In many human endeavours, performance improvement arises through the accumulation of a run of small gains over time. No one gain seems particularly important, but top-performers tend to be those who ‘bag’ each and every small gain as it comes along.
For the SOTA Activator, the question of whether to carry a coax feeder heavier than RG-174 often comes up.
The table below summarises the numbers for a notional 10 metre line.
Preferring RG-58 over RG-174 seems to require an additional weight of some 270 grams to be ‘lugged’ up the hill.
Whether this justifies the 14MHz loss-reduction of some 0.5dB is a matter for each Activator. But remember the incremental gains argument. A lower-loss balun or ATU might offer a further 0.5-1.0dB, a different antenna choice another 1dB, and so forth.
In cycling, people often ask: “What is the most cost-effective way to improve performance on the bike?” The sage reply is always: “Reduce the weight above the saddle!”
Similarly, for the SOTA Activator, there doesn’t need to be any weight increase when moving up to 10m of RG-58.
A week off the pies and puddings should readily deliver the 270 gram reduction required to achieve ‘net zero’
Should he/she persist for say a month, then ‘net zero’ with 10m of Mini-8 hoves into view. You get the idea.
73 es HNY
Dave GM4EVS
PS Over the holidays, some may have wrapped the equivalent of 10m of RG-213 round their waist. They have rather more work to do
I mostly use RG174 because it is much easier to handle than RG58 - it will wind on a figure of eight winder easily. I do have 3m of RG58 in my activation kit but even that is awkward to deal with especially in cold weather. I carefully wind it in a circle to avoid kinking. Any longer and it’s a right pain.
I even use RG174 for 2m. On FM the extra loss is not really worth worrying about.
Engineering isn’t about producing the best but about the best compromise between competing factors such as quality, cost and convenience.
Fair comment - 270 grams is very little extra to carry, probably worthwhile for 6/10/12/15m operation but you probably won’t notice one (s)iota of difference on the other HF bands. When the 2024 10m Challenge started I made up a “flowerpot” end fed dipole for the 10m band using RG-58. I tuned it in the garden for perfect SWR on 10m but never used it due to the extra weight of the coax wound on a piece of Open Reach fibre cable duct, around 50mm diameter I think. I wished I had used RG-174 then I might have tried using it, but I didn’t have any in my spares store… Instead of using the “Flowerpot” I made up some lightweight OCFD dipoles and they both worked very well for me on the 10m band during the first half of the year.
As Richard @G4TGJ said convenience if of great importance in SOTA for sure.
A 4 finger Kitkat weighs 41.5g in the UK at present. Saving 270g on coax allows an additional 6.5 Kitkats to be taken on the activation. Obvious what the action should be here.
Not wanting to be pedantic, but the worry with lightweight cables is degradation through repeated flexing. This can be difficult to detect merely by external inspection.
According to the reference below, the minimimum bending RADIUS for RG-174 is some 15mm.
As such, would those with 30mm (min) diameter fingers please step forward
You all must implicitly be talking about coax feeder lengths (e.g. 10m) for centre-fed dipoles. I no longer (often) take my CFD’s with their 6m or 10m of RG174 coax. I prefer EFHWs and need only 2-4m of RG58 coax from the Z-match box on the bottom of the antenna pole out in the open to my operating position hunkering down in the heather or behind leeward rocks. Talk about diminishing returns on reducing rucksack total weight especially when many of us are carrying many kg’s of excess fat.
I’m going to change from using a winder to this approach. When RG-174 comes off a winder and it is cold, the feeder zig-zags up the pole and can be a right pain to straighten out. I have far less trouble with the 5D-FB feeder that I use for 2m/70cm which is coiled up around 15cm diameter to go in the backpack.
Morning David.
It’s so true about OP weight. I was about 14st-2lbs when starting SOTA and 12st-5lbs later on. More than the difference between VHF and HF even considering the SLAB’s of the day I had to carry (7.5Ah or 9.5Ah - sometimes more than one). There were no Li-Po’s then.
As for coax. I haven’t come across RG174. I use RG178 or RG316 coaxes for HF - (about 8.5m long) and for VHF up to 2m-band (approx 2 to 3m long). For UHF I use RG58. Our technical expert at Scarborough Amateur Radio Society (G4DAX) laughs or grimaces at this in equal measure but I’ve never bothered about loss because of the lack of significant length.
RG178 is very light indeed; looks like a piece of wire - only 1.8mm dia and very high quality PTFE/ Fepsil/ Silver plated conductors and durable considering its lack of weight. I wouldn’t like to have to buy it though. An advantage of working with aircraft. They supplied the avionic kits with fixed lengths and there was always some left over.
I purchased a 4m length of that exotic semi-rigid stuff after reading that you used it. I’ve always coiled it very loosely, no tighter than 30cm diamater, for fear of damaging it, or being unable to straighten it out.
As for the RG-174, I carry 5m, plus a 20cm tail containing a CM choke. I can fig 8 wrap the whole lot easily.
The specified minimum radius for the cable is 5cm, so 10cm diameter. I’ve had my two cables for many years and had little trouble with them other than having to remake the BNCs once in a while after a bit of corrosion set in due to them getting wet. I think they started out at 4.7m long, but one is now about 4.5m long which is adequate when I’m sat beneath the pole so I can turn the antenna.
