Why should coax cable length matter?
I suspect those who install these antennas either have great results or bad because of coax length. My clone antenna (Tram 1498) is so inconsistent in length of coax and antenna length setting and height. I realize this is part of the comedy and real life examples of these type of antennas and if in the right setup they perform as good as a vertical dipole. (and BTW the Tram is built way better than the Solarcon Antron shit)
Maybe it's because the solar cycle but I think my antenna isn't getting out as well as it did new. Same SWR, tested at the radio output and over a length of coax. Getting ready for winter after all.
I weather proofed the whole setup, but starting to wonder if my whole setup is becoming a dummyload or if I am.
To the point here.. I've noticed these type of antennas are very sensitive to coaxial lengths, and I'm not talking about your usual common mode, but literally the tuning of the antenna itself.
I originally had this antenna tuned to 28MHz to get it to work flat on 27.2MHz. Started out with 85' of RG8/U coax, the fat stuff.
It contacted SDR receivers up to 800 miles away when in that configuration, SWR was down to 1.25 across the band.
Added an inline SWR meter and coax and suddenly the damn antenna was off tune going up to 28MHz like the dimensions in the instructions said, only thing I did and tested was adding 15' or so of coax.
So I started testing jumper coax cables I made, longer = higher frequency of resonance. Going by instructions that came with the antenna it said dimensions of fine tuning was exactly what it works out to if I have specific coax lengths, and all of them are the standard you can buy, 25' 50' 75' 100' and so on.
With those lengths IT WORKS... I think?
Between those lengths things get weird, SWR climbs on higher or lower frequencies and it won't tune up.
I'm well aware of the "magic coax numbers" and how stupid that idea is if the setup works properly, so does this prove my A99/clone is a coax radiator or a giant dummy in the air? I make contacts but it's hard to tell if I have things right given how few are on.
I know enough antenna and feed line theory that this should be obvious to me, if coax length changes SWR that means I'm getting a false reading, but at the base of the antenna it's fine when tuned up per instructions that came with it.
Sorry for the long post, too tired to compile simplicity.
I suspect those who install these antennas either have great results or bad because of coax length. My clone antenna (Tram 1498) is so inconsistent in length of coax and antenna length setting and height. I realize this is part of the comedy and real life examples of these type of antennas and if in the right setup they perform as good as a vertical dipole. (and BTW the Tram is built way better than the Solarcon Antron shit)
Maybe it's because the solar cycle but I think my antenna isn't getting out as well as it did new. Same SWR, tested at the radio output and over a length of coax. Getting ready for winter after all.
I weather proofed the whole setup, but starting to wonder if my whole setup is becoming a dummyload or if I am.
To the point here.. I've noticed these type of antennas are very sensitive to coaxial lengths, and I'm not talking about your usual common mode, but literally the tuning of the antenna itself.
I originally had this antenna tuned to 28MHz to get it to work flat on 27.2MHz. Started out with 85' of RG8/U coax, the fat stuff.
It contacted SDR receivers up to 800 miles away when in that configuration, SWR was down to 1.25 across the band.
Added an inline SWR meter and coax and suddenly the damn antenna was off tune going up to 28MHz like the dimensions in the instructions said, only thing I did and tested was adding 15' or so of coax.
So I started testing jumper coax cables I made, longer = higher frequency of resonance. Going by instructions that came with the antenna it said dimensions of fine tuning was exactly what it works out to if I have specific coax lengths, and all of them are the standard you can buy, 25' 50' 75' 100' and so on.
With those lengths IT WORKS... I think?
Between those lengths things get weird, SWR climbs on higher or lower frequencies and it won't tune up.
I'm well aware of the "magic coax numbers" and how stupid that idea is if the setup works properly, so does this prove my A99/clone is a coax radiator or a giant dummy in the air? I make contacts but it's hard to tell if I have things right given how few are on.
I know enough antenna and feed line theory that this should be obvious to me, if coax length changes SWR that means I'm getting a false reading, but at the base of the antenna it's fine when tuned up per instructions that came with it.
Sorry for the long post, too tired to compile simplicity.
Last edited:
...runna pile-up on 6m SSB