On Nov 17, 6:16 pm, wrote:
On Nov 17, 11:36 am, Tony Giacometti wrote:
Anyone familiar enough with receiving loops to be able to assist me in
figuring out whats wrong here?
TIA
Tony
I use a lot of solenoid loops. You should not need a preamp
with a decent size loop using an R4C in most cases.
I'm wondering if you are actually tuning the loop to resonance.
Do you notice a sharp, fairly high Q peak of noise and signals
at the point where you think it is tuned?
There will be no mistake hearing this peak if it's working
correctly.
400 pf seems kind of low to me...
IE: lets take a regular solenoid loop, being calculated by
Reg Edwards loop program rjeloop3.exe..
It's fairly accurate.
I set up a one turn loop using a 20 mm wire, each side
of the loop 5 ft, or 1525mm. I set 1900kc as the
desired frequency, which is the middle of the band.
It shows a stray capacitance of appx 9 pf, and requires
appx 1350 pf to tune to 1900 kc.
See my problem with your meager 400 pf?
Hummm, I see you say you have only used it on 80m.
According to the program, using a 2.5 ft per side loop,
you would need appx 850-860 pf to tune 3700 kc.
I guess the capacitance of the coax is making up
the rest.. ??? IE: I think RG-58 and RG-8 is good for about
28-29 pf per foot or so. Even if you added that say extra
290 pf, you still come up a bit short from the 850+ pf
needed for a plain wire loop.
I think I would disconnect the preamp, at least for
testing, and see if you can determine a noise peak
into the receiver. You need to find out of the loop
is actually tuning to resonance. Make sure both
conductors of the feedline are connected to each
connection of the loop, with the variable cap in
parallel across those connections.
If it's tuning, you should hear a distinct noise peak,
and I really doubt you would need the preamp to
hear it into a R4C. Once you get that going, it should
be downhill from there.
I have a R4C, along with an old original R4 too, so I know
they should have enough sensitivity to hear the noise
peak with no preamp. Well, unless it's broke..
MK