put it on the list. The problem is that you either need to know the velocity factor which seems like a hassle.
I'm using 50 ft of rg8x on gmrs and the SWR increases when I step up the power on my radio. Is that normal? I know it sounds silly but I go down to two watts. I got 1.01 I go up to 25 while that's all I'm looking at. 1.7
As crazy as that sounds, it happens.
The major issue all hams have is they think about coax in loss only.
No one looks at the noise incurred by cable leakage.
Say you have 100ft and you want to DX on 7mhz 40m, well RG58 will be something like 20% or 30% loss at like 1.5 to 2:1swr fairly standard stuff, the LMR400 might be something like 10% or better.
This looks to most hams that there's no point in using LMR400 as it's like a quater of an S point difference.
But what nobody realises is that there's probably going to be an S point in noise floor increase using the RG58, thus making the SNR way worse using the cheaper cable.
Of course putting the coax underground helps and if you're in a quite rural area it might not make that much difference, but if you're in the city and it's noisy and you can't put the cable in a trench so it's above ground get the best cable you can.
Thanks for the info Shane, it’s helpful 👍
@@TheSmokinApe no worries 👍
I just got 50 ft of RG316. It’s a SWR nightmare. I will never use it again. 1.2 to 10 every other second.
Sorry to hear you’re having problems with it
Can you use the same test to test through a BalUn/UnUn?
You can do the same measurement for a balun / choke. Here’s a video where I show how to measure the UnUn Random Wire Antenna FT140-43 Toroids Tested
ua-cam.com/video/6j1Yc1Y4Ly0/v-deo.html
@@TheSmokinApe awesome, thanks!
👍
Thanks Lee 👍
real good. I have the Nano VNA-H4 . putting a coil in the coax buy antenna helps with common mode current. but warping threw ferrite gives more attenuation per turn. I have the M & P POTAFLEX 7 and that tested great at VHF/UHF . also coax length can be a factor at select frequency's . resonate length . don't see that much at HF unless the shield is acting as a counterpoise. I found that using a end fed half wave dipole with 49:1 UNUN. length of coax can effect SWR and RFI back to radio. this was worse on my 9:1 . longer feed line was a big help at lower frequency's . also a 1:1 after antenna and a counterpoise also works. each portable setup can tune different. nice job on coax loss . best to read data sheet before you buy. for HF RG-8X works great for 50Ft runs or less. can take some power as well. but not all RG-8X the same. ABR makes a real nice 8X type. 73's
Hey Robert. I noticed more RFI with my 9:1 than the 49:1 as well. I pretty much always go the counterpoise and choke route these days 👍
How long is the cable
I believe it’s 35’ but I could be mistaken
unable to read nano saver screen, very blurry. :(
Sorry man, I will try to have it bigger next time!
I use 75 bc im broke, damn kids lol, also I got 1k foot box for free, and I can't see a loss great enough to make me care, I use resonant and efficient antenna
Using 75 is fine if you take what into consideration which it sounds like you have done. Thanks for the comment 👍
Rg11 is actually pretty good, I use it for everything.
You never showed how to measure the co-ax, just the results. Video title says measuring co-ax cable loss. Get with the program and show people how to do it. This is just click bait.
If you want me to show you have to use a NanoVNA I have videos on that as well.
The title of the video states "Measuring Coax Cable Loss For Ham Radio Beginners" people expect to be shown , if you are not going to show what title states then a link should be given. The word measuring says that you are going to be measuring and not just showing the results.@@TheSmokinApe
@@keithwilliams3028😢😭. 🤦🏻🤣🤣
@@keithwilliams3028 What are you talking about? He showed you exactly how to measure the cable loss at any frequency. You thought he was going to show you how long the coax was? You wanted to see a tape measure?