That’s not always true. The stuff used at SOTABEAMS is a stranded copper inner. We did try the steel stuff but it was horrible in nearly all respects.
You live and learn Richard. I’ve only ever seen the copper coated steel. I now know where to get some better 174 from as my current feeder has earned its retirement.
The answer to the question is RG58.
That’s for clumsy oafs like me who are not the most “practically adept”.
That said, I successfully built my 30m GP with RG174. My dipoles for 40, 60 and 80 have RG174 - but someone else made those. My GPs for 30, 20, 17, 15, 12, 10 and 6 all have RG58 feeder - I built all those.
My experience is the RG58 makes a slight enhancement to performance on the higher HF bands. Thicker core wire for the actual antenna is good too, because then you get a wider usable frequency band. Of course, these combine to make your antenna potentially twice the weight it might otherwise be - albeit still compact and lightweight in the grand scheme of things.
Yep. I just placed my first SOTABEAMS order in the post-CWI era last week - to get all the ingredients to build my new 17m antenna for the August flavour. What I particularly like about the products is that they (to use a topical phrase) “level up” access to antenna building, to those of us lacking the higher levels of practical skill.
The Frij milkshake carton is not a SB product btw. No doubt they’ve got something for making choke baluns too - I forgot to check.
Good use of “available materials” for the balun form Tom… you get a gold star from me and you had the benefit of drinking a tasty beverage. If only you had a discarded Big Kahuna Burger wrapper in the picture!
You can use a sharp craft knife to cut the ends off the bottle and save a bit of weight and volume. Get a responsible adult to supervise you when using sharp tools Tom as we don’t want you losing any digits.
That’s some cable Tom, are you intending to jump start a Saturn V 1st stage ?
I just checked and Sotabeams price for RG174 is tasty and £5.50 for a BNC plug fitted makes it hardly worthwhile to switch the soldering iron on. I feel my credit card sweating!
There are a lot of good comments here. Ultimately for portable work—hard portable work—you realistically are probably looking at RG-174 For HF at least some of the time. I was down on it initially and questioned why SotaBeams used it on the band hopper, but Richard knows his stuff and I came around. It is much smaller, much lighter, and easy to use. There is definitely more loss and it is more fragile as noted by others. I have pulled a BNC connector off the end when rolling it up. But for strenuous hikes and QRP operation for no more than 14 MHz I will sacrifice a bit more loss at the practical lengths For the benefits. The weight and size of larger cable just are not worth it on many hikes and on a few it is not safe Adding imbalance or bulk when climbing.
If I am trying to get all the signal possible, go with a larger cable, maybe even RG-8x. Larger would be much more inconvenient. I personally would never use RG-174 for 2 meter or higher frequency no matter how short due to loss.
The truth is, you will probably end up with a variety of antennas and choose which to take based on the factors of your particular activation. My primary antenna for this last Field Day has a problem During the event. I had some backups but for convenience of putting up only one more antenna I raised the BandHopper in the tree for 20/40 and continued on with QRP.
Andy @MM0FMF - are we liking #2 - the kitchen roll mod?
We are. Neat coil with turns held in place.
It’s a good choke, because the input and output ends are well separated from each other. If they are not, current on the outside of the coax (the stuff we want to suppress with the inductance of the coil) can leak across to the other end of the choke by capacitive coupling, making the choke useless.
that said, I don’t use a choke with my centre fed, centre supported dipoles, which are all fed with RG58 Coax. Which has never directly caused a collapse of the pole, to my knowledge. Tying it to the pole to reduce flapping in the wind is a good precaution.
The lack of a choke has not caused any problems in my scoring rate, which is as high as anyone else’s apart from the activators that spend 5 hours on the summit.
Dipoles in text books are drawn as a horizontal wire supported at the ends, with a feedline drooping down in the middle. The centre supported, coax fed dipole is electrically equivalent and actually works better than a dipole with a droop in the middle, as the centre support puts the part of the antenna with the highest current highest above ground. Also, only one support is actually needed. And the inverted Vee format makes it omnidirectional, within a db or so, making the orientation immaterial.
As a short length of feeder, RG316 and even RG178 are probably fine. However, my experience is that the outer jacket on these types of coax is very thin and fragile. It’s not a major factor for us in SOTA (my portable End-Connected Windom is still going strong), but it is not really suitable for long term outdoor installations.
I have had 2 End-Connected Windoms start to leak through the jacket and the copper braid has corroded. The antennas still work but it’s not ideal. I reinforce these types of coax with clear heatshrink if I am winding them on a ferrite. For a home station antenna, normal RG174 is probably better as the jacket is far more UV resistant. Thankfully, I still have plenty of DXW174 in the attic; I do hope they get some more in stock, it’s ideal for us SOTA activators.
73 de OE6FEG
Thanks for all the responses. As with most things, it appears there is no “one size fits all” here either. I will find an inexpensive piece of RG58 with BNCs on it on Amazon and cut it and solder it for my tape measure yagi. If/when I do more SOTA antennas, I’ll look to get some high quality RG174, ends and tools to build them.
Good fun tape-measure Yagis. They don’t work in the wind though, they collapse. Been there and discovered that. The question to ask is “will it ever be windy on top of a mountain?”
Be aware there is coax and there is cheap coax and there is cheap Chinese coax.
Not sure why you want to buy a cable with fitted connectors and then cut them off?
<<Good fun tape-measure Yagis. They don’t work in the wind though, they collapse. Been there and discovered that. The question to ask is “will it ever be windy on top of a mountain?”>>
Tape measure antenna will be for exploring satellite, not SOTA.
<<Not sure why you want to buy a cable with fitted connectors and then cut them off?>>
I need a length with a BNC on one end and no connector on the other. Cutting this will give me two of those for experimenting. If I already had the tools, or access to them, I’d buy the coax and components.
Quick warning on cheap RG58 coax with ready to use connectors. I had very bad experiences for VHF and higher frequencies. SWR high. 2m J-pole antenna just not getting resonant.
Understood. Any recommendations for quality small jumpers, ~10’ or so?
Hi Doug -
I may have missed it in all the excellent responses here, but I’d suggest that you might also consider “none” for what feedline to use. There are several options for EFHW where you connect the antenna directly to the rig. Here’s an example: Trail Friendly – LNR Precision Inc.
I once bought some good RG58 with an N type plug pre-fitted. Unfortunately, when I tested it with my multimeter it was shorted and I had to cut it off and install my own. It was from a reputable dealer as well. I would always check custom cables with a multimeter before transmitting.
Matt, looks like quality controll failed on their side.
It was not that bad with the one I had. A 3m RG58 50 Ohm with 2 BNC from an electronic discounter. Visually it looked nice overall.
As written the J-Pole just would not work at all. Antenna analyzer always showing strange readings.
Replacing the piece with a good quality RG58 and BNC solder connector solved the problem.
The shielding of the cable was just very very poor quality and on 2m just not sufficient at all.
I found Palstar RG58 is pretty good, but yeah, some RG58 is really shocking; just a few wispy strands for the braid.
I started off using RG58 but switched to RG174 to reduce bulk/weight. My main interest is 5W/QRP/HF, so I don’t have to worry too much about power rating or loss. I got some decent RG174 (from SOTABEAMS) and made up a 0.5m, 3m & 10m lead with BNC plug on each end. When I construct an antenna, I usually fit a BNC socket at the feed point. This means I can use the 10m length for something like a centre fed dipole and the 3m length for end feds. The 0.5m length is if I need to put a matching unit or SWR bridge inline. Most QRP equipment have BNCs but you can use a BNC to PL259 etc. adapter if you need to connect to something different.