On Tue, Jan 11, 2022 at 04:40 PM, Bob Benedict, KD8CGH wrote:

The isolation between transmit and SDR receive is not good enough on this product.? It will work OK for QRP but not with a transmitter using more than 10 watts.?

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I have the DX Engineering switch that adds a antenna port for receiving. It works super but is a pricey bugger. ?I am using a simple 2 position coax switch to use 2 different radios.?

Or you could easy make one..relay..transistor, cap or 2, resistor or 2.. little metal box, 3 so239’s and 12v in.oh and a phono socket.

Would need to go in non 12v powered rx line…

Simon

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On Wed, Jan 12, 2022 at 12:43 PM, Steven, M0OYR wrote:

I'm worried about the pre-amps within the base of the loops. Additionally will my receivers front-ends be blown??

Generally speaking the loops are unlikely to be damaged.

However you raise a good point about any receivers that may be connected to them whilst you are transmitting.

Most receivers will withstand up to +10dBm (10mW) at their input, but in order to provide good strong signal handling performance, many active antennas such as broadband loops have amplifiers that may be capable of producing a saturated output power well in excess of +10dBm, so some form of protection is required.

You can buy dedicated receiver protectors that are designed for this purpose, but the cheapest option is simply to connect two 1N4148 silicon small signal diodes across the receiver input. One diode connected with its Anode to ground and the other with its Cathode to ground. These back to back diodes will start to conduct when a sufficiently high level is signal is present and limit the input power to a safe level.

I have used this technique for many years, and it has been very effective in preventing any damage from occurring. The conduction point of the diodes is sufficiently high that when used in a 50 Ohm system, they will generally not produce unwanted distortion products that are audible above the system noise floor.

Regards,

Martin

Hiya

Hope this is suitable for this group.

I've been using a couple of Wellbrook 1530 active receiving loops for the past 20+ years for shortwave listening with FRG100 and AR3030 receivers.

Finally got my full license and now transmitting - looking forward to building a transmitting loop!! ( I certainly have a beast of a variable capacitor for it.)

I've got a small garden with currently a W330S 10m long folded dipole and a sigma eurocomm XF-80 vertical, currently up to 100W but soon
will have antenna suitable for UK 400W once I have finished building my valve amplifier.

How resistant to damage will the wellbrook loops be when in close proximity to my transmissions? The furthest I can put them is at ground level about 3m from the dipole.
Do I have to disconnect their power supplies??? I'm worried about the pre-amps within the base of the loops. Additionally will my receivers front-ends be blown??

Cheers

Steve
M0OYR

If one is designing a loop amplifier from scratch or modifying a design, then test equipment (big name brand, low end, or homebrew) is desirable, but if duplicating a well known and highly regarded design, a soldering iron, and perhaps a voltmeter is usually all that is required.

John KK6IL

Hi Bob, the diagram on that page only shows a SDR and Transceiver sharing a single antenna. It doesn't seem to separate 2 antennas one for tx and one for rx.

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? 73
??? Bob? KD8CGH

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Hi is there a tx/rx switch for the?lz1aq amp so I can use my EFHW for tx and the?lz1aq loop antenna for rx on a HF radio that doesn't support a separate rx input.

Kind regards?
Steve
VK4SJB?

Hi Dave

Ok 1m dia.. in which case I would not even bother to try it on 160.. bandwidth will be soooo small it will be nigh on impossible to tune.( let alone the efficiency) .I suspect 80 is equally as “fun” to tune..( not far off it anyway.)

I would just make a bigger one for 80-160.. for those “stormy days”

Simon

Hi Chris

You may never find it, or if you do cure it..solar cells on roof? possibly, no chance there of course of asking neighbours to remove it..

My i suggest buying/ building a noise cancellation device/ phaser..even if just to you do cure the noise ( good luck with that if not on your property!)

I use 2 here..( london) without them more often or not 160m would be a waste of time..

Also much as you not want to use a 1m loop but it can null out the noise IF from a single point..

Simon g0zen

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So to sum up: building a DIY loop is really cheap, once you've already shed 1000 commercial loop-equivalents in cash to gather all the necessary equipment and build an electronics shop in advance

My shop is NanoVNA ($60), TinySA ($80), DVM ($20), soldering station ($80) and some other tools, programmable PSU ($30), bunch of parts accumulated over the years (a few hundreds of $). The Rigol scope is $300, but I rarely use it to debug the antenna stuff. I don't count the computers, and the software is free, thanks to Open Source. So the shop cost is less than 2-3 commercial high end loops :)
The costly part is my time, but I have fun doing these projects and learning new stuff, so this counts as a benefit, not a cost.
Luckily, I have a job that pays the bills, so I can release my hobby designs to public domain. I understand that not everybody is in such situation.

73, Mike AF7KR

Hello Sean,

Tuesday, January 11, 2022

Thanks sean and everyone who has replied so far. I am sceptical as to it being a washing machine as it has been present for eight hours today, with no more than ten minutes between sequences. Now, my wife knows how to keep Scottish Power happy and in profit, but eight hours plus washing?

It's definitely not from here, I turned the mains off again and no change, and for sure the Wellbrook some way back in the woods hears it far less than the horizontal quad loop that runs nearest overhead 240 V mains and telephone wires, and two other properties. There is a big chicken shed fairly near, probably half a million birds, and avian flu is also local, I wonder if it's that and they are running the cooling blowers more to achieve good airflow? I wouldn't have thought big blowers would cycle on and off so frequently though...

Next door but one do, probably 70 yards away do have solar panels on the roof of a big stables building, do solar panels and their associated "stuff" shut down at night, as I don't believe I ever see this noise during the hours of darkness? Today has been very overcast, yet one of the worst times for continuous noise on top band I can recall seeing.

I'll investigate a portable radio, it needs to hear 160 meters, sod's law says this noise ius bang in the middle of the band, any recommendations please?

Thanks for the ideas.


Best regards,
Chris mailto:chris@...


SG> Hi Chris,

SG> That is a washing machine making that pattern – it’s exactly the
SG> same as ours, which is an Indesit so it’s probably the same across
SG> the other makes that employ the same motor system. I spoke to an
SG> engineer about it and he said that it was something to do with the
SG> motor or the way they had it configured. Ferrites on the mains
SG> lead did nothing for it. If it is a big issue, you may have to
SG> resort to putting some filtering components around the motor area.
SG> Not my area of expertise so can’t make a suggestion there.

SG>

SG> 73, Sean G4UCJ

SG>

SG> From: [email protected] [mailto:[email protected]] On Behalf Of W0LEV
SG> Sent: 11 January 2022 00:36
SG> To: [email protected]
SG> Subject: Re: [loopantennas] Anyone perhaps able to ID this noise source on top band please?

SG>

SG> I can not look at the link. My PC cautions of a possible security risk.

SG>

SG> Dave - W?LEV

SG>

SG> On Mon, Jan 10, 2022 at 1:33 PM Chris Wilson <chris@...> wrote:

SG> 10 January 2022


SG> Only daylight hours, AFAIK, and MUCH louder on a big (about 380
SG> feet in circumference) horizontal quad wire loop that along one
SG> leg runs parallel to overhead phone and mains LV power lines.

SG> On my wide aperture Wellbrook loop about 70 yards away from the
SG> overhead lines and 20 yards away from the horizontal loop it's
SG> much reduced. The noise lasts 2 minutes or so mainly, disappears
SG> and comes back few minutes later. (Usually, but fairly random
SG> other times). It's not emanating from my house, it's there
SG> running batteries and all power off. If you can spare the time to
SG> look any ideas are much appreciated, it's a well defined pattern
SG> some may have come across before, thanks.

SG> File names should be pretty self explanatory

SG>



SG> --


SG> Best regards,
SG> Chris mailto:chris@...

Please don't forget to trim your replies.

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Steve Greenfield AE7HD