I built a fair number of these, starting in the '70s shortly after Radio Shack started carrying the NE555 timer. I usually used the Micronta 50uA panel meters for the readout. I'd watch for project boxes on sale in Radio Shack and surplus electronics stores. I used the dry transfer rub-on lettering, or sometimes I'd make the front panel out of PCB and etch lettering into it.

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Would suggest Tonne software ELSIE to design crossover filter. Tonne software is exceptionally good.

73, Alan G8LCO

Hello Andrew,

I have an elderly ALA100 amplifier & power injector.?

It is working very well, but I was wondering what recommendations you might have regarding the actual loop.?

I currently have a vertical rectangle approx 25ft horizontally & 15ft vertical with the bottom of the loop around 8ft AGL all supported on 2 fibreglass poles as far from housing as possible.?

Any suggestions for me? I don’t have any specific problem but wondered whether a different loop size or format might bring benefits?
My naim interests are MWDX, amateur bands reception from 160-10m & generally tuning around between 10KHz & 30MHz.
My environment is unusual, sandwiched between the M4 motorway / Welsh hills & the steelworks in Port Talbot about 800 yards from the Bristol Channel.

As it stands, it works very well for me.

Any input welcomed!

On Tue, Jan 4, 2022 at 07:34 PM, чавдар левков wrote:

I was not aware about your postings on this topic. Excuse me for that, you are ahead of me in technology.

Hi Chavdar,

No need to apologise, my webpage regarding the system is quite well hidden, and I haven't done any further work on it for several years.

At the time I was trying to develop a low cost system around an RTL dongle that could be used to map VDSL noise by driving around the affected area. The intention was to encourage local radio clubs to have a system that could be borrowed by members, in order to locate VDSL hot spots, and then to be able to provide evidence to the UK telecoms regulator in order to try and get the problem resolved.?

However there wasn't as much interest as I'd hoped, and the available software wasn't that easy to use. So in the end the project got put on hold, and in the meantime a new set of other interference sources, such as Solar PV and Car chargers have become more problematic.

I'm still hopeful that one of the SDR software authors will at some stage add the ability to use GPS co-ordinates. But at the moment Winradio is the only company I know of who are offering software a price that is unfortunately still not quite affordable to the average hobby user.



Good luck with your experiments, and thanks for all of the really useful and detailed information on your website.

I have found your recent index of articles to be particularly helpful in finding items of interest.



Regards,

Martin

On Wed, Jan 5, 2022 at 04:00 AM, Tom Seeger wrote:

You mean anything below 14 MHz?comes from the loop and anything above 14MHz?comes from the dipole? I think you would have to make your own.

The device you require is called a diplexer.

Tonne Software provide a free design tool.



Don't worry about making it too complicated. Two coils and two capacitors should be adequate for your purpose, but there will be some interaction between the two antennas around the cross over frequency. So I'd try to make this cross over away from any frequencies of particular interest, and chose a bit of the spectrum that is relatively quiet instead.

Send me a PM if you need any help with the design and construction.

Regards,

Martin

Hi Steve,

Maybe you could possibly help me out. I?just purchased the Chameleon RXL receive loop. And now I wish I had found this thread before doing so. I’m very new to these antennas. I currently use a Ciro Mazzoni Baby Loop antenna for transmitting and receiving. And I wanted to have a receive antenna that didn’t have such a narrow bandwidth. So I opted for this. The RXL.

The problem that I am having is an extremely high noise floor with the RXL. Well over an S9. It completely blankets the lighter signals. I think the guy from Chameleon said it was a really hot signal. So my question to you is, Can I put something inline like some sort of receive filter to attenuate some of that noise??Or would it require a different preamp??Like I said, I really don’t know much about these loops.?

But what I do know is that when I rotate the loop, the really hot part of the signal goes away on the scope but I still have a noise floor of an S7 to S8. It’s louder than any interference that I get on my Ciro Mazzoni mla or my portable vertical antenna.?

I’m hoping you could possibly help me identify what’s going on with this loop. Hopefully you will have some sort of idea as to what I’m up against. Let me know if you need any other details.?

73,
Phil Schuyler, ?KN6NNO?

?

You mean anything below 14 MHz?comes from the loop and anything above 14MHz?comes from the dipole? I think you would have to make your own. You will need a lowpass filter on the RX side of your loops' bias-t and a high pass filter from the dipole. Both will feed a combiner, who's output feeds the Kiwi. Here is a link to a good filter design tool:

Here is a link for DIY splitter/combiners:

73 Tom

Is there a good band pass filter you would recommend that I could have anything below 14Mhz goes to loop and anything above goes to my Dipole?? (For KIWISDR receiver)

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Hi Martin,
I was not aware about your postings on this topic. Excuse me for that, you are ahead of me in technology. I read them with great interest. I will add them to the links in my article. Yes GPS sync is a need if a "noise" map? must be drawn but I have made these recordings just of curiosity to see? what is going on with the man made noise in my county. The most important result was that I compared? the minimal recorded noise with the noise at my house - so now I know "where I am" . The VDSL systems are very rarely used here.- most common are LAN cables and cable TV. The telephone lines do not exist here any more - everything is GSM.? I choose 3.5 MHz as a center frequency? because in semi-urban areas I have noticed that there the noise level has a peak (between 2 - 4 MHz) I do not have an explanation for that.? It will be interesting? for someone else to make similar recordings in order to compare the noise pollution.? We do not need? precise calibration - the level of the noise in quiet places is a good reference point. The merit of pollution will be? Nc/Nq?? where Nc is the current noise level? and? Nq is a quiet place noise level measured in the same date and time(approximately) . (or Nc-Nq in dBm). This can be done by car (or bicycle? : -)
Chavdar lz1aq

On Tue, Jan 4, 2022 at 05:30 PM, чавдар левков wrote:

I have made some measurements of the ambient electromagnetic noise during car drive.

Hi Chavdar,

A very interesting post, and something I would like to be able to do better.

If you could capture GPS co-ordinates you could produce a heat map, something like this on one of my webpages.



I used a mapping add-on in Excel to combine the data and overlay it on the satellite map images.

I've been trying to persuade various popular SDR software authors to include the option to add GPS derived co-ordinates to recorded signal strength logs in order to make this task easier, but no luck so far.

Good luck with your work.

Martin

I have made some measurements of the ambient electromagnetic noise during car drive.

?Happy New Year to everybody. ?
Chavdar LZ1AQ

May I suggest also the Elad S2 ?
I have both the Perseus and the Elad S2, and have performed A/B comparisons, and to my ears they perform similarly.
The Elad S2 is quite sensitive down to 10 kHz. I have used it last Christmas Eve to receive the annual SAQ transmission, and you can see the results here :


And the Elad S2 is about half the price of the Perseus....

73? Alberto? I2PHD

But do remember that active antennas are normally powered with DC down the coax too!? You only need to put substantial capacitance in the common ground to avoid issues or use an autotransformer with a C in the common.? Turns ratios of? 5:4 or 6:5 work well but 11:9 is almost perfect.


73 Alan G8LCO

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Q. Why would anyone use locking compound on plastic?

A. Because they think it will lock parts together without the risk of cracking when overtightening.?? (You advised locking compound with nylock nuts.)

People generally use too much compound, only a minute amount in the thread space is needed. If excess runs off onto plastic parts then they can disintegrate over time. There are a very wide range of plastics nearly all of which are compounds with various additives to improve moulding properties, colour, flexibility and toughness so the reaction to compound solvents is hard to predict. People may think that Plastics are solids and impermeable however that's not true for many plastics. Nylons absorb water for example as do some uncured silicone rubbers which " set" through their bulk? by exposure to water.

Thread locking compounds set to a plastic mass when squeezed between metal surfaces, the exclusion of oxygen and the presence of metal ions trigger the reaction. So the compound cannot work on plastic parts but the solvents may enter microcracks in plastics and cause extensive damage to some plastics. Obviously the product is supplied in a plastic bottle -not all plastics are at risk!

See

A safer option is to use two nuts, the second being used as a lock-nut.

73, Alan G8LCO.

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I appreciate this SDR discussion, and the information/links provided!

I have been on the fence for awhile between the HF+ and the RSPdx.

-- Andy - Arlington TX

If you have a complaint about posts, email the moderators. No one should be taking it into their own hands to decide what is on or off topic and complaining directly to anyone here.

Reply off-list.

--
Steve Greenfield AE7HD