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Re: Experimenting with Loop Antennas

Roland
 

Drawing of measurement points /g/loopantennas/photo/300189/3878148
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Re: Experimenting with Loop Antennas

Roland
 

I have no control over my external RF environment. It is what it is. OFCOM is helpful but things like residential PLC networks remain a PITA.
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I measured the inductance of my parallel loop construction at various measurement points. I disconnected the cables from the Amp before measurement.
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A) 2.3 μH (disconnected cables from the loop)
B) 3.0 μH
C) 1.6 μH
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For comparison, I measured A on my single loop --> same inductance. I was expecting a much lower inductance at C). The cables add a considerable amount of inductance. I have to consider reducing the spacing between the loops to allow for shorter cables and see how this impacts overall system inductance.
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Re: Experimenting with Loop Antennas

 

Hi Roland

Low noise floor is to be found in a rural location. Ie I have s0 ( sometimes s1) noise on a full size 40m vertical. Where as in london it was s9 if lucky.

See itu/r p.373-13 or similar..
Re: Experimenting with Loop Antennas

Roland
 

I will try the LZ1AQ Amp next. I live in a far from a "quiet" location. I wonder what you define as a low-noise floor.
Re: Experimenting with Loop Antennas

 

Roland..

You maybe improving the loop but not able to detect it or it may even seem worse IF your amplifier is not correct for the now lower impedance of loop.
This is why am suggesting use a good amplifier, one with a low impedance input that tracks the loop impedance as frequency increases.

Re noise floor, do you live rural, urban etc??
Re: Experimenting with Loop Antennas

Roland
 

The use of four connection cables of the same length (connected in parallel) has not brought any improvement
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Roland
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Re: Experimenting with Loop Antennas

 

A report of the value of the low noisefloor and bandwidth for each iteration would be useful for those of us on the email thread, please.

Dave - W?LEV


On Tue, Jan 21, 2025 at 5:28?PM Roland via <roland=[email protected]> wrote:
One step at a time, no need to rush. I change one thing at a time and observe the difference.
Define “low noise floor” and on which band.
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73
Roland



--
Dave - W?LEV
Re: Experimenting with Loop Antennas

Roland
 

One step at a time, no need to rush. I change one thing at a time and observe the difference.
Define “low noise floor” and on which band.
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73
Roland
Re: Experimenting with Loop Antennas

 

Hi

Try a better amplifier, one that tracks the impedance of loop..ie in production the Lz1aq. .plenty of info on here how to make an “ improved” one.
NOTE.. that is improved over the 2222 one on his website, NOT Lz1aq’s production model ( which is a different beast.)

I have built single loop, parallel loop ( similar to yours) and crossed parallel loops. All with tracking amps. ( improved” Lz1AQ’s using 5551’s.)

Single loop the “ worst”
The twin loop,
Crossed parallel the best..

BUT to get any real improvement one does need low noise floor at qth, or you will never really notice the difference. ( unless you built them wrong/ using poor preamp.)

Regards Simon
Re: Experimenting with Loop Antennas

Roland
 

RR Martin,
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that's exactly what I did. But the results were worse than before. I am now using 4 cables of the same length (430mm) and connected them like in the photo in the opening post (parallel). WSPR comparison has been running since midnight UTC. Unfortunately, it doesn't look like there will be any significant improvement, but let's wait until midnight (24-hour period).
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Interestingly, most of the bands (2200 - 80m) are better than my single loop. Only 40m is worse.
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73
Roland
Re: Experimenting with Loop Antennas

 

Hi Roland,
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I think we misunderstood each other.
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I meant for the parallel loops to remain connected in parallel, and in the same phase as before, but just swap one of the amplifier connections, across to the other end of the existing thick interconnecting cable you have between the two loops. This is to make the circumference of the two loops, including the interconnecting cables, the same as each other. At the moment, one loop has a longer electrical path than the other.
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Regards,
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Martin
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On Mon, Jan 20, 2025 at 11:56 PM, Roland wrote:

As I mentioned, crossing the connections had a negative impact
Re: Experimenting with Loop Antennas

 

On Mon, Jan 20, 2025 at 11:23 PM, Roland wrote:
I can no longer add inline pictures to a post for some reason.
Hi Roland,
you can upload photos to an album in the "photos" folder and put a link that leads there.
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regards
Fred
Re: Experimenting with Loop Antennas

Roland
 

I meant VGA
Re: Experimenting with Loop Antennas

Roland
 

As I mentioned, crossing the connections had a negative impact. The VAG of the RX888 has its limits and can't compensate for every situation. Now that I have connected 4 cables of the same length, the RF gain is the same on both RX888
Re: Experimenting with Loop Antennas

 

开云体育

should not rf gain etc be the same in both pictures??

dg9bfc sigi

Am 21.01.2025 um 00:23 schrieb Roland via groups.io:

I can no longer add inline pictures to a post for some reason.
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Crossing the cables at the amplifier has made it worse. I can easily determine this by looking at the input signal of the RX888.
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Dual Loop crossed connections at Amp. RX888 signal input level
Single Loop. RX888 signal input level
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WSPR confirms the negative impact of crossed cables at the Wellgood Amp
I will make cables of the same length for all 4 connections from the loop to the amplifier and test again.
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Re: Experimenting with Loop Antennas

Roland
 

I can no longer add inline pictures to a post for some reason.
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Crossing the cables at the amplifier has made it worse. I can easily determine this by looking at the input signal of the RX888.
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Dual Loop crossed connections at Amp. RX888 signal input level
Single Loop. RX888 signal input level
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WSPR confirms the negative impact of crossed cables at the Wellgood Amp
I will make cables of the same length for all 4 connections from the loop to the amplifier and test again.
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Re: Experimenting with Loop Antennas

 

Hi Roland,
If you are doing cross parallel connection with loop configuration on your earlier pictures (cannot see the newer ones) with 2nd loop sitting behind the first one then its going to make things quite worse. You only should cross parallel loops when they are in the same plane (like described by LZ1AQ), so that your loop's currents are in phase. For your config it should be strait parallel.
Regards,
Simon

On Mon, Jan 20, 2025 at 3:07?PM Roland via <roland=[email protected]> wrote:
Crossing the cables at the amplifier has made it worse. I can easily determine this by looking at the signal input level of the RX888
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WSPR confirms it
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73
Roland
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Re: Experimenting with Loop Antennas

Roland
 

the cable lengths differ by 10 cm. I connected them crosswise on the amplifier.
Re: Experimenting with Loop Antennas

 

A cross connected pair of loops, or 4 cross connected loops as described by LZ1AQ, is likely to produce better results, but you should have noticed some improvement with the parallel loops relative to a single loop.
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As it is configured at the moment, the length of one loop is considerably larger than the other, and this will result in some phase and amplitude differences.
Before you move on from this configuration, I'd try to make the connections to the amplifier from both loops to be the same length. Maybe by crossing one of the amplifier connections across to the other loop.
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Regards,
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Martin
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Re: Experimenting with Loop Antennas

Roland
 

For the WSPR Results:
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HB9VQQ/RW3 = Single Loop
HB9VQQ/RW4 = Dual Parallel Loop
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