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21. LF: Re: SMT-Hell (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sat, 24 Feb 2001 19:53:45 +0100
Tnx for the report. I was playing about with the settings looking for suitable sets of frequency span / pixel intervals for Argo, and decided to leave it going at high power as conditions seemed quie
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-02/msg00063.html (8,093 bytes)

22. RE: LF: Re: Another code (score: 1)
Author: "Andy talbot" <[email protected]>
Date: Mon, 19 Feb 2001 10:50:35 +0100
Correct :-( But someone has now forwarded the semaphore alphabet so when a few idle few minutes come along .......... More seriously, we can go on inventing new signalling methods and alphabets ad-in
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-02/msg00218.html (9,422 bytes)

23. LF: Re: Another code (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sun, 18 Feb 2001 18:55:46 +0100
Sort of suggests a Multifrequency Version similar to SMT Hell. There's a thought. :-) Easy to do with the DDS driver. What is the Semaphore alphabet ? Andy G4JNT One other mode that never failed (see
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-02/msg00235.html (8,265 bytes)

24. LF: DFCW Transmission (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Mon, 12 Feb 2001 20:38:42 +0100
If 350mW can be heard then there is a slight hope for me yet :-) At 1920z, just started transmitting transmitting a DFCW signal with 0.05Hz shift and 90s dot period (for compatibility with Argo on it
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-02/msg00333.html (7,980 bytes)

25. Re: LF: GPS-Disciplined BPSK (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Mon, 12 Feb 2001 18:21:19 +0100
The GPS25 module - one of those recommended by TAPR for the "GPS Disciplined Frequency Standard" - is specified as having a 1 PPS output accurate to within 1 microsecond of UTC. Additionally, it is s
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-02/msg00341.html (11,559 bytes)

26. LF: Re: Signals around 135.923 (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sun, 04 Feb 2001 10:57:05 +0100
So 'JNT was visible and understandable then :-) I was finishing off the DFCW software for the DDS module after seeing Laurie's signal in real time, and modding it so gap length could be programmed se
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-02/msg00569.html (9,788 bytes)

27. LF: Re: Beacon signals (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sat, 03 Feb 2001 15:21:39 +0100
--Original Message-- From: James Moritz Subject: LF: Beacon signals long dots and dashes, and took about 1hour 20mins to send the complete call. Does anybody know of a keyer program available for .lo
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-02/msg00589.html (7,958 bytes)

28. LF: Re: test (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sat, 03 Mar 2001 17:29:23 +0100
No messages from this reflector - is it working properly, or in quarantine for Foot and Mouth :-( Andy 'JNT
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-03/msg00394.html (8,273 bytes)

29. LF: Re: LF Forum (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sat, 14 Apr 2001 10:40:53 +0100
There has been so much discussion on Wolf and BPSK spectra on this reflector recently that it seems a prime topic for the forthcoming LF Forum on 20 May at Flight Refuelling HQ nr Wimborne. Has anyon
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-04/msg00196.html (8,145 bytes)

30. LF: Re: Modulation pattern on 16kHz ? (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Mon, 28 May 2001 10:37:39 +0100
The 16kHz transmission is MSK (Minimum Shift keying). An efficient, constant amplitude, data modulation format. There was quite a bit of discussion about the mode on this reflector a few months ago,
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-05/msg00052.html (10,999 bytes)

31. LF: Lost EMail (score: 1)
Author: "Andy talbot" <[email protected]>
Date: Wed, 23 May 2001 11:24:17 +0100
Due to a major c__k up here, I have not received any external EMail on the works account since yesterday morning, including any messages from this reflector. So Mike 'XDV, if you have posted a summar
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-05/msg00102.html (7,989 bytes)

32. Re: LF: Measurement of antenna current (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sun, 13 May 2001 15:34:26 +0100
You've made me think about it a lot more now. The AC/DC resistance argument is certainly valid. It does indeed mean that any capacitive field will be captured with less loss than letting it end up in
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-05/msg00192.html (10,242 bytes)

33. LF: Re: Radiation from loading coil causing difference in current at top and bottom? (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sun, 13 May 2001 15:26:43 +0100
But these harmonic currents will upset your readings somewhat - where on a scope trace is the RMS value of a) the total waveform and b) the fundamental ? The harmonic currents will obviously be out o
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-05/msg00193.html (9,785 bytes)

34. Re: LF: Measurement of antenna current Correction (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sat, 12 May 2001 21:06:07 +0100
I measured the thinkness of some (Sainsbury's own brand) foil at 0.03mm. This equates to 0.13 skin depths. It is even worse. I read the micrometer wrong, a very ancient one calibrated in those US uni
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-05/msg00202.html (8,144 bytes)

35. Re: LF: Measurement of antenna current (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sat, 12 May 2001 20:53:45 +0100
Steve and group Aluminium kitchen foil is much thinner than the skin depth at these frequencies, so you are getting nowhere near the full screening effect. Skin depth is given by 503.SQRT(Rho / Freq)
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-05/msg00203.html (10,532 bytes)

36. LF: Re: Measurement of antenna current (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sun, 6 May 2001 22:31:14 +0100
I would have thought the stray capacitance associated with the ammeter when measuring current at the top of the coil would cause more than enough detuning to reduce the current by this much. But ther
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-05/msg00258.html (9,502 bytes)

37. LF: Re: Coupling between two antennas (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sat, 5 May 2001 19:00:27 +0100
The measured voltage was 8 volts peak-to-peak, corresponding to a power of about 60 mW. 8V p-p in 50 ohms is 0.16W, not 60mW So you have 34dB coupling - you were right to expect more than 40dB ! Andy
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-05/msg00272.html (8,009 bytes)

38. LF: Re: Re: RE: LX1PD (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Mon, 25 Jun 2001 18:24:20 +0100
Why ? I did look at this, and came to the conculsion : Peak of one cycle falling to the 60 degree point, SIN(60) = 0.866. So ripple = 1 - 0.866 = .134 hence 13.4% I did hear once that some high power
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-06/msg00059.html (9,938 bytes)

39. LF: Re: Near field of 9kHz antenna IV (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sat, 14 Jul 2001 23:03:59 +0100
Wait a minute ! I = SQR(W / R) so current in the loop = 51.2A and voltage at the feed is this current in the 60 ohms reactance, ie. 3077V Andy G4JNT --Original Message-- From: Dick Rollema <d.w.rolle
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-07/msg00107.html (9,156 bytes)

40. LF: Re: re 9kHz NOVs (score: 1)
Author: "Andrew Talbot" <[email protected]>
Date: Sat, 14 Jul 2001 23:16:41 +0100
Alan - We need to be realistic about the types of inductor feasible for transmitters at this frequency. With an antenna capacitance of 270pF and inductor of 1.2H or so at 9kHz, the number of turns ne
/rsgb_lf_group-archives/html/rsgb_lf_group/2001-07/msg00108.html (9,984 bytes)


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