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Old 10th Sep 2019, 11:21 am   #1
budkor22
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Default Antenna recommendation for 40 and 80M bands

Hi All

Trying to get back to HF after a few years of QRT. I just got an HF rig, and ATU.

I am thinking of putting a wire antenna for 40 and 80M bands, but what would be the best? I am not too fussy about DX, but would like antenna that is efficient and free from RF Feedback into the shack.

Ones I am thinking of are,

G5RV
Fan Dipole cut for the bands
Inverted V Dipole
Random / Long wire with ATU and ground.

I have plenty of wires for the element, and would like DIY rather than buying ready made antennas.

Thanks
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Old 10th Sep 2019, 11:34 am   #2
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Default Re: Antenna recommendation for 40 and 80M bands

I'm using a 20/40m inverted V fan dipole. Wire from Sotabeams and RG58 "milspec" feed from Moonraker. Feed radiation and RF into the shack is sorted with a small stack of 4x material 43 toroids that the feed is looped through four times and cable tied at the antenna end of the feed. I managed to cut it with just the aid of my TX and built in SWR meter so that it's a 1.3:1 match across the band worst case. Took a while to get that right! The thing is quite low down and wedged between my house and some trees and I only run max 10W and have had plenty of contacts on it.

SSB is hell at the moment though due to the solar cycle. No luck there. Digital modes and CW for me.

WSPR spot at ~2W out on my QRP Labs QCX on 40m got me a spot in Tasmania!
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Old 10th Sep 2019, 11:36 am   #3
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Default Re: Antenna recommendation for 40 and 80M bands

Carolina Windom!
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Old 10th Sep 2019, 1:04 pm   #4
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Default Re: Antenna recommendation for 40 and 80M bands

Choice of aerial: the first determining factor is usually 'How much space is available?', where 'space' means space well-clear of earthed objects and sources of interference - such as power lines radiating PLT. Plus, in most cases, with the aerial being mounted as high as possible.

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Old 10th Sep 2019, 2:10 pm   #5
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Default Re: Antenna recommendation for 40 and 80M bands

Symmetrical dipole (whatever length fits!)

open wire feeders (about 4 inch spaced) to Z-match balanced ATU

Forget unbalanced ATUs with baluns after them, a balun to handle the range of impedances and frequencies is problematical.

The fully balanced nature rejects local QRM
The isolation of the ATU handles issues of PME safety.

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Old 10th Sep 2019, 2:37 pm   #6
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Default Re: Antenna recommendation for 40 and 80M bands

Yes, the bands seems really poor these days. When will they get better again?

My garden is not too big about 20M x 20M square shape, and it has a few large trees. Several cables are passing above the lawn coming from a telegraph pole at the corner feeding a few houses nearby, and they must be the BT internet broadband lines. So it will be tricky to dodgy the cables when hanging and stretching radio antenna in the garden.

My ATU is CAPCO SPC300, so it is not Zmatch? I think Zmatch tuner is EZtune one either by Isle of Man or Wight. I saw them a lot but never had one of those.

How would inverted L compare to others?

What happens when you attach feeder in the middle of radiating element instead of feeding from the end? How does the band coverage change, or would be the same?

Last edited by budkor22; 10th Sep 2019 at 2:42 pm.
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Old 10th Sep 2019, 3:32 pm   #7
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Default Re: Antenna recommendation for 40 and 80M bands

Hi
Easiest and probably the best antenna you can have for 40 and 80 metres will be a fan dipole, easy and cheap to make, use any wire that you can find copper coated preferred.
Just adjust the length of the 40 metre first for best swr at mid band and then do the same for the 80.
No need of balun or tuner, will definitely do what you want.

If you would like more help contact me at address shown on qrz.com
cheers mm0hdw
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Old 10th Sep 2019, 3:46 pm   #8
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Default Re: Antenna recommendation for 40 and 80M bands

Thank you James. Yeah, it seems simplest and cheapest option. I was a bit weary about using balun, because it could be tricky tune for some part of the band, even if it could be resonant on some. Also I have seen where antenna has good SWR, but it wouldn't radiate efficiently, so it was not making any contacts.

And Fan dipoles could be configured as inverted V under some situations, I suppose.

I was reading up about the Doublet, and was a bit wondered if the twin line feeder coming into ATU might radiate and cause RF feedback problems? But then I recall some people using Doublets were putting strong signals on 40M without sign of RF feedback or distorted audio.
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Old 10th Sep 2019, 3:54 pm   #9
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Default Re: Antenna recommendation for 40 and 80M bands

Conditions are very poor at times due to Sun spot cycle.
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Old 10th Sep 2019, 4:28 pm   #10
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Default Re: Antenna recommendation for 40 and 80M bands

Quote:
Originally Posted by budkor22 View Post
Yes, the bands seems really poor these days. When will they get better again?

My garden is not too big about 20M x 20M square shape, and it has a few large trees. Several cables are passing above the lawn coming from a telegraph pole at the corner feeding a few houses nearby, and they must be the BT internet broadband lines. So it will be tricky to dodgy the cables when hanging and stretching radio antenna in the garden.

My ATU is CAPCO SPC300, so it is not Zmatch? I think Zmatch tuner is EZtune one either by Isle of Man or Wight. I saw them a lot but never had one of those.

How would inverted L compare to others?

What happens when you attach feeder in the middle of radiating element instead of feeding from the end? How does the band coverage change, or would be the same?
We're around the bottom of the sunspot cycle so things should begin to improve, BUT the last cycle was rather anomalous, so you can't be too sure about predictions.

Inverted L is an unbalanced antenna, so it misses out on the QRM reducing properties of balanced ones. They can work, but they do require a reasonable earth, and are best in a quiet location.

Capco SPC300 is an American design, found in the ARRL handbook. Series-Parallel-Capacitance 'SPC' version of the classic American 'Transmatch design. It is a good ATU, but it is unbalanced. It's great for long-wire inverted-L and such asymmetric antennae. The designers thought that if you want to drive balanced antennae, just stick a balun on the antenna end of it. Simples! no very much not simples. It leaves a difficult job for the balun to do. SPC transmatch is a good circuit, but SPC transmatch into a balun is asking for balun problems, and there are better overall balanced ATU designs.

The Z-match was an amateur design, and over the years many firms have sold ready made versions and kits. SEM you've mentioned. A really nice version was made by KW and called the Supermatch 107 and supermatch 109 (a higher power variant) these were later branded Decca. They are lovely and well sought-after. I use a supermatch 109 and keep the auto ATU turned off in the Icom IC7700.

People ask 'How much power can xxxx ATU handle?' well they aren't limited by power. At some voltage the variable capacitors will flash over, at some current the coils etc will unsolder themselves. What power these happen at depends a lot on the ATU settings. Gauge ATUs on the spacing of the variable capacitors and the heftiness of inductors and the generosity of cabinet dimensions around the coils. Good construction gives low loss, and low loss is as beneficial on QRP as it is on QRO.

Confession time. I built an SPC transmatch with large capacitors and a nice roller-coaster coil. It's the size of an HP spectrum analyser (It's in an actual HP spectrum analyser cabinet!) I included directional power metering with log scales from 100mW to 1kW along with computed VSWR/return loss, and even a phase meter.

Then, I found out it effectively forced unbalanced antennae on me, and those antennae picked up every switch mode power supply in the village.

So I went balanced and I picked up the Decca/KW 109 atu from a silent key stall at a rally. In view of where the money was going, I didn't mind the price.

So my SPC transmatch is a wonder to behold. It would run away with any construction contest, but as a unit built by a professional RF designer it would be grossly unfair to enter. It sits unused in the attic and just comes out occasionally as a display item.

I'm fairly well known in technical circles, and one of the ARRL handbook authors, and that big ATU is my biggest goof in amateur radio. I leapt in and threw a lot of effort and a fair bit of lucre into building exactly the wrong thing! The better the job I made of it, the more stupid I looked!

Band conditions and sunspots limit things, but the new kid on that block is all the RF crap from every gizmo in christendom. Antenna choice is now steered somewhat by reception difficulties. If you can't hear 'em, you can't work 'em.

George Burt GM3OXX had a simple doublet between chimneys on the 4-storey flats he lived in - about the lendth of your garden. He ran 1 Watt, CW only and was far over 300 DXCC countries. Nice chap, absolute legend and sadly missed.

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Old 10th Sep 2019, 5:40 pm   #11
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Default Re: Antenna recommendation for 40 and 80M bands

For me the important thing is the physical layout of the site: dipoles are OK if your shack is in the middle of your plot, if your shack is at one end then a dipole implies a long length of feeder. My shack is at one end of the site so I've got a 100-ish-foot end-fed longwire here, along with an old 1960s Redifon ATU.

As an earth I've got my "extended fence-spike network" as described here:

https://www.vintage-radio.net/forum/....php?p=1092363

The longwire is about 20 feet above ground, and works surprisingly well both for throughout-Europe working (ot also covers 60Metres - and I regularly work Iceland with 30 Watts from my PRC320 on that band) and also during the dark-hours of the winter months I can work into Canada/Eastern-US on 80Metres with 100 Watts.

Height is less important than you may have been led to believe - indeed, an antenna that's only 0.1-wavelength above ground is precisely what you need for "NVIS" communication over a few hundred miles.

I like my "Cloudwarmer"!
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Old 10th Sep 2019, 6:54 pm   #12
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Default Re: Antenna recommendation for 40 and 80M bands

Great posts David and Tanuki. Enjoyed reading them thank you.

I have seen the KW107 atu many times in the rallies and eBay as well, but passed them rather foolishly. It was because maybe I associated them with the KW2000 valved tranceiver. All the KW2000s I have seen, none of them worked. They all needed work done to them.

I also read about GM3OXX. Very interesting radio and engineering story.

When I was very active on HF many years ago - it was early 1990s, I used to run Inverted L at one time, and it did make many good contacts on all bands. But then it was the Sun spot maximum time, when dummyload with 5W could work some strong European stations. Every morning 20m was full of VKs and JAs. At night North Americans would come on with vengeanes warming up the bands all night with their multi kilowatt amps and multi element beams until the dawn.

I got my DXCC within a few months with indoor dipole and quarter size inverted L. The good old days.

Now? I heard nothing but hash on 20m all day, and when I heard ON4s and F5s, I felt they were some exotic DX.

I thought it is time to cut a proper LF band antenna.

Last edited by budkor22; 10th Sep 2019 at 7:02 pm.
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Old 10th Sep 2019, 8:17 pm   #13
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Default Re: Antenna recommendation for 40 and 80M bands

I'm surprised that there as been little mention of noise of the type produced by numerous wall-warts and other electronic sources. Putting up a dipole for 60m about a year ago, I just found I was getting an S8 level of noise as soon as the feeder connected to the transceiver.

However, I do have the particular problem of both overhead telephone and an overhead power line coming in to the front of the property and being all together too close to one leg of the dipole for comfort. If my problem comes from them, that is very hard to avoid. The whole village has overhead power lines, and the sub-station is only about 80m away from me. The noise is not being generated by anything inside my house.

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Old 10th Sep 2019, 10:42 pm   #14
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Default Re: Antenna recommendation for 40 and 80M bands

Quote:
Originally Posted by budkor22 View Post
Thank you James. Yeah, it seems simplest and cheapest option. I was a bit weary about using balun, because it could be tricky tune for some part of the band, even if it could be resonant on some. Also I have seen where antenna has good SWR, but it wouldn't radiate efficiently, so it was not making any contacts.

And Fan dipoles could be configured as inverted V under some situations, I suppose.

I was reading up about the Doublet, and was a bit wondered if the twin line feeder coming into ATU might radiate and cause RF feedback problems? But then I recall some people using Doublets were putting strong signals on 40M without sign of RF feedback or distorted audio.
You will have no rf returned if you correctly cut your dipole.
SWR only occurs when the antenna is unbalanced or you tune out of band,
The antenna plays no part in audio quality, that depends on the settings in the rig.
if you use ladder line or window line you would need a matchbox matching unit ( tuner) to alter the impedance back to 50 ohms, ladder line etc has various impedance depending on the spacing, 200 and anything up to 2000 ohms.
ladder line terminated into a matcher does not radiate.the old 60's matchbox and heathkit tuners are the best for ladder line.the newer tuners are not at all as good.
However if you carefully make and prune a trap dipole you will have no problems at all.it can be nearly any shape but straight seems best.
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Old 10th Sep 2019, 11:20 pm   #15
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Default Re: Antenna recommendation for 40 and 80M bands

Yes, the RF feedback on my HF rig seems 100% caused by either the rig or microphone, because the distortion is noticed even when it is TXing to a dummyload.

I am waiting for other microphones to arrive for testing the audio problem.

But the CAPCO SPC 300 ATU does not have ladder line input. It is an earlier version with just one coax input. There is another input just next to the coax input, which looks like just a socket for a wire.

I also recall when running a G5RV for 40m, I cut the end of the twin line connector, and joined two lines into one, making it like a long wire, and connected that to WIRE input of the AT-230 Kenwood ATU. It worked OK on 80m at the time. The AT-230 was also a good tuner, but sold it off years ago. Not sure if the CAPCO can do that.

What about ground plane vertical antenna? Are they any good for 40 and 80M?
What are the goods and bads for the GP?

But yes, the dipole seems most easy option to try out, because I have the wire and also coax. It will cost me nothing to cut it and try out.

Any one fancy a SSB chat on 80M / 40M? when I cut the dipole for giving us reports? Please let us know here.

If it is not working for me well for environmental reasons such as too many overhead cables and trees and shrubs causing high SWR ... I don't know, but I think it would work OK. If not, then I could always try something else and compare.


Maybe we should make a 80M net for UK vintage radio forum. UVRF net or something like that on 80M or 40M?

Last edited by budkor22; 10th Sep 2019 at 11:28 pm.
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Old 10th Sep 2019, 11:26 pm   #16
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Default Re: Antenna recommendation for 40 and 80M bands

Quote:
Originally Posted by James Duncan View Post
You will have no rf returned if you correctly cut your dipole.
SWR only occurs when the antenna is unbalanced or you tune out of band,
The antenna plays no part in audio quality, that depends on the settings in the rig.
if you use ladder line or window line you would need a matchbox matching unit ( tuner) to alter the impedance back to 50 ohms, ladder line etc has various impedance depending on the spacing, 200 and anything up to 2000 ohms.
ladder line terminated into a matcher does not radiate.the old 60's matchbox and heathkit tuners are the best for ladder line.the newer tuners are not at all as good.
However if you carefully make and prune a trap dipole you will have no problems at all.it can be nearly any shape but straight seems best.
60M band, I have not tried yet. For that, I need to buy a new rig, either modern SDR like ICOM IC7300, or maybe get older rig with GC, and wide band it to get the 60M.

But I heard it could be a noisy band. But yes, the noise on LF is very bad here too. I mean, every electric appliance in the house is potential cause for the noise, but also I am sure it comes from nearby outside places too.

I have confirmed noise causing source into HF in the house is, the worst is the Samsung LED TV, and then tumble dryer, washing machine, all the small switching power supplies and LED security lights and Radio Scanner and Computers and Monitors.

The only way I could tackle the noise was using RF attenuator button in TS-130SE. It works well, and really quieten down the hash noise. And I found balun could also choke the noise down.

Last edited by budkor22; 10th Sep 2019 at 11:32 pm.
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Old 11th Sep 2019, 12:14 am   #17
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Default Re: Antenna recommendation for 40 and 80M bands

Aerials tend to be in one of two types: balanced and unbalanced. Balanced required balanced feeder (75 Ω twin is available for a dipole); unbalanced requires an earth connection. The size of your garden (or other available space) and the location of your equipment (i.e. your 'shack') will tend to limit your choice. If your shack is approx. central to where you can erect your aerial, use a balanced aerial; otherwise use an unbalance type, but fit an earth connection which does need to be fairly short.
For your stated need, seems that a balanced fan dipole is your best choice.

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Old 11th Sep 2019, 7:47 am   #18
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Default Re: Antenna recommendation for 40 and 80M bands

My house is at the edge of the garden not in the centre, so it will make feeder very long, which may be not ideal.

For earth connection, what about earth post at the back of the HF rig and also at the back of ATU, do they all need to get connected to outside earth connection?

What are the uses / functions for the earth posts at the back of the HF radio and ATU actually?
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Old 11th Sep 2019, 8:01 am   #19
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Default Re: Antenna recommendation for 40 and 80M bands

There is only one aerial for those bands I'm afraid...open wire fed doublet. And not the G5RV version.

The open-wire is essentially losses and will take much abuse - ideally run it through space or, as in my case, past the house, hooked over a conservatory gutter, through a plum tree and finally down the garden to the feeder through some branches. My feeder is about fifty feet long.

Im being picky of course, you certainly hear more types of aerial on the bands but over the years two aerials have really seen more entries in my logbook in the "what's he using" column...the dipole and the doublet. One and the same really, sort of.

My own open-wire fed 55m top doublet has been challenged by many newcomers over the years yet still beats everything else I can throw at it. I made my own feeder and balun and the aerial runs about 20 feet up in the trees, roughly east-west.
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Old 11th Sep 2019, 8:48 am   #20
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Default Re: Antenna recommendation for 40 and 80M bands

Yes, Doublet seems really interesting antenna. I am still amazed how the wire feeder coming into the shack to be connected to ATU, doesn't radiate.

It must be special ATU, as said, the Zmatch? or Transmatch atu?

I would love to try it out, but will need the ATU. My CAPCO SPC300 has only coaxial feed. Just one input - this must be the very earliest model. Built like a tank, and weighs tons.
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