[RFI] tracking RFI with a marine direction finder

[AA5CT]

Do not under-sell the usefulness the cardioid (unidirectional) antenna pattern 
adds (via the "Sense" antenna function) when DFing noise or other signals
when using a Coastal Navigator/NAV 101 receiver.

Riding a bicycle and continually 'rotating' the cardioid antenna I can practically
'drive up to' any interfering signal on the 160 or 80 meter bands when DFing
same.Using a loopstick alone (with only nulls to go by) is a little trickier.
Nowadays I feel quite confident when taking compass bearing readings
for later plotting when using the Coastal Navigator/NAV 101 DF receivers,
first confirming the direction of the source using Sense and then refining
with a null (if sufficient signal strength allows). ALSO NOTE the ferrite
rod antennas in these units employ internal shields to eliminate E-field 
response and/or interactions with the operator's hands when in proximity
with the rotatable ferrite bar antenna..

About the Pilot - The Pilot lacks the Sense antenna feature that the Coastal Navigator/NAV 101 DF receivers have. I have a couple of these too,
but be CAREFUL when putting the batteries into the holder. There are
markings for Mercury batteries which in the day had little 'posts' on the
opposite of what we expect today (polarity is reversed) and the marking
on the batt holder can be confusing. Incorrect insertion of the batts can
kill the receiver.

Also, I have found that the Coastal Navigator is the ONLY Marine DF 
receiver that has a functioning Sense antenna feature. The Benmar/Bendix 
series model 555 Sense function does not operate, and neither does the 
Sense function on the one model (6140) Ray Jefferson I have. A couple 
of us here locally have owned the Bendix/Benmar model 555's and the 
Sense feature did not work on any of them.

Additionally, the so-called "BFO" on the NAV 101/Coastal Navigator 
modulates the final IF amplifier with a 400 Hz tone so a CARRIER ends
up with a tone on it; this does NOT aid on SSB reception.

de AA5CT/Jim







On Wednesday, January 27, 2021, 8:12:13 PM GMT-6, Dennis Monticelli <dennis.monticelli at gmail.com> wrote: 





Scott,

Yes, the Pilot series is good and easy to lug around too.  Like the others,
they are inexpensive.  I have one awaiting restoration.

Dennis AE6C

On Wed, Jan 27, 2021 at 5:56 PM nm8rmedic <nm8rmedic at rocketmail.com> wrote:

> Another good portable RDF is the Pilot Pal series, with its long
> rotateable ferrite rod antenna and S-meter.  Same NDB/MW/Marine Band
> coverage.  The model I have, Pilot II, also has a DF level potentiometer.
> Scott.
>
>
>
> Sent via the Samsung Galaxy S8+, an AT&T 5G Evolution capable smartphone
>
>
> -------- Original message --------
> From: Dennis Monticelli <dennis.monticelli at gmail.com>
> Date: 1/27/21 18:18 (GMT-05:00)
> To: rfi at contesting.com
> Subject: [RFI] tracking RFI with a marine direction finder
>
> All,
>
> Another useful and inexpensive tracking tool is a vintage marine direction
> finder.  My particular model (Newmar NAV 101, but sold under many a private
> label) is battery powered and has three bands: Beacon, BCB, and Marine (1.6
> to 4MHz).  It has an RF gain control, sig strength meter, a BFO of sorts,
> and of course a big lovely azimuth calibrated rod antenna that is capable
> of nice nulls.  I found mine on the local CraigsList but there is always
> eBay.  Many different makes and models were made.
>
> Dennis AE6C
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
_______________________________________________
RFI mailing list
RFI at contesting.com
http://lists.contesting.com/mailman/listinfo/rfi