You are correct there is some rf on the coax. Note
the power box , the small one with metal plate. this has a type M coaxial power
socket and an F connector, a 7805 IC drops the voltage to 5v. I can use any
spare wall wart transformer with correct polarity and a plug that will
fit.
?
I can touch the plate and see a slight bump in the
signal on my own receiver. I will put a choke in each leg of the? power
coax next time I take it down. Or maybe a bifilar wound choke.
?
Note also I drilled two 1/8 inch holes in the
bottom of the tx box to drain any moisture out.
?
I regularly check the grabbers on the digilander
site, so fara no DX. Our stateside forums dealing with the Lowfer beacons have
developed a very good reporting system. I have 19 states confirmed on my
185.3khz beacon. Thats all the states where active listeners reside. I encourage
all that listen to post screen captures, and where possible edit the captures in
Microsoft picture viewer by adding the text of the calls received.
?
Check out our lowfer sites at and the
lowfer mailing list on? ?
click on side bar, email lists, and scroll down to "lowfer". I have been using
the Argo and Spectran software chasing weak signals? on 137khz, 160-190khz
and 13.555 to 13.565 mhz for about 9 years now. I've made lots of friends and
had lots of enjoyment. It is a two way partnership between those who beacon and
those who listen. A great learning experience.
?
73 Paul
toggle quoted message
Show quoted text
----- Original Message -----
Sent: Tuesday, June 22, 2010 7:40
AM
Subject: [QRPLabs] Re: 30 METER BEACON
PHOTOS AND CAPTURES
?
Hi Paul
> I HAVE CREATED A PHOTO FILE "K5WMS" WITH PHOTOS OF
MY BEACON CONSTRUCTION AND INSTALLATION.
[Snip]
Congratulations
on the success, the screenshots, and I'm glad you're having so much fun! I
hope you will look for your beacon on the worldwide grabbers too and soon see
some DX reception when the conditions are right!
One question I had...
I see that you have mounted the PCB nicely in a box with hooks on the side,
which look like they are designed so that the transmitter sits directly at the
centre of the dipole... the dipole attaching to those two hooks. Then the coax
brings power in at the "bottom" of the box (when it is hung on the
tower).
I'm no antenna expert at all, but I wondered about something...
The LPF output is designed for 50 ohms output so putting it at the middle of
the dipole should be Ok. However one arm of the antenna would also be
connected directly to PCB ground, which is itself connected to the coax power
feed cable. This means that the coax feed cable would form effectively part of
the antenna "dipole", unbalancing it and probably no longer matching it to 50
ohms.
I wonder if the results might be even better if this situation
could be avoided. Perhaps a balun between the TX and the dipole? Or perhaps
you could fit a couple of RF chokes at the two power connection inputs, to
stop RF going back down the power feed cable?
Feel free to ignore me if
I'm talking giberish, as I say, I'm no expert on antennas (or anything else,
for that matter).
73 Hans G0UPL
