Can RG8X Really Handle 1500 Watts? Jim, W6LG, Ham Radio Elmer Finds Out

[@mjames1842]

Thanks for doing the test. Only thing I can criticize in your test it that you have all of it coiled up in essence you have created a heating element out of coax. A more real world example would be to have it all stretched out and use a contact temp probe as the IR probe is picking up an average over a larger surface area.

[@locknload6852]

Exactly what I was thinking!

[@MrAdolfmanson]

I agree

[@buzzsah]

Being coiled can make a big difference, I would think anyway. However, over a conversion, it can heat up but when up and rolled out how much. I would not test it.

[@homebrewham2786]

great video again, if god was a ham he'd have the voice of jim 👍

[@batfalcononyoutube]

Why did you use SSB and not a continuous FM or AM with the same power?

[@Justin-bd2dg]

20m FM? LOL

[@ham-radio]

It was hard enough on the dummy and the amp with the low duty cycle. 73, JIm

[@Justin-bd2dg]

@@ham-radio I bet!

[@antycyponek2706]

because it was not a real test.

[@PF9Z-HamRadioDXStation]

Jim...i'm sure that the dummyload is more heat'n up 😉 nice vid buddy. 73s Sascha PF9Z

[@timmack2415]

Don't forget, a dummy load is way different than an antenna with an SWR of, say, just 2:1 would yield significantly different results.

[@713allen]

Belden's 9258 Coax - RG-8X Type specification not only lists 300V rms for max operating voltage, it also states max power: 1000W @ 10Mhz, 370W @ 50Mhz along with a max op temp of 80degC.

[@jonme5652]

I have run 1500 watts through rg8x but it was not in a coil, it handled it just fine

[@n8sdr473]

Jim, nice test, however I ask the following: Since your into a dummy load that presents a good SWR, if your using on an actual antenna and lets say the SWR 2.0 I would think that heat would be even higher correct? Also if the run was shorter the Heat maybe even higher, as a longer run presents more loss the heat would dissipate. Also since your only test on an intermitted mode like SSB a roughly 40-60 % duty cycle, I'd like to see what happens on a continuous mode like a 2 tone test at 1500 or there about I am sure the temp will rise much faster and higher. de N8SDR

[@ham-radio]

Agree with everything. Thanks as alway Rick for a great comment and increased knowledge. 73, JIm

[@KC4VYY]

yes that would be the only concern, the SWR. I perfect match would not be a problem. Those smaller dia cables can arc too if the right condition are present.

[@bladedspokes]

It depends entirely on the frequency. It can easily handle 1500W at sufficiently low frequencies.

[@DK5ONV]

Hello Jim, we had 102°F yesterday with 49% humidity. I wouldn't suggest putting more than 500W - pep into a RG-58 or RG-8X. Thx for another neat web presentation

[@jacusmc]

Hey Jim, If the coax were not in a roll would the temp dissipate faster? Interesting. Tnx NB2Q

[@ham-radio]

Yes, I am certain it would have. 73, Jim

[@MrAdolfmanson]

Correct, you should alway place extra coax in a figure eight configuration.

[@J0HN3]

Would shorter runs heat up more/faster? I’m thinking it would take more sustained power to heat up more coax and less power for less coax.

[@richarde735]

Jim, have you deciphered the FCC’s antenna radiation exposure self evaluation yet?

[@dougtaylor7724]

Perhaps when all the shortages end there will be enough paper available to complete the 4,813.756 calculations needed for a typical evaluation.

[@thomaspressy3410]

great video jim makes me wonder if i was contesting or just good ole rag chew for lets say 15 min how hot will it get then im a big fan of lmr 400 maybe i should try the same test on my lmr 400...thanks great video as always

[@n4hnhradio]

Hi Jim! Love your channel! Subscribed earlier this year after you read the letter you wrote to the ARRL. Thank you! I watched this video about RG8X and the subsequent video when you responded to the comments posted here. When I watched this video, the first thing I thought of was the fact that the coax was coiled. I have coiled the coax of my OCF dipole and clipped ferrite chokes on the coil. It improved the SWR for 80 meters. There can be some affects from coiling coax, both good and bad. But that isn’t what comes to my mind when you are measuring the temperature of the coax. I work in engineering. Part of the reason for the increase in the temperature of the coax has to do with the fact that the coax is coiled, thus derating the ampacity of the conductors themselves. There are ampacity charts available for each wire size. These charts list the current carrying maximum according to whether the wire is installed in free space or bundled and confined. I would say that a coil of coax the size of the one in your video constitutes bundled and confined. So this derates the ampacity of the conductors within the coax. I will add, anecdotally, that I have a 75 ft. run of RG8X that came with a G5RV I bought at HRO in 1991. I ran up to 1,000 Watts into it over the years, but usually 700-800W. The G5RV has been gone for several years. I replaced it with a ZS6BKW. But I still use the same, circa 1991, RG8X coax. All of my other antennas are fed with RG-213, RG8, or LMR400. I have 75 feet of LMR400 standing by for the next time I tinker with the ZS6BKW. So last year, I purchased an Elecraft KPA-1500. I usually run 800-900W but sometimes I unleash it. So far so good, even at 1,300 to 1,500W. I know that I’m pushing the RG8X beyond its factory rating, but I plan to replace it anyway. I’ve been pushing it to make it fail. But the SWR remains fairly consistent so far. It must be a good quality RG8X. Come to think of it…I think it is Belden. Thanks again for the practical knowledge that you pass along to us in the amateur radio community! 73, de N4HNH N4HNH Radio KZbin channel

[@TelecasterRon]

Thank You for your work. I like the fact you are a hands on ham. My brother was and I was lic. in 1981.. I still hold my General Class. I am old school. I believe in hands on and am not a store bought ham. My amps are re-worked or home brew. 4-1000 and 3-1000z. I ran a lot up until 95. Still do some. My Drake TR-4 RV-4 still work. Now a day if I ask a ham can he go to a junk TV or device and scavenge parts and build a C.W. xmitter they seem to think I am kidding? We can never win a War or Build anything with a Nation of Lawyers and Salesmen. I am concerned. It isn't about how many Chinese or radios you can buy. It is about knowledge to make and or maintaining a Station. This isn't a put down. I want hams to know the craft old school and new. I need to put my Station Back On Line instead of once or twice a year on 75. GOD Bless Sir 73's. KA4WYO FM America.

[@davidvelen9835]

Thanks Jim 73's hope all is well, stay cool.

[@DonDegidio]

Hi Jim, Glad to see you making another video. I would use RG8X as patch cables, but have gone to using RG400 for that use. A little pricey, but the quality of the cable is worth it. You and the family stay safe. 73 WJ3U

[@richards1191]

I would be more interested while transmitting on AM.

[@energy102]

Thanks for your time. and effort Jim. Always have learned something on your channel, through the years. You're a credit to the craft. N4IBK

[@Roddy1965]

Ask the bloke over on Photoinduction channel. He'll 'test' (blow the crap out of) anything. If it cools faster than it heats then you want the delay between Tx and measurement to be very small.

[@dandypoint]

Some cable, like Belden RG-58 is rated for 60C or 140F. Other cables are rated for 40C or 104F. I have experienced hot spots where the standing wave of current exists on the cable. A test using a dummy load would not heat the cable up as fast as operating with a 2:1 SWR. I have run RG-8X for many years with about 750 watts output. I normally do not operate with higher than a 2:1 SWR except on 160 meters. I do mostly contesting so the cable gets a pretty good workout. Sometimes 60 Qs an hour for several hours straight. I tend to CQ and run for hours. I would not do that with 1500 watts with my RG-8X. Only once did I melt coax. About 55 years ago, my Tri-Band beam was apparently not rated for 400 watts of long winded AM and I melted the traps, the SWR went up and I had a hot spot in the coax that also melted through. No damage to my home brew 813 amplifier but I never forgot the lesson!

[@ham-radio]

Those 813 tubes were really tough with that carbon plate that was so thick. Getting a pair on 10 meters was not easy. All of that was lots of fun. I heated up some terrible Radio Shack RG8 with my 4 dash pair and about 5kv. 73, Jim W6LG

[@josephderose320]

There's a nice chart in the ARRL Handbook showing power handling capability of various coax cables at various frequencies and RG-8X is one of them. It's in chapter 22 on page 22.49 of the 2020 edition.

[@ham-radio]

Thank you. 73, JIm

[@ai5dd]

How would RG8X handle 600 watts? I use an Ameritron ALS-600 but only push around 500 watts (600 PEP?)

[@russboden5792]

my kind of experimenting!..and all that test equipment!,,,I love iT!

[@ham-radio]

Glad you like it! There is a really knowledgeable guy...maybe Mr. Carlson's Lab or something like that. Floor to ceiling, wall to wall test equipment and he knows how to use it all. 73, Jim

[@russboden5792]

@@ham-radio yes,,I have watched several of his videos, Amazing site

[@lynnbailey1948]

Thanks for your video Jim. It would've been interesting to do a comparison of RG8x versus RG8 or LMR400. Another option occurred to me but you would have to use a fixed power input, and that would be to check the power going into the coax versus the power exiting the coax. Then compare the losses of RG8x vs RG8 or LMR400. Keep up the good work Jim. I enjoy all of your videos ... de K5AVJ, hamming since 1960

[@douglaswilliams6834]

And that's into a perfect load. Would probably heat up even more at, say 2:1 SWR. I would say 500 - 600 watts for RG8X. The thing about RG-8X is the quality can vary. Would like to see the same test with some Times Microwave LMR-240, which is about the same thickness as RG8X.

[@ham-radio]

It was so hot in that room that I did not do the 2:1 SWR test. But, it would heat much faster and have more loss. The quality of RG8X is all over the place. You are right on every point that you talk about. Thanks Doug. 73, Jim

[@AlreadyThere1965]

I check the manufacturers specifications. There is a lot of variance in quality of cable. I am looking at one now that specifies 3.0kW @ 5 MHz and 1.2 kW @ 30MHz.

[@ham-radio]

What coax? Is that an RG8X??? 73, Jim

[@AlreadyThere1965]

@@ham-radio Hi Jim, yes it is RG8X. This is from the DX Engineering Coaxial Cable Reference Chart. Hopefully this link will work. static.dxengineering.com/global/images/chartsguides/d/dxe-8x.pdf

[@Mannymoe7]

So if it’s not the right choice what is?

[@glennstevenson6242]

Hi Jim, another great video! PS; please keep the hot weather up there mate. 73's from VK land.

[@ham-radio]

Hot hot hot. Way the heck too hot. About 112F yesterday. More of the same due the next few days. Slight cooling overnight. Fires are likely, as you know down under. Take care Glenn. 73, Jim

[@wildbill1]

Nice test Jim thanks for that

[@francismcclaughry3794]

I'm wonder about the rug 8x cable would that make a difference. I would not like to run that stiff cable.

[@markhod1960]

most of us do more receiving than transmitting

[@mikeoswald8053]

Thanks for the test, it was very helpful. And it was so great to find you had done a new video. We had not seen or heard from you in a while and one always learns so much from you. Best. Mike-AA7MO

[@indymac7]

Wouldn't a coiled setup render more heat in a setting like that? It would be like a coil on a car. I use to pick up wattage by building a coiled RG58. Was a good trick that worked. Saying that. Would any coiled test be a consistent test for heat?

[@ham-radio]

Great point! I did test is stretched out and it did heat. I will do that video soon. I am still working on the amp as time permits between medical appointments and tests. 73, Jim

[@kb6dxn]

I would think with the wire coiled up your "coil" will induce some heat while creating a magnetic field.

[@louisseaman8455]

Coiling should only matter if there is a mismatch in the load impedance and RF is then present on the shield.

[@g0fvt]

While you are in a destructive mood Jim, maybe try RG58, short term it will certainly handle 1500w of SSB on HF (not tried it in a coil/bundle). For short HF patch-leads in the shack my choice nowadays are the PTFE insulated cables, pretty crush proof if you sit a piece of equipment on it accidentally, well screened, super easy to solder without melting the dielectric and the smaller variants are flexible enough that your expensive power meter won't go flying off the bench. Great to see you challenging the myths! 73

[@amateurshooter6054]

Thanks Jim 73 AB7RR Bob

[@jimkeappock7558]

You said the room temp was 93 degrees, the heat sensor went slightly over 93. What wattage were you using when it got 97 98??

[@arthurpeterson1010]

Thanks for the information but then what cable do we use for jumper for 1500 watts? I’m in Wasilla, Alaska and we have had only 3 days so far this summer over 70. Enjoy the heat…

[@Aikikris]

It should handle 500 to 600 watts. That’s all I plan to run.

[@douglaswilliams6834]

I agree.

[@ham-radio]

And keep the SWR as low as you can. 73, Jim

[@greasydot]

Hey Jim nice to see you. I hope all is well at your home. I figured it would have been like a fusible link with 1500 watts. 😅😅 Good experiment Jim.

[@JayN4GO]

Best just to run lmr 400 to everything. No cmc issues either. 73 Jim. Hope you’re doing well

[@jmasseys]

Coiling the cable will make a difference. We run 60Hz load tests on UPS products and you cannot test with coiled conductors. They will overheat. Rerun the test with an uncoiled cable for a better simulation. Other than an intensional common mode coil, that’s the only way to be sure. That said, a temperature rise of a few degrees is not that much.

[@dsavage128]

Been running 1000 W through RG8X for a decade and seems ok. For what it's worth.

[@TS950SDX]

Is it because coax is coiled which is not a normal situation

[@MatthewRulla]

Were you using the Henry linear amp for these tests?

[@ham-radio]

It was....but highly modified. 73, Jim

[@rentacowisgoogle]

Thanks Jim, this is interesting stuff. I was wondering the other day what could happen/ what to expect if you put too many watts into some coax. Now I know!

[@TelecasterRon]

The coil will induce more heat and the 90% turns will always heat up because you create an inductance and capacitance variation on the feedline which is a radiating element never a 90% bend. My old Cantina would be getting warm by now. Some of these guys run pretty high SWR's and the losses or heat can become a lot higher. Beldin Cable charts are good. Thank You again Sir. KA4WYO

[@Justin-bd2dg]

You made it easy on the coax using SSB. With no carrier the only time its getting max watts is when you talk loudly. AM or a digital mode would have whooped its ass! Lol

[@ham-radio]

No doubt about that. Thanks, Jim

[@javierpolendok5mhc]

Hi Jim. So is it safe to assume that the better coax for HF at that much power would be regular Rg8 then? If that so would you be willing to do Thames same experiment with Rg8? Thanks 73 de KI5GLT

[@ham-radio]

I use RG216 and RG218. Research that size of coax.73, Jim

[@wvsparkey1]

Is that 100ft coil? I like your experiment Jim. You may want to consider putting marks on the cable with a hi-liter to refine your comparison measurements next time. Thank for the vid, de N8ON 73

[@cousinvinnie2180]

Nice test! I always wondered....

[@russboden5792]

I have a friend who lives less that one mile from your QTH, if I come out to visit can we have a cup of coffee nearby or maybe I can see your new and previous location...I may be taking a nice long road trip...., K3RBZ ..love your videos...been a Ham now almost four year ,I am 66 better late then never :)

[@ham-radio]

Yes of course!who is the friend?

[@russboden5792]

@@ham-radio not a Ham,,someone I know in Rocklin

[@jeffschall3784]

The coax in a coil like that is bound to heat up, i would suspect a different result with it not coiled up. 8x can handle 1500w but it will turn black quicker from heat because of the size of the conductors within. Is used within its limits freq and power one should be fine.

[@vk3aqz]

No coax is perfect. All conductors have some resistance and that will always increase in temperature when passing current through the conductor. All dielectrics have losses and they will always heat up when there is an alternating potential across the dielectric. It is a fundamental law of physics. The movement of charged particles will result in increased energy and movement of the atoms - that is what heat is. Coiling up up the coax is always going to produce an increase in temperature which is higher than if the cable was not coiled and able to dissipate the heat. The best data on what a cable can handle is the tests conducted by the manufacturers and specified in the data sheets. They have professional test facilities which are far better than someone with a hand held thermometer! Proper laboratory tests are required to specify a cable for sale to such buyers as the military, broadcasters, and communications companies. In my experience, we had to water cool very high quality coax in our broadcast facility simply because no cable is perfect. This sort of test is misleading and just a waste of time - best way to asses a cable is to put power in and find out what comes out the other end. The difference is what the losses are. Skinny cable with thin wire loses more than fat cable. The higher your power, the hotter it gets. If there is any SWR it will always get hotter at the current nodes. Low SWR, the same cable is not so hot. So is the increase in temperature caused because the cable is no good or because you have a high SWR?

[@bobbydartonhricko4068]

I put 1788 watts pep through rg 8x I melted the Insulation from the center conductor to the outer ground. But the 8x held up just needed better Connectors. 12ny…

[@DuhBiggestDog]

Jim, as some have already mentioned, it is not practical to use a coil of coax for your testing. RG8X has a matched line loss of .88db per 100' at 14Mhz. You are using a dummy load (perfect match) so .88db should be representative of your set up. Your 1500W should result in ~1225W into your dummy load. So it appears that 275W are being dissipated in the RG8X. However since the duty cycle of SSB is ~33% that would amount to only 90W dissipation in the RG8X. I doubt that 90W in 100'of RG8X would cause any heat build up. On CW, with a 50% duty cycle, that would increase to ~138W, still not a problem. I believe the small temperature variation you are seeing is caused by Eddy current flowing in the cable because it is in a coil.

[@2metercrew389]

👍 LP 100a 👍

[@ham-radio]

I love that thing. Great device. 73, Jim

[@72tx340]

I love these im not sure what will happen videos! Great job!

[@ham-radio]

Glad you like them! After 58 years at this, I usually do have an idea about what might happen. 73, Jim

[@ErnestGWilsonII]

Thank you for making another great video and sharing it with all of us! I am at a point where I'm ready to finally purchase my first HF amplifier, but I have been using 100 w for so long and I don't know much about issues that I might face when going to a higher power level. I have excellent grounding and resonant antennas that can handle 1500 watts and I have LMR 400 and a nice electronically quiet setup with an Icom 7300. I also have electricians in the family and have 240 volts easily available and excellent grounding. When it comes to HF amplifiers, I find myself lost in a sea of choices and I don't have access to local hams that have successfully set up high power. Can you please recommend a full power HF amplifier that is fully automatic such that I can also use it remotely? Thank you very much, I am of course subscribed with notifications turned on and thumbs up! 73 W3GUY

[@paul.phillips]

That's why we use LMR-400

[@donalddavis581]

Does being all coiled up skew the test???and I have little trust in a LP-100.... instructions on how to make a really big ugly balun,

[@lampa2001]

Roll. ?? Is a coil. Extended and take meassure again

[@antycyponek2706]

about as accurate as a pcr test

[@billmccullough777]

You need a straight key and a brick! Old style.

[@busarob1969]

Pasternak and Beldon, state rg8x is ratted to 1000 watts, at 10 MHz. I am sure SSB at 1500 watts, un coiled won’t be a issue. Since we are talking SSB and the cable is rated to 1000 watts, 1500 watts pep would be less than 500 watts average, Or half the cables maximum rating. If your a Elma, then ham radio is in trouble, your propagating these meaningless results as science that concludes Rg8 can not handle 1500 SSB. Your cable did handle it and it only gain 3 degrees at best in a coiled state. Un coil the coax , use it how a ham would and put a thermal camera on it. You could barley keep the laser dot on the coil and when you did not, it was showing a Background temp of 94 deg F and a coil temp of 96. Yet the cable has a working Temp of -40 to +80 degree C. Hardly a conclusive test that the cable can’t handle 1500 watts SSB.

[@whatsascrewdriver5572]

After the first second of transmitting, Jim showed that the RG8X would not arc over from 1500 W peak. I thought that was a relevant show-and-tell right there.

[@ronyatziv2917]

On top of that the real test is if the insulation is broken by voltage.....

[@justdoingit.43]

If you have to have small coax just spend the money and get rg142 or rg400. The rg400 is the better of those two because it has a stranded center conductor.

[@alanjames4526]

Hi, Jim. Great information.

[@smithderf]

The coiling, and lack of large air heat sink is causing 90 % of the heat.

[@Atomshamradio]

If an swr a .2 would heat up

[@hooberdoober576]

I take it you mean the current drawn by a 1500W load. Ciao.

[@salat]

Testing with SSB/voice only? At 1500W PEP with a crest factor of ?? the average power is surely

[@ham-radio]

In my attic, it is about that hot right now and so is the coax. Thanks, Jim

[@SteveWrightNZ]

I put 2KW down RG58 and its only caught on fire once..

[@ham-radio]

I laughed out loud when I read that. Thanks Steve. I needed something to laugh about in recent days after a bone biopsy and diagnosis. 73, Jim W6LG

[@SteveWrightNZ]

@@ham-radio Lucky ham radio is nice and distracting Jim. It's not real ham radio unless it catches on fire mate ;)

[@paulziminskin2ghr282]

Transmit at 50 mhz 6 Meters and I guarantee the cable will become like a limp spaghetti !

[@ham-radio]

Yes sir! Thanks Paul and 73, Jim

[@KE5ZZO]

flawed test ------------ any coax coiled up will get hotter -- the layers amplify the heat stretch out the coax and then test the room temp around the single layer will be cooled by the room think of why birds build a nest -- the wrapping layers around helps keep them warm

[@ham-radio]

I did it that way on purpose. Many, like me, at the end of the run, coil the coax to create a choke balun. Today, that coax in the sun will likely be well above 115 degrees before RF is applied. My coax in the attic will be much hotter. It could be 140 degrees. So David, I will stick with the results that RG8X is not good for high power. Thanks as usual David. 73, Jim

[@ward5821]

Hello Jim, I did not watch your video, but no it cannot. You may push it though, but the dialectic will rapidly become resistive and not reactive. This will cause an eventual failure. Remember, carbon conducts! I love your videos (WB6DNE)

[@kschroll666]

Nobody puts 1500 watts through RG8x lol First time I did I melted the pl259 and i never did it again lol

[@dannygreeng0szi450]

So disappointed Nobody answered your CQ lol

[@fredmetcalf]

Appreciate your videos.....73.......AK5XX....La Grange TX

[@ham-radio]

Thanks for watching Fred. 73, Jim

[@paulhastings3109]

Jim. Use rg213 period

[@ham-radio]

Yes. And do the connectors yourself. 73, Jim

[@ahbushnell1]

Losses will go up with frequency. Cable life will depend on temperature like you are testing but it's over a long time. The other factor is electrical breakdown. Which is over life. I don't think this is a very good test.

[@Atomshamradio]

It's like behaving like a choke that's stuff can handle 1500w

[@Atomshamradio]

1500 pep I worked someone running close to 1500w it was out in real time use with no coils what have you if an antenna isent resonant it would heat up really fast. 2:1 swr.

[@ham-radio]

Thanks! 73, JIm

[@Atomshamradio]

@@ham-radio your welcome sir de. N1SCA

[@Atomshamradio]

@@ham-radio love your information just found your channel I subscribed thank you we need old school hams on here👍

[@justdoingit.43]

Rg8x is garbage for a serious radio broadcaster

[@dkabell]

First rg8x has a max power rating of 1kw at 10mhz - see Belden or RF Davis specs, so while it may be entertaining to run 1500w it seems a bit pointless, unless you are trying to prove the manufactures correct. For the average ham, especially your target audience, it appears misleading to be so critical of rg8x when most operators are running 100 watts.

[@nicknitro4420]

Crap !