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Old November 26th 14, 10:20 PM posted to rec.radio.shortwave
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Default Successful indoor antenna at last - I think

Le 26/11/2014 17:53, Ross Archer wrote :
I do have a Sony SW7600G so if I came across an(other) AN-LP1 I could pair them up and try the pair against it. Not in my immediate plans as they're a bit hard to find and not that versatile if I recall -- being tied to Sony radios if memory serves.


No the AN-LP1 is usable with any radio. The only advantage of - some -
Sony radios is they can switch on the antenna module remotely when you
switch on the radio.

I used it with a Sony ICF-100, Tecsun PL-390 and Sangean ATS-909 with
success. My best antenna remains my (grounded) external long wire that
lays along my roof...

Charly



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Old November 27th 14, 12:04 AM posted to rec.radio.shortwave
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Default Successful indoor antenna at last - I think

On Wednesday, November 26, 2014 2:20:08 PM UTC-8, Charly wrote:
Le 26/11/2014 17:53, Ross Archer wrote :
I do have a Sony SW7600G so if I came across an(other) AN-LP1 I could pair them up and try the pair against it. Not in my immediate plans as they're a bit hard to find and not that versatile if I recall -- being tied to Sony radios if memory serves.


No the AN-LP1 is usable with any radio. The only advantage of - some -
Sony radios is they can switch on the antenna module remotely when you
switch on the radio.

I used it with a Sony ICF-100, Tecsun PL-390 and Sangean ATS-909 with
success. My best antenna remains my (grounded) external long wire that
lays along my roof...

Charly



On your roof antenna, is there any kind of transformer/balun between the antenna wire + ground and the lead in wire/coax/ladder line?

There's something tricky about coax you probably know, because you grounded your antenna.

People often think that coax is a magic noise cure because the shield prevents signals from getting into the center conductor from the outside. But there's something very tricky that happens because signals can travel along the OUTSIDE of your shield just like any hunk of metal.
Noise which hops on the outside of your coax in the shack can be conducted outside to the vicinity of your antenna, where the antenna "legitimately" picks it up and sends it down across both the inside of the shield AND your center conductor just like any other signal your antenna picked up. Then the noise you tried so hard to eliminate is still making it into your gear.

So grounding, especially near the antenna, is important. As you knew but for the benefit of anyone who didn't

-- ross AF6BV


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Old November 27th 14, 03:17 PM posted to rec.radio.shortwave
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Default Successful indoor antenna at last - I think

On 27/11/2014 01:04, Ross Archer wrote :

On your roof antenna, is there any kind of transformer/balun between the antenna wire + ground and the lead in wire/coax/ladder line?

There's something tricky about coax you probably know, because you grounded your antenna.

People often think that coax is a magic noise cure because the shield prevents signals from getting into the center conductor from the outside. But there's something very tricky that happens because signals can travel along the OUTSIDE of your shield just like any hunk of metal.
Noise which hops on the outside of your coax in the shack can be conducted outside to the vicinity of your antenna, where the antenna "legitimately" picks it up and sends it down across both the inside of the shield AND your center conductor just like any other signal your antenna picked up. Then the noise you tried so hard to eliminate is still making it into your gear.

So grounding, especially near the antenna, is important. As you knew but for the benefit of anyone who didn't

-- ross AF6BV



Hello Ross

Yes it is grounded AND I use a home-made balun between the antenna wire
and the coax inside the house. (Equivalent to circuit C as shown here :
http://www.dxing.info/equipment/impe...er_bryant2.doc)

Certainely far from perfect, but so far it has the best signal/noise
ratio in my place, better than the commercial antennas I mentioned earlier.

Charly
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Old November 27th 14, 03:23 PM posted to rec.radio.shortwave
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Default Successful indoor antenna at last - I think

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



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