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Old 6th Jul 2020, 11:21 pm   #21
ORAWA01
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Default Re: ATU vs. Preamp vs. Active Antenna

On 11810 kHz, I was able to receive the BBC via Woofferton OK, but at 2200 GMT, the KBS was totally silent, or just the band noise only.

I went to an SDR site on the Internet, which is located somewhere in England. The SDR site is running a Kiwi SDR and Wellbrook Mag Loop, and it is receiving it OK on 11810 kHz KBS in English service, albeit very quiet about S2-3. But it was listenable.

But sometimes, the SDR site cannot hear what I could hear on my Long Wire and PalStar AA-30 amp. So, I was wondering if it is the path of the signal or propagation rather than the equipment. But I am not sure.
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Old 7th Jul 2020, 1:23 pm   #22
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Default Re: ATU vs. Preamp vs. Active Antenna

If its a relay via a UK site then it probably different skip to you and the other SDRs, it was loud and clear enough here in East Anglia

If it were really coming from Korea it would probably be more consistent around Uk but even that is not certain

Fred
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Old 7th Jul 2020, 3:50 pm   #23
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Default Re: ATU vs. Preamp vs. Active Antenna

14:45 GMT 9785kHz and 9630kHz are quiet. There are other broadcasters around so the band is open from some places. I'd expect to hear Wooferton, though.

I'll try to remember and have a listen at grey-line time.

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Old 8th Jul 2020, 10:02 am   #24
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Default Re: ATU vs. Preamp vs. Active Antenna

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Originally Posted by dodgy-dxer View Post
If its a relay via a UK site then it probably different skip to you and the other SDRs, it was loud and clear enough here in East Anglia

If it were really coming from Korea it would probably be more consistent around Uk but even that is not certain

Fred
Transmissions coming from the Relay stations are usually very loud and clear, no problems. I can copy them even without antenna connected to the radios. The one you were hearing S9 was the BBC from Woofferton by the way. The schedule is in GMT, not UK local time. I have attached the program schedule from the SW schedule site on my last post.

The transmissions coming direct from the countries are struggle to copy.
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Old 8th Jul 2020, 10:09 am   #25
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14:45 GMT 9785kHz and 9630kHz are quiet. There are other broadcasters around so the band is open from some places. I'd expect to hear Wooferton, though.

I'll try to remember and have a listen at grey-line time.

David
Yes, the transmissions from Woofferton are very good copy usually unless there is unusual skips at the time.

I was copying the KBS 9680 kHz in Korean service via Woofferton 59+10 this morning 0700-0800 GMT.

But after that they are mostly direct from KBS transmitters in Korea, which gets difficult copy. The mid afternoon one on 15575 kHz in English used to be copyable in the spring with good signal. Recently it became difficult or no copy for my setup here. But the SDR station in England with his KIWI SDR and Wellbrook copies it very well. http://g0luj.ddns.net:8073/

73s
J.
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Old 9th Jul 2020, 8:48 am   #26
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I was copying the KBS 9680 kHz in Korean service via Woofferton 59+10 this morning 0700-0800 GMT.
Sorry, correction on the frequency => 9860 kHz

This morning, no reception on the frequency via Woofferton on my radios.
The G0LUJ SDR site was receiving it very faint, not intelligible reception.

I have visited a few KiWi SDR sites in UK, and this particular site was receiving best reception with 59+ loud and clear for the transmission on 9860 kHz 0700-0800 GMT of KBS in Korean service.
http://websdr.uk:8078/

The antenna it is supposed to be using is a 80m dipole.
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Old 12th Jul 2020, 8:44 am   #27
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Default Re: ATU vs. Preamp vs. Active Antenna

I have been checking out a few SDR sites, and this site is the best in reception. It hears everything, even all others are quiet.

http://websdr.uk:8077/

The site is in;;
Weston-super-Mare, United Kingdom | Grid: IO81MI, ASL: 108m.
Antenna: 160m Beverage for 80m facing South-Wes
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Old 19th Jul 2020, 2:29 pm   #28
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Default Re: ATU vs. Preamp vs. Active Antenna

Hi
what radio are you using? what is the given sensitivity specs, ie is it
capable of weak signal reception?a good radio will be -50 to -100 Dbm.
does it have S meter to indicate the received signal level? does it have filters or some means of reducing band with.
A simple antenna match will be useful but amps etc will not be of much use as most/ all just boost the inherent band noise
Wire in the sky and a matching unit will be your best and simplest way to go
MM0HDW
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Old 19th Jul 2020, 4:25 pm   #29
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Default Re: ATU vs. Preamp vs. Active Antenna

I use a few different radios for SWL / BCL. They are,

Sangean AT-803A
Realistic DX-392
ICOM IC-751A
TRIO 9R59DS
TECSUN PL-660
XHDATA D-808

They are all sensitive enough radios. I used think the RF amps would also amplify the noise too, but it doesn't seem always the case. Sometimes switching on the amps quietens the band, and bring up the weak audio making it possible to be intelligible.
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Old 19th Jul 2020, 4:57 pm   #30
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Default Re: ATU vs. Preamp vs. Active Antenna

I also use a Palstar AA30 active antenna preamp in the setup with the radios.
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Old 20th Jul 2020, 8:19 am   #31
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Default Re: ATU vs. Preamp vs. Active Antenna

This morning I was listening to 9860 kHz 7:00-8:00 GMT. The signal came through very nicely for a few minutes, and then it disappeared into the noise again. And it came back and disappeared again.

It seems it is more than the radio and antenna involved in this process, which is actually more important factor in the reception, namely the propagation.
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Old 20th Jul 2020, 8:40 am   #32
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Default Re: ATU vs. Preamp vs. Active Antenna

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I use a few different radios for SWL / BCL. They are,

ICOM IC-751A
You know about the battery maintained firmware issue of this era of Icom radios?

Many had no ROM and the operating firmware was kept in battery-powered RAM. This is fine until batteries die, and then replacing the battery is not enough, you need to get a copy of the firmware and a means to load it.

David
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Old 20th Jul 2020, 12:00 pm   #33
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Default Re: ATU vs. Preamp vs. Active Antenna

Yes, I read about it, and checked it out when I got the IC-751A a couple of years ago 2nd hand used one.

The previous owner already had replaced the problematic original RAM board with the newly updated ROM board designed and made by an Italian Ham operator (I forgot his callsign now, but he is a very famous Electrical Engineer.).

From the eham forum, the new ROM board got very nice reviews, and it doesn't wipe out the radio even if the battery runs out.

The battery in it is also in good condition, will last another a couple of years I reckon.

This IC-751A is a good general coverage receiver, and getting used for that quite often in here.
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Old 23rd Jul 2020, 8:57 am   #34
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Default Re: ATU vs. Preamp vs. Active Antenna

Quote:
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Quote:
Originally Posted by ORAWA01 View Post
I use a few different radios for SWL / BCL. They are,

ICOM IC-751A
You know about the battery maintained firmware issue of this era of Icom radios?

Many had no ROM and the operating firmware was kept in battery-powered RAM. This is fine until batteries die, and then replacing the battery is not enough, you need to get a copy of the firmware and a means to load it.

David

David

The transistors arrived. Thank you for your kindness and generosity.
I have an old Magnetic Loop Antenna Preamp, not working. It has a transistor on the board, and I am planning to replace it with these transistors you sent me, and try to revive the device.

I think the fault seems in the power supply, which I would replace it with battery power. If it goes well, it might be operational rather quickly.

But thanks again David, much appreciated.
Best 73s

J.
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Old 23rd Jul 2020, 2:21 pm   #35
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Default Re: ATU vs. Preamp vs. Active Antenna

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I think the fault seems in the power supply, which I would replace it with battery power. If it goes well, it might be operational rather quickly.
I assume you are referring to a Wellgood clone about to be revived with 2N3866? Remember that the two transistors should be matched for gain and then balanced when installed to take equal current. Although the board is intended to to take 12V (and around 120mA) I find that it begins to work at about 3V, and certainly shows no advantage above ~5V, at which point the current is appreciably lower and the 3866 appreciably cooler. They will need heatsinks if run at 12V.

B
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Old 24th Jul 2020, 12:32 pm   #36
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I assume you are referring to a Wellgood clone about to be revived with 2N3866? Remember that the two transistors should be matched for gain and then balanced when installed to take equal current. Although the board is intended to to take 12V (and around 120mA) I find that it begins to work at about 3V, and certainly shows no advantage above ~5V, at which point the current is appreciably lower and the 3866 appreciably cooler. They will need heatsinks if run at 12V.

B
No, it is not a Wellgood clone. It is an old Mag Loop Preamp made in Germany commercially. It is so scarce in information that no schematic or manual is found in anywhere. Even the mighty Google doesn't know about it.

I think the company is called REFCOM, and had been in business for some time many year ago, but went bankrupt or disappeared. Couldn't even find anything about the company.

This old set looks well made, but not functional due to possible problem with the power supply.
I was thinking of ripping out the faulty psu, and make it work from batteries of 12V, but yes I think it would even work from much lower voltage.

And also try replacing the original transistor with this Wellgood transistor David sent me.
Because all the infrastructure is there on the pcb, it would be interesting to see how it would perform if ever, rather than trying to build a Wellgood from scratch.
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Old 24th Jul 2020, 3:02 pm   #37
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Default Re: ATU vs. Preamp vs. Active Antenna

I've not heard of REFCOM. You are obviously working in the dark without having the circuit diagram; wonder how many transistors it uses?

I've built two magloop amps; one designed by Paul Tempest which used 5 transistors and the other being the Wellgood using a pair of 2N3866. The Wellgood is presently outside hanging from a tree. At this time of year, so much of my time is taken up with looking after the garden that there's not much left to do radio stuff.

There's absolutely no doubt that the use of a magloop is a very effective way of countering RFI problems, though of course, as well as the amp, the design of the loop is an interesting issue.

B
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Old 26th Jul 2020, 8:55 am   #38
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Default Re: ATU vs. Preamp vs. Active Antenna

The REFCOM uses only 1x transistor. I will see what it is next time.
It looks simple design inside. Not too many parts.

But yes, it is problem that there is no schematic or documents about the set, and the pcb has no markings for + or - on the power lines, so if DC was applied with wrong polarity, some parts might be destroyed? Once I find out the right polarity from the power supply to the circuit on the pcb, it would be easy to replace the power source as battery power, and then desolder the original transistor with the new one, and it would be operational hopefully

But yes, I think the whole point of mag loop is for suppressing QRN / QRM, and better / quieter reception.

Depending on the loop element design, they could be omni / bi-directional? What advantages thicker diameter loop element (e.g. using copper pipe) give over thin wire element for the loop?

Have you tried to receive the BC programs on the freq. in the previous post with your Wellgood antenna? How does it perform?
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Old 26th Jul 2020, 3:49 pm   #39
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Default Re: ATU vs. Preamp vs. Active Antenna

Last point first; no I haven't listened to any BC stations as I only have my ham-bands only rig in the shack at the moment. I'll see if I can find time to extract something else from the wardrobes.

My understanding about the loop is that it is good if it exhibits very low inductance. My current loop comes in at 4-5uH, but some suggest the target should be about 1uH. But then we need to address unshielded loops v shielded loops and non-resonant loops v resonant loops, and so on.

Here's the interesting thing; for sure, magloop aerials really do work and Wellbrook have sold lots of them at over 300 with no complaints about performance. But, here's the BUT...you can read tons of stuff on the net about how to make a good magloop, but it seems to me that there is a lot of contradictory info out there, and that suggests that much of it is unreliable.

I understand that Wellbrook are now selling a new aerial, improved from their original, and various other manufacturers have jumped on the bandwagon, so Wellbrook will need to work hard to stay at the front.

I'm really distracted by other "non-radio" stuff at this time of year, but I'll no doubt get back to this seriously when the days are cooler and shorter!

B
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Old 28th Jul 2020, 12:40 pm   #40
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Default Re: ATU vs. Preamp vs. Active Antenna

No probs. please take time as no rush.
But how do you measure inductance of the loop element?
What meter do you need for the measurement?

I feel that active antennas must be in good specs. and good quality ones, because it they are not, they could bring problems with intermodulation, cross modulation and overload problems especially to the cheap receivers with ultra sensitive front ends, which are designed to run on builtin whip antennas, or very short wire antennas.
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