I will be installing a GMRS J Pole antenna on one of my trees. The total cable run to my 50 watt base radio will be 150’. I am afraid LMR-400 will be inadequate. Any suggestions to what cable I should use and where to purchase it?
Thanks! Mark
150ft is a significant cable loss type length, and worse, you have decided to use an antenna with no appreciable gain to offset the cable loss. It is also a significant financial outlay to move to lower loss feeder. Lots of the locals her in the 70s used slim Jims, made by the inventor, Fred Judd G2BCX. I have to say i found it totally unremarkable. If you need to have such a long run, then i would be looking at something with as much gain as you can get, if your budget can run to cable suitable for the distance.
What cable is suitable?
Well, your length means nearly ¾ of the signal is lost in the cable, and its about £150 worth of cable. Thicker LMR-600 loses ½ the signal on that length at double the cost, £300 in the UK, plus the expensive connectors. Keeping with the same brand as an example, lmr-900 at £1200 gives you just over 2dB loss.
£300 on feeder and £120 on the antenna, bringing that 8dB down to 4-5dB GAIN, is better than £1200 plus £25 on a slim jim and getting a 2dB overall LOSS.
This is the problem.
For around £120 you can buy a base station antenna with perhaps 9dB gain than the slim jim. So you have to compare the total gain (or loss) of the entire system.
Sounds like good advice. I just bought a 9 db gain antenna and I will connect it to LMR-400. I appreciate your help, thank you.
Oddly, slim Jims are not terrible antennas, but Fred used to bang on about them being so wonderful - a handful of his friends had them, but they were no stronger locally than those who had ordinary dipoles, and a few with ⅝ designs clearly worked better.
I was told for long runs to use heliax ld4-50a. This is what I am using as a newbie as well.
1 Like
4-50 is nice cable but while it is not too expensive, shipping is because it’s rigid and comes in HUGE coils. If you have antennas designed for distance working with 10dBd or more gain, then 4-50 is great - BUT - don’t forget at the ends you need to converts to flexible cabling, and that of course is a loss potential if you mess up.