To transform 22-j25 close to 50 Ohms you need a shunt reactance of +j44 To transform 17-j24 close to 50 Ohms you need a shunt reactance of +j36 Hope that helps 73, Steve G3TXQ Has anyone an answer to
I forgot to say that the HyGain Beta match works out at about +j131 on 40m - that's much too high a reactance to be effective. It would transform the 22-j25 load to 32-j24. If I were you I'd wind an
I've been getting good results with a 600mm diameter loop of 10mm coper tube feeding the amplifier here: http://www.qsl.net/m0ayf/active-loop-receiving-antenna.html I'm currently building the amplifi
If the antenna has an impedance of 50 Ohms, and the coax is close to a quarter-wave or odd multiple long, you'll see an SWR(50) of 2.25:1 at the shack end instead of 1:1. 73, Steve G3TXQ A 100 metre(
The SWR on the 75 Ohm line will be 1.5:1, but if the line is a quarter-wave or odd multiple long, the 50 Ohm load impedance is transformed to 75*1.5 or 112.5 Ohms - that's an SWR(50) of 2.25:1. In fa
The Op asked a simple question: "... would I notice any serious difference in the aerial matching etc, between the use of 50 ohm and 75 ohm coax at HF" I gave him a factual answer: if he has an anten
Jim, It behaves just like any other horizontal antenna: http://www.karinya.net/g3txq/hexbeam/height_2/ 73, Steve G3TXQ On 07/03/2013 15:53, Jim Hoge wrote: Has anyone modeled hexagonal beams with reg
The Driver/Reflector tip spacing is a critical element in the performance of beams such as the Moxon, Hexbeam, VK2ABQ, etc. Take a look at Section 6 to see how it affects the F/B of a hexbeam: http:/
EZNEC gets close enough for most practical purposes http://www.karinya.net/g3txq/hexbeam/eznec2/ The EZNEC predictions of the relationship between F/B and tip spacing are borne out by practical measu
Even with a perfect 50 Ohm antenna, there can be significant coax braid current and stress on any balun that is installed! With a perfect 50 Ohm antenna, at the 1500W level the differential-mode feed
If the choke is primarily reactive, and the coax braid impedance is also reactive but the opposite sign, adding the choke may *reduce* the net CM path impedance and *increase* the braid current. Maki
Yes, the choke reactance may add to the coax braid reactance producing an increase in the net CM impedance; in fact with certain lengths of coax the braid impedance is high enough that you don't need
Something similar here - it formed the basis of my QST article "What's the best height for my beam?" in the May 2009 edition. http://www.karinya.net/g3txq/hexbeam/height_2/ Look in particular at the
You need to remember that there is a large resistive component in the choke impedance, so you'll not see "High-Q" effects. I just checked four turns of RG213 on four stacked FT240-31 cores; there was
Jim, That's correct - otherwise you are providing a path for CM current that bypasses the choke. 73, Steve G3TXQ I'm planning to ground my coax at the top and bottom of my tower and of course bond it
It's worth mentioning that Jim's method needs the dipole to be at a reasonable height - 40ft or more - to avoid having a low resonant feedpoint resistance. Once you go much lower than 40ft, and the r
If you feed a perfect 50 Ohm load through a length of 75 Ohm transmission line, the SWR(50) at the input of the line will vary from 1:1 to 2.25:1 depending on the length of the line. 36% of all possi
Correct! These "couplers" typically measure the voltage at a point on the line (V1=Vfwd+Vref) and the current (I=Ifwd-Iref). Given a value for Zo they then generate a voltage V2=I.Zo which is equal t
That's right - and it doesn't have to be that close to a 1/4 wl or odd multiple to be a problem. If you feed a 50 Ohm load through a 75 Ohm line, any line length from around 0.15wl thru 0.35wl (or re