... Do I want the feed point to start a new wave or does it matter?
why does this guys j-poles have the center conductor going to the short pipe while all the calculators I have seen have the center conductor going to the long pipe of the j-pole?
2 Meter Amateur Radio J-Pole Antenna | KB9VBR J-Pole Antennas
Also, Do I want the feed point to start a new wave or does it matter?
He likes to be different?
Since RF is AC it makes no difference really which way the coax connects to a J-pole. Same idea as a dipole. Which wire gets connected to the center lead? I know Doc would say the pink wire.
jeez,... ya mean I was wasting my time when I put a red rubber cap on one of my ground planes radials and then used a rotor to turn it?:headbang
Like I said, I'm new to all of this so please, bare with me.Maybe I just can't see the forest for the tress but what on earth does this mean?
Like I said, I'm new to all of this so please, bare with me.
I have 9' of lmr400 sitting here and I worked some math like this and please tell me if I did something wrong. Aiming for a center frequency of 432.5mhz
300/432.5=.6936 meters x velocity factor of .85=.5895meters x 3.2808 to get into feet=1.9343 looks like 1' 11 3/16"
To get the antenna up as high as I can with what I have, would be 4.5 waves on the feed line. Could I feed a dipole at a half wave and still get it to perform well. Or should I feed it at the beginning of the fourth wave. School me please!
OK now I understand what you were meaning. Sorry for the confusion but a lot of folks refer to "the first wave" or something and leave off the word "length". then it should read wavelength which has a whole different meaning than simply "wave". Forgive me for being precise. It's the old broadcast engineer in my rearing it's ugly head again after almost 8 years out the field. What you are asking about is if you should run a certain length of coax between the transmitter and the antenna such as cutting it off to make 4 wavelengths of cable since the cable you have is not long enough to make it out to 5 full wavelengths.
ANSWER: No. Install the antenna at the end of the cable and run the rest back to the transmitter. There are very few times when you need to make sure the cable is a precise length and this is not one of them. On 70cm you want to keep cable losses to a minimum and that requires using the best cable you can in addition to the shortest length you can get by with. It gets tricky up on VHF and UHF when trying to deal with multiples of wavelengths anyway because a small error gets multiplied a great many times in the end. A 1/2 inch of error at 1/2 wavelength will add up to an extra 1/4 wavelength on 2m if the total cable is about 65 feet long effectively negating any precision one was trying to obtain in the first place. this is why I like using an analyzer on the total length of cable and tuning trimming the final length if I have too.
Like I said, I'm new.... Could I feed a dipole at a half wave and still get it to perform well. Or should I feed it at the beginning of the fourth wave. School me please!