On Wednesday, November 26, 2014 8:48:19 AM UTC-8, Charly wrote:
Le 26/11/2014 00:57, a écrit :
On Tuesday, November 25, 2014 3:44:35 PM UTC-8, Kevin Alfred Strom wrote:
On 11/25/2014 2:05 PM, Ross Archer wrote:
Hey folks,

Thought I'd share the results of some recent successful indoor
antenna experiments. I wanted something to take on the road and
also use when an outdoor antenna isn't convenient or practical.
[...]




Sounds very good. I imagine it would really improve hotel-room
reception over the whip built in to my Eton E1.


Thanks,


Kevin, WB4AIO.

It's interesting when you break the loop circuit (switch located halfway between the ends of the loop) how the signal sometimes goes up (though more often it goes down) but the noise nearly always increases.

There's definitely something about the loop configuration that is rejecting electrical noise.


Hello Ross,

It would be interesting to test it against some commercial products such
as the Sony AN-LP1 loop antenna, Tecsun DE31/Kaito KA31, or the
Wellbrooke used by Drifter (certainly not in the same category).

Can you have this opportunity ?

Good SWL,

Charly

My goal for this "product" is to beat the signal-to-noise performance of any feasible end-fed indoor wire antenna. Next up I'm thinking of a small amplified loop for travel but this one is intended as a substitute for the generally mediocre end-fed wire to whip or antenna jack solution that mostly just boosts noise along with signal. The kind of thing you can throw in a suitcase and if it breaks or gets lost you won't cry. Try that with a Wellbrook loop.


I'm now logging signals on a recent listening test I have never before received with any *indoor* antenna. All India Radio on 9870 (1414), CKZU on 6160 Khz (1423), VOIR Iran on 9800 with strong signal on 1442, and R. Romania Int'l in Russian on 11985 (1453) - tentative ID for that one. I am relatively certain this antenna delivers plenty of signal and at least in the environments I've tried it so far, noise is definitely lower.

TI has some interesting differential video amplifiers that might make a good small travel loop that could be made cheaply. If I start fiddling with this, that's when I'd get a KA31 for comparison.

-- ross

On Tuesday, November 25, 2014 11:05:38 AM UTC-8, Ross Archer wrote:
Hey folks,

Thought I'd share the results of some recent successful indoor antenna experiments. I wanted something to take on the road and also use when an outdoor antenna isn't convenient or practical.


I'll preface by saying I've played with various active and passive antennas over a period of years and discovered that very few improved the signal to noise ratio of signals and so I've always given up and gone with an outdoor antenna. This means travel = no shortwave

But, Success. If I thought there was a way to monetize this I'd build and sell it, but instead I'll share it with you guys for free.

Quick summary: it's a loop.

Longer summary: It's a physically big-ish (sort of dominates a small room) but electrically "larger sized small" indoor loop with a transformer coupling

Details: 25 feet of copper hookup wire with the ends soldered to the secondary terminals of a mini-circuits T9-1 transformer (used because I have them in a junk box. The ratio is probably far from optimum but it works well -- it was chosen because it's what I had.) I cut the wire in half and joined the ends electrically at the center to experiment with both closed-loop and sorta-dipole configurations. (Short answer: closed loop works better, often much better, most of the time.) Also, if you travel with it it WILL get tangled, so being able to separate and untangle the ends is important..)

The secondary (with the dot) goes to a mono 1/8" plug to the portable radio's antenna input. It doesn't seem to matter in theory or practice which terminal goes to tip and which to ground. I used a twisted pair of regular wire to the radio but in theory a shielded cable would be more appropriate..)

Hang antenna with two supports to form a big triangle. This part can require some creativity. I have wooden shelving which serves brilliantly for this purpose.

Mechanically this antenna is a mess. You'd want to build a box for the transformer and a plug for the cable to the radio. That's next and I leave the mechanical details to you.

The point is it's simple, uses no batteries, requires no tuning, can be packed easily, and seems to outperform an end-fed wire every single time in the test environment I tried it.

Some notes:

Noise pickup is reduced -- which is the hardest part! Signal strength is more often than not higher when the antenna is a loop than when the center wire is disconnected in the same physical layout. Even when it's not stronger, the noise level is better in the closed-loop configuration. So far.

WIthout the transformer, many radios I've tried will overload badly due to broadcast band overload well into the 60 meter band. The transformer also may help reduce noise transfer, though the results were so poor without it for other reasons I didn't bother doing any further testing. I think some kind of magnetic coupling (ratio may be relatively unimportant) is an essential part of why this works, but I'm really not sure of the reasons. Point is, the transformer is apparently an important part of success.

Signal strength does not appear to be particularly affected by antenna orientation. Probably the mix of horizontal, vertical, and diagonal wire is helping reduce polarization fading.

You could wind your own transformer with a toroidal core. The winding ratio is probably not so important although a step-down configuration may be better if you're trying to match a coaxial cable.
The only thing is you want to be sure the transformer passes 3-30 Mhz range. The mini-circuits part does that, but surely that isn't a hard thing to accomplish.


If anyone feels like fiddling with this "transformer coupled medium-sized indoor loop" they are welcome. I can't guarantee results in the general case but it's the best thing I've tried so far by a big margin as far as pulling real signals out of the indoor noise soup.

I finally caught CKZU on 6150 with this which was simply impossible before in the noise soup of this condominium.

Cheers and hope all are having or planning to have a great Turkey Day

-- ross

Sounds like you have a pretty good setup to pick up skybouncing goodness. Glad you are having success. What you have is what I want to set up next.

-- ross