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End Fed Wire Antenna Questions (5 replies)

(unknown)
9 months ago
(unknown) 9 months ago

Hello All

I am currently in training under Pete M0PSX for my foundation license and I have been advised that someone from here can help me out with a question I have about my HF antenna build and that it would be best to post my question here…

I have already made my UnUn and it is on the wall of my house positioned by a 96 foot single run steel core washing line and I have also made my counterpoise (18ft with 6” folded over with simplex clamps to hold a dogbone insulator with heat shrink sealing the ends), making a total of 17.5 feet (This is another question I have does the fold matter is my counterpoise 17.5 ft or 18ft? My antenna wire has the same heat shrink and ceramic dogbone insulator and is a total of 72 ft with 12” folded over making my antenna wire 71 ft (Or is it still 72ft?)…

The question I asked on the foundation course follows, thanks in advance for any help or advice you can give me…

I am making an end fed random wire antenna so I can listen to HF on my rtl-sdr dongle by following a YouTube video and I was wondering if you could help me out by telling me if my design will affect the signal. I have made a 9:1 UnUn and have installed this on the wall of my my house just above a newly installed single length steel core washing line that runs the length of my garden which is 96 feet, the earth wire is going to run off at a right angle from the UnUn through screw eyes which I have positioned every four bricks and is 18 feet folded at 17.5 foot using simplex clamps so I could install a dogbone ceramic insulator and then seal the end using heat shrink making the counterpoise a total of 17.5 feet long and to support this wire I will be using cable ties through the screw eyes and around the wire. The reason I ask is I am using the washing line to support the antenna wire which is 72 ft long, folded over at 71 ft so I could install a ceramic dogbone insulator and finish the end with heat shrink and simplex wire clamps making a total length of 71 feet for my antenna.

My question is this, I was thinking that I could support my 18 gauge silicone wire using U clamps at every 5 feet or so along my washing line although I notice in the foundation exam that pictures of end fed random wire antenna drawings that the wire is only supported on the ends one at the height with the chimney/roof support and one support at the end of the wire and the middle is just left hanging down…

Will putting U clamps every 5 feet to support my 71 foot antenna and clamp it to my washing line affect the signal running along the wire and bouncing of the ionosphere or should I only use clamps on either end?

Many thanks

Shane

Peter M0PWX (2E0PWX)
9 months ago

Hi Shane, 

the one thing that springs to mind is having a wire support for the actual antenna wire is going to cause issues as it will act as another element and distort the radiation pattern of the antenna

have a look on ML&S, moonraker, nevada radio etc for 50m/100m drums of guy ropes these won't affect the tune or radiation pattern of the antenna

the other option would be to use the steel cored washing line as the antenna element, possibly using a screw terminal block for the connection so long as it is suitably waterproofed using something something like self-amalgamating tape or heat-shrink, it won't be quite as good as steel has a higher resistance than copper but will work

if you plan to use it for transmission once you pass your foundation then don't forget to take into account the EMF regs, which for foundation power levels (10w) are pretty simple but you still need to do the calculations and ideally print the results as proof should anyone ask,

if you plan to go onto intermediate or even full license levels then they are more demanding, but so long as the antenna is more than 4-5m in the air and away from your property boundary where people can access for up to 50w you are pretty good (but do the calculations on the RSGB EMF calculator spreadsheet for all bands you will transmit on as the exclusion distance changes with wavelength / frequency as well as power output) 

note:- you can put notes on the EMF calculation results that you won't transmit while people are in your garden if you have issues with enough room in your garden for the exclusion EMF zone

Latest version of RSGB EMF Calculator - Radio Society of Great Britain - Main Site : Radio Society of Great Britain – Main Site

one last thing that springs to mind is the direction of the antenna, remember long wire antennas radiate and are more sensitive to received signals that are at right angles to the antenna wire, put simply if your antenna wire runs north/south the strongest signals you transmit and recieve will be east/west so it is something to take into consideration when planning your antenna

hope this helps

Peter 

M0PWX

(not Pete M0PSX who runs this site)

Peter M0PWX (2E0PWX)
9 months ago

one other thing i forgot was insulators

you mention dog-bone insulators, these are in tension (being pulled apart by the tension) as opposed to egg insulators which are in compression (being pushed together by the tension)  and so can take more stress / tension before they fail

hope this helps

Peter 

M0PWX

(not Pete M0PSX who runs this site)

(unknown)
9 months ago
(unknown) 9 months ago

Hi Peter M0PWX

Many thanks for the detailed reply, sounds like I’m going to have to rethink my antenna wire, and like you said maybe even use the steel core washing line, or grab some of that rope and apologies for delayed reply, I never got any notification, anyway much appreciated and yes I would like to go for my intermediate and eventually my full license as I have been looking at the exam guides and all the math involved looks like it will give me the brain work out I need. Still I need to get my foundation first. I also doubt I will be in a position to transmit on HF for a very long time. I plan on learning and passing my full license first before I dive in too deep and until then I shall just stick to the 70cm & 2m bands.

Thanks for such a detailed and helpful response.

Best Wishes

Shane

(unknown)
9 months ago
(unknown) 9 months ago

Ok, I’ve done the earth wire and reverse the UnUn Box. So now I can go straight up my wall from the antenna terminal on my UnUn, into an eye hook that i covered in electrical tape for insulation, then I will screw together some battens to get to the same height at my hook eye which is 4 metres from the ground then use these in my tables umbrella stand with a V cut in the top to support my Antenna wire. I will then use some more batten with holes in over the umbrella holders base with tent pegs pushed through the holes into the ground and finally use some more tent pegs and some wire to support the upright batten. Then I think that’s job done, thanks again for your input Peter M0PWX much appreciated. Hopefully I can put the rest of it together this weekend. Hope you are having as much fun?

All the best

Shane

Peter M0PWX (2E0PWX)
8 months ago

Hi Shane, 

sorry for delay had issues with my account on here,

i assume you are using something like a RTL-SDR.com dongle for HF reception, if so have a look at my qsl.net page M0PWX Mode and Frequency Page (qsl.net) it has a fair list of digital mode frequencies and the free software to decode them, can be a fun way to start your HF journey

also depending on your budget have a look at a xiegu G90 (about £450) Xiegu G90 - Portable HF SDR Transceiver (moonrakeronline.com), HF (160m-10m) all mode (SSB,CW,AM,FM), built in ATU and 20w, you can get a digital mode interface for about £50 or less, then just need a laptop / PC for digital modes

i run a G90 here for my WSPR setup, it was my first radio when i passed foundation with Pete (M0PSX) and have a Xiegu X6100 i use for field / POTA with a mag mount HF antenna on the car

if you are looking at intermediate after foundation my comment would be to go straight onto it as its the same material just in a bit more depth, google "gm6dx training", its a free course similar to EssexHam, but there are no study group calls, it has plenty of questions at the end of each section, i used it for my intermediate exam

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