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Beginner's curiosity

Posted: Sun Sep 09, 2018 6:41 am
by Paul
Whilst searching for NDB's (could be habit-forminlisted correct frequency.g!), I occasionally come accross valid beacon idenifiers audible in CW only and displaced (with at least one exception) from the correct flisted frequencies.
I understand that anomalies may occur as a result of nearby strong signals, but if anyone has the time and inclination, could anyone conffirm, or not, reception of the Horta (FIL) Ndb on 378.975 khz CW (should be centered on 380 khz) and Vigo (VON) on 433 khz (should be centered on 434 khz) both
received 5X5.
On th other hand, the St Brieuc NDB (SB) on 353 khz is received here spot on frequency with no apparent SSB transmission in CW only 5X5.
There are others but that's probably sufficient to illustrate my query.
Now that I "understand" the directional qualities of the Wellbrook antennae, I am finding "interesting anomalies" in that I am finding additonal (new to me) beacons that are considerably offset from the plane of the antenna ((not necessarily on the "reciprocal" bearings).
Wuth the antenna somewhat imprecisely orientated NE/SW, I also receive well from a generally easterly direction (are "side-lobes" to be expected and if so, are they regular with regard to orientation).
I appreciate that these questions may make any knowledgeable person tear their hair out, but (even at my age) curiosity is a curse...

Re: Beginner's curiosity

Posted: Sun Sep 09, 2018 8:11 pm
by Roger
You will probably find your answer in an NDB group like this one.

You may find this NDB article interesting...

Lots of good info here on NDB's

Re: Beginner's curiosity

Posted: Sun Sep 09, 2018 10:25 pm
by Mike2459
Hi Paul:

I am in the USA so I can't receive any ndb's from Europe. Here is the info I found on the Horta NDB.

Carrier freq: 380 Call: FIL LSB:1017 USB:1024 Period:13.6 Details:ID+10" gap Loc:Horta / Faial Island AZR Gridsquare of TX: HM58pm

The LSB & USB fields show the modulation frequency for the lower and upper sidebands. Adding the USB freq 1024 (it's in hertz) to the carrier (380 khz) gives 381.024 kHz. Subtracting the LSB from the carrier yields: 380-1.017= 378.973kHz, only 2 hertz difference from the value that you found. Actually the modulating frequencies are probably the same (1020hz) it's likely the carrier freq is off about +3.5 hz. This format is similar to the format used in beacons in the USA which are modulated around 1000 Hz. Canadian beacons incidentally are modulated with a 400 Hz tone. Occasionally you will run into a beacon that has one of it's sidebands suppressed. If this is confusing, suggest you google "amplitude modulation" others could probably explain it easier than I could!!

Here is the data for VIGO:
433 VON 1024 1022 17.4 Vigo ESP IN52qe 200Watts WAS VGO (till 1998)

In a noisy environment I use CW mode to find NDB's. Many times they will be impossible to hear in AM mode but clear when tuned properly in CW mode. Narrowing the cw bandwidth manually and using SDRUno's notch filters also helps in blocking interfering signals.

Here is a link to the excellent resource for help in identifying NDB's. It is updated regularly. There is a lot of data available in addition to Callsign and carrier frequency.

Re: Beginner's curiosity

Posted: Sun Sep 09, 2018 10:44 pm
by Mike2459
PS: When using the ClassAxe Database if you don't know the call simply enter the frequency in khz in the freq field. It will list all NDB's using that frequency (and several Khz above the entered freq in ascending order)

Re: Beginner's curiosity

Posted: Sun Sep 09, 2018 10:53 pm
by Mike2459
PPS: It appears SB on 353 khz uses an unmodulated carrier, or ON-OFF keying.

Re: Beginner's curiosity

Posted: Mon Sep 10, 2018 6:05 am
by Paul
Thanks for the VERY lucid information re: Horta NDB Mike. It's at alevel that I can understand and answers that one, serving me as an example for some others. Also the St Brieuc is clearly addressed by you, leaving me content on that score - there are others like it in France at least.
I do listen mainly in AM (DSB), as I know do tohers far more experienced than me.
I often find that the signals are better audible in this mode. However, I could probably do with refining my sue of the CW functions of the RSP as it can sometimes work better.
For CW I use the Peak Hold function and as narrow a bandwidth as possible, tweaking the RSP's HP filter FC to produce a higher-pitch that suits me a little better.
And thank you Roger for the informational links.