Other SOTA sites: SOTAwatch | SOTA Home | Database | Video | Photos | Shop | Mapping | FAQs | Facebook | Contact SOTA

Loop 40m


#1

Morning have i missed anything :smile:

Been in garden taken down the G5RV and building a 40mb loop about 44m in length and in triangle shape. 75ohm feeder RG6 straight into the ATU. Its more away from the hedge and house yeahhhhh, Its well aired.

Can hear voices :smile:

Straight through the ATU its already 1.3 on 7160 oh wow :hushed:
7100 its 1.1 oh even more wow :stuck_out_tongue:

Well happy

First thing noticed using the RF less when having to back the noise down on the TS120V

Karl


#2

Hi Karl,
Good to hear you have the loop up. It is quite a forgiving antenna as I have said in our direct emails, but I’m very surprised at 1.3 or 1.1:1 - the best I get is 2:1, however the important thing is what you can now hear and work. At the moment there has been very little activity on 40m or 20m so nothing to compare with. Hopefully later there will be more activity.

Check the SWR on 20m by the way - it may be at around 2:1 but anything under 3:1 is acceptable for most rigs, I find the 40m horizontal loop actually works better on 20m than on 40m!

Planning to get out to DM/BW-088 Rangenberg tomorrow morning, so hope to work you from there.

73 Ed DD5LP.


#3

Cheers Ed
it surprised me too

so far MX0XTT on 40m

F/G3TTC/P EU-052 20m
S52Q/P S5/KA-017 20m

will be listening for you

Karl


#4

A low SWR on an antenna that might not be expected to show a low SWR is not necessarily a good thing Karl…


#5

I was thinking the same thing…

Brian


#6

Please explain.
Wondering why, will be use antenna analyser borrowed off friend but seems to be working OK so far.

Karl


#7

Hi Karl

Wx permitting I’ll be on Beacon Batch G/SC-003 on Saturday and planning to use 40m - I’ll keep an ear open for you and let you know how the new antenna is doing.

All the best
Martin


#8

I think it’s a good thing. It clearly isn’t the only important thing to say an antenna is working well, but having a good impedance match is definitely a good thing to start with.
Best 73 de Guru


#9

[quote=“M3FEH, post:6, topic:11002”]Please explain.[/quote]A good dummy load has a 1.0:1 SWR. That doesn’t mean it’s radiating. (Well, if it’s intended to be a dummy load you’d hope it wasn’t radiating.) A low SWR on an antenna is just an indication that not much power is being reflected. In a good antenna, that’s because it’s being radiated. In a bad antenna, it might be that the power is just warming the local environment somehow or other, or being soaked up in the feeder, rather than being reflected. You’ll find out when you try to use it to make contacts. If folk start giving you two-and-two reports… :wink:

Me, I have the reverse problem. An antenna that was behaving quite nicely now has an SWR off the scale. I suspect a feed-line break. Time to check for tooth-marks and dry joints…


#10

I Built and been using now for over a year the SUPERLOOP 80 and I have it at about 60 FEET and I works great. 80 thru 10 meters plus WARC Tunes Great with the TS590S uses a 4:1 balun and a 300 ohm matching stub in the middle which just hangs loose. I put a heavy fishing line to a brick to hold it still and down vertical.
W4DOW (Dow Pierce) #1 Chaser in W4V


#11

Rick is on the money there. A long run of cheap coax will reduce the apparent SWR, sometimes by quite a lot. I’m not saying that you have that problem, but a lower than expected SWR would make me double check things before I was an entirely happy bunny! It is a nice little irony that replacing a long run of, say, URM-202 with RG-213 will give you a higher SWR AND a better result!

Brian


#12

Hi Brian,
Lets wait and see what the Antenna Analyser says. My guess is that the loop isn’t quite the correct length but the quarter wave Q-section of 75 ohm coax is making an apparent 50 ohm load for he SWR bridge on 40m. This doesn’t mean that the loop wont perform, only that (IMHO) that it will perform better when at resonance.

By the way Brian, you were putting out a nice signal in this direction when you were chasing this afternoon.

73 Ed DD5LP.


#13

Hi Dow,
That looks interesting, but I think its a loop that is hung vertically isn’t it? Radioworks says it is somehow both horizontally and vertically polarised.

In any case the loop that Karl is putting up and I have used for about 4 years in different locations is a horizontal one. Someone called it a DX_buster I think. In any case, it’s simple. cheap to construct and fun to use. My 40m one works well on 20m as well but is a compromise on other bands. My article on the antenna if anyone is interested is in the February 2013 Central Coast ARC “Smoke Signals” magazine here - https://www.dropbox.com/s/irenyywe2umrgao/SS%204101%20February%202013.pdf?dl=0

73 Ed.

P.S. I have used a cut down version (3.5m instead of 7m poles and ultra-thin wire-up wire instead of gardening wire) on a SOTA summit once. It worked well but needed an 11m square piece of ground to set it up. Perhaps the 20m variant would make more sense.


#14

Its hanging just like the picture the (2) 56 ft sections is Hoz and the twin lead hangs down ver. Thats where I used the fishing line onto a brick to hold it stright down and not flop in the wind. It works great for me…
Dow


#15

Well no appear to be heating clouds working into Southern France, S52 and OM on 20m.

BUT main noticeable thing is on 10m
Lot easier to bring down the SWR via the ATU and the reflected needle is nice and steady now at rock bottom.
Before it did move around a bit on the G5
Just for the forwards one does it bit now as normal

must be doing something right :wink:

PS yes it is a hoz antenna

Karl


#16

Hi!! Congrats for your loop. In my opinion, this antenna is a real winner in terms of efficiency. But have in mind that you can adapt the Z, trimming the RG6 (V.F. 0,66) to 1/4 lambda x 0,66 segment and then straight to 50 ohms coaxial (any length) to rig. I always have good efficiency in all bands when feeding loops with this method. It´s easy, cheap, less noisy, light and efficient.
Regards
Javier
EA2GM


#17

Thank you

The RG6 is trimmed to 1/4 wave length X.7 of the 75ohm RG6 am using.

My friend says now next stage is to get hold of analyser and fully tune it in
But have noted how much easier it is to tune in on 10m through the ATU .
Now can leave the ATU set on 20m and go through ATU for 40m and 10m little adjustment on antenna matcher on E

15m still needs band changer to B as before

BUT main difference on the G5 when on 10m had to tune it to about 1.7 or the ALC would cut off on me T120V even backing off mic gain no help.

Plus had back reflection on the reflector needle moving about. NOW can tune straight 1.1 and below no reflector movement and the ALC behaves, so much easier and its working as good as the G5 was with some what less noise.

Making some nice contacts across Europe at moment on 40 and 20 awaiting 10m to open as feel its going to work better on there than before with minimum of loss to antenna.

But the main feature is its a lot tidier than the G5 was with ladders here coax there posts here to take away from ground the coax etc. And the other half ain’t whining about it so there’s a bonus. she not even mention it surprised me, when G5 went up there was some moaning and whining LOL

Karl


#18

I have made and used several Delta Loops in triangle config /_\ _ fed in one of the bottom corners. I got the most use out of a 30m delta loop at home working into USA any night of the week on cw. During the last SOTA 12m challenge I used a 12m delta loop fed the same and worked dx. For a vhf contest I quickly made up a 6m delta loop to use out portable and worked vk4s and vk2s in that particular contest… The one I had for 40m worked well but the limb of the gum tree fell down and I was never able to set it up again in my yard. Now formula for all those loop was.
frequency divide into 300 then divide that figure by 6 . That is how long the 75 ohm coax needs to be to become the matching transformer , then into 50 ohm coax to rig. Quad shield is good but I can not solder it and that could be a problem if making a long term use antenna.


#19

Hi Karl,

You sounded OK when I heard you working Rod MI0JLA a short time ago.

Do you have any sort of Balun where the loop meets the coax? You really should have, as the loop is a balanced antenna & coax is un-balanced.

If your ATU will accept balanced feeder then using ladder line all the way from the loop to the tuner would be better, although maybe not as convenient with walls & things to pass through.

That said, feel free to experiment :smile:

I don’t know if you’ve mentioned how high above ground the loop is, but at that length it should be good on 40m when the F2 critical frequency is high enough for NVIS on that band or for local EU contacts.

On higher bands you may find it works better in some directions rather than others, this can sometimes give you surprising DX contacts. My antenna was originally an 80m circumference loop, but I now use it in various configurations. I mostly use about 60m of the loop (plus a large coil at the far end) tuned against ground, or with the other 20m section connected out of phase to reduce my local noise. It wasn’t designed that way, I found it had that effect by happy accident.

Thanks & 73,

Mark G0VOF


#20

Another thing you could look at Karl is WSPR.

Apart from being fun, its also an excellent tool for analyzing antennas accurately. I have recently just set up an Rpi through a low pass filter to emit some 10mW of power on 15M. You can leave it running through the night when your not chasing.

You will receive reports in dBm from other users who leave receivers running.

Jonathan.