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Best Coax?
- Thread starter 717seemore99
- Start date
Just a FWIW thingy.
Velocity factor has very little, if anything, to do with how 'good' a feed line is. Doesn't contribute anything to how well it carries an RF signal. It does figure prominently in calculating electrical lengths, but that's about it. Need to 'cram' that electrical length of feed line into a smaller space? Use something with a lower VF, which means a shorter piece of coax, which means less volume. Deals with 'mechanical' efficiency, not electrical efficiency.
The 'best' coax to use in any particular circumstance is a matter of dollars and 'sense'. Sort of like using a 'Rolls' to haul rocks out of a pasture when an old 'junker' Ford would do exactly the same thing at a lot less cost. 'Course, if you just happen to have an 'extra' 'Rolls' parked out back... why not?
- 'Doc
Velocity factor has very little, if anything, to do with how 'good' a feed line is. Doesn't contribute anything to how well it carries an RF signal. It does figure prominently in calculating electrical lengths, but that's about it. Need to 'cram' that electrical length of feed line into a smaller space? Use something with a lower VF, which means a shorter piece of coax, which means less volume. Deals with 'mechanical' efficiency, not electrical efficiency.
The 'best' coax to use in any particular circumstance is a matter of dollars and 'sense'. Sort of like using a 'Rolls' to haul rocks out of a pasture when an old 'junker' Ford would do exactly the same thing at a lot less cost. 'Course, if you just happen to have an 'extra' 'Rolls' parked out back... why not?
- 'Doc
Amen.
For 27Mhz, 8X is fine. Only use better if the power capability is needed.
Look at any loss chart of 8X at HF, I use better coax at higher frequencies, LMR400 for VHF/UHF.
Remember, it takes a gain of 3db( over whatever you use as a base) to even notice.
@27 MHZ: DB loss/100 ft
RG 8x(mini) 1.55
RG 8 .935
9913 .644
LMR 400 .633
LDF5-50a .185
Coax Calculator
it just depends on the size of your wallet
You're right, it does depend on the size of your wallet. But if the coax run is 100 feet or less, you will never hear that difference in attenuation so RG-8X does just as well as LDF5-50a. If the numerical difference, which you can't even hear, is worth that difference in price, then by all means use that LDF5-50a! If that un-hearable difference isn't worth that much to you, use the RG-8X. Since the feed point of almost every HF antenna I've ever had has been less than 100 feet or so, RG-8X has worked for me just fine. I'm not particularly thrilled with it's performance on VHF/UHF, but it has still worked well enough considering the length of the feed line (not even close to 100 feet).
But you're absolutely correct about that wallet thingy.
- 'Doc
But you're absolutely correct about that wallet thingy.
- 'Doc
yep, it's a lot like the "i gotta have a flat match" concept.
you can MEASURE the difference, but, in the real world (unless you are doing EME or other "weak signal" contacts) you won't HEAR the difference..... and neither will the station on the other end.
the main reason for some of the "confusion" is the relationship between a DB and an S-unit is often not understood.
..... hey!, i think i'll start a thread about DB's
LMR-400 is $ .81/FT or $75.00/100'. this is about the best price I have seen. got my RF Davis bury flex there. $ .85/FT and got 100 FT for $ 81.00.
This was with best 259 connectors and sealed with heat shrink.
AP
This was with best 259 connectors and sealed with heat shrink.
AP
Last edited:
Hello All:
One thing that has to be considered about Coax is that its apart of your antenna system. That is its just as important to use good Coax as it is to install the antenna right the first time around, I know the feeling to come outside and see the new Wa-Zoo Antenna lying down in the back yard in pieces.
New Antenna installations should have new Coax! The Coax also has to last a few years to make it worth the install.
RG58 is good for tying up trash, and brush for the trash pick up truck guy. A short jumper or even using to rope up a tool bag on a tall tower.
Same for RG8X, makes great short jumpers, and also used as rope to haul real Coax up on a tall tower. I have used RG8X successful as Christmas wrapping ribbon. Wrapping old Luggage with RG8X looks a little redneck, but will get ya there.
The Coax's job is to transfer the RF Energy from one end to the other with a minimum of loss. The loss amount is inversely proportional to the cost, more cost means less loss, usually. Unless you screw up the PL-259 Connectors.
I suggest for new antenna installations and upgrades, using the good stuff. Like RG8, RG213, 9913, LMR400, and now I use the LMR400 Superflex.
I wish I had a Dime for every antenna installation I have found to use old crappy, lossy, water soaked, Radio Shack 1968 date coded Coax. And the PL-259 Connectors are only soldered the center wire, and shield wire is expected to make a good RF Contact by just rubbing up next to the PL-259 Connector.
In about every 20 to 30 Interceptor 10K Antennas sold, Steve or I will get a call about the I-10K not working right. We even get calls asking about other manufactures antenna problems not working right. If the antennas were assembled to the assembly instructions
and its not working we start looking at the antenna installation and coax. Most of the time we are assured the coax is premium and brand new coax, but photos sent to us show another story. And a new length of coax fix's most all new antenna problems.
Its always cheaper and easier to install the antenna right the first time around.
Jay in the Mojave
One thing that has to be considered about Coax is that its apart of your antenna system. That is its just as important to use good Coax as it is to install the antenna right the first time around, I know the feeling to come outside and see the new Wa-Zoo Antenna lying down in the back yard in pieces.
New Antenna installations should have new Coax! The Coax also has to last a few years to make it worth the install.
RG58 is good for tying up trash, and brush for the trash pick up truck guy. A short jumper or even using to rope up a tool bag on a tall tower.
Same for RG8X, makes great short jumpers, and also used as rope to haul real Coax up on a tall tower. I have used RG8X successful as Christmas wrapping ribbon. Wrapping old Luggage with RG8X looks a little redneck, but will get ya there.
The Coax's job is to transfer the RF Energy from one end to the other with a minimum of loss. The loss amount is inversely proportional to the cost, more cost means less loss, usually. Unless you screw up the PL-259 Connectors.
I suggest for new antenna installations and upgrades, using the good stuff. Like RG8, RG213, 9913, LMR400, and now I use the LMR400 Superflex.
I wish I had a Dime for every antenna installation I have found to use old crappy, lossy, water soaked, Radio Shack 1968 date coded Coax. And the PL-259 Connectors are only soldered the center wire, and shield wire is expected to make a good RF Contact by just rubbing up next to the PL-259 Connector.
In about every 20 to 30 Interceptor 10K Antennas sold, Steve or I will get a call about the I-10K not working right. We even get calls asking about other manufactures antenna problems not working right. If the antennas were assembled to the assembly instructions
and its not working we start looking at the antenna installation and coax. Most of the time we are assured the coax is premium and brand new coax, but photos sent to us show another story. And a new length of coax fix's most all new antenna problems.
Its always cheaper and easier to install the antenna right the first time around.
Jay in the Mojave
In the RG/8 or 8U, I have heard that the heavy stranded twisted core is very much better than the solid core. Is there any truth to this and why if it is true. Thanx. Scott
The more suface area that exists on a wire ('multi-core vs solid core'), it is better against resistance to flow. It is called the 'skin effect'; as there is more surface area on a stranded wire than a single solid oned. Because electrons flow on the outside of a metal wire, and there is more surface - overall - on a multi core center wire. Provided that the diameters are equal, the multicore is generally more pliable and conducts better. I understan that there is a new variety of LMR-400; they now have a multi core center and is far more flexible. Probably cost more too - of course!
Thank-You for te answer. Now, I rememeber being told the same many years ago. I just forgot. Again. Thanks. 3's Scott
B
BOOTY MONSTER
Guest
not to argue , but an honest question . wouldnt the skin effect be negated by the surface area of the center pl259 connector ? seems the copper stranded center may allow for more surface area but it cant add more than what is passed by the 259 . or can it ? im not even taking into effect the lil wire from the amps board to the center of the so239 .
Negated? No. Affected? Sure. But not much really. That's why some connectors are more suited to specific usages than others. 'Skin-effect' isn't that big of a deal in the overall scheme of things. Other characteristics are certainly more important, such as resistance/impedance, which still aren't going to make a huge practical difference in most cases. In some cases, sure. But not all of them.
Little 'bumps' don't mean a great deal individually. Lump all them 'bumps' into one huge big one, and you can have problems. Sort of why they grade roads to make'em smoother, right?
- 'Doc
Little 'bumps' don't mean a great deal individually. Lump all them 'bumps' into one huge big one, and you can have problems. Sort of why they grade roads to make'em smoother, right?
- 'Doc