G4NSJ - Coax cable uses loss shield screen attenuation EMI ham amateur radio
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- เผยแพร่เมื่อ 1 ส.ค. 2024
- In this video, I look at different types of coax. RG58 RG8X RG213 RG414. Attenuation through loss is important. Sheilding is also an important factor when chossing coax. EMI problems are often neglected.
www.radio-workshop.co.uk/g4ns... - วิทยาศาสตร์และเทคโนโลยี
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Thanks Ray. I’m fascinated by all the magic around cables. Started my career in electronics as a trainee in a firm manufacturing process control equipment for the big cable making firms. Fibre optics too. Should have stuck with it really; just think how much cable and fibre has been made since the 1980s!
Haha, you're right. Millions of miles of fibre must have been manufactured!
Glad to see your still doing videos...
Yes, indeed. And I’m working on the next one.
Very interesting , informative Ray .
Thanks!
The definition of "loss" in the world of coax cables has a few components.
The main one that scares everyone is - Capacitive Reactance loss - because at the end of the day your run of coax is a long tube with two plates (like a capacitor). As you go up in frequency the reactive resistance literally shorts out the RF. This is basic electronics stuff.
Then there is the pure - Ohmic Loss - the same reason you run thick speaker cables the longer you run the cable.
Then we have the one you are mainly talking about - Seepage - It's a rule of thumb not to use ANY braided sheild type cables (namely 213) on comms sites. Because you run them any length side by side in a cable tray there will be some sort of bleed over. Not what you want when this is a separate RX and TX aerial style repeater. That relies on the fact the aerials are directly above and below to assist with isolation. Cables with foil in them like LMR400 would be a reasonable compramise. But usually at VHF and UHF frequencies your cable run is near 30m so LMR400 at UHF will sell you short on the Cap Reactance loss. You would use LDF450 minimum (and here in Australia that is the standard). LDF450 is the corregated ridgid stuff.
Having all this bubbling around in your head. It should become apparent that using LDF450 in the likes of an AM broadcast aerial system is not needed. You should be able to use thin stuff even RG58 if my Cap Reactance thing is right. Well you can... but the ohmic losses will get you! The runs are long given the wavelengths you are using. Same again... out comes the roll of LDF450 for building an AM broadcast service. Mainly done for Ohmic losses and the fact it has to cop a few RF amps 24/7/365.... it's not 30% duty cycle.
73's from VK2 land
Hi Peter, thanks for all the very interesting information. I shall print it for future reference. All the best, Ray.
Yes, very true. That's why the RG6 quad shield (75ohm) is used for Foxtel dish installations.
Wow good to see a new vid ray.. Hope your well.. You don't look any diffrent from last year.. Please make more again like the old days. Jess. M3zeg....
Hi Jess, great to hear from you. Perhaps I’m getting younger! 😂 I’m working on another video at the moment. Take care, Ray.
Hello Ray , I hope that all is well & good & that life is treating you well .
Thank you for sharing your technical findings regarding the coax cable .
By and large we have been using RG58 for decades & have had many contacts & fun with radio over many years , the RG58 general coax I'm sure you would agree has served us well , the later RG58 now has an aluminium film between the dielectric insulator & the screen , I've found RG 58 for general use very good & highly cost effective , I'm sure that you are correct with your recent coaxial cable findings & more power to you for finding this information out .
I think the RG58 for general use is ok , it's been around forever a bit like the PL259 & SO239 , those plugs & sockets was developed by the USA for military in the early 1930's & still being used today , the U.S military designed the PL259 so it could be successfully and reliably be attached to the end of a coax cable by just using a knife , or even teeth if their strong enough , the PL509 & RG58 it's a bit like the wheel or loud speaker design , some designs don't change & just last forever .
What I would say is that it would be ideal to run coax conductors through a copper tube between the floors of the house , just have one copper tube going from the ground floor to the attic , run any coax of your choice through the tube , you don't even need to solder copper tube joints , you can connect the coax conductor to your regular favourite antenna & you'll notice a significant reduction in noise rest assured & the closer the copper tube is to the base of antenna the better , you can even ground the copper tube to earth to slug down any unwanted electrolysis , hence the ground would become sacrificial rather then the copper tube becoming an anode , if you want to ground the tube it would then be advisable to heat up & bond the copper tube join connectors , you can simply use an earth strap on the copper tube & connect it to the earth of the
property .
Try to also arrange the copper tube as close to the transceiver as possible , if the table is against the wall it should be relatively easy , there's also small flexi copper tubing available , like flexible copper plumbing stick , they can be inter joined too to add more flexibility length if required , you can purchase various metal flexi tube up to approximately 6 inches from the PL259 to the copper tube & the same on the antenna end ,you'll bless the day & won't look back , the whole project will be inexpensive & highly effective , I hope this has been of some help.
73
Julian CT4952
Hi Julian, thanks for all the useful information. I do like the idea of copper pipes. Thanks again and all the best, Ray.
Hello Ray , Thank you for your reply , your very welcome , you could just provide a pipe from the upper floor to the attic to begin with , it won't cost much , I forgot to mention that you can purchase the nylon clips to hold the pipe to the wall , alternatively you could use additional pipes for more cables ,ideally it's best 1 small diameter pipe for each cable , if you try it & are happy it would be nice if you could share your findings to others . Kind regards, Julian . @@g4nsj
@@julianrobertson3303 thanks, Julian. There are no straight runs really as the cable goes all over the place. But if I do try a pipe, I will certainly let you know how I get on. Thanks again, Ray.
Thank you Ray , the copper pipe can be applied to the external of the property if that helps . Kind regards, Julian .@@g4nsj
2:05 I remember seeing RG-8 mini advertised in the mid to late 1990's, by various CB shops like Knights and Truck King, etc.
I've used Westflex 103 on both 2m and 70cm. I've even used it on 10m and 6m. I bought some so called 'mil spec' RG-213 the other day from a reputable seller, only to find that the screen on it isn't as good as stuff I bought over a decade ago! 😮
I didn’t realise it had been available for that long.
Thanks again Ray
👍
Hmm food for thought, thanks Ray another headache lol. g1wae.
Yes, indeed!
I'm also not a fan of different coax for tails.....
I've seen repeaters where the LDF450 is brought directly in and goes to the radios via a short run of something like RG58. The repeater worked "OKish". But I was always suss. The tail was done for convenience as the LDF450 doesn't like to bend enough. I was never happy... So I decided to fit a right angle connector of the exact type and do a little re routing of the LDF450 to come directly to the back of the RX radio. Boom.... picking up mobiles in area's never heard before.
My working theory is Velocity Factor of the different cables. We've all been driving on a freeway at max speed and come to road works where we must slow and merg down to a single lane etc. It's never fun and you deal with rude people that just can't drop into line and crack on! I think this is what happens when you use odd types of coax in a feedline. Only time this is acceptable is when there is something inline like cavity filters. You can have coax A coming in with all coax B on the output.
I could have been on the wrong length of coax too as there was alot of "other RF" floating about. I'll never know for sure. But that's the theory. 73's
Thanks, Peter.
I heard the two metre repeater, while you were chatting, I’ve got a realistic scanner ,
Excellent! 👍
With the price of copper it is well worth being wary of cheap cables, some flavours of RG58 have a very wispy braid. Double-screened cable is favoured on radio sites, although types using aluminium foil over copper should not be used. FWIW RG400 and similar are great for patchleads. 73
Thanks, it’s good to hear from you.
EMI used to have some big names and bands signed up to them, back in the day. 😉🤣
Along with Decca, Polydor etc.
@@g4nsjother record labels were available! 😂
I use a 213 feeder to my 11m vertical. But RG8x for everything else.
I switch out rg58 to rg8 for car magmount applications etc. simply because 213 doesn't go well around bends!
Good point!
Thanks OM Ray. Good to see you again.... New shack ?? Best 73 ..
Shack now moved indoors. The shed was too cold in winter. ☃️
Excellent information Ray I have always avoided the cheaper thin stuff and dependant on the run so to speak now stick to the 213...as you said its a better braid....Good to see you again..73s
Thanks! Great to hear from you. Cheers, Ray.
I know it's over kill but I half my hyperflex 10 for VHF/UHF I use on my HF line as well, and found 80m noise level lowered submissively!
Hi Paul, I think that’s a good idea, not an overkill. We have to do everything we can these days to reduce noise. Cheers, Ray.
Good to see you Ray. 73
Thanks!
Thanks ,very useful .
Currently using 8x on 4m and Ultraflex 7 on 2m
Excellent!
Hello Ray , I just wanted to add another note regarding led back lights to transceivers , I've furnished a switch to switch off the back light on my transceiver & there's now far less noise on AM .
Thanks interesting. Thanks for sharing that info. Cheers, Ray.
Thanks again Ray. Most informative. What's the little radio to the left of the A4 sheet of paper in the video?
There's a Tecsun S-2000 to the left of the paper. Small transistor radios above.
@@g4nsj Ah sorry. I meant just below that, what looks like a little transceiver, the one with the mic cable trailing down.
@@PeddyrCubberley See here for the info on that radio... www.radio-workshop.co.uk/g4nsj-baojie-bj-218-transceiver-2-metres-70cms/
SO why isn't foil screened with a drain wire used? I am a novice too but we use the foil screening in audio and it is great to remove interference.
Possibly because there may be a fairly high RF current flowing. The thicker the conductor the better.
Can you buy so259 wallplates these days?. My intension is to run the coax down inside the plasterboard wall and use a patch lead from the wall outlet to the radio , rather than have coax and cable clips or surface mounted trunking on show (attempting to keep the Mrs happy)
I’m not sure. I suppose you could buy a blank plate a fit a socket.