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Setting up an half wave end feed. (2 replies and 1 comment)

M7LGC
4 weeks ago
M7LGC 4 weeks ago

Hi,

I’m new to this malarkey, and am setting up my HF antenna as a HWEF. It’s roughly 20m long, going into a 49:1 balun. 
I get SWR of 3:1 at 40m, and off the scale at 20 & 10m. Am I correct in thinking it needs to be trimmed a bit?  I’m getting conflicting advice, which really isn’t helping. I am putting in a counterpoise tomorrow, so I gather that should help a bit. 
Any help would be great!! 

Peter M0PWX (2E0PWX)
4 weeks ago

i use a fan dipole, but there are a lot of pages on the net about EFHW / HWEF antennas and yes it should really have a counterpoise 

EFHWslides.pdf (w7yrc.org)

Multiband End-fed Half-wave EFHW Antenna | VU2NSB.com - Amazing Amateur Radio

if its 20m long, being a halfwave that means the lowest band you can work is 40m 

have a look also at Slide 1 (gnarc.org)

the best EFHW is 40m long for 80m as you can see from that last link how it works on many bands (remember an antenna works best if it is in one straight line, but will work with some degradation if you dog-leg it or bring it back on itself )

but being built for 40m, will mean it will only really work on 40m, 20m, 15m & 10m, 

so 30m, 17m, 12m etc are unlikely to be a good tune / swr

antenna design and radio is all about experimentation and working with the space you have. Very few antennas are perfect, and are a compromise in many ways

antenna analysers are not expensive look at a NanoVNA, less than £30 for the smaller older one on ebay, plenty of video's on youtube about how to set it up and use it not only for SWR / Antenna tuning, but measuring response curves of filters and much more (look for nanosaver program for windows and it makes it much more friendly to use)

the RSGB radio communication handbook (RSGB Radio Communication Handbook - Radio Society of Great Britain - Main Site : Radio Society of Great Britain – Main Site) is a mine of information as well on all topic radio

what sort of rig you got, and does it have a built in ATU / AMU?

73

Peter

M0PWX

(not pete M0PSX who runs essex ham)

M7LGC
4 weeks ago

Hi Peter,

Thanks for the advice, I’ll get the counterpoise in the ground today. I like the idea of the NanoAV, would certainly save me from running up and down the stairs to press the PTT to see what the SWR is!
I’ve got a Yaesu FTdx10, which has a built in ATU that can handle up to 3:1. The EFHW is run on the roof, following the soffits, and along the roof line and back down again to allow for wish of QXY to minimal visibility of any antennas. This will, I suspect compromise the performance somewhat, as it’s very much not in a straight line for more than 5m max. Joys of having a hobby that needs to be stealthy. I couldn’t run it in the loft, as the house has metal grids all round it to hold the render on, so It acts as a faraday cage.

I’ll certainly look at all the info you’ve shared, thank you, and get the analyser before making adjustments.

73

Chris M7LGC

Peter M0PWX (2E0PWX)
4 weeks ago

they do make tuning easier, as you can see what frequency the antenna is actually resonant at, so you can see how much high or low it is

also do not fixate on getting a single band spot on for SWR, look at all the bands you intend to use it on as you will need to compromise some bands to get a workable SWR on other bands

as the NanoVNA only measure 101 points for the frequency range you set it to if you do a scan 6mhz to 56mhz it will only give a check ever 0.5mhz, good for a rough idea of which bands you will be able to work, but not good enough for actually tuning, for 40m (7mhz) i usually start with a scan range of like 5mhz to 10mhz or 25mhz to 35mhz for 10m (28mhz), then narrow it down as i home in on the tune i want

also make sure you calibrate it before each session or the reading will be wrong, idealy to the range you will be checking, eg 1mhz to 30mhz if only checking HF bands, or 1mhz-60mhz if doing HF +6m

i work digital modes only, so i tend to tune my antenna low down in the bands as the digital mode centres of activity tend to be just above the CW areas at the lower end of the bands

also as you have HF + 6m with the FTdx10 you may get a pleasant surprise with the antenna and get a workable 6m SWR, 

i have a FT-991a, and my fan dipole as i tune my antenna low on the bands my 30m wire gives me a usable 5th harmonic for 6m

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