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Author Topic: Lets Talk Feedlines  (Read 629 times)

LWolken

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Lets Talk Feedlines
« on: July 22, 2018, 12:10:18 AM »
With so many options available I was wondering what coax feedline everyone uses for portable operations?  My primary focus is weight, bulk and durability.  Lets hear your suggestion and why.


*Needs to be compatible with RF SO239 connections (without adaptors)


*Minimal losses on HF and VHF. some losses on UHF are acceptable.


*Rated for 100 watts max ssb.


*Overall Length approx. 40'-50'
« Last Edit: July 22, 2018, 12:12:09 AM by LWolken »

Jon_Garfio

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Re: Lets Talk Feedlines
« Reply #1 on: July 22, 2018, 02:54:08 AM »
I used RG-174, only for QRP HF, great performance, lightweight and foldable to carry into the backpack.

Also I just buyed a RG-316, It seem less losses than RG-174.

If you don't use too much long feed line I think don't have a apreciable losses.

Enviado desde mi Redmi Note 4 mediante Tapatalk
« Last Edit: July 24, 2018, 01:47:30 AM by Jon_Garfio »
Sapere aude

gil

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Re: Lets Talk Feedlines
« Reply #2 on: July 22, 2018, 03:50:03 PM »
I used to use RG-174, but now I prefer RG-316, even though it is less flexible.
Gil

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CroPrepper

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Re: Lets Talk Feedlines
« Reply #3 on: July 24, 2018, 05:13:15 AM »
I ordered 174 to use as the feedline on the 6m mast for my linked dipole. The RG58 is heavy and if the cable is not attached to the mast all the way, it will bend the top of the mast. So I decided to take RG174 for the mast and then attach my RG58 to the RG174. I can say that the reception and transmission was much worse than without the RG174. I could barely make any contacts, most of them could not copy my callsign. Maybe it's caused by the damn BNC crimp connectors, I dont know (I prefer soldered connectors). Anyway, I discarded the RG174. With 5W I am losing more than 25% of signal with the RG174. That is noticeable on SSB. Yesterday I went to activate a SOTA summit, used RG58 and my linked dipole. Had more than 10 QSOs in the first 2 minutes. I prefer RG58, although it's heavier and bigger, but it has much less attenuation.

Jon_Garfio

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Re: Lets Talk Feedlines
« Reply #4 on: July 24, 2018, 05:27:50 AM »
I think 25% losses may be a bad conectors, not cable specs.

RG-174 and RG-58 at low same RF power hace the same specs.

Enviado desde mi Redmi Note 4 mediante Tapatalk

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gil

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Re: Lets Talk Feedlines
« Reply #5 on: July 24, 2018, 05:49:38 AM »
I agree. No doubt RG-58 is better, but you should not lose as much power with RG-174. I don't know about the characteristics of RG-316. I only use it because it is mechanically stronger. There is always LMR-240/UF...

Gil.

CroPrepper

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Re: Lets Talk Feedlines
« Reply #6 on: July 24, 2018, 06:09:46 AM »
Looking at common coax loss calculators on the internet, it's always about 1/5 of power lost in RG174.  In numbers, it's about more than 1W loss @ 1.1SWR (on 14Mhz). With RG58 I am barely losing 0.5W.
Maybe that's not so tragic for CW, but I do see it on SSB. Yeah, probably the connectors do the rest - but in the end, I prefer RG58. I attach it on a Molle attachmenet on my backpack and it can hang outside, I don't see any disadvantages in using RG58 (except a bit more work when setting up the mast).


CroPrepper

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Re: Lets Talk Feedlines
« Reply #8 on: July 24, 2018, 10:33:18 AM »
wow thats expensive

LWolken

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Re: Lets Talk Feedlines
« Reply #9 on: July 26, 2018, 01:03:40 AM »
Looks like the RG174 has some pretty big losses at QRO power levels.  Just for comparison on 70cm 50 watts of input at 50 ft. of length yields a whopping 4.8 watts at the antenna???  On HF with a 100 watts of drive you loose 30 watts in a 50 ft. feed line??  Looks like the losses are acceptable running 5 watts of QRP.  Guess  I'll stick with some RG 8x for now.  Thanks for the recommendations.  Will be ordering a MFJ 464 Keyer/Decoder soon so maybe I'll catch some of you guys on CW.

Radio Preppers

Re: Lets Talk Feedlines
« Reply #9 on: July 26, 2018, 01:03:40 AM »