Discussion in 'Amateur Radio News' started by KD5W, Jul 18, 2021.
I always wondered what kind of receive antenna you could make with one of those!!
It's up to each person to decide what's enjoyable to them. That's what's great about this hobby, so many aspects to enjoy!
Great point. I care not one single whit about FT anything - for me, it's too much computing and not enough real radio. Thankfully, what I think shouldn't detract from those who do find it to be cool and the thing for them. I enjoyed playing with PSK and Olivia modes (and a couple earlier sound card modes. Not too bad - but looking at the FT modes, I just came away with ... 'nah' after loading it and playing with it a touch.
As Onno, VK6FLAB is fond of mentioning from time to time, this is a hobby with almost endless facets. Folks should do what they like.
Unless I missed it in the thread, the balun should really be a 9:1. I believe you said it was wound to match the 75 ohm coax which will hamper performance. It should be wound to minimize the mismatch of the antenna feedpoint impedance to the characteristic impedance of the coax thereby reducing feedline loss. Typically a 9:1 is a better choice and the use of mix 77 beads will enhance low band performance. I have attached a pic for reference
Ref Antenna laying on ice- A family friend, KL3BD (sk) Bob Douglass from Kotzebue, AK (just above the Bering Land bridge) told us about the time he made the first 6m activation from up on Denali (Mt. McKinley) using a dipole laying on the ice. He wk'd a few stns on cw and phone, direct and via Es. Bob climbed Denali a few times. Any KL7- Motley & Bush Net hams reading this might have more info.
I live on a very small city lot with no chance for a long straight dipole. My OCF dipole is above the house and goes out back and makes a 90 degree turn. Also have a 5BTV with ground radials. Both antennas work ok, but not great, they get me on the air. Came across the KK5JY.net web page about the LOG. Being in a very dense area of the city I get all kinds of noise on both the horiz and vert antenna's. Decided to try Matt's LOG antenna, figured what do I have to loose. Hooked it up to my 7610 as a RX antenna and gave it try. That's what we ham's do right! Is it an end all RX antenna, NO, but does it pull in the signals at a lower SNR sometimes so I can copy them. On the RX LOG the signal might be S3 and on the OCF dipole the same signal will be 10 over 9. Both are 59 copy, only the LOG is a lot easier to listen to with a much lower SNR.
While on the 7610 I will often time just mute which ever RX is not working good and/or noisy. I simply view this LOG antenna as just another tool that gets the job done once in a while.
I've never considered using a LOP for a receive antenna. But I have experimented with 600 foot long BOG's.
I found one to hear pretty darned good in the desert north of Las Vegas. In reality with the poor ground conductivity the electrical height was maybe 20 feet above ground, a total guess?
I ran the same receive antenna in the upper Texas coast but well inland. The ground conductivity was high there so the BOG didn't work at all.
Normally I keep my beverage antennas approximately 10 feet above ground.
Well, here's my 2c worth on the LoG antenna.
Like all antennas, it is a compromise. It is not perfect in all situations.
It's advantage is low noise. OK, it takes everything down to S-Zero. But, most times, a signal buried in to noise will work it's way to the top and be readable where it was not before.
I use a 60ft loop on desert sand. During the last SSB contest I worked 13 countries on 15 meters using the LoG as a Rx antenna.
On 75M, I can have an S-9 noise sometimes. The LoG works great on 75M as well.
Does it work great on all bands for all stations. No. But good enough, often enough for me to leave it in place and use it as needed.
Give one a try. Crud, it only takes 60ft of wire. If you don't like it, pull it up.
Here is the one I designed mine after.
I have had a 60 foot diamond shaped loop on the ground deployed in my front yard for a little over a year. At first it did not work very well, until I wound a beverage antenna transformer and put it at the feed point. Now it works very well on all bands 40-160.
I have 120' deployed and can pick out signals on 80M that would be buried in the QRN hash. There is a 2:5 transformer required at the feedpoint. 73
Useful, thanks. I'll give one of these a go this winter. I've experimented with all sorts of RX loops in attempt to get past the crud polluting HF these days and had heard about LOGs before/
I think a big part of the trick with these RX antennas is to choke off the RF from the coax braid to prevent pickup of crud as they get near the house. I also use multi turn toroid chokes on the outside wall before the coax comes into the shack
A LoG has directionality too, unless all the models and measurements are wrong and it's really the world's first Actual Isotropic Antenna.
And yes, it has rather low "efficiency" (peak gain), but as anyone knows, efficiency is not a figure of merit for receive antennas. Unless it's extremely low, efficiency has no effect on the usability of a receive antenna. A K9AY has similarly low gain; is that a "poor" antenna that's being "rescued" by something-or-other? No, it's a great receive antenna, that would be poor if you were silly enough to use it for transmit.
Now, is a LoG a great receive antenna like a K9AY? Nope. Its pattern is nothing great, with just a few shallow nulls in the horizontal plane, and a generally NVIS elevation pattern, as you'd expect for a low horizontal antenna. But it's a perfectly usable receive antenna, that can be built for cheap, that can be set up in an hour, that can be installed in places where various obstacles would prevent other kinds of antennas, that requires practically zero maintenance. It's not a dream antenna, but it's a perfectly reasonable one, worth playing around with, especially for people who can't move their TX antennas away from a noise source, and for one reason or another can't put up another design (or can't do it yet).
In all the discussions and articles on the LoG, including kk5jy's, I have not seen info on the actual antenna wire which should be used. Will just any wire -- insulated single solid strand or multi-strand work? I have a spool of 18 gauge, originally meant for underground electronic dog fence. Will this work? Thanks.
That would work fine for a LoG. Solid or stranded wire works.
I've used both on my LoG. (100'x100' square). Hooked up to my SDR, the signals on the LoG would swamp my RSP2. Low band only. Performance north of 40 meters is terrible.
My 60' perimeter LoG is made with CAT6 UTP, all strands twisted together. Works pretty well. I would assume just about anything that is 18 ga or larger and is not shielded would suffice.