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Re: Is this Wellbrook wide aperture loop faulty?
On Mon, Jan 3, 2022 at 09:33 AM, Chris Wilson wrote:
Downside is MF / LF amateur digital performance has markedly deteriorated. Is it the smaller circumference of the new loop?
Hi Alan, That looks good, your work has definitely made a further improvement. I'm not sure how you are judging the change in MF/LF performance between loop sizes, but with the antenna connected, you still seem to have at least 10dB higher noise floor than the KiWi alone. Which is probably just about optimum. Any higher noise floor and you would e eating up the KiWi's valuable dynamic range, and any less, the wanted signals would start to become degraded by the system noise figure. For the HF noise, as an experiment you could try some ferrite on the coax at the loop amplifier end of the cable. Looking at Steve (SK) G3TXQ's charts Maybe 10 turns on an FT240-61 core seems to be the best option, but even just a few (4 or 5) clip-on style beads could be worth trying. Keep on picking away at it, although it may bring diminishing returns it will be worth it, and if you kept any screen grabs of how it originally was, you will be able to see what a difference you have made. Regards, Martin
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Re: Is this Wellbrook wide aperture loop faulty?
On Mon, Jan 3, 2022 at 07:46 AM, John Kolb wrote:
However the losses in this approach might be higher than the slight loss caused by the mismatch of using the 75 ohm cable alone.
Hi John, Yes that's the flaw in the plan, but apart from in lab grade stuff, equipment input and outputs are rarely the nominal impedance that they aim to be. You can obtain ready built connectorised matching transformers specifically designed for the purpose of 50 / 75 Ohm conversion, which are sometimes used in applications where mismatch could be a concern, and these typically introduce around 0.5dB insertion loss. However the cost of decent designs is such, that it would probably be cheaper to buy better quality 50 Ohm cable instead. Building one yourself is possible, but it does require a reasonable amount of effort to optimise the performance. The cheapest solution for many folks may be to buy a SMT transformer and put it in an enclosure of your choice. Resistive 'minimum' loss networks can also be used, but they typically introduces just under 6dB insertion loss, which would be excessive in this application. Regards, Martin
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Re: What is your preferred antenna for SWL'ing on a balcony.
mind sharing some links/diagrams for dummies like myself?
many thanks.
The Mini-Whip antennas do not function very well indoors and
probably not very well on a balcony. If you're into a bit of home
construction, a YouLoop or Moebius antenna is definitely worth a
try and is very cheap to build yourself as it is basically two
short lengths of coax cable and a small 1:1 transformer on a
binocular ferrite core. I have two home-made ones used indoors and
I use a BN73-202 core with 5 turns of 30 AWG wire-wrap wire for
each winding of the transformer. Although better results are
obtained with the Airspy HF+ or Discovery, it does give reasonable
results with the RTL-SDR v3 and Spyverter. I have used a HiLego
LNA from e-bay to improve results, but careful adjustment of its
gain by varying the supply voltage was necessary. Fortunately I
don't have any strong transmitters near me which might cause many
spurious signals. As this LNA needs a supply of around 6 to 12
volts, depending on required gain, the dongle's bias-tee cannot be
used. I use up to 8 rechargeable AA batteries. The e-bay UK link
is as follows:
Ian Brooks, Verwood, UK.
On 02/01/2022 22:36, Paul Egan wrote:
I have a 10th floor balcony and would like a no tune solution for
an rtl-sdr v3 with an upconverter.
I've tried a miniwhip from aliexpress. It was pretty deaf.
The youloop looks interesting but I think it needs a more
sensitive SDR and using an LNA with the rtl-sdr v3 only elevates
the noise from what I understand.
I have a homebrew magnetic loop for transmitting between 17m and
40m but tuning is cumbersome and I would like to receive below
7Mhz.
So what would you install to get a decent signal from 0.5 to
30Mhz? Some sort of passive loop?
Thanks.
.
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Re: What is your preferred antenna for SWL'ing on a balcony.
My balcony is at 4th floor. I tried: wellgood clone, Lz1aq and N4CY moebius, all with 1m dia 20 mm PeXAlPeX multilayer tubing. Well good is the best, but all have too much gain even if the sdr lna is off. The last I built is a modified youloop made as N4CY loop, but 60 cm dia, with a 1:3 transformer (3 on the loop side) and passive. This is the best balcony antenna, coupled to an Airspy hf+ modified (discovery like) with its LNA on.
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Re: Is this Wellbrook wide aperture loop faulty?
Hello Alan, Martin et al,
Saturday, January 1, 2022
People must be getting bored with my saga by now, so I will keep it as short as I can. Basically, yesterday lent me the opportunity to do some more tests. Running the injector box off a 12V accumulator made zero noticeable difference. Running the KIwi as well, off my mobile phone 5V power pack made a minute difference to overall noise. Disconnecting the coax to the antenna at the injector box still left some strong signals. Wrapping about 10 turns of the coax out to the loop around a BIG ferrite ring (I have the spec but can't recall it off hand) made a noticeable difference.
Then I had the idea to wrap the short (2 foot or so) of coax from the injector box to the Kiwi as many turns as possible around a similar ferrite ring. I think I got about 5 or six turns on, the BNC plug limited this. Now THAT made a big difference!
I am pretty pleased to have persevered and enormously grateful to those who stuck with me.
Downside is MF / LF amateur digital performance has markedly deteriorated. Is it the smaller circumference of the new loop? The 30 to 35 or so degrees rotation of the loop form its orientation looking down from the sky (plan view)? Originally the loop in plan view ran almost east to west, it's now skewed about 35 degrees or so anti clockwise and a bit lower overall....
Testing has been made a bit problematic as my TS-580S which has had a hard, no, very hard life, has started to lose sensitivity and sometimes goes totally dead on receive. It seems heat related, but it's years old and had one incident where I managed to shove a kilowatt of LF 137 kHz up the receive antenna port.
Needless to say it didn't like it and I amazed and astounded myself by managing to repair it with my scope and a sig gen. More good luck, strong coffee and a good light source, plus a huge taped together print out of the schematic.
I think I might treat myself to a newer (if still secondhand) rig soon. As an aside what modern transceivers hear well at LF and MF and will TX a milliwatt or so on LF and MF to act as an exciter, anyone here any experience of anything suitable or should I just get a newer TS-590?
Critical comments welcome:
Thanks again everyone.
Best regards,
Chris mailto:chris@...
A> Martin
A> As Andrew said shorting the input is not a good idea and will not do
A> what you think it will. Leaving the terminals open will but you need to
A> disconnect both terminals. The amplifier is a Zwischenbasis type, as
A> you have plotted in the past the input reacts to the signal source
A> impedance. This form of noiseless feedback is the complement to the
A> Norton Amplifier where the output impedance is a transformed version of
A> the input impedance, here the output impedance hardly matters but you
A> get to optimise the matching to the source over a much wider range than
A> a conventional "dumb" input , it is NOT a virtual earth amplifier in
A> the normal sense ( which also goes nuts with a shorted input !) but a
A> much cleverer configuration due to Cantz from 1953.
A> However before disconnecting the loop I would remove the power to the
A> injector then disconnect the coax to the injector. That would show what
A> is leaking into to the coax and then what remains after the coax is
A> removed. It seems futile to disconnect the loop when you can just power
A> it down.
A> I used a naked ALA100LN until recently, it works very well from LF to HF
A> and beyond. The IMD performance is outstanding six miles from Brookman's
A> Park. I now use a new arrangement that drops BP signals an additional
A> 30dB. I spot to PSK reporter from a tiny urban back garden, Don't do too
A> bad for an antenna 3m high surrounded by switchers although BT has
A> blocked 30m very effectively.
A> 73, Alan G8LCO.
A>
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Re: Is this Wellbrook wide aperture loop faulty?
A transformer with a 5:6 turn ratio would convert 50 ohms to 72 ohms, so a 50:72 could be used at one end of the coax and a 72:50 at the other. Selecting a suitable ferrite core and winding technique is left to the student :)
However the losses in this approach might be higher than the slight loss caused by the mismatch of using the 75 ohm cable alone.
John KK6IL
toggle quoted message
Show quoted text
On 12/31/2021 5:59 AM, Michael.2E0IHW via groups.io wrote: Martin,
I was thinking of asking about using 75ohm sat cable
when I saw your preference for this.
I have read elsewhere that such coax can be used
in lieu of standard 50hm.
How would you use it for rx and tx?
"Better" NewYear to all!
Michael
2E0IHW
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Re: Good Vibrations? / locking compounds
Good?morning all.??
I have been following all the comments about vibrations on the antenna causing mounting hardware to loosen.? I have used the following type of hardware for years at commercial sites and can't remember where we have had any hardware loosen up for whatever?reasons.? The attached link below uses one nut and one split ring washer at every point where any tightening is to happen for mounting.? All the big boys, 2 way communication, cell site antennas etc use this type of hardware and once it is up it is never touched again until it has to come down or be moved.? No criticisms intended, just my opinion.
Fred - N4CLA
Good fit-for-purpose cautionary advice here Alan....
Leigh
VK5LT
-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Alan
Sent: Monday, 3 January 2022 10:50 AM
To: [email protected]
Subject: Re: [loopantennas] Good Vibrations?
I would NEVER USE LOCKING COMPOUND ON PLASTICS. Many locking compounds can destroy plastic parts over time, they are formulated for locking metal part not plastics.? Same goes for some greases. One former employee used locking compound on plastic nuts, cost ?35,000 to replace the parts.
One Italian manufacturer used a grease to ease driving screws into plastic pillars. After a year the pillars disintegrated and cost the manufacturer a lot of money.
73, Alan G8LCO.
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Thermal cycling is not mentioned on the wikipedia site but I thought that
thermal cycling may have been the reason that Belleville washers were used on the link hardware of aircraft Nickel Cadmium batteries.
To clarify, Belleville washers are spring washers, much better than split ring if your intent is to provide a spring pressure that allows some movement and change in length. Much stiffer than a spring and less likely to bounce and break contact than a battery spring. I think the guidelines for Belleville washers may include that they should not be torqued down flat. I do know even the Wikipedia page specifically says they are NOT a locking mechanism. The Wikipedia page Ron links to makes a fascinating read. In any case, for antenna mounting we need hardware that can sit up there for years in the sun, wind, snow, rain, etc. without requiring constant inspection and tightening. -- Steve Greenfield AE7HD
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Re: What is your preferred antenna for SWL'ing on a balcony.
Thanks to all for the excellent information.
I'm going to give Ian's solution a try. The youloop looks easy to build. I've got the parts already. I also have an LNA that I can put at the feedpoint and power with the Bias from the Miniwhip. As you say I might need to adjust the power.
I assume that a round toroid can be used in lieu of the binocular core. 5 turns on one side, 5 turns on the other. Keep 'em separated.
I have a magnetic loop for transmitting which works quite well. For example, I made an FT8 contact with Japan from Toronto today on 30m. Not the best antenna in the world but probably the best thing for a small balcony, three floors below the roof.
I'm looking for a solution that fills in the coverage gaps (0 to 7mhz, 7.5 to 10 mhz) and is more broadbanded. The range is about 30 khz which means constantly tuning the capacitor.
Thanks again to all. I'll be sure to report back.
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Re: What is your preferred antenna for SWL'ing on a balcony.
Since you aren't going to use a high end receiver, and you aren't wanting longwave reception I would recommend the inexpensive MLA-30 loop. Sure, in a super quiet location with an excellent receiver, there would be better options than the MLA-30. However in your case the MLA-30 could have a few advantages. It has a gain pot that can be adjusted up or down to help keep your rtl-sdr v3 from overloading, its fairly invisible to keep nosey neighbors and landlords from asking questions, it can be rotated to help null out some of the noise, and its dirt cheap. It will definitely pick up tons of shortwave and broadcast stations.
Tom
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Re: What is your preferred antenna for SWL'ing on a balcony.
Hi Paul
Other thing to mention is..if you have caught the swl ¡° bug¡± then maybe invest in a better sdr as well. Not that expensive ?100 or so gets you an ok one.certainly better than an rtl dongle by far.
Can you get to the roof?? As that WOULD help with antennas!! ( you say on 10th floor)
Simon
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Locked
Re: What is your preferred antenna for SWL'ing on a balcony.
The Mini-Whip antennas do not function very well indoors and
probably not very well on a balcony. If you're into a bit of home
construction, a YouLoop or Moebius antenna is definitely worth a
try and is very cheap to build yourself as it is basically two
short lengths of coax cable and a small 1:1 transformer on a
binocular ferrite core. I have two home-made ones used indoors and
I use a BN73-202 core with 5 turns of 30 AWG wire-wrap wire for
each winding of the transformer. Although better results are
obtained with the Airspy HF+ or Discovery, it does give reasonable
results with the RTL-SDR v3 and Spyverter. I have used a HiLego
LNA from e-bay to improve results, but careful adjustment of its
gain by varying the supply voltage was necessary. Fortunately I
don't have any strong transmitters near me which might cause many
spurious signals. As this LNA needs a supply of around 6 to 12
volts, depending on required gain, the dongle's bias-tee cannot be
used. I use up to 8 rechargeable AA batteries. The e-bay UK link
is as follows:
Ian Brooks, Verwood, UK.
On 02/01/2022 22:36, Paul Egan wrote:
toggle quoted message
Show quoted text
I have a 10th floor balcony and would like a no tune solution for
an rtl-sdr v3 with an upconverter.
I've tried a miniwhip from aliexpress. It was pretty deaf.
The youloop looks interesting but I think it needs a more
sensitive SDR and using an LNA with the rtl-sdr v3 only elevates
the noise from what I understand.
I have a homebrew magnetic loop for transmitting between 17m and
40m but tuning is cumbersome and I would like to receive below
7Mhz.
So what would you install to get a decent signal from 0.5 to
30Mhz? Some sort of passive loop?
Thanks.
.
|
Why would anyone use locking compounds on plastic?
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Locked
Re: What is your preferred antenna for SWL'ing on a balcony.
Or.. a 1m loop with suitable preamp..
Ie ccw, Lz1aq, wellbrock etc.
Advantage of loop is you can null out a local noise source..disadvantage is bigger than e probe. Both need 12v dc supply.
I would start with a ccw ( cross country wireless) as good and cheaper than the rest.
No point in spending $$$$ for a try out antenna .( incase you dont get on with,) Please avoid the mla30.
Simon
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Re: Good Vibrations? / locking compounds
Good fit-for-purpose cautionary advice here Alan....
Leigh
VK5LT
toggle quoted message
Show quoted text
-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Alan Sent: Monday, 3 January 2022 10:50 AM To: [email protected]Subject: Re: [loopantennas] Good Vibrations? I would NEVER USE LOCKING COMPOUND ON PLASTICS. Many locking compounds can destroy plastic parts over time, they are formulated for locking metal part not plastics. Same goes for some greases. One former employee used locking compound on plastic nuts, cost ?35,000 to replace the parts. One Italian manufacturer used a grease to ease driving screws into plastic pillars. After a year the pillars disintegrated and cost the manufacturer a lot of money. 73, Alan G8LCO.
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I would NEVER USE LOCKING COMPOUND ON PLASTICS. Many locking compounds can destroy plastic parts over time, they are formulated for locking metal part not plastics.? Same goes for some greases. One former employee used locking compound on plastic nuts, cost ?35,000 to replace the parts.
One Italian manufacturer used a grease to ease driving screws into plastic pillars. After a year the pillars disintegrated and cost the manufacturer a lot of money.
73, Alan G8LCO.
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Locked
Re: What is your preferred antenna for SWL'ing on a balcony.
I would seriously consider an active E-Field antenna.? I built and used one while on the third (top) floor of an apartment in an extremely large complex.? It worked quite well from VLF through 20 or so MHz.? Activity at the time above 20 MHz was non-existent.? If you don't want to build your own, you can pay (too much) from a number of suppliers on the www.
Dave - W?LEV
On Sun, Jan 2, 2022 at 11:25 PM Paul Egan < paul@...> wrote: I have a 10th floor balcony and would like a no tune solution for an rtl-sdr v3 with an upconverter.
I've tried a miniwhip from aliexpress. It was pretty deaf.
The youloop looks interesting but I think it needs a more sensitive SDR and using an LNA with the rtl-sdr v3 only elevates the noise from what I understand.
I have a homebrew magnetic loop for transmitting between 17m and 40m but tuning is cumbersome and I would like to receive below 7Mhz.
So what would you install to get a decent signal from 0.5 to 30Mhz? Some sort of passive loop?
Thanks.
.
-- Dave - W?LEV
Just Let Darwin Work
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Re: EZNEC Antenna Simulation Software - FREE
toggle quoted message
Show quoted text
On Sun, Jan 2, 2022, 5:30 PM Steven Greenfield AE7HD via <alienrelics= [email protected]> wrote: The website says:
Use of EZNEC Pro/4 and EZNEC Pro/4+ require a license from Lawrence Livermore National Laboratory (LLNL) because of their incorporation of NEC-4.2 code for which LLNL retains the rights.
It also says:
The introduction of EZNEC Pro/2+ v. 7.0 has been unavoidably delayed. The estimated time of introduction is Jan. 14, 2022, but I'll do my very best to have it ready before then. It is now undergoing extensive testing and updating of the manual.
?
EZNEC Pro/2+ v. 7.0 will have all the features of EZNEC Pro/2 v. 6.0, plus extra features including wire loss for individual wires and the ability to run external NEC-4.2 and NEC-5 programs for calculation.
?
Until EZNEC Pro/2+ v. 7.0 is available, you can download EZNEC Pro/2 v. 6.0 by clicking here:
Download EZNEC Pro/2 v. 6.0
--
Steve Greenfield AE7HD
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Locked
Re: EZNEC Antenna Simulation Software - FREE
The website says: Use of EZNEC Pro/4 and EZNEC Pro/4+ require a license from Lawrence Livermore National Laboratory (LLNL) because of their incorporation of NEC-4.2 code for which LLNL retains the rights. It also says:
The introduction of EZNEC Pro/2+ v. 7.0 has been unavoidably delayed. The estimated time of introduction is Jan. 14, 2022, but I'll do my very best to have it ready before then. It is now undergoing extensive testing and updating of the manual.
?
EZNEC Pro/2+ v. 7.0 will have all the features of EZNEC Pro/2 v. 6.0, plus extra features including wire loss for individual wires and the ability to run external NEC-4.2 and NEC-5 programs for calculation.
?
Until EZNEC Pro/2+ v. 7.0 is available, you can download EZNEC Pro/2 v. 6.0 by clicking here:
Download EZNEC Pro/2 v. 6.0
-- Steve Greenfield AE7HD
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Locked
What is your preferred antenna for SWL'ing on a balcony.
I have a 10th floor balcony and would like a no tune solution for an rtl-sdr v3 with an upconverter.
I've tried a miniwhip from aliexpress. It was pretty deaf.
The youloop looks interesting but I think it needs a more sensitive SDR and using an LNA with the rtl-sdr v3 only elevates the noise from what I understand.
I have a homebrew magnetic loop for transmitting between 17m and 40m but tuning is cumbersome and I would like to receive below 7Mhz.
So what would you install to get a decent signal from 0.5 to 30Mhz? Some sort of passive loop?
Thanks.
.
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Steven Greenfield AE7HD
Ian Brooks
Leigh Turner