Trying a fence loop antenna (with a balun this time)
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- Опубліковано 4 вер 2021
- A follow-up from my previous video at • Trying a fence loop an... where I tried 30m of wire around a fence with very noisy reception.
This time I try 20m of wire to form a sort of a pulled out folded dipole on 14 MHz. But now I feed it with a 4:1 balun and compare with an unbalanced feed (which should be inferior). Is there much difference? Watch and find out.
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Hi Peter thanks for the video it was great and you are on the right track. I have spent 12 months working on a ground loops and and have perfected it to the point that I have been able to demonstrated it at workshops and ham clubs to the amazement of the onlookers. My ground loop system comprises of many parts.
1 Is a ground loop for 20mt with no earth contact.
2 Low noise preamp powered by a single lithium cell also in a utility plastic box with a power led with an electro across the leads of the led to reduce noise and changeover switch.
3 Inside the box is a isolation balanced 400 ohm input toroid transformer red or yellow 3mhz -40mhz out of a (computer power supply) wound as 12-14 turns 75% coverage to 400ohm balanced to antenna 2-3 turns overwound output to 75 ohm held in place with hot glue.
4 The preamp amp using a BFR 91(25 @$10 AliExpress) construction is simple solder a 100k resistor to base and collector then 1k resistor from collector to +supply and a 50pf cap from the collector to output to radio via 75 ohm quad tv coax.
5 Input to the preamp solder a 100pf cap to the base of the transistor to the toroid connect the spare wire to the emitter of transistor and from there to the negative of the battery.
You may ask why 75 tv cable quad covered? the answer is it is low noise and low loss up to 800mhz and good for long runs plus cheaper then the 50 ohm, that plugs into a RX-TX box with a 75 ohm toroid to 50 ohm that connects to change over relay in a plastic box that sits behind my I-com 718, the relay is in the plastic box is activated via the PTT line to an RCA in the back of the rig to the relay box.
So the end result is one antenna for TX and the LOG for RX only.
The RX loop is so good I can hear nearly all the beacons on 10mt as well as the CB heterodynes on ch5. the other day there was a fluttering on 20mt that I thought was a fault in the radio, stupid me the LOG was picking up a Doppler effect from a big plane in the distance arbour 10 degrees above the horizon.
I am so impressed with the low noise and the gain of overseas QSO from the west coast stateside every afternoon.
PS I am going to use LITZ wire on the transformers for higher Q and varicaps to tune the loop into resonance.
Thank you for allowing me to post this as it has been an adventure for me as I hope it will be for you and anyone interested (that is what ham radio is about lots of fun!)
73,s VK4ZOW
Hey Peter,
I was using an Icom 7300 at 100W with a Hustler 6BTV vertical on 20m when you worked me on FT8 in this video.
My noise floor on 20m isn't amazing and around dinner time the neighbours turn their kitchen LED lights on which increases the noise floor two or so S units..
- ZL4KYH
I read somewhere that baluns mostly help to even out the radiation pattern of symmetrical antennas. So noise could actually become worse if it's from a direction the pattern shifts to under balanced conditions.
TeamReplay for the win
I ran a 43m loop antenna support between 2 points at 35 feet hjigh then sloping the wire down to a 6 foot high wooden fence.The antenna wire was insulated from all points of contact.The two ends of the wire was fed into a W&S cheap 4:1 balun which was attached to a Ugly balun 4 inches diameter with 25 feet of RG8 mini coax terminated with a SO238 ,the outerside of the SO238 was connected to a earth going into the ground below the balunThe antenna was fed with 15m of RG8 mini coax straight into my Kenwood TS570 with a good earth.The prime frequency of the loop was 6.83 MHZ,the radio had no problems tuning when it had to (80/160m) and I made contacts all over the world with no problems.The noise level was lower than my other antennas and the signal incomming and out going was better on the loop.
Hey Peter - interesting result. Kind of surprised that there was zero difference in noise. It appears that the loop was better at general receive performance, but that noise is pretty intense.
Have you tried listening in AM and seeing if that buzzing is 100/120 Hz? Maybe there's a leaky powerline near you?
Thanks for doing an A/B comparison. I've thought about doing a loop on the fence, but for now, I'm loading up my rain gutter and have hung multiple 1/4 wave counterpoises on the fence. It works decent, but is still quite the compromise. From Texas, I've worked Japan and central Europe on 80M. It gets me on the air in an HOA-restricted area. :-)
As a receive antenna, have you tried a loop on the ground? They seem to be lower in noise and gaining popularity again here in th UK.
Peter if you are going to sit that far from the camera, you need to wire a microphone (Wired or wireless) You'll be easier to hear with less ambient noise. G7VFY
Loop on the ground antennas are meant to be quiet receive antennas
A couple of things: How noisy is your QTH? Have you swept it and surrounds for local QRM/RFI? Also, that antenna is very close to the ground.
Hi Peter! Can you compare to any other antennas that might give you better signal / noise in your garden? Mag loop, vertical?
Or a Beverage (receiving) antenna
Was that definitely a balun? Just it has UN UN written on the side.
I was waiting to see how long it would take for someone to notice. I might try a different one and see if there's a difference!
That noise sounds like RFI, so no surprise the balun makes no difference. The noise is all being picked up by the antenna, not just from the feedline system
Peter, can you describe how you connect your laptop to your 817's data socket, and how you manage the transmit of your WSPR? (i.e, do you use the PTT button at the right time, or have a relay set up, or some kind of super secret setting?) Cheers! VK3FLTR
FS: I've got a video on an interface cable that describes it. Uses the transceive's VOX.
ua-cam.com/video/3wmxyo1RzaE/v-deo.html
@@vk3ye Thank you!!!!!
@@ssbfmcw Thanks for the link!!!