If I have a 75 ohm transmitter, 75 ohm coax, and a 75 ohm load, and I put a 50 ohm Bird in the middle, what does it read. I think 1:1 (or FWD = something, REV = low) No - it will read 1.5:1 From the
If I have a 75 ohm transmitter, 75 ohm coax, and a 75 ohm load, and I put a 50 ohm Bird in the middle, what does it read. I think 1:1 (or FWD = something, REV = low) No - it will read 1.5:1 From the
It will depend on which version you buy. Here's the relevant K4KIO page: http://k4kio.com/towers.html Steve G3TXQ On 23/03/2014 16:02, K7LXC@aol.com wrote: Howdy, TowerTalkians -- What mast size is t
Some that I know of: http://k4kio.com/index.html http://www.dxengineering.com/parts/dxe-hexx-5tap-2 http://www.hexbeam.com/ http://www.g3txq-hexbeam.com/ http://sp7idx-hexbeam.eu/ http://www.foldinga
A UK supplier - Spectrum Communications - had some 75 Ohm specially made, but I see he recently stopped supplying that in favour of 100 Ohm twin. First item here: http://www.spectrumcomms.co.uk/Aeria
One of the problems with using ordinary twin flex as an HF transmission line is the relatively high dielectric losses associated with the typical insulation materials used; so our usual assumption th
I made some further measurements this morning on a length of 10A Figure-8 power cable typical of the sort I've seen UK Hams press into service as RF feedline; the dominance of the dielectric losses w
Jim, They do, by virtue of the way the data is derived! I make Open-Circuit and Short-Circuit S11 impedance measurements of the line; from which Zo=SQRT(Zoc.Zsc). Loss is determined from the input re
OK.. so you didn't actually independently measure the copper and dielectric loss (I haven't had my coffee yet, and I'm not sure how you would do that other than by how you did it); You fit the measur
Jim, I forgot to say that the line distributed parameters - R, L, G and C - are all directly calculable from Zoc and Zsc; to that extent you can then calculate the losses associated with R as distinc
Here's a method I use: Terminate the line with a short circuit. At the other end of the line use the analyser to find the frequencies where the line impedance is lowest resistance and zero reactance
That method can work well if you simply want to distinguish between a couple of cores with widely spaced "cross-over" frequencies; but if the core is a complete unknown, it may not work so well. For
It's also worth noting that some of these "bead baluns" can be a significant fraction of a wavelength long; because the CM signal is a standing wave, that means there can be significant current varia
W2FMI's book is heavy on Differential-Mode performance, but says little about Common-Mode performance; some of what he does say on CM performance is plain wrong! It's relatively easy to build a choke
That's right - the losses in good quality 600 Ohm open-wire line operating with an SWR of, say 10:1, would be less than the losses in the same length of matched RG213. The balance tips slightly the o
I guess there are many different ways of looking at the issue; here's another. If I have a system comprising: Source(50 matching unit so that the Source is presented with a 50 Ohm load, as far as the
Steve, You say you want maximum common-mode impedance at 28 MHz. The best I've achieved is around 15,000 Ohms using 9 turns of RG58 on an FT240-61 core, Mouser part 623-5961003801. Replace the RG58 w
That's right - to get meaningful results you need to understand the stray capacitance added by the test structure. Steve G3TXQ _______________________________________________ ________________________
Jim, I don't disagree - I just don't consider a "Q" of 1.3 to be particularly high for a choke! Steve G3TXQ On 19/05/2014 22:08, Jim Lux wrote: I think the take home thing here is that when it's a "c
The OP asked about a 10m choke. Take a look at the Fair-Rite complex permeability charts and you'll see that at 10m the ratio u'/u''for #61 material is 1.3 - that's a _lower_ ratio (lower Q) than #31