I am currenty looking at antenna cables for SOTA activations on VHF/UHF and maybe also for HF.
Looked into the already published bits, but could not find any similar discussion. Although I am sure somewhere there will be something similar. Apologies If I missed a discusson from the past.
Requirements:
waterproof
flexible
light
low losses
Cable size approx.: 6m / 20 feet
Antenna to be connected is a 7element 70cm/ 3element 2m antenna.
The options I am currently considering are:
Airborne 10
Hyperflex 10
Ecoflex 10
Ultraflex 10
Any suggestions, advice what cable to take into consideration and what to avoid?
For QRP operation and lightweight consideration I would say RG316 or if you insist on a bit less losses something like a H-155.
Everything else is just to bulky and makes no sense.
Waterproofing connectors with shrinking tube (with internal hotglue) or something like the liquid tape (sotabeams shop) make sense.
Easy. But you can’t have all three at the same time !
For VHF/UHF you probably want LMR-200 type cables as a minimum. That is the same size as RG-58 but less lossy per unit length. You will need to adapt RG58 plugs to fit it or buy LMR-200 plugs.
If you want to do UHF I’d suggest looking at LMR-400. But the weight will be noticeable.
The weight of good cables is the problem. I have a 3m length of RF400-UF for use on 13cms and boy do you notice it when you have that in the bag compared to a more lossy RG400 cable.
Agree with Andy that you should be looking at LMR-240 or LMR-400 types.
LMR-300 would be a good compromise, but availability is limited and often more expensive than LMR-400.
In the UK these cables can often be purchased from commercial wi-fi suppliers in standard lengths with connectors of your choice fitted.
It sounds terribly lazy or suggests to some you’re not a proper ham if you buy cables with fitted plugs. But when you see that the cost of cable and connectors is maybe £75 and with those connectors correctly fitted is only £5 more then it’s not too hard a choice to buy the ready made one. Especially as I don’t have a crimp tool for RG-213 sized cables!
The other item to watch out for Ingo is some of the lower loss cables have poorer minimum bending radius. Too much and you can crack the foil screens. Go for UF/ultra flex option if you can as it will last much longer being wound and unwound for use.
I made up a cable for 6m using Ultraflex7 after seeing it has low losses at 50MHz compared to cables like RG58 although over a few metres the difference probably isn’t noticeable. The connectors sold for it by the manufacturer Messi & Paoloni are easy to fit if you have a soldering iron and can find the video on YouTube but they are heavier than other connectors.
Not been at this long so the technical subtleties are still being learned. I chose RG58 as it’s relatively cheap for something that will get trodden on, soaked, dragged between rocks and stuffed in a rucksack. A utilitarian rather than technical approach.
I’ve been using 7mm semi-rigid for SOTA for many years. Mine is 5D-FB, but LMR300, Ultraflex 7, etc are near equivalents. I find this cable far far easier to handle in cold weather than RG-58 . There is a school of thought that says you will either work a station on VHF/UHF or you won’t… but it’s not entirely true. I often work 600km paths on 2m SSB from summits with 41/51 reports. In such instances, having a low loss cable certainly helps!
Saw that for cables with a size of 5 certain connectors are not available e.g. UHF/PL.
Would like to avoid having crimped connectors. Not sure if my thoughts are right.
Somehow I hope that soldered connecters will last longer.
Tried to collect some info about the mentioned cables. Then excluded the highest weight values (yellow). Later the highest losses on VHF (blue and green). Finally ended with the four unmarked options.
Currently I am considering either the Airborne 10 or the Ultraflex 7 for VHF.
Need to find out if any of these cables have problems with humidity.
Further, if I would have to replace the RG58 probably I would go for the Hyperflex 5.
It’s not EME so the lowest loss cable isn’t justified. A 10m cable would suit an application where the mast is 8m high. what mast are you carrying in your hand that supports a 3/7 element yagi (like the Arrow) at 8m above ground? It’s far more likely to be up about 2m or maybe 3, so you don’t need such a long cable. For a higher antenna you need a longer, hence heavier mast, and longer hence heavier feed cable.
Like running more power there are consequences, as a higher power radio weighs more and needs a larger battery unless you are happy with a 15-30 minute activation time. Somewhere back at 5 to 10 watts and a 3 element beam at 2-3m there is a happy medium that works almost as well as the higher antenna, and it is all practical to carry, erect and will also stay up in the air in windy situations (hilltops = winds).
I suggest starting simple and cheap. See what can be done with 5 watts and a short length of RG58 cable. You might be surprised. Then consider how many more contacts, or longer distances you might work if you had 0.5 db more radiated signal.
Buy quality rg58. 5m is not a problem even on uhf. If you want (I do) something better buy lmr200. It is similar in size and weight but losses are smaller.
For home use buy lmr400.
It is always a compromise. Weight, loss, cost, wishes.
Having installed about 2km of LMR 195 around work, I can say it is very good coax!
I use Crimp BNC (Crimp pin and outer) with glue lined heat shrink
or
I use Crimp N type (Solder pin, Crimp outer) with glue lined heat shrink
The other “connectors” begin with a PL - is a screened 4mm banana plug and should be no where near any radio equipment (whether it is DC or UHF)!!!
for 6m of coax that will be fine, the loss will be negligible, but as Andy says, LMR400 would be nice to use, you could use LMR240 as a compromise
In the UK, a company called CCS who make/stock an LMR equivalent that is much cheaper than LMR and has a an almost identical specification as per the Times Microwave stuff
