my local electronics place that sells coax and ends will assemble it for you at a small charge. we used to have cb shops that would do it too, but those are long gone.
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Where to buy a 1/2 wave pre made Coax with ends?
- Thread starter Galaxy 959
- Start date
If you cut a piece of coax, the "ends" are where the cable stops and empty space begins. You mean "connectors", and probably "PL-259 connectors" to be specific.
You can make your own and they'll be just fine. Don't overthink the VF. If you're an inch off at 11 meters you'll never know the difference and neither will the guy at the other end of the contact.
Like Captain Kilowatt says, use the MFJ-259B or something similar to cut half-wavelength pieces. Works just fine. I had to cut five pieces of RG-11 as matching sections for my quad. Not counting assembling and soldering the connectors, it took me about 45 minutes total.
You can make your own and they'll be just fine. Don't overthink the VF. If you're an inch off at 11 meters you'll never know the difference and neither will the guy at the other end of the contact.
Like Captain Kilowatt says, use the MFJ-259B or something similar to cut half-wavelength pieces. Works just fine. I had to cut five pieces of RG-11 as matching sections for my quad. Not counting assembling and soldering the connectors, it took me about 45 minutes total.
whew,,,,,,, i use my mfj 259b with a 6 foot jumper to do base antennas and mobile i just use the coax hooked to antenna,,,,,to me seems like a lot of work to do a simple job,,,, how i do it gets it close enough , if it changes any way i know i have done something wrong and will start over,,, of course my mfj 259 is 21 years old now and still kicking so these new ones my need something extra to make measurements,,,,,
The reason I use 1/2 wavelengths of coax is because I want to see the actual antenna impedance and not just the SWR. SWR may not change along a cable length but impedance sure does and a 1/2wave of coax repeats the actual impedance and allows me to be a bit further away from the antenna while testing it. I just used some old R/S RG8x.
using an electrical half wave length of cable will show precisely the same R value as not using a cable at all.
I think that is the point he is trying to make
Thanks everyone for all the replies. I'm just going to see what mine reads when I get my MFJ in the mail. I'm going to use my coax I have for now. If I'm not happy I will try something different.
It's not anything to do with the coax itself 959. To tune your antenna properly with the mfj antenna analzyer you need to either use an electrically tuned 1/2 wave coax jumper cut for desired freq using the coax of your choice. Just use the formula I gave you. And use the VF (velocity factor) of the coax being used, whether it be rg8x, lmr400, and so on. Or do like said and just use a PL259 to PL259 at the antenna feedpoint. This would be easier as far as parts are concerned. But for a coax jumper using rg8x the coax needs to be 14.82ft for 27.205mhz. Or 177.83". You can order this from most any shop that sells coax and such. And yes, rg8x will work fine like stated. Once you have your antenna tuned with the electrically tuned 1/2 wave coax jumper, and get values of
R=50
X=0
VSWR: as low as possible. But the numbers above should remain the same.
After this is done, you can use whatever length coax you wish from the antenna to the radio and it should not change any of the readings if done correctly.' Like said, there is more than tuning for a low VSWR.
JMHO, but best bet for you it would seem is to use the mfj meter directly at the antenna feedpoint. This will remove any chance of having skewed readings. Again, JMHO. Once you get the meter and start using it, you will understand what we are speaking of when it comes to tuning an antenna with the analyzer correctly. If you do it right, any length coax will work after the antenna has been tuned to the above readings I posted. If you are just concerned with tuning for lowest VSWR, a smile swr meter will work. You want to tune the antenna correctly and get it right, use the analyzer at the feedpoint or get yourself an electrically tuned 1/2 wave coax jumper or one that falls on a 1/2 wave length. Again, JMHO. And again, have fun with the MFJ meter. Once you get used to using it, you'll ask yourself how you managed without one LOL!!
R=50
X=0
VSWR: as low as possible. But the numbers above should remain the same.
After this is done, you can use whatever length coax you wish from the antenna to the radio and it should not change any of the readings if done correctly.' Like said, there is more than tuning for a low VSWR.
JMHO, but best bet for you it would seem is to use the mfj meter directly at the antenna feedpoint. This will remove any chance of having skewed readings. Again, JMHO. Once you get the meter and start using it, you will understand what we are speaking of when it comes to tuning an antenna with the analyzer correctly. If you do it right, any length coax will work after the antenna has been tuned to the above readings I posted. If you are just concerned with tuning for lowest VSWR, a smile swr meter will work. You want to tune the antenna correctly and get it right, use the analyzer at the feedpoint or get yourself an electrically tuned 1/2 wave coax jumper or one that falls on a 1/2 wave length. Again, JMHO. And again, have fun with the MFJ meter. Once you get used to using it, you'll ask yourself how you managed without one LOL!!
And THAT is a rabbit hole I have been learning about as of late! So true.
A 1' jumper is way cheaper than multiple 1/2 wave coax, but can be interesting to achieve if the antenna is mounted way up there. I prefer that method first btw.
Just check it at the of the coax. Trust me you'll be close enough.
NOOOO. In an ideal world you'd have the analyser socket connected directly to the antenna feedpoint.
The correct answer is the absolute shortest length of coax you can get away with because the coax forms part of the antenna system so the MFJ isn't just measuring the antenna but the coax as well.
While I agree that the best point to measure is right at the feedpoint sometimes that is not possible or practical so therefore multiples of 1/2 wavelength of cable is indeed the way to go since the feedpoint impedance is repeated. Most antennas do not tune properly when mounted within arms reach of the ground and must be raised some distance to be properly tuned if one is at all interested in the actual impedance and not simply SWR. Most of the time this involves being physically located some distance from the antenna. Standing in the middle of a pair of stacked 2m or 70cm antennas while trying to tune them is not a great idea because of detuning.
Which begs the question, when are we going to see a bluetooth capable analyzer and dongle?
If somebody runs with this idea I don't want money, just the hardware
If somebody runs with this idea I don't want money, just the hardware