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 doublet feeder in rain/wet conditions 
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Post doublet feeder in rain/wet conditions
Ive read the tests that Steve has on his page regarding loss on 300/450ohm ladderline fed antenna systems in wet conditions.

I can appreciate that there will be some loss occurring, but can anyone share their experiences of

A) - operation in wet vs dry
B) - horizontal ladder line runs, which are in the clear.

My doublet feeder will drop then run horizontal for about 15m at about 15ft before it goes into the shack.


Any tips/experience will be appreciated.

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Mon Oct 02, 2017 12:27 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
300-ohm ladder line from when I had my doublet(s) caused minor tuning woes when the rains came and I was tweaking the tuning dials to maintain it steady.
As for the run from the shack, it was in a bow shape underneath the antenna as it came out of the shack wall at a low point and travelled horizontally along a wooden trellis and then created a gentle curve until it was then vertical in the centre section of the doublet and this allowed it to flow freely in the wind and shake off some of the rain in the process, hope that makes sense.


Mon Oct 02, 2017 12:35 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
Did you notice much of a difference in performance when there was rain on the feeder.......

How did your doublet perform in general.....what was its lowest usable frequency?

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Mon Oct 02, 2017 12:40 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
MI0HEZ wrote:
Did you notice much of a difference in performance when there was rain on the feeder.......

How did your doublet perform in general.....what was its lowest usable frequency?

As for performance, it is hard to say as that is subjective for all of us, and the rain seemed not to cause any RX issues just the slight variation of tuning needed and all other signal reports remained the same when wet. I always went back to some form of doublet antenna after many other antenna experimentations simply because I felt it was very efficient on both TX and RX. I had heard people comment that they were noisy and I can agree with this comment for sure. But in comparison to other antennas I have built before it, the noise ratio was raised but so was the signal to noise ratio, so in a nutshell, the G5RV I had slung up was rather quiet on RX and this was nice but all it meant from my findings was that it was somewhat deaf!

The originally built doublet was a single 20m-20m total 40m horizontal element with around 20m of a 300-ohm feeder and was resonant on 80m with a 4:1 balun as I had a small coaxial feed to the balun then out to the ladder line feeder. I have since built a folded version of the doublet with 60m-60m =120m of element folded back on themselves in a large S to allow for a 40m total span and this would allow work on 160m easily, aka cobra antenna variant.


Last edited by 2E0JGR on Mon Oct 02, 2017 1:14 pm, edited 2 times in total.



Mon Oct 02, 2017 1:11 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
I have run my 300Ω feed back to the shack inside 20mm electrical conduit, that has little if any affect on the feeder properties and it keeps the feeder dry. The feed to the top of the centre mast is wide spaced feeder, so the weather doesn't affect that so much. This is feeding a 2x15M doublet at 9M high.

The length of the 300Ω feeder run is about 26M, it will match top band to ten, but as you would expect the efficiency on 160 is low, I think there is something like 1000:1 standing wave on the 300Ω line, so even on 160M there is quite a loss, but it does work OK for the locals.

This is what I posted on another thread.

viewtopic.php?f=59&t=88945


Mon Oct 02, 2017 1:11 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
Thanks for the info gents, duly noted, very much appreciated.

I think the conduit sounds like a winner, that what i think i'll attempt. My facia boards are white PVC, so im sure some nice white conduit will blend in. :)

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Mon Oct 02, 2017 2:26 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
MI0HEZ wrote:
Thanks for the info gents, duly noted, very much appreciated.

I think the conduit sounds like a winner, that what i think i'll attempt. My facia boards are white PVC, so im sure some nice white conduit will blend in. :)


That sounds like a plan. I haven't tested white conduit for RF, but you can simply do that by placing a sample of conduit in a microwave oven with a cup of water next to it as a load and run it for a couple of minutes to see how it stands up to that, if nothing happens then you are good to go.


Mon Oct 02, 2017 2:43 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
I run homemade open wire, about 4" wide and see no effects of rain at all

David

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Mon Oct 02, 2017 2:55 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
David, did you make your own spacers, or did you buy commercial ones?

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Mon Oct 02, 2017 3:07 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
I made my own from 16mm oval plasticB and Q electrical conduit. I cut a. Slot in tje end, drilled a hole at tje end of the slot to trap the wire and stopped it sliding by tightening a nylon tiewrap rohnd the wire within the open end of tje spacer.

D

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David G4YVM

"For scientific leadership, give me Scott. For swift and efficient travel, Amundsen. But when you are in a hopeless situation, when there seems no way out, get on your knees and pray for Shackleton.â€

Priestly.


Mon Oct 02, 2017 3:47 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
G4YVM wrote:
I made my own from 16mm oval plasticB and Q electrical conduit. I cut a. Slot in tje end, drilled a hole at tje end of the slot to trap the wire and stopped it sliding by tightening a nylon tiewrap rohnd the wire within the open end of tje spacer.

D


I did the same several years ago, but found the feeder really heavy. How far apart did you space them?
I found some ready-made ones in the States, but the postage was ridiculous unless you bought a hundred. If enough people are interested we could do a bulk buy?


Tue Oct 03, 2017 6:50 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
Mine are about 14-18" apart. Its a long run of about fifty feet supported in the middle

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Tue Oct 03, 2017 7:21 pm
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
Would it be possible to run 2 x RG213 as a pair and use the centre cores as your feed line in both, and connect braid to tuner at the end to have a shielded feeder.....the spacing between both centres must be near that of 300ohm stuff or am i barking up the wrong tree here......

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Wed Oct 04, 2017 8:38 am
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
The losses would be huge on certain bands where the antenna is voltage fed, that's if you can even match it, at 100pf per metre, that would be a challenge.


Wed Oct 04, 2017 8:49 am
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 doublet feeder in rain/wet conditions 
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Post Re: doublet feeder in rain/wet conditions
Thought as much but wasnt sure. Im just glad to be getting back into the hobby from a 2 year break, so new house, new plans, new antennas and such like.
cheers paul.

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Wed Oct 04, 2017 9:08 am
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