Magnetic Loop or Cobweb...?

[MrWeetabix]

So I finished the install of the 7 Band Cobweb last night by finishing the Coax run to the shack. Aprox 15m UG-213 was used.

Vs end-fed on comparable bands it seemed to perform better with less noise. The Imax vrtical had a distinct advantage on 10m (as expected) and also 12m (again, as expected), but 17, 15 & 20 were all very good on the 7BCW.

I know its subject to conditions etc, but I ran some WSPR last night, with band hopping enabled across 20/17/15/12/10/6/4m bands. I had zero hits on 4/6m which is likely due to conditions and/or time of day really, but surprised to hear nothing at all. I was quite surprised how good a proper 'resonant' length for each band could be after years of living with some sort of Balum and/or compromise antenna on the end for HF.

Cobweb_TX_260623.PNG

Cobweb_RX_260623.PNG

Break down by band

Cobweb_TXRX_260623.jpg

Hoping to get some tests done on 4/6m soon.

[MrWeetabix]

Come home to find 6m wide open, great I thought. worked a few stations and I thought it best to check SWR....A miles out! its the same on all bands. Had read some reviews that they weren't great in wet weather. Didn't think it would be so pronounced

[MrWeetabix]

Once the rain buggered off the SWR slowly returned to normal. Its quite frustrating truth be told.

20m seems less-affected by the rain so I at least am able to run that band when its raining.

May have to have a think long term if this is something I can be chewed with. Long wet winters could render the antenna useless for most of the time. I guess time will tell.

[MrWeetabix]

Well, I can confirm that the Cobweb don;t like rain. The SWR sweet spot drops below the usable frequency after a good soaking, which can be frustrating as its bandwidth is quite narrow on most bands.

I have took to leaving the Tuner inline most of the time, even when dry just to protect the radio should it have a sudden downpour, especially at night when I am running WSPR.

6m been open most days this week and I am enjoying working some EU stuff on that band for the first time in a few years. I am still tempted to go down the 'high-gain' vertical route for this band, but maybe thats a project for next summer now.

At least I am being heard, which is good. :-)

Last Night

7BCW_6M_300623.JPG

This Morning

7BCW_6M_010723_am.JPG

[ch25]

It have nothing to do with antenna. It is just too low over mounting place, that's why wet/dry SWR is changing.

[MrWeetabix]

I would say it has everything to do with antenna.... another one wouldn't do that Might see if I can get higher, but its problematic.

[Alan Pilot]

Got my cobweb from Paul in Poland.
It was tuned at 4mtr so i put it up at 4mtr to test it and it is still there 2 years later.
Rain has no affect on mine at all.
Is the box water tight.

[MrWeetabix]

Got my cobweb from Paul in Poland.
It was tuned at 4mtr so i put it up at 4mtr to test it and it is still there 2 years later.
Rain has no affect on mine at all.
Is the box water tight.

I'll pull it down before the end of the summer and make sure. To be honest, I didnt do any weather proofing other than self amalg on the PL259. I had assumed the unit would be sufficient sealed from the maker.

As CH25 says, could well be the wet slat roof under the antenna which is having an effect

[ChipButty]

Apologies for coming to this conversation late but, would like to add a comment about Magnetic Loops.

I look forward to the flames.

I live in a location where installing optimal antennae is not possible. It is windy and we live in an area where planning permission for such structures is not feasible.

So.. To the comments.

"A Mag Loop is a compromise" - Unless you live on a 30 acre plot, near the sea, on the top of a cliff, have unlimited cash and have both the expertise and staff to install wavelength high masts and associated, multi element antennae for each band you wish to work and hard line, loss less coax, EVERY antenna you put up is a "compromise".

The trick is to buy, build, install what works for you. Be it fan dipoles in the loft, NVIS for 80m bent along the fence around the garden... 10m mobile vertical on a ground spike.... etc, etc.

When a band is open, you need minimal power and antenna to get surprising results!

So.. I work with Magnetic loops. I do have two of the 2E0ERO Loops. One is manual tune, the other is motorised. My preference is the manual. I will explain later.

The have a very, very high Q which indicates they have quite a low loss. So, tuning is an art. You do get used to it quite quickly. Just listen for the highest amount of noise. An antenna analyser is useful and a Y switch so you can flick between the radio and the analyser. Most newer radio's have decent SWR meters internally! The issue with a high Q antenna is you must tune the antenna as you move around the band.. Do not use an antenna tuner/matcher as this defeats the object of the Mag loops advantages. Yes, it does have advantages. SWL's swear by them due to their low level noise on receive.

Back to my situation.

My Magnetic loop sits on a satellite dish tripod in the corner of my conservatory. Do not install them too high off the ground - increased height off the ground provides no advantage, and impedes SWR. Take a look at the CIRO stealth loop which is actually designed to sit on the ground. My wife has decorated the base of the tripod with fairy lights and it looks rather 'contemporary'.

I run mainly digital. 20m gets me across most of Europe and on the right day across all of the US. Usually run 10 to 20 Watts. Most radio manufacturers recommend no more than 30watts for digi anyway.

Back to tuning. Manual is a bit more precise. Do not touch the capacitor when transmitting. Unless you live next door to A&E!!

Yes, a full size dipole at half wave about ground is better, but I also, cannot do that!

My tuppence worth.

[Ant]

Interesting write up. Aren't the 2E0ERO looks receive only and not for transmit? Most loops are aren't they?

[Agent 48]

I've bought a 2E0ERO mag loop they work well... the only issue is that you can't put much power through them. Magnetic Loop antennas are a very good alternative for apartment dwellers where antennas can not be put up anywhere and space is limited. They cut out noise and are the smallest HF antenna you can get. A mag loop on a boom out of a window you can work the world.

Its not all about being the strongest station, there are some Hams they spend there time looking for weak stations for contact as well those who like to run milliwatts, there are people who use mag loops and so on.

More & more people who are coming into the radio hobby or are currently in the hobby are facing antenna restriction issues & rather than just giving up, its important that we work to get around these difficulties because without operators the hobby will be finished. We need as many people as we can get into the hobby to keep it enjoyable and fun.

[DX-Digger]

Any help and advice greatly appreciated.

Pack her bags and put proper antenna.