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NDB reception

Posted: Mon Jul 24, 2017 8:01 pm
by Paul
I am about to display my ignorance yet again - Whilst I receive excellent quality cw/morse code signals all over the HF bands and have two antennae connected to Port A (Active mini-whip) and long-wire to the Hi-Z port pf an RSP-2, that perform well in the 190khz and upwards range, I have been unable to find any (even after having resorted to listed beacon frequencies).
Although it is not my primary area of interest, I would be grateful to anyone who could offer a suggestion as to why this may be the case.

Re: NDB reception

Posted: Mon Jul 24, 2017 8:36 pm
by Mike2459
It's been a long time since I've listened to NDBs, but perhaps I can help. If there are any within a 50km radius of your location they should be readable 24 hours a day. Otherwise listen after dark. Using sideband or cw mode will help pick the carrier out of the noise, as it can detect signals that are inaudible in AM mode.

Re: NDB reception

Posted: Mon Jul 24, 2017 11:15 pm
by g1hbe
Hi Paul. I occasionally listen around the beacon band and there are certainly beacons to be heard. There may be a couple of reasons why you aren't hearing much: First of all, neither of the SMA ports works well at LF (especially port B, which has a very poor LF response due to the bias-T circuitry), and this is covered in the user guide. The Hi-z port works very well from 10 KHz to 30 MHz and I see you are also using this port.
I wonder if you have a high noise level? My noise level has recently taken a turn for the worse and even my Wellbrook loop sometimes struggles to hear the beacons because of it. Noise from TV's, computers, phone chargers and anything that uses a SMPS is always worse at the LF end of the spectrum.
How is your wire antenna connected to the Hi-z port? Does the wire come straight into the shack or do you have some kind of coax feeder? If it comes straight in, that may be the problem, as the wire will pick up all the rubbish generated by the stuff in your home. It's also worth checking that you have wired the Hi-z connector as shown in the diagram. Sorry, I can't recall which user guide/cookbook the diagram is in!
Finally, in my experience mini-whips are just as bad as wires when it comes to picking up local noise, which is why I chose the Wellbrook loop. Nine times out of ten, it makes a signal audible when a wire (or my homebrew mini whip) just sees noise.

Re: NDB reception

Posted: Tue Jul 25, 2017 7:07 am
by Paul
Hi Mike/Andy
Thanks for your responses - I am in a rural location and apart from some "frying" that I believe emanates from overhead three-phase power lines, probably about 50M from my qth, things aren't that bad (I think) and unless ndb's are particularly weak signals, I would have expected to be able to find at least one.
Perhaps my setup isn't as good as I think or would wish it to be, but in general everything seems to work pretty well.
Just for the record, the mini-whip on port A can equal or often exceed the 20M longwire on occasion as conditions vary.
Port B is a h/v/uhf discone, primarily used for v/uhf, but does perform fairly reasonably on HF, with the anticipated roll-off around 3-4MHz.
The longwire is orientated NNW/SSE (my best option) and attached according to the detailed instructions of the supplier and SDRPlay directly to the Hi-z terminal, being brought in via a >5M length of coax.
I did experiment with a 9:1 balun but wasn't sold on it.

Re: NDB reception

Posted: Tue Jul 25, 2017 8:33 am
by g1hbe
Well it's a bit of a mystery! Do you get good sigs from the LW broadcasters? I'm clutching at straws now, but despite your rural location, it is worth looking at what SDRUNo reports as your background noise level. When my local noises are not on in the daytime, I get around -110 to -120 dBM at LF on the Wellbrook, but at least 20dB worse than this on my random wire and on the active mini-whip. This almost completely buries the beacons.
Just one final question, and I hope you won't feel insulted by it. Are all other signals on their expected frequencies? I ask this because a new user on one of the forums was bemoaning 'no signals and images all over the place', and to cut a long story short he had inadvertantly reversed the I and Q channels, putting everything out, plonking stations where they shouldn't be and silence where they should!
Sorry to have to ask, but sometimes it's easy to overlook these things.
The only other thing that springs to mind is de-sensitisation from big sigs in the MW band. Do you have any huge MW sigs there? The LF filter on the RSP2 reaches all the way up to 12 MHz, so everything gets in! It's also worth looking at the LNA gain level and reducing it (or increasing the 'gain reduction' setting).

Re: NDB reception

Posted: Tue Jul 25, 2017 3:27 pm
by Paul
Thanks for the last Andy
I will persevere - all taken aboard - and no you would have to work harder than that to make me feel insulted...
I'm always grateful for any constructive comment.Best Wishes

Re: NDB reception

Posted: Sun Nov 19, 2017 9:22 am
by Paul
Hi Andy
Thanks for all the useful advice re NDB reception.
Did a bit of antenna "fettleing," replacing the RAS0Ms mini-whip on port A with another version from the Ukraine (I doubt my ability to make my own) and using it on Port A, I am now able to get pretty good NDB reception (mainly using your preferred AM mode for most) in the 320 - 430 KHZ area.
Generally receiving beacons out to about 200NM from my QTH, with the single exception of Horta in the Azores.
Apart from finding this little antenna a great deal more sensitive in this area, your advice was invaluable.
I recognise that using the HI-Z port would be a better option, but I've dedicated that to the simple end-fed long-wire, which works well, so there I'll leave it (I think).
It was an interesting exercise and ultimately satisfying, but I'll try not to get "hooked."

Re: NDB reception

Posted: Sun Nov 19, 2017 4:31 pm
Perhaps there are less NDBs about than there used to be - I suppose a great deal depends on your location??

Re: NDB reception

Posted: Sun Nov 19, 2017 6:10 pm
by 13dka
Glad you get reception "down there" now. :) However, while a miniwhip-style antenna gives surprisingly good results even "down there", a simple wire loop will beat it on many occasions.

Here's a comparison of VLF and NDB reception with a dipole vs. a loop of the same wire length. Actually it's the very same antenna, which is a rather odd contraption I made (by accident) specifically for the RSP, meant to give both good SNR, good wideband capabilities and some built-in attenuation to keep the RSP overloading in check. It's basically a 2x10m dipole with a deliberately not matching balun (the infamous NooElec 9:1 balun) used on both sides of the coax. Putting that thing at the very same spot (in some trees in my case) into a delta (or whatever kind of) loop configuration by simply connecting the wire ends is fundamentally changing its properties of course, to the benefit of low frequency reception.

Here are some animated GIFs to demonstrate:

VLF_crappole_vs_craploop.gif (163.95 KiB) Viewed 3363 times

This shows the impact of the configuration on VLF reception. As you can see, the difference is quite noticeable, spurious signals tend to disappear and actual on-frequency signals get a much better SNR. You can clearly see (and hear of course) the 60 and 77kHz time signals, that were much in the noise before in the dipole configuration.

Here's the NDB band:

NDB_crappole_vs_craploop.gif (212.67 KiB) Viewed 3363 times

The difference is obviously even more pronounced here. The NDB band more or less doesn't exist in the dipole configuration, in the loop configuration I get some additional muck but also a lot of NDBs. Here's what the band typically looks like then:

NDB_Love2.jpg (224.57 KiB) Viewed 3363 times

As you can see, there's quite a lot of them to see clearly, and a lot more of them to pick up in much noise using narrow CW filters and a lot of patience (since they're often fading in and out slowly, interfering with others on a nearby frequency and so on). To my own surprise, I found hunting NDBs a fun challenge, at least for a few days and I'll most likely do it again!

Here's a typical log of 3 days of NDB hunting, they're from all over Europe:

Code: Select all

517   JBR   Jaszbereny (Budapest)   HU      1069km
514   GO   Amari Airbase      EST      1093km
492   TBV   Trebova         CZ       723km
490   WAK   Vakarel         BG      1684km
488   ILM   Illesheim        D       528km
485   IA   Indija            SRB (Belgrad)   1330km
484   HOF   Hof         D       473km
478   MF   Larionovo      RUS      1854km*
468   FTZ   Fritzlar           D       335km
458   LP   ?
452   ANS   Ansbach         D       550km
448   HLV   Holesov         CZ       803km
448   LQ   Landsberg      D       698km
438   KO   Kozala         CRO      1057km
434   MV   Melun-Villar.      F       755km
433   VNS   Castor Platform      ESP      1650km
433   CRE   Cres         CRO      1095km
432   PK   Pardubice      CZ       656km
431   KBA   Karlsruhe                    D       571km
430   SN   St. Yan         F       924km
429   LOS   Losinj         CRO      1123km
428   MUS   Nice Cote d'Azur        F      1165km
428   CTX   Chateauroux      F       958km
427   RY   Royan         F      1179km
426.5   MIQ   Mike Ingolstadt      D       623km
426   GBG   Gleichenberg      A       948km
424   PIS   Pisarovina      CRO      1074km
424   PHG   Phalsbourg      F       606km
423   ZO   Nis         SRB      1532km
423   FE   Odense         DK
421   BL   Borlange                               S       809km
421   MF   Halmstad                    S       379km
419   EMT   Epinal         F       683km
419   RD   Vasteras                    S       767km
418   MK   Mark Calais      F       590km
417   AX   Auxerre Branches       F       792km
417   AH    Angelholm      S       346km
416   BCS   Bacchus         S      1052km
415   OL   Linkoping Saab      S       633km
415   RTB   Rothenbach      D       542km
414   HD   Hestad         NOR       818km
414   BRI   Bristol         GB       824km
414   BOA   Bologna         I      1069km
412   SE   Strasbourg      F       622km
410   ETN   Etain         F       590km
409   SG   Satenas         S       534km
406.5   BOT   Bottrop         D
404   Y   Kemi         FIN      1378km
404   LW   Luxembourg      LX
404   MRV   Merville          F       572km
403   OJ   Jonkoping      S       523km
402   LX   Ekilstuna         S       745km
401   COD   Codogno         I       999km
400.5   EJ   Esbjerg         DK
400   EN   Orebro         S       690km
400   ONO   Oostende                    BEL       514km
396   YG   Enge         NOR      1386km
395   GE   Billund         DK
394   NB   Bromma (Stockholm)   S       801km
394   NV   Nevers         F       890km
392.5   TOP   Torino         I
392   RAN   Lappeenranta      FIN
388   BR   Lyon         F       973km
388   COR   Corner (Stockholm)   S
388   KRU   Kruunu         FIN      1412km
387   SLT   Sylt (aua)      D
387   SLV   Spa         BEL       453km
387   ING   Saint-Inglevert      BEL       601km
386   O   Kardla         EST      1005km
386   LNE   Linate         I       966km
384   TY   Torsby         S       712km
383.5   GUL   Gulpen         NL
383   ERK   Erken         S       865km
382   SBG   Salzburg         A       762km
381   RG   Rygge         NOR       596km
380   FLR   Trondheim      NOR      1038km   
380   HO   Colmar/Houssen      F       681km
379   VEN   Venezia         I       999km
379   EB   Saint Etienne/Boutheon   F      1018km
378   RSY   Rennesøy (Stavanger)   NOR       583km
378   OS   Sundsvall                    S      1041km
377   KN   Norkoping      S       670km
377   SM   Siljan/Mora      S       576km
377   ORI   Orio Al Serio      I       942km
376   HAN   Hahn         D       478km
376   HP   Esbjerg         DK
375   RB   Orebro         S       690km
375   GLA   Gland         CH       876km
375   CV   Calvi/Corsica      F      1286km
374.5   ANC   Ancona         I      1218km
374   BGC   Bergerac         F      1194km
373   NW   Maastricht      NL       423km
371   HAA   Hamar         NOR       753km
371   ODR   Odderoy         NOR       448km
371   LEV   Levaldigi        I      1070km
370.5   LB   Angelholm      S       346km
370   PSA   Spessart         D
370   BSV   Besancon                    F       792km
369   NL   Landvetter      S       446km
369   ELU   Luxembourg      LX       515km
368   RK   Roskilde                    DK
367   BYC   Bueckeburg      D
367   VAT   Vatry         F       671km
366   UTH   Uthaug         NOR      1067km
366   KM   Kalmar         S       551km
365   VS   Vesilahti                     FIN      1181km
365   LJ   Koeln/Bonn      D
364   NW   Stockholm      S       805km
363   PI   Poitiers          F      1032km
363   OEM   Kristianstad      S       398km
362   BVK   Baatvik         NOR       984km
362   NN   Ekilstuna                    S       745km
361   NB   Bordeaux        F      1235km
361   MAK   Mackel         BEL       502km
360   ASK   Bergen Askoy      NOR       739km
360   SR   Ensheim         D       483km
360   ULV   Ulvingen                    NOR      1290km
359   LOR   Lorient         F      1109km
358   GRK   Grakallen                    NOR      1036km
357.5   FAL   Falconara      I      1214km
357   SME   Olbia Costa Sardinia   I      1470km
357   KD   Kolding         DK
357   VZ   Eelde         NL
356   SGO   Sagunto         ESP      1747km*
355   ONW   Antwerpen      NL       441km
354   PAD   Paderborn      D
352.5   DD   Oostende                    BEL       540km
352   PLA   Pula         CRO      1090km
352   LAA   Laarbruch      D       335km
352   PSJ   Seinajoki                    FIN      1255km
351   OV   Visby         S       704km
351   ROT   Rotterdam      NL       382km
349.5   SZA   Solenzara (COR)      I      1368km
349   JX   Vaxjo         S       483km
349   TAR   Tarva/Orland      NOR      1075km
348   WA   Arlanda         S       823km
347   CVT   Chalons         F       654km
346   AU   Stauning                        DK
346   WLU   Luxemburg      LX       515km
346   LHO   Le Havre                    F       791km
345.5   CF   Caslav         CZ       648km
345   BN   Birkeland                    NOR       468km
343   KUS   Kaunas         LIT       973km
342   SL   Landvetter      S
342   LL   Leirin         NOR       766km
341   NKS   Karlstad          S       648km
341   IS   Ajaccio   (Corsica)                 F      1358km
339.5   SD   ?
338   OA   Jonkoping      S       523km
337   MY   Myggenes      FO      1261km
337   LHR   Lahr         D       648km
336   LT   Halmstad                    S       379km
335   BER   Bern         CH       805km
334   POY   Paris Orly      F       750km
333   LE   Vasteras         S       767km
332   NV   Nieuwkoop      NL
332   VOG   Voghera         I      1016km
331   TUR   Tours         F       943km
330   SO   Eelde                      NL
330   SKS   Karlstad                    S       648km
330   OB   Bratislava      SLO       879km
329   NMS   Namsos         NOR      1158km
329   VX   Vaxjo         S       483km
329   SB   Sonderborg      DK
327   LNZ   Linz         A       749km
326   LM   Le Mans         F       909km
325   PG   Trollhättan      S       508km
324   ON   Norkoping      S       670km
324   DP   Diepholz                    D
323   ONC   Charleroi        BEL       511km
322   OU   Stockholm      S       805km
321   VO   Val D'Or                    F       653km
320   VE   Chabeuil                    F      1063km
319   VAR   Varhaug         NOR       536km
318   LP   Ronneby         S       469km
318   RW   Tegel West      D
318   CP   Parduc         HU       974km
317   OZ   Kardla         EST      1005km
316   TNJ   Tounj         CRO      1091km
316   IN   Sonderborg      DK
314   HOL   Villacoublay      F       752km
314   OZ   Brussels Natl      BEL       475km
311   LMA   Lima (DUS)      D
309   DO   Dole Tavaux      F       824km
307   DIK   Diekirch                    LX       505km
306.5   AV   Avord         F       902km
300.5   CMP   Compagnano      I      1269km
300   SC   Linkoping      S       633km
299.5   KN   Svolvaer                    NOR      1596km
293   OB   Brussels          BEL       475km
290   ONL   Bieset         BEL       450km
285   LCF   ?         S
284   FSB   Fassberg                    D

(Grr, seems there's no way to keep a tab-formatted list aligned.)

As you can see, the most distant ones are 1700-1800km away and I've seen logs with even bigger distances, and I can feel a bit of that urge to improve my rig to get even more distant NDBs myself. It think that is the magic of NDB hunting, you have very weak signals from fixed and known locations on published frequencies that sit there and transmit all night, giving you the ideal counterpart for improving your stuff to receive them and improving your skills to search and identify them, which can be quite some detective work. Utterly nerdy fun. :)

GM4FDM wrote:Perhaps there are less NDBs about than there used to be - I suppose a great deal depends on your location??

Well yes, some NDBs have been turned off in the past 10 years but surprisingly it seems VORs are more affected by cost reduction attempts than NDBs, which may have to do with the higher maintenance efforts and the fact that many NDBs are still important waypoints on ILS approaches (such as marking the Initial Approach Fix etc.). Most NDBs I still get are located on or near an airport, rather than "enroute"-style beacons. This does matter in that the co-located beacons usually have much less power output.

But location is important too of course, as well as antenna orientation (which is probably less of an issue with a miniwhip tho).

Re: NDB reception

Posted: Mon Nov 20, 2017 9:03 am
by CaptainNemo
very impressive
can you post some details about your loop? horizontal I suppose...
(I have already tried a loop but with no success)
thanks in advance