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21. Re: LF: what causes this on wspr (score: 1)
Author: Andy Talbot <[email protected]>
Date: Wed, 1 Jul 2015 18:22:27 +0100
Hi Andy   Problem there  is  it  lasts  , what  seems  to  be  the  full  duration  of the  data  phase  [ phase as  a change  from  cw  to data .. etc ]   wspr  via a  ssb  rig ,  overdriving  usua
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-07/msg00012.html (13,853 bytes)

22. Re: LF: what causes this on wspr (score: 1)
Author: Andy Talbot <[email protected]>
Date: Wed, 1 Jul 2015 19:58:21 +0100
I don't think  its  stability Andy  ,  could  be step  response and  settling  time ,   the  new  U3 kit   uses  a  PLL and produces  , what was thought to  be  key  click's  but  is  PLL   settling
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-07/msg00015.html (17,450 bytes)

23. Re: LF: Today's soldering (score: 1)
Author: Andy Talbot <[email protected]>
Date: Wed, 15 Jul 2015 06:37:46 +0100
OK, I'm all confused now. The [HEF] 4013 is a dual Flip-Flop;  how have you made it oscill with a crystal ? (Or have you hidden something under the board) Andy  G4JNT On 14 July 2015 at 22:16, DK7FC
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-07/msg00074.html (12,534 bytes)

24. Re: LF: Today's soldering (score: 1)
Author: Andy Talbot <[email protected]>
Date: Wed, 15 Jul 2015 14:00:33 +0100
Yes, there's a JFET on the other side. So far a BF245A. It works well. But the circuit consumes 3.5 mA. I thought it could be less. It is running at 5V DC and the xtal frequency is 1.8432 MHz. I loo
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-07/msg00076.html (15,612 bytes)

25. Re: LF: OT: AOL email bounces (score: 1)
Author: Andy Talbot <[email protected]>
Date: Sun, 19 Jul 2015 14:09:11 +0100
I found this email in my spam box (I use GMail).   The reason given, was that it had failed some test relating to AOL sources ( ?? ) I unspammed it, then forwarded to the "anti-spam team" as suggeste
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-07/msg00083.html (11,365 bytes)

26. Re: LF: F6CNI to night testing a tuned loop TX on MF (score: 1)
Author: Andy Talbot <[email protected]>
Date: Tue, 28 Jul 2015 10:12:48 +0100
That is interesting, and encouraging.  I inserted your loop parameters into a spreadsheet I wrote many years ago in the early days of LF to calculate the properties of loop antennas.   As the spreads
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-07/msg00143.html (43,312 bytes)

27. Re: LF: Protecting a MOSFET driver chip from MOSFET failure? (score: 1)
Author: Andy Talbot <[email protected]>
Date: Mon, 10 Aug 2015 13:31:22 +0100
Yes there is.  Or , are: several. Don't drive the MOSFET directly from the IC.  Instead use a capacitor and DC restorer circuit.  That guards against both  the driver staying high permanently if driv
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-08/msg00089.html (14,085 bytes)

28. Re: LF: Protecting a MOSFET driver chip from MOSFET failure? (score: 1)
Author: Andy Talbot <[email protected]>
Date: Mon, 10 Aug 2015 14:25:40 +0100
Forgot to mention, although I hope it is more than self-evident to readers here, the diode is orientated so it points 'upwards';  allowing a positive drive voltage to appear on the gate and clamping
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-08/msg00092.html (15,114 bytes)

29. Re: LF: Protecting a MOSFET driver chip from MOSFET failure? (score: 1)
Author: Andy Talbot <[email protected]>
Date: Mon, 10 Aug 2015 16:15:57 +0100
Maybe also worth to mention:  Capacitive coupling of the driver to the gate will reduce the peak voltage at the gate by half (assuming 50% duty cycle). The IC driver voltage should be at least 12V i
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-08/msg00096.html (19,364 bytes)

30. Re: Re[2]: LF: Protecting a MOSFET driver chip from MOSFET failure? (score: 1)
Author: Andy Talbot <[email protected]>
Date: Mon, 10 Aug 2015 17:50:11 +0100
There is Miller feedback present, where the drain change of voltage is fed back to the gate via internal capacitiance.  The effect is to magnify the Cdg value by the voltage gain, so its bound to giv
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-08/msg00099.html (15,734 bytes)

31. LF: Folded monopole - Food for thought (score: 1)
Author: Andy Talbot <[email protected]>
Date: Fri, 14 Aug 2015 17:52:26 +0100
On the RSGBTech group recently G3RZP described his folded monopole topband antenna.  he runs an insulated wire up the side of the lattice mast to which it is bonded at the top.  The bottom of this wi
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-08/msg00119.html (12,025 bytes)

32. Re: LF: Re: RE: Folded monopole - Food for thought (score: 1)
Author: Andy Talbot <[email protected]>
Date: Fri, 14 Aug 2015 22:38:03 +0100
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-08/msg00123.html (11,378 bytes)

33. Re: LF: Re: RE: Folded monopole - Food for thought (score: 1)
Author: Andy Talbot <[email protected]>
Date: Sat, 15 Aug 2015 19:16:11 +0100
I believe it's neither 3dB nor 6dB increase for ERP. What is squared by doubling the effective height is is Rrad. The increase in ERP is by far not so high and depends much on Rloss (ground and matc
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-08/msg00133.html (13,227 bytes)

34. Re: LF: Some LF again (score: 1)
Author: Andy Talbot <[email protected]>
Date: Sun, 16 Aug 2015 20:26:06 +0100
6dB per bit 'jnt On 16 August 2015 at 20:19, Graham <[email protected]> wrote: That's one  of those urban things  :) Sure the  abs range  is  3 dB per  bit + 3 But the reference  point is  floa
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-08/msg00151.html (15,862 bytes)

35. LF: Fwd: [rsgbtech] IMD performance (score: 1)
Author: Andy Talbot <[email protected]>
Date: Fri, 28 Aug 2015 09:59:36 +0100
A while ago I made a medium power (~ 50 watts) linear PA for use at LF to MF. Details are here http://www.g4jnt.com/linear_LF_PA3.pdf After a discussion about linearity on IMD in switching FET PAs on
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-08/msg00245.html (9,854 bytes)

36. Re: LF: First MF TA since a longer time (score: 1)
Author: Andy Talbot <[email protected]>
Date: Fri, 25 Sep 2015 10:13:51 +0100
Hi Stefan,   a wspr -6dB sgnal is audible ? The question is this: with this condition and if necessary a bit more power it is possible a cw qso?   73, Fausto IK4NMF     -- Original Message -- From:
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-09/msg00115.html (17,377 bytes)

37. Re: LF: Coherent BPSK on LF using EbNaut (score: 1)
Author: Andy Talbot <[email protected]>
Date: Fri, 25 Sep 2015 12:23:40 +0100
EbAnut is a new one here - I hadn't heard of it.   After Googling I found the page and read up / downloaded the software.   Unfortunately, I see it is not standalone, and requires Spectrum lab to act
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-09/msg00119.html (13,445 bytes)

38. Re: LF: Coherent BPSK on LF using EbNaut (score: 1)
Author: Andy Talbot <[email protected]>
Date: Fri, 25 Sep 2015 17:20:50 +0100
That gives me an idea ... For some time I've been toying with the idea of writing  a utility that reads audio in blocks based on UTC timings and saves to a .WAV file . It woudl form part of a long te
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-09/msg00126.html (18,154 bytes)

39. Re: LF: Coherent BPSK on LF using EbNaut (score: 1)
Author: Andy Talbot <[email protected]>
Date: Sat, 26 Sep 2015 15:41:03 +0100
Yessss... Hadn't appreciated that was what it was doing until I read the description in more detail.   I suppose that if soundcards are going to be used as the interface some sort of locking will hav
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-09/msg00136.html (16,411 bytes)

40. Re: LF: Coherent BPSK on LF using EbNaut (score: 1)
Author: Andy Talbot <[email protected]>
Date: Mon, 28 Sep 2015 12:21:39 +0100
No, this doesn't work as the sampling of the I and Q information must be simultaneous.   Doing it your way, they are offset by a cycle of Fc In fact, I had this very discussion with G3PLX back in 199
/rsgb_lf_group-archives/html/rsgb_lf_group/2015-09/msg00157.html (22,201 bytes)


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