[Lf] Re: DFC39 Reception in Mechanicsburg ????

[Frank Gentges]

Dick,

I am not sure what the RX320 problem is in going below 50 kHz.  Based on 
this lack on detail I would suspect the ferrite core is not high enough 
mu.  Most ferrites are well below the "J" mix which would put the 
transformer low end around 50 kHz.  In this case either get a new core or 
wind more turns.  With more turns the leakage reactance will go up and 
the top end around 30 mHz will suffer.

Frank K0BRA


On Sat, 29 Jan 2000, Andre' Kesteloot wrote:

> Richard Goodman wrote:
> 
> > There have been many
> > times that when I tune 138.830,  I see something right on my receiver
> > offset frequency of 750 HZ.  There are also times when it is not there at
> > all.  Late this afternoon,  it was so strong that I could actually audibly
> > hear it... albiet   very weakly.
> 
> did it sound like the audio file we received last week, a tone and then a
> chirp?
> 
> > When I look at the top oscilloscope
> > display on Spectran,  I see the signal pip moving up & down .... like
> > there's propagation involved....
> 
> does it fade out after 0700 Zulu ? Other European LF broacast stations can only
> be heard until about 0800 Zulu
> 
> > Tonight with it being this strong however,
> >  it's not moving in amplitude very much.  The other signals that are on the
> > graphic in the attached file,  don't move at all ... I think they're local.
> 
> could these be harmonics of Loran ?  In Europe, you see them all over the place
> 
> >     I'm also in the process of getting the parts together for the
> > "Synchronous Noise Blanker" by John Reed,  KA5QEP.  I found this on the
> > Longwave Home Page.
> 
> I have recently built a dual unit of that blanker (you usually need more that
> just one channel). Let me know if you need some details on how to implement it
> a little better than the original design, which has some weak points, IMHO
> 
> > There are times (like right now) that I have serious
> > line noise problems...
> 
> that blanker works very well in the presence of 120 Hz spikes
> 
> > . anyways,  it's been years since I've done as much
> > homebrewing as I'm doing now & it's fun !
> 
> I agree, LF is the last frontier wherewe can still have real fun
> 
> 
> >  It was also discovered that the Palomar downconverter was a full
> > 1 KHz low in frequency.
> 
> The Palomar thing consists of a crystal oscillator and a 1496 dbm.  Although
> rather old in design, itstill works pretty well. The Crsytal is usually less
> than accurate. A TCXO would certaily help.  New designs have been created that
> use a 4 fet analog switch instead of a 1496, claiming less noise. But tome, the
> RX320 is as good as it gets anyway.
> 
> 
> >  I also made a discovery about the RX-320...
> > even though I did the VLF mod.... the darned thing seems to be deaf below
> > about 50 KHz.
> 
> check with Frank K0BRA, whose address appears aboce in the "cc"
> 
> >
> >                 73
> >
> >                 Dick,  WA3USG
> 
>