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

[Andre' Kesteloot]

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