On Thu, Dec 30, 2021 at 02:26 PM, Emil 'Todd' Zelasko - KA8GEF wrote:

Someone posted a link to a site where the LOG was tested quite thoroughly and improvements were suggested. This is an excellent assessment of the LOG.

Maybe this one ?



Another bit of shameless self promotion :-) But maybe at least some of it is helpful to others.

Regards,

Martin

On Wed, Dec 29, 2021 at 06:08 PM, vbifyz wrote:

Note that the key to noise mitigation is a good ground. Without it not much can be done.Hi Mike,

It depends upon the antenna configuration, for example balanced antennas don't require a ground, and also how do you provide a 'good ground' when you have a first floor radio room or live in an apartment complex ?

However if by a 'good' ground, you really mean that all items of equipment should be properly bonded together, in order to maintain a low value of impedance between them, then that's a different issue.

Personally, for this reason, I don't think the commonly used term 'grounding' is the best to use in this instance (maybe equipotential bonding would be preferable), as for many it simply conjures up connecting everything to an earth rod in the hope that this will somehow magically resolve all known interference problems.

Maybe it's just me.........

Regards,

Martin

There are certainly some great suggestions/alternatives here.

Specific to the LOG antenna, I have tried this due to an unbearable power line noise level when it rains.

Here are my thoughts FWIW:

- First- be prepared for a much lower level of signal strength (obviously) compared to a dipole. This takes some getting use to. A low noise pre-amp is required to improve this condition.
- I used 15 foot sides with a feedpoint in the center of the side facing intended directivity (albeit slight). If you intend to go above 10Mhz, 30ft per side may work better.
- Wire placed ~3 inches above the ground will perform better than the LOG buried or at ground level.

Someone posted a link to a site where the LOG was tested quite thoroughly and improvements were suggested. This is an excellent assessment of the LOG.


-?

On Thu, Dec 30, 2021 at 11:27 AM, Chris Wilson wrote:

I wonder why the spare injector box is so dire, there's not much to go wrong with such a simple circuit, surely

It is indeed amazing that something apparently so simple can be so hard to get right.

I've gone though several iterations of bias tee designs, before I'd got something that actually performed as I'd hoped it would.

The main problems with many commercial versions are the lack of proper DC supply filtering, and the use of inductors that are far too small with insufficient current ratings. When they carry DC the core saturates and the inductance value can be further reduced, in some cases by a very large percentage.

Regards,

Martin

Hello Alan,

Tuesday, December 28, 2021

I did check the coax from the connector to inside of the injector box, but the issue is one box is potted and the coax disappears within the potting compound. However, the outer shell of the flying lead coax connector has perfect continuity to the outer shell of the BNC antenna connector socket on the box.

I found and tried the spare injector box, which is not potted, and it was as I recalled, very poor, the signals were very week and running the spare box for about 18 hours of WSPR on the Kiwi gave dismal results.

Having sacrificed DATV stuff for a long test results with all power to the external dish pole mounted DATV box has shown the best performance so far from the loop.

I intend physically moving the loop out into the back woods, and running a maybe 75 meter coax. The coax will have to be suspended from trees above head height, burying it amidst thousands of roots is just too much hassle and destruction.

I have made a lead up to power the Kiwi from a battery, so will start going after other noise sources. i suspect my Trimble Thunderbolt 10 MHz GPS locked frequency source and frequency divider may be one, but I need to clamber up into the loft to turn it off, and it looks like the wife has got Covid, so I am keeping out of the house and in the workshop as much as possible, and sleeping in the spare room!

Thanks Alan, I hoped and thought you'd found something there, what with it picking up BC stations so well with no antenna connected. A good shout though, for which I thank you.

I wonder why the spare injector box is so dire, there's not much to go wrong with such a simple circuit, surely


Best regards,
Chris mailto:chris@...


A> Chris

A> You did an amp powered/unpowered , while some signals went many strong
A> signals were there with no power. PLEASE check the coax from the power
A> injector to the receiver, if the screen is open that would produce your
A> symptoms. Best done by substituting the cable for a known good one.

A> Please check the coax Chris! Your results on PSK reporter don't look
A> too bad.

A> 73, Alan G8LCO.




A>

--

And to further underscore the point you can read the? response. That? ?allows garbage and polluting equipment to? enter the market because of petty money making objectives rather than enforcing the law or doing the right thing.

https://op.europa.eu/en/publication-detail/-/publication/45cfa024-1440-11ec-b4fe-01aa75ed71a1/language-en

You would almost think that is true.

I live in a remote rural/farming area. All big farms. 200 to 900 acres big, 3 phase electricity etc etc.? I built a EMC OATS for CISPR 32 testing as well as general EMC testing. It has become unusable because from these farm house there is so much high levels of? interference from electronic devices that is wiping out large chunks of the spectrum. Battery chargers that spew hash and birdies? well past 100MHZ. LED lights that use "Open Frame Meanwell style power supplies" These were meant to be used by professionals that build in filtering into equipment. They are being sold raw or naked without filtering to end users and consumers without? any EMC measures. They wipe out the whole HF spectrum right to above 50MHZ.

The whole EMC legal framework is being totally ignored by authorities when? it comes to the importation of this equipment and how its marketed or sold. If I bought a radio jammer that jammed aeronautical HF communications or VHF communications I would be in jail. Yet if I bought a piece of equipment that behaves the same way by charging a battery, LED light, or running pump or chicken incubator its legal? even thought it fails all EMC laws. So you cant? fully understand the hypocrisy that is now standard practice in governments.

We have invested? millions in testing equipment? to test these products and now companies just ignore these laws and governments let them get away with it. So the conclusion is that they don't care or deliberately? want the total pollution of the? radio frequency spectrum as we know it despite the laws that they make and that they don't enforce.? I have not even mentioned the rubbish solar inverters that I can I can hear at -40dbm from 3 kilometers away thats being sold right now. Then legitimate companies like Fronius and SMA face massive discrimination in marketing, legal and a cost to their profits because they have to compete with equipment that is unregulated. So it seems that our politicians also want to wipe out our industries by unfairly targeting them with laws and regulations that simply dont apply to the garbage manufacturing countries. So in conclusion you have to wonder if they do have any agenda because the evidence is there for everyone to see in practice!

Thanks Simon,
You must be right. A possible choice could be this QRP transmatch, which can be bought in kit or fully built and tested :?
From a former station on board a sailing boat I had found the following values for the length of an all Hambands tunable length of wire (always away of lambda/2 length) by a transmatch :? 8.84m or 10.82m or 12.50m or 17.68m or 21.64m ...
73 - Pierre - FK8IH

Hi Mike

Yes good earth is very helpful, but not required for removing a hell of the noise in house...ie removing offending items, common mode chokes on all smpsu stuff, antenna cables, power cables in shack etc..alot of people on here dont even have a garden to talk about, so a real earth is a non starter..ie Gordo in Thailand..oh and me..( yet i work ssb dx on 160m)


So moving on to shack..this applies to a single rx, sdr, multiple rx’s or full blown multi rig multi antenna systems.

So hopefully one has found, cured most/all of in house noise..but you are still connected to the mains power in..

This can/will bring in noise, from Neighboors etc.

A separate supply to shack is favoured coming from electrical distribution board..this supply filtered.
But this is often hard to do..( read ..yes my Wife, i am ripping up the new floor to lay down screened cable to my shack..honest my love, you won’t notice the holes and mess.)

I have to use the existing power socket next to radios..wonder why??

From this socket a cable feeds a common mode choke plus a noise filter, then to my distribution “ box” that feeds the various radios/ phasers etc.
This filter crt does help alot..stops rf going into supply and visa versa.

If memory serves me right it is a g3tso design..

The pc AND monitor is also on its own mains filter.

Then to all the antenna cables, power cables from psu to radios, usb cables etc..FERRITE rings..on everything.!

G3TSO..google and see his results on cm chokes..though, i use the “green” china ones with good results.
Having said that i use proper cm g3tso recommend chokes on the antenna cables..the “ green” cores on the power cables..

Martin and others please chime in with ferrite core recommendations..

NOTE..Important!! Cm choke/ filter on mains supply in MUST be up to job..by this i mean WELL over rated..NO ELECTRICAL FIRES PLEASE.

So next..Antennas..

Note that the key to noise mitigation is a good ground. Without it not much can be done.

73, Mike AF7KR

One way to identify the ferite mix, is to wind three or four turns of wire though the core and measure the values of X and R with an antenna analyser or VNA.

The lowest frequency at which X=R roughly corresponds to the point at which u' and u'' cross over on the material Permiability vs Frequency graph.







Further information on common materials can be found here.



Regards,

Martin

I have retrieved similar small green ones from defunct shredder and printer power supplies, about 0,8" outside diameter. They often have only about 6 spaced turns on them. I measured them at around 350uH, so quite high permeability. I also noticed them on sale last time I went to the local Hamfest in 2019.

Ian Brooks, Verwood, Dorset, UK.

On Wed, Dec 29, 2021 at 12:56 PM, Simon wrote:

Please put a link in to your diagram showing cm chokes on rx antennas.

Hi Martin

This thread is not for me, but as so many peoples asking about noise it seems a good idea to put as many cures in one place as possible..
Please put a link in to your diagram showing cm chokes on rx antennas.

Also when hunting down your own noise in house as Martin suggested Do not forget, lighting, fridge, pc, washing machine etc..Expect everything to be noisy unless prooved otherwise.

So what if it’s your phone charger? Easy dump it and buy another..
Led bulbs..dump it and buy another that is hopefully better.
Fridge..not so easy..can’t just dump that..cure here is to extend the power cable so can wrap lots of turns though a big ferrite ring or even 2. Get ring as close to unit as possible.
Tv, washing machine etc..see fridge.
INCLUDE. Phone line, if possible especially any cables from wifi router to phone socket etc..

I use recycled ferrites from welding equipment, they are used by manufacturers to suppress the smpsu noise from said equipment..they are free to me, and large..no idea what they are other than they work..( green in colour.)

Remember 1/4db here, 1/8 db noise there, removed all add up..

Next to attack your shack..lots can be done here..then the antennas and feeders.( or visa versa…)

PLEASE remember to do above safely using appropriate cable and safe means of extending if needed.

Simon

开云体育

Rick,

You are right about the unfired ceramic being called Green in the factory, that's a very old Pottery term BUT unfired cores would not leave the factory, too soft physically and the magnetic properties are different. But outside the factory a green core is one that has been dipped or sprayed the colour green to denote the properties of the core.

Generally? cores that are unpainted ( dark grey ceramic colour) or one painted colour all over are most likely ferrites, dust iron cores are often not sprayed all over, one face is the grey natural colour, other surfaces are coloured. There is a two colour version where the core is sprayed one colour on one face then the rest painted another colour. However Chinese cores often don't follow Western colour codes, you cannot be inscrutable and always follow conventions- too easy!

Most cores come from China, the properties may not be exactly the same from different manufacturers and the colours can be not so distinct. Cores can be dipped or coated in a thick paint or clear varnish to avoid the edges damaging enamelled wire.

The green all? over core is a very widely used mix for switch mode inductors. Also can be green/blue,? 5-7 turns on a half inch core is around?? 1-2 uH. The grey/blue cores produce around 3.5uH for 7 turns. All are dust-iron.

Most toroidal cores used in switchers are not ferrite but dust-iron. However ferrite transformers in E or U core are very common, they often use an air gap to avoid saturation which can be a plastic shim or sand in paint.

The whole subject of ferrite and dust-iron cores is very complex, impedance for most cores is very frequency dependant and some cores are deliberately designed to produce very low Q for filtering.? There are two certainties, if you think you know all about it you certainly don't and sucking it and seeing is a valid approach greatly improved with a few hints. There is a useful book " Ferromagnetic Core Design And Applications Handbook" by Doug DeMaw? which has some useful info.

73, Alan G8LCO.

The type of core material and how it is wound are important factors.

There are many different types of ferrite (and other mixes of materials) that are used to produce ring cores, some of which are more suited for use at particular frequencies than others.

Plus you can have too many turns, to the point where the inter-winding capacitance and self-inductance form a tuned circuit. Although this can produce a very high value of choking impedance, it does tend to be over quite a narrow frequency range, and overall may not be as effective in comparison to a lossy core material wound with fewer turns. Ideally we require a choke with a high value >1K Ohm of mainly resistive impedance over the whole of the desired frequency range.

G3TXQ's (SK) webpage and charts show this quite clearly.

I also find that the large (and relatively expensive) clip-on ferrites from Fair-Rite are a very useful trouble shooting aid to be quickly attached to mains and other cables in order to determine if it can help resolve a problem.

Some other notes (which really need updating) on fixing domestic noise problems can be found here.

Anything is better than nothing, but a good choice of core material with an optimised number of turns, will usually provide much more 'bang for your buck'.

Regards,

Martin

If you are suffering from a very high level of noise and electrical interference, it is more than likely it is being generated in your own home. Tune to the unwanted noise with a battery powered receiver, and turn off your mains supply at the master switch to see if the noise goes away. If it does, power up each mains circuit one by one to track down the source.

Wherever possible try and use a balanced antenna in conjunction with an effective common mode choke, or better still multiple chokes. Unbalanced antennas such as end fed wires, OCFD's, and verticals fed against ground can be used with care, but they require much more effort to prevent noise ingress.

These two simple things will often resolve the most severe problems. After taking these initial steps, things start to get progressively more complicated to fix.

Regards,

Martin

Hi

Good choice with the hl2.. excellent sdr for the money!

I would see if you can get the long wire to tune up..small atu and counterpoise. With 5w the wonderful loop thing would never work indoors
With only 5w you won’t ( should not) cause rfi issues with a tuned long wire.

Or even a dipole for 40..10m wire outside and 10m wire hanging down from window etc..no atu then , work on 15m too..( with a small atu)

Simon

Thanks for your comments. I think I'll go anyway for this wonder-loop-750 antenna. I loved building my units but here in New Caledonia it's nearly impossible to buy components because they don't exist here and the major suppliers do not supply components to this island or at such a price with DHL or FEDEX!
I plan to use this antenna inside my home mostly with WSJT-X, JSCall, Quisk and a Hermes Lite 2 TCVR for transmit and have a long wire antenna to receive broadly.
73 - Enjoy the coming festivities - Pierre - FK8IH