Coax cables I used for SOTA/POTA – A horror story

2023-05-08 10:37:43

by Thomas (DM1TBE)

I feel each transportable operator thinks about their coax cables and the way to use extra gentle and versatile sorts. Throughout the previous few activations, I’ve switched from my inflexible Aircell 5 to the light-weight and versatile RG316. I’ve purchased a few totally different lengths, primarily from Chinese language on-line sellers at AliExpress.

Nevertheless, I had some arduous to outline points just like the obscure feeling that I’m not getting out nearly as good as I ought to, or a altering SWR throughout an activation. So I assumed I ought to verify my cables earlier than taking a look at different elements of my gear.

My skilled and academic background doesn’t have something to do with electronics, and I don’t have the gear to measure the cable loss immediately. However my objective was to verify if the cables had been defective, to not measure the precise attenuation.

I’ve an SWR and Energy meter from DJ9PK as per picture under. It could actually measure PEP and has, based on the vendor, an accuracy of +/-4 p.c. You will discover extra particulars about it right here in German or right here in English (Google / auto translated).

My KX3 with a CW paddle served as sign supply. As giant variations are simpler to identify than smaller, I switched to the 10-meter band because the HF band with the best attenuation.

I then measured a brief cable with a really low loss, a 1 m / 3.3 ft RG213, which ought to have an attenuation of lower than 0.1dB (excluding plugs).

I merely checked how a lot energy got here out on the different finish of the cable. That worth I’ve used as reference. This cable (and all others) was plugged immediately between the KX3 and the ability meter, no ATU concerned wherever. The facility meter was set to measure PEP.

I repeated all measurements, however the outcomes had been very constant, with solely small deviations.

The outcomes had been a nightmare. Two RG316 cables out of three from AliExpress had an attenuation of greater than 4dB, i.e. lower than half of the ability got here out on the different finish.

The opposite cables had been effective, with the losses broadly in vary with the cable specs.

I can’t say, if it’s a free connection, a defective plug or if my dealing with was too tough. It might be that each one cables arrived effective, and I broken the cables throughout my utilization. However to be trustworthy, I don’t care. If a coax fails after some weeks, then it isn’t an possibility for me.

I’ve briefly mentioned the findings with native ham radio membership members after which determined to go for a Hyperflex 5 cable till I discovered a dependable supply for RG316 cables.

Why Hyperflex 5 you could ask? It is rather versatile, versus Aircell 5, and has a a lot decrease attenuation when in comparison with RG58.