[Elecraft] 75ohm Impedance question K3S and Antenna side.

[John K9UWA]

Supposedly the feedpoint impedance is 52 ohms ??? Yes, I question that a bit. 
Read all about it here. Sorry I doubled the 1/2 wave mults. 

https://www.dxengineering.com/search/department/antennas/section/hf-vertical-a
ntennas/brand/hustler-antenna/product-line/hustle

Hustler Antenna 6BTV - Hustler 6BTV 6-Band HF Vertical Antenna and DXE 
Installation Guide Packages
Antenna, Vertical, HF, 6-Band, 80, 40, 30, 20, 15, 10 meters, 1.5 kW, 24 ft., + 
DXE BTV High Perf. Guide, Each $241.99

Performance provided by the Hustler 6BTVs is better than any other antenna of 
this type. Broad-banding is such that one measurement and setting permits both 
phone and CW operation. The antenna provides nominal 52-ohm base 
impedance when installed and tuned according to the instructions. The radiation 
efficiency is equal to, or greater than, other trap verticals.

73
John k9uwa


On 1 Apr 2020 at 8:14, Bob McGraw K4TAX wrote:

> Based on TLW calculations for 1/2" CATV 75 ohm hard line, 200 ft at 28 
> MHz should show a 1.87:1 SWR at the transmitter.  Assuming 35 ohms load 
> Z.  This equates to 1.027 dB total loss with 0.207 dB being attributed 
> to the SWR on the line.   Thus going through the efforts and matching 
> process would only net an improvement of 0.207 dB on 10 meters.  Lower 
> frequencies would be less.
> 
> Since this is a 5 or 6 band antenna, I doubt the Z at the feed point 
> will always be 35 ohms.  In order to determine what is actually needed, 
> one would need measurements for each band.
> 
> Conclusion:  Feed it with 200 ft of 1/2" CATV 75 ohm hard line, use a 
> short jumper of RG6, or 8X or whatever to connect the hardline to the 
> radio and be done with it.
> 
> 
> NOTE:  I just noticed that the numbers below are somewhat in error.
> 
> 468/3.540 = 132.2 which is 1/2 wavelength.  Thus 132.2 X 2 = 264 ft 
> which is 1 wavelength, not 2 wavelengths as stated.   I didn't run the 
> math on the others.
> 
> 73
> 
> Bob, K4TAX
> 
> 
> On 4/1/2020 7:28 AM, John K9UWA wrote:
> > Ah YES I noticed it is for a multi band antenna.
> >
> > 2 wavelengths 3540 = 265'
> > 4 wavelengths 7080 = 265'
> > 6 wavelengths 10600 = 265'
> > 8 wavelengths 14160 = 265'
> > 12 wavelngths 21240 = 265'
> > 16 wavelengths 28320 = 265'
> >
> > Multiply the 265' by velocity factor of the coax and you will be someplace
> > just a bit over 200 feet.
> >
> > the 10mhz band is off a bit. So OK... other than that 80, 40, 20, 15,10 are
> > all harmonically related.   As I said 50 in and 50 out. If the OP runs this
> > vertical on 17 and 12m then yes he will have maybe a 1.5 / 1 mismatch caused
> > by the coax. But the antenna isn't designed for 17 and 12.
> >
> > I cut all the 3/4" CATV in my system with a Hewlett Packard HP 4815A Vector
> > Impedance Meter. Any 1/2 wave mult the the SWR is the same in as out.  Any ODD
> > 1/4 wavelength multiple creates a transformation With Multiple 4 hi stacks of
> > yagi's I have many of those in the system as well. 75 ohm cable works well to
> > put pairs or quads of yagi's together.
> >
> > The only thing that maybe won't be perfect is the actual vertical itself may
> > not be a 50 ohm input.  His vertical is a  Hustler 6BTV. 73 John k9uwa
> >
> >
> 
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John Goller, K9UWA & Jean Goller, N9PXF 
Antique Radio Restorations
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