Topics

Long wave reception

Allan Isaacs
 

Long wave reception here in the south of England is not easy because of local QRM so I decided to try a unan.
There are lots of construction details around so I made one using a toroidal ferrite from a scrap equipment, winding three lengths of 18SWG enamelled copper wire making 9 turns.
Fitting to my Andrus SDR which usually works well down to a few KHz on a random long wire, results were quite surprising
I found I can now clearly hear the Romanian broadcast station on 153KHz.
Using a long wire via the unan I see it at a strength of 98.3dBm and adding an 5 metre earth connection (small metal plate pushed into soil) this improves to 87.7dBm.
Removing the unan I see 103.1dBm and adding an earth connection has no effect.
The unan with an earth gives me an improvement of 15.4dB.
I'm now thinking I could make a unan specifically for LF and MF. Would I just need to increase the number of turns?

My SDR uses a mini USB socket for power.
I have one of those Y-USB cables that came with an external hard drive and this has twin plugs, one wired for power and data, with the second having just power with no data.
Using the power/data cable results in a comb of interference spikes 1KHz apart from 40KHz to 220KHz with baseline noise at -115dBm
Using the power only plug the baseline drops to -125dBm and no spikes of noise.
Allan G3PIY

Kriss Kliegle KA1GJU
 


My 124’ EFW’s with a 9:1 UNUN works just fine. The higher the better though!
Here’ s a good image of the windings:
https://vk6ysf.com/unun_9-1.htm






My 124’ :

73 Kriss KA1GJU

Alan G4ZFQ
 

I found I can now clearly hear the Romanian broadcast station on 153KHz.
Using a long wire via the unan I see it at a strength of 98.3dBm and
Allan,

I've never used an unun for any purpose. So cannot comment about that.
But with my HF+ I find a discone (Old Icom with 50MHz whip 32' above my bungalow) gives the best reception on LW and lower.
Romania here at Cowes gives the carrier 40dB over noise level. Better than any wire or loops/eprobe at the end of the garden.
I found this by accident, amazed that such a small antenna could work so low.

73 Alan G4ZFQ

colin glass
 

unbalanced to unbalanced .... explained 
thanks sharing Alan.
Send a photo of your discone curious!?
-Colin

On Tuesday, 14 January 2020, 15:05:38 GMT, Alan G4ZFQ <alan4alan@...> wrote:


> I found I can now clearly hear the Romanian broadcast station on 153KHz.
> Using a long wire via the unan I see it at a strength of 98.3dBm and

Allan,

I've never used an unun for any purpose. So cannot comment about that.
But with my HF+ I find a discone (Old Icom with 50MHz whip 32' above my
bungalow) gives the best reception on LW and lower.
Romania here at Cowes gives the carrier 40dB over noise level. Better
than any wire or loops/eprobe at the end of the garden.
I found this by accident, amazed that such a small antenna could work so
low.

73 Alan G4ZFQ





Bert Vierhout
 

Is an unun a kind of balun with only one point for incoming antenne (no dipole but for longwire)

On moonraker I saw a red receiving balun with one antennapoint en other baluns with 2 antennepoints


Bert

Op 14-1-2020 om 22:44 schreef colin glass via Groups.Io:

unbalanced to unbalanced .... explained 
thanks sharing Alan.
Send a photo of your discone curious!?
-Colin

On Tuesday, 14 January 2020, 15:05:38 GMT, Alan G4ZFQ <alan4alan@...> wrote:


> I found I can now clearly hear the Romanian broadcast station on 153KHz.
> Using a long wire via the unan I see it at a strength of 98.3dBm and

Allan,

I've never used an unun for any purpose. So cannot comment about that.
But with my HF+ I find a discone (Old Icom with 50MHz whip 32' above my
bungalow) gives the best reception on LW and lower.
Romania here at Cowes gives the carrier 40dB over noise level. Better
than any wire or loops/eprobe at the end of the garden.
I found this by accident, amazed that such a small antenna could work so
low.

73 Alan G4ZFQ





Allan Isaacs
 

Seems we are quite close Alan. My p/code BH23 8DU.
153KHz is running at about 48dB above noise (-81.8/-130dBm) on my long wire.
I tried my discone, which can receive the IOW beacon at S1-S3 (but haven't
tried recently), but virtually nothing received with it on LW.
I also tried my 80m dipole but that didn't pick up the 153KHz station very
well.

I just tested my SDR Play with the same setup as the Andrus.
It received the 153KHz station at -88dBm and noise floor -115dBm which gives
27dB compared with 48dB from the Andrus. Oddly the earth connection made no
difference at all.
With the SDR Play the signal level value is meaningless because the Video
Gain shifts the signal strength up or down but with the same difference
between the signal and noise floor.
There isn't a way of showing S/N.
73 Allan G3PIY

-----Original Message-----
From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf
Of Alan G4ZFQ
Sent: 14 January 2020 15:03
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Long wave reception

I found I can now clearly hear the Romanian broadcast station on 153KHz.
Using a long wire via the unan I see it at a strength of 98.3dBm and
Allan,

I've never used an unun for any purpose. So cannot comment about that.
But with my HF+ I find a discone (Old Icom with 50MHz whip 32' above my
bungalow) gives the best reception on LW and lower.
Romania here at Cowes gives the carrier 40dB over noise level. Better
than any wire or loops/eprobe at the end of the garden.
I found this by accident, amazed that such a small antenna could work so
low.

73 Alan G4ZFQ

Kriss Kliegle KA1GJU
 

Bert,
 
Unun is a transformer, UNbalanced to UNbalanced.
Balun is a transformer for BAlanced to UNbalanced.

A dipole is balanced, so use of a balun is recommended when coax fed.
An end fed wire is unbalanced, so an Unun is used due to the high impedance from feeding the ‘dipole’ at the end of the wire (high impedance, high voltage).




Coax is unbalanced, ladder line is balanced.

Ham Radio 101

Cheers de Kriss KP2/KA1GJU/MM

Allan Isaacs
 

I made a second unun and found it worked even better at picking up long wave stations on my long wire than the first.

I wound three lengths of wire, each 220cm long on a cylindrical toroid 3cm long x 2.5cm dia giving me about 22 turns. The three lengths were slightly twisted together to aid threading on the ferrite.

I got better than a 3dB increase in signal strength over the standard type with 9 turns and can now clearly hear several new broadcasts including two from Iceland, Morocco, Czech Republic and Poland. The long wave band at night now looks very busy although there are still patches of local noise as you can see.

Allan G3PIY


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of Kriss Kliegle
Sent: 14 January 2020 23:11
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Long wave reception

 

Bert,
 
Unun is a transformer, UNbalanced to UNbalanced.
Balun is a transformer for BAlanced to UNbalanced.

A dipole is balanced, so use of a balun is recommended when coax fed.
An end fed wire is unbalanced, so an Unun is used due to the high impedance from feeding the ‘dipole’ at the end of the wire (high impedance, high voltage).




Coax is unbalanced, ladder line is balanced.

Ham Radio 101

Cheers de Kriss KP2/KA1GJU/MM

Allan Isaacs
 

Hi Kriss

That version is the same as mine but I read that they are best at HF.

Have you seen details for an LF or MF version?

Because I use it for receive not transmit I wonder if I can use say three windings of 50 turns of thinner wire still using a 9 to 1 step down.

 


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of Kriss Kliegle
Sent: 14 January 2020 14:44
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Long wave reception

 


My 124’ EFW’s with a 9:1 UNUN works just fine. The higher the better though!
Here’ s a good image of the windings:
https://vk6ysf.com/unun_9-1.htm






My 124’ :

73 Kriss KA1GJU

_._,_._,_

 

Gert Gremmen
 

An UNUN seen from the antenna wire is a kind of (auto)transformer to the coax, being 50 Ohm. The wire antenna sees (if a 9:1 UNUN) 450 Ohm, being 9 x coaximp.

If one disconnects the coax, the impedance at the wire antenna should rise to infinite (ideally) but is limited by the total of turns/toroid self induction.

The higher this self induction (when idle), the better the UNUN can function, up to the point that the "leakage impedance" (imperfections of the coil) creates a series impedance that stops the current to enter the UNUN. This latter inductance is probably not of a concern to you at LW, unless your a using hundreds of turns.

The number of turns determine the low frequency of operation (as well as the ferrite properties, of course), the accuracy of creating low leakage impedance by accurately winding / coupling the coil(s) determine the high frequency point of operation. In general the ratio of inductance versus leakage inductance will not be better than 10000:1 limiting the frequency range of operation to SQR(10000) to 100:1. A good balun operates from 300 kHz to 30 MHz.

That is why you see an improvement by adding wire turns to your UNUN ; the former design was probably based on 300kHz off.

The twisting helps to increase the narrow coupling between windings, and lowers the leakage induction, but is not essential at LW reception.

Depending on the ferrite type, further improvements can be expected with even more turns, at the cost of the high frequency side. Especially if you need to receive below 150 KHz, you may benefit from much more turns.

If you are interested in LW only you might try the same topology with 4 windings of 22 turns, by (assuming a standard 9:1 topology) adding an additional winding on top, increasing the impedance of your UNUN to 16x50 Ohm (16:1 UNUN) . Especially if your long wire does not come close to a 1/10 th of the wavelength (not probable).

Next step might be replacing the UNUN by a FET preamplifier, but at the costs of receive only. FETS do by design have a very high input impedance. Othe rproblems my rise however, such as intermodulation..just experiment.  But it's a hobby isn't it ?

Just my few cents, my assumptions might be wrong, but may be the explanation helps....

Gert

On 15-1-2020 0:43, Allan Isaacs wrote:

I made a second unun and found it worked even better at picking up long wave stations on my long wire than the first.

I wound three lengths of wire, each 220cm long on a cylindrical toroid 3cm long x 2.5cm dia giving me about 22 turns. The three lengths were slightly twisted together to aid threading on the ferrite.

I got better than a 3dB increase in signal strength over the standard type with 9 turns and can now clearly hear several new broadcasts including two from Iceland, Morocco, Czech Republic and Poland. The long wave band at night now looks very busy although there are still patches of local noise as you can see.

Allan G3PIY


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of Kriss Kliegle
Sent: 14 January 2020 23:11
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Long wave reception

 

Bert,
 
Unun is a transformer, UNbalanced to UNbalanced.
Balun is a transformer for BAlanced to UNbalanced.

A dipole is balanced, so use of a balun is recommended when coax fed.
An end fed wire is unbalanced, so an Unun is used due to the high impedance from feeding the ‘dipole’ at the end of the wire (high impedance, high voltage).




Coax is unbalanced, ladder line is balanced.

Ham Radio 101

Cheers de Kriss KP2/KA1GJU/MM

-- 
Independent Expert on CE marking 
EMC Consultant
Electrical Safety Consultant

Alan G4ZFQ
 

photo of your discone curious!?
Colin,

It looks like this one https://www.universal-radio.com/catalog/scanants/0828.html With a base loaded 50MHz whip.
It is old, many years ago (30?) in a moment of madness I bought an Icom R7000 and it was included. It has been up untouched since then and still seems to work OK.

Allan,
I turned my Wellbrook a little, Romania was near the null. It now receives with the same SNR. About 2 years ago the discone was the only antenna that would receive the Russian Alpha stations, ~10-16KHz. It does not maintain the advantage at higher frequencies.
I did wonder how it was working, a 70cm beam on the same mast did not work, nor did a temporary whip on another mast. Using the coax outer was useless.
The HF+ has a very quiet front end, maybe another RX would need a preamp. Also a LPF helps many SDRs.

73 Alan G4ZFQ



> I found I can now clearly hear the Romanian broadcast station on 153KHz.
> Using a long wire via the unan I see it at a strength of 98.3dBm and

Allan Isaacs
 

Thanks for the explanation Gert.

I had an idea to test the UNUNs to see how they perform on the bench.

The plan is to feed each with a tracking generator, perhaps via a resistor roughly equivalent to a typical antenna impedance and see how it performs across LF and HF.

I might try 4 wires as you suggest, to increase the ratio to 16:1.

The length of my horizontal long wire is about 80 metres including lead in and about 12m high so is about 0.05 wavelength at 1500m, so LONG is a misnomer. Maybe, SHORT wire is a better description.

I suppose a UNUN is the poor relation of a tuned circuit with a coupling loop, but has the advantage of not needing to be adjusted.

Allan G3PIY

 


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of Gert Gremmen
Sent: 15 January 2020 07:46
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Long wave reception

 

An UNUN seen from the antenna wire is a kind of (auto)transformer to the coax, being 50 Ohm. The wire antenna sees (if a 9:1 UNUN) 450 Ohm, being 9 x coaximp.

If one disconnects the coax, the impedance at the wire antenna should rise to infinite (ideally) but is limited by the total of turns/toroid self induction.

The higher this self induction (when idle), the better the UNUN can function, up to the point that the "leakage impedance" (imperfections of the coil) creates a series impedance that stops the current to enter the UNUN. This latter inductance is probably not of a concern to you at LW, unless your a using hundreds of turns.

The number of turns determine the low frequency of operation (as well as the ferrite properties, of course), the accuracy of creating low leakage impedance by accurately winding / coupling the coil(s) determine the high frequency point of operation. In general the ratio of inductance versus leakage inductance will not be better than 10000:1 limiting the frequency range of operation to SQR(10000) to 100:1. A good balun operates from 300 kHz to 30 MHz.

That is why you see an improvement by adding wire turns to your UNUN ; the former design was probably based on 300kHz off.

The twisting helps to increase the narrow coupling between windings, and lowers the leakage induction, but is not essential at LW reception.

Depending on the ferrite type, further improvements can be expected with even more turns, at the cost of the high frequency side. Especially if you need to receive below 150 KHz, you may benefit from much more turns.

If you are interested in LW only you might try the same topology with 4 windings of 22 turns, by (assuming a standard 9:1 topology) adding an additional winding on top, increasing the impedance of your UNUN to 16x50 Ohm (16:1 UNUN) . Especially if your long wire does not come close to a 1/10 th of the wavelength (not probable).

Next step might be replacing the UNUN by a FET preamplifier, but at the costs of receive only. FETS do by design have a very high input impedance. Othe rproblems my rise however, such as intermodulation..just experiment.  But it's a hobby isn't it ?

Just my few cents, my assumptions might be wrong, but may be the explanation helps....

Allan Isaacs
 

Scroll down this page and you can see my Moonraker discone here.
I scanned it some time ago and it did appear to work down to well below the
specified 25MHz although I only checked it down to 1MHz, but as a low
frequency receive antenna it would not provide much in the way of microvolts
because of it's small capture area.
A pretty weird response. Is this correct??
http://www.radiomuseum.co.uk/power.html
Mine is ancient and has seized parts so I can't dismantle it for checking
the coax connections.
Allan G3PIY

-----Original Message-----
From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf
Of Alan G4ZFQ
Sent: 15 January 2020 09:43
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Long wave reception

photo of your discone curious!?
Colin,

It looks like this one
https://www.universal-radio.com/catalog/scanants/0828.html With a base
loaded 50MHz whip.
It is old, many years ago (30?) in a moment of madness I bought an Icom
R7000 and it was included. It has been up untouched since then and still
seems to work OK.

Allan,
I turned my Wellbrook a little, Romania was near the null. It now
receives with the same SNR. About 2 years ago the discone was the only
antenna that would receive the Russian Alpha stations, ~10-16KHz. It
does not maintain the advantage at higher frequencies.
I did wonder how it was working, a 70cm beam on the same mast did not
work, nor did a temporary whip on another mast. Using the coax outer was
useless.
The HF+ has a very quiet front end, maybe another RX would need a
preamp. Also a LPF helps many SDRs.

73 Alan G4ZFQ



> I found I can now clearly hear the Romanian broadcast station on
153KHz.
> Using a long wire via the unun I see it at a strength of 98.3dBm and

Allan Isaacs
 

I might try a 49:1 unun Vince.

I carried out tests on my smaller 9-turn home brew 9:1 unun and its response was virtually dead flat from 10KHz to 100MHz.

Allan


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of DXer
Sent: 16 January 2020 01:33
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Long wave reception

 

Long thread, so forgive me if it's repeat information.

Regarding EFHW antennas. There appears to be a kind of consensus now that a 1:49 transformer with a 100 pF capacitor is the most efficient combination.

As for longwave reception. I have very good results with the much maligned cheap eBay clone of the Mini-Whip.

A sample of one, as always.  YMMV.

Regards,

Vince
Ottawa, ON

_._,_._,_