can still get the radial and coax work done.
Jerry – AE4PB
73
..
From: donov...@starpower.net
Sent: Friday, April 3, 2020 2:27 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] 75ohm Impedance question K3S and Antenna side.
Hi Jerry,
What coax do you plan to use (manufacturer
: Re: [Elecraft] 75ohm Impedance question K3S and Antenna side.
So I found a formula for feedline length and just need some eyes on it to make
sure I applied it correctly.
I want to measure twice and cut once. Then I can use my antenna analyzer with a
dummy load on the line to trim
So I found a formula for feedline length and just need some eyes on it to make
sure I applied it correctly.
I want to measure twice and cut once. Then I can use my antenna analyzer with
a dummy load on the line to trim it.
The columns are band, freq in Mhz, Multiplier to give multiples of
Ummm ... not quite. A "perfect" half-wave transmission line will
reproduce the impedance of the load [which has been alleged to be 35
ohms but this is an all-band antenna so that may vary some] at the
source [TX] end. The real line will come close, its loss will have a
small effect. His ATU
I agree with those who say just try it with TV cable connected,
direct. Tuner will keep the transmitter happy. If you can cut the
run to integrals of half wave that might be marginally better on
Tx. Back before WWII hams never worried about SWR and just maxed RF
current. Open-wire
Subject: Re: [Elecraft] 75ohm Impedance question K3S and Antenna side.
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
Bob and all,
One problem is that you are using '468/fMhz' to compute the length of a
half wavelength. That is the common 'cutting formula' which includes an
end-effect factor of about 5% which reduces the length of a half wave
radiator. An actual half wavelength is longer.
The actual
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 -
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
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
You can also use coax to make matching transformer however I don't
know how either of these methods would work for AE4PB's 6 band vertical.
John KK9A
John K9UWA wrote:
Cut the hardline to multiples of 1/2 wavelength and the swr will be 1
to 1 on both
ends. 50 in 50 out. In this case
Very true, and in fact due to those ground losses the feedpoint
impedance might be higher ... and therefore provide a better "match" to
the 75 CATV line than if it was 35 ohms. The loss just shows up in the
ground instead of in the UNUN (they aren't lossless), on the line, or in
the rig
On 3/31/2020 8:52 PM, John K9UWA wrote:
Cut the hardline to multiples of 1/2 wavelength and the swr will be 1 to 1 on
both
ends. 50 in 50 out.
Did you notice that this is for an all-band antenna?
73, Jim K9YC
__
Elecraft mailing
Cut the hardline to multiples of 1/2 wavelength and the swr will be 1 to 1 on
both
ends. 50 in 50 out. In this case the OP needs around 200 feet. Once your get
the
velocity factor for the 1/2" hardline... that is ballpark 80 to 83%. for 3.540
mhz is
265 feet x .8 = 212 feet. If you don't
Cable TV hardline (1/2") 75 Ohm, that's where the UnUn would go
(maybe).
Jerry Moore
Cell: 803-431-1870
-Original Message-
From: Victor Rosenthal 4X6GP
Sent: Tuesday, March 31, 2020 1:58 PM
To: elecraft@mailman.qth.net; ae...@carolinaheli.com
Subject: Re: [Elecraft] 75ohm Impedanc
craft] 75ohm Impedance question K3S and Antenna side.
I don't think you need a unun because the additional loss due to SWR running
RG/6 at 2:1 is only 0.381 dB, and the unun itself would certainly have some
loss.
But the loss in 200' of RG/6 even at 1:1 is about 2.9 dB! That is almost half
your
So you end up with < 2:1 SWR on the line. Actually TLW shows the input
to the line SWR as 1.87:1, at the load 2.15 and the total loss at 28MHz
as 1.017 dB. Nothing wrong with those numbers. You don't need a 2:1
UNUN.
Keep the length of RG6 to a minimum as it has higher loss than the 1/2
That CATV hard line is pretty low loss, so the excess loss from the
small mismatch isn't much. I wouldn't worry too much about the impedance
mismatch if your radio has the tuner installed. Hook everything up with
the CATV hard line, no Unun, and if the tuner makes the radio happy,
declare
Forgot to add: I used 28 MHz for the calculations in my previous email.
Losses will be lower on lower bands.
73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 31/03/2020 19:39, ae...@carolinaheli.com wrote:
I'm about to pull the trigger on a Hustler 6BTV
I don't think you need a unun because the additional loss due to SWR
running RG/6 at 2:1 is only 0.381 dB, and the unun itself would
certainly have some loss.
But the loss in 200' of RG/6 even at 1:1 is about 2.9 dB! That is almost
half your power. RG/8 would have only 1.9 dB loss, and with a
I'm about to pull the trigger on a Hustler 6BTV (6-Band, 80, 40, 30, 20, 15,
10 meters). It will be temporarily installed (with radials) about 200' away
from my house. I'd like to run CATV "hardline" but I'm not sure how to get a
2:1 UnUn with a wide enough bandwidth on the antenna side (the
21 matches
Mail list logo
