Re: Antenna recommendation for 40 and 80M bands
 

loop antenna plus 4:1 balun for the lower bands

https://www.m0mcx.co.uk/sg-230-feedi...oop-deltaloop/

https://www.yccc.org/Articles/Antenn...rt_version.ppt

I managed to get 128ft of wire up in a small back garden by going from the back fence, up to the rear corner of the house, along the gutters, and back down to the other corner of the garden, works relatively well.

10m extending fishing pole with a 1/4 wave vertical wire for the higher bands

Re: Antenna recommendation for 40 and 80M bands
 

You need to be careful about bringing an external earth into the house. There is an RSGB booklet about this, which basically says don't do it but if you must do it get it checked by a qualified electrician.

For an antenna which needs an earth connection you may need rather more than a spike in the ground. You either need radials, or a different antenna type which does not require an earth connection (e.g. some form of dipole/doublet).

A twin balanced feeder does not radiate (provided there is no common-mode current) because it is balanced and has close spacing. You can ensure no common-mode current by using a choke 'balun', although in many cases you can get away without one.

Re: Antenna recommendation for 40 and 80M bands
 

If all of your mains-powered equipment to which to intend to connect an 'RF earth' is connected to the supply mains via an isolation transformer, then that equipment has no connection to the supply earth. Therefore you can connect your 'RF earth' to that equipment.
Is there a flaw in that idea, somewhere?

Al.

Re: Antenna recommendation for 40 and 80M bands
 

Extraneous.

Lawrence.

Re: Antenna recommendation for 40 and 80M bands
 

I am not an expert in electrical supply grounding, but the isolation of the isolation transformer would be one issue. Not just 240V, but under fault conditions including a nearby lightning strike raising local ground potential.

Also, you don't want two different 'grounds' within the same room so everything in that room would have to be run from the isolating transformer.

Re: Antenna recommendation for 40 and 80M bands
 

What would be the effect of connecting the HF rig and ATU's earth posts to outside earth system, say old cooper pipes for mains water system? I have an outside tap on the wall in the back garden, and checked the conductivity of that tap, with the water pipes running under the kitchen sink, and they are all connected.

What difference does it make, when they are not connected at all? I suppose there would be two different situations where one is for balanced antenna system when earth connection is not needed, and the other case where the antenna is unbalanced and needing earth system.

Is it Must or Optional? Is it good or bad or no difference for the radio system?

Re: Antenna recommendation for 40 and 80M bands
 

Last night, cut the wire, and put up an antenna. I had to just go by with the garden limitation. I thought the garden was 20m x 20m, but it wa actually about 16-17m at max. And due to trees and hedges, it could only accommodate maximum 15m stretch of wire, and hung on the tree and bent L shaped for another 5m. And that is the centre element to 50 ohms coax.

And 5m of wire was connected to the coax outer braid, and then to the outside water tap, which is connected to the copper pipe of the mains water under the kitchen sink.

And it tunes 15, 20, 40 and 80m band with almost 1.1:1 SWR.

I worked a station in ST. Albans on 80M band CW at late night. I got 569, and he was 569-599 QSB. I was using about 40W pep.

The receiving on all bands has got really quiet (I mean much much less band noise but received signals were same or better), and I heard a 9K and VEs and K9s on 20M in early evening.

I will keep on experimenting with the LF band antenna getting more parts such as baluns, open wire feeders and wire for radials in the future. But will see how this antenna will perform for a while, and if it is no good, then will move on to maybe the Doublet or Loop or GP. Balanced dipole seems a challenge for this QTH due to the house building being at the side of the garden, and making feeder very long.

Here is rough sketch of my LF band antenna I put up last night. I don't know what it should be called. But I decided to make use of the outside tap as part of the earthing, and it seems working OK for tuning at least.

And the PSU doesn't make buzzing noise when tuning the 80M band either. Before it was quite bad with the buzz from the PSU. So some improvements are showing with the HF antenna now being outside.

Re: Antenna recommendation for 40 and 80M bands
 

That setup will be injecting RF currents into your house ground wiring, assuming that the water pipes are cross-bonded to the electrical earth. It may be fine, or it may cause problems of RFI with broadband routers, TVs etc. What you are effectively doing is using the mains supply as the ground, which you could do just by connecting a wire from your rig ground terminal to the mains ground in the shack. The fact that you are running fairly low power will help.

If the water pipes are not cross-bonded to the mains earth then you are using water pipes as the earth, which may or may not be a good RF earth. Be aware that ease of tuning is a sign of a low efficiency antenna, as well as a sign of a good tuner. You will also have two earths in your shack, which may have quite different potentials under electrical fault conditions.

Re: Antenna recommendation for 40 and 80M bands
 

Good point.

I will do check on the possibility that mains earth is connected to the water pipe. I have a cut mains plug with 3x open wires at the other end.

I will plug it into the mains socket, and read connectivity from the earth wire from the plug, and the water pipe. If they are connected, then yes, the mains system is using the water pipe as earth too.

If not, then likely it is separated, and clear?

Without the ATU, SWR on all bands are between 1.5:1 to 3:1

Re: Antenna recommendation for 40 and 80M bands
 

Coax feed is quite normal these days. Feed coax to a balun, then open wire to the doublet thereafter.

Re: Antenna recommendation for 40 and 80M bands
 

I feel that you are getting too much conflicting info
I worked for 35 years as a TX engineer and was also involved in antenna research which really exposed the crap published by sellers.
The best factual web site that I have seen is http://www.dj0ip.de/vertical-antenna...band-vertical/
have a look, simple but factual
Our antenna research found that apart from UHF and SHF there was nothing new in practical antenna design since the late 1930's
MM0HDW

Re: Antenna recommendation for 40 and 80M bands
 

Great site. Thank you for the link.

Just found out with DMM that the water pipes are not connected to electrical mains system.

Re: Antenna recommendation for 40 and 80M bands
 

That vertical, non-resonant dipole looks very interesting, but I think it's a new idea to me. Has anyone tried anything along those lines?

B

Re: Antenna recommendation for 40 and 80M bands
 

Therein lies the problem. There are as many recommendations as there are people. All of them will work, to different extents. All are affected by your location.

But which is best?

The measurement of any antenna, with enough precision to make comparisons valid, is a major undertaking and is famously expensive. Such undertakings are inevitably done only for military, broadcast, etc. applications where the money is available. This means users with however much clear land it takes.

The evaluation of HF antennae in cluttered domestic environments has been left to the amateur community, which seems appropriate, because we are the people who actually use such things.

Unfortunately we can't afford open area test sites and tons of equipment. We form our opinions of antennae from using them. S meters have various sensitivities, differing by much more than the gains of most antennae. Band conditions vary be even more. Some people are more careful than others, using relible beacons rather than whatever distant stations they come across. Beacons are fixed power and fixed antenna pattern so received strength variations are left to propagation and your antenna.

No-one else has quite the same location as you, so you really are on your own, I'm afraid.

There are pages and pages of articles on antennae in the likes of QST, all based on finite element analysis by programmes like MININEC. They can be interesting, but don't model your surroundings.

So that leaves generalisations:

If you live in a housing area, there is going to be terrible levels of RF noise across the lower HF/MF bands through all waking hours. Loops and balanced antennae in general, are less susceptible to this noise, and if the noise is a few dB lower from an antenna, then you can read signals a few dB lower. Insensitive antennae are OK on receive if they make the noise go down more than they reduce the signals. Verticals and asymmetric antennae are moresensitive to enviromnental noise.

Verticals can give better low-angle radiation than too-low dipoles. A popular DXers delight is the Four-Square array of verticals with a phasing box to steer it.

There is no best antenna. It's all just compromises.

There are a few things which are dependable.

Open wire feeders are much lower loss than coax cable. Coax is more convenient, though.

If you use an antenna which is not naturally resonant on your chosen frequency, you can fix this with an ATU. But this meens your feeder is running mis-matched and that multiplies the effect of feeder losses. So low loss feeder comes into its own - If you have a clear route into the ATU in the shack. Or you could build a remotely operated ATU and mount it at the antenna feedpoint. Then, coax is a great choice.

It's quite easy to lose more than half your transmitter power in an ATU and feeder. Running a balun on the antenna side of an unbalanced ATU can be even worse.

Coax cable works best in a controlled-impedance environment. Use it between a radio and an ATU or between a radio and a matched antenna. Avoid it between an ATU and an unmatched antenna.

Open-wire feeder is the least-bad choice for unmatched operation. It doesn't need screening from things away from it, but it you don't want things too close to it. Routing it can be a pain.

Expect to try a number of different antennae. Set things up so you can change things around. Use temporary lash ups. Only invest real effort or money when you've found what works for you.

Of course, we'd all like you to duplicate whatever we have 'cos it gives a nice boost to the ego :-)

I had access to a nice, large, anechoic screened room along with calibrated measurement antennae and spectrum analysers. It was fun to make a few scale model antennae and try them out. But I didn't learn as much about the antennae as I did about modelling their environments!

Have a play, have fun.

David

Re: Antenna recommendation for 40 and 80M bands
 

We have trees in the garden, but also power cables above the lawn, so it is very tricky to raise the antenna higher than about 7-8 metres, which doesn't help.

I don't want to bring the wire antenna near the mains power cable or touch it.

And the antenna I just put up is not too efficient. I have switched over to another ATU from the CAPCO, and it is having difficulty matching the antenna this time. Lowest SWR I get on 3.750 Khz is 3:1, and 3.510 is better at 1.5:1

So the Capco was tuning up anything thrown at it. It is a really great tuner, but that doesn't mean the antenna is radiating the power. The reflected power from antenna could have been either being soaked back into the Capco, or heating up the P.A of the rig?


Having said that, I worked HB9 near Zurich on 3.557 Khz on CW. I got 339, and he was struggling copying me.

I am waiting for 1:1 balun coming from China, and it is taking ages to arrive.
But if this antenna is not doing well (looks like it), then will maybe try adding 1:1 balun on it. If even at that, no good then, will move to Doublet with open wire feeder, or ground plane vertical, or even Loop.

What is the acceptable SWR for TXing with ATU?
3:1 on 3.750 khz sounds too high.

Re: Antenna recommendation for 40 and 80M bands
 

I used to have a long dipole, 200', made from blue telephone wire, centre fed with twin feeder into a balun, it would tune up on any band, any that were not spot on could be made so by adjusting the length of the feeder. Unfortunately after many years it fell down back in the winter, probably been up for 20 years though. I am going to replace it but with a shorter one as I have a redundant tower that supported a wind turbine for one end.

I also have a 40m dipole made from figure 8 telephone wire, I split it to make an approximately 40m dipole and used the twin part as the feeder. I used this when on holiday in Scotland with my IC706 via a KW Easy Match balanced only ATU and it worked brilliantly, worked well on 20 and 80m with more or less zero SWR.

My original 40 and 80m antennas were home made and could easily be tuned by making them a bit long and then cutting a bit off at a time until min SWR was in the middle of the band.

Peter

Re: Antenna recommendation for 40 and 80M bands
 

Yes these work well and good where space is restricted BUT note you MUST use a good tuner, the newer ones with internal balun will not work, use one of the old Matchbox types with well spaced tuning vanes and good coils.
This design and nearly all the others on the site are very old designs and can not be faulted, were in use many decades ago so have stood the test of time.
We installed a medium wave TX in the Middle East in the 1970's, 1480 was the frequency and output One Megawatt, the vertical antenna was of this design,
MM0HDW

Re: Antenna recommendation for 40 and 80M bands
 

Hi Pete
that is the way to go, make your own,
Next time you make a dipole and need to shorten just fold back the excess wire , wrap around the antenna wire and tape or cable tie.
If you cut sods law may require you to make it a few inches longer.
cheers
MM0HDW

Re: Antenna recommendation for 40 and 80M bands
 

Whatever you do, don't go for the "End-fed Zepp" design - despite being published in loads of antenna-handbooks for 50+ years it "Doesn't work" either in theory or practice.

Mr. Moxon G6XN reported such in his "HF Antennas for all locations" book in the 1960s, despite which the design still shows-up regularly.

There *ARE* ways to make an end-fed half-wave antenna work well; they just don't involve ladder-line feeder with one end 'terminated' into the infinity of free-space!

Re: Antenna recommendation for 40 and 80M bands
 

What antenna have you created?, any antenna can be made resonant and the way it has been designed will get it resonant in mid of the frequency band you choose, Why are you messing with a 1-1 balun. it will do nothing.
you are doing something wrong,
Just create an antenna from one of the designs in the site I sent you,
People try for a 1-1 match, if that is achieved with coax feed something is wrong, a dipole has a impedance of 73 ohms, the coax feeder is 50 ohms, so 1.5 to 1 is the best one can get,
In practice anything up to 2-1 is acceptable.
If you create a correct antenna your tuner will not have much to do so don't try to design an antenna yourself, it has all been done successfully such a long time ago
cheers
MM0HDW