Need advice for Transamerica homebrew loop
 

I am gathering parts for a large loop for MW & 75m AM window. I'll be
taking the loop across America at the end of September. I hope to
fatten up my MW & 75m logbooks. I hope to get up early every morning
and do about 5-6 hours driving a day. Camping out at night with my
Loop. I wish I could take my dog, but I'm flying back and I can't risk
problems a dog might cause on that type of a trip.

Loop has to be sturdy and fit in a 4'x4' space in my pickup. I'll
cobble up a case for it so it don't get smashed. So loop is going to be
near 4' on each side and I suppose enough turns to resonate a 450pf air
variable. The variable has two 20pf-450pf sections. I'm told this
variable came out of a Heath SB220 linear. I suppose I could wire the
sections in series for 10pf to 225pf.

So there is one question. How do I want to wire this thing up? More
inductance and less capacitance? I'm afraid I might have problems
tuning this thing if I wire them in parallel and i have a lot of Q. I
might turn the shaft a microdegree and have the peak blow right by the
station I'm going to tune.

Now I think I can just stick the radio Degen DE-1103 portable near the
loop and do ok. I shouldn't have to hardwire the thing into the radio,
right? Not sure how to couple in 75m. Now how critical is the loading
on the loop? Can I wind one turn and find a sweetspot in the way of
coupling for best signal? I understand the loading -vs- Q issues with
coupling.

Now does the secondary suffer from some kind of balancing issues? In
other words if I send the one turn secondary into a single ended preamp
will that be a problem? Should I do a double ended preamp with a pair
of Jfets? 3904s?

Does this thing need to tilt, or is just spin around enough?

Ok, I think that about covers it for now. I am leaving in a month, so
I don't have a lot of time for research and experimentation. I know
there are those here who know loops - I have read your posts.

73
NEO

Need advice for Transamerica homebrew loop
 

Come on guys. Give me something I can use here.

N9NEO wrote:
I am gathering parts for a large loop for MW & 75m AM window. I'll be
taking the loop across America at the end of September. I hope to
fatten up my MW & 75m logbooks. I hope to get up early every morning
and do about 5-6 hours driving a day. Camping out at night with my
Loop. I wish I could take my dog, but I'm flying back and I can't risk
problems a dog might cause on that type of a trip.

Loop has to be sturdy and fit in a 4'x4' space in my pickup. I'll
cobble up a case for it so it don't get smashed. So loop is going to be
near 4' on each side and I suppose enough turns to resonate a 450pf air
variable. The variable has two 20pf-450pf sections. I'm told this
variable came out of a Heath SB220 linear. I suppose I could wire the
sections in series for 10pf to 225pf.

So there is one question. How do I want to wire this thing up? More
inductance and less capacitance? I'm afraid I might have problems
tuning this thing if I wire them in parallel and i have a lot of Q. I
might turn the shaft a microdegree and have the peak blow right by the
station I'm going to tune.

Now I think I can just stick the radio Degen DE-1103 portable near the
loop and do ok. I shouldn't have to hardwire the thing into the radio,
right? Not sure how to couple in 75m. Now how critical is the loading
on the loop? Can I wind one turn and find a sweetspot in the way of
coupling for best signal? I understand the loading -vs- Q issues with
coupling.

Now does the secondary suffer from some kind of balancing issues? In
other words if I send the one turn secondary into a single ended preamp
will that be a problem? Should I do a double ended preamp with a pair
of Jfets? 3904s?

Does this thing need to tilt, or is just spin around enough?

Ok, I think that about covers it for now. I am leaving in a month, so
I don't have a lot of time for research and experimentation. I know
there are those here who know loops - I have read your posts.

73
NEO

Need advice for Transamerica homebrew loop
 

N9NEO wrote:
snip

Will told me that in the synch detector group you requested some info
regarding my experiences with various audio amps for SW applications.
Please post a valid email addy there and I will send you the same info
I sent Dallas Lankford.

Graphics, diagrams, can't be posted in a text group and I don't/won't
have a web page.

Terry

Need advice for Transamerica homebrew loop
 

Hi Terry,

Yes, I would like to copy your setup. I like the idea of elliptical
filter and the precision detector driving a nice amplifier. I'll try to
get it all on a small express pcb board. I looked at the Dallas
Lankford filter and wasn't sure a headphone jack would drive the filter
because the filter was terminated in 8 ohms. If I scale the caps and
inductors for say a 100 ohm termination then the inductance values go
up by the same factor. I suppose the currents go down by the same
factor, so it should actually all wash out out in the physical size of
the parts. Anyway, for now the present project is a loop for
broadcast and 75m. I'm leaving at the end of the month for a MW /75m
DXpedition over to the left coast, and need to prepare antennas for
that trip.

Tell Will thanks for mentioning me and my address is


I look forward to the project.

regards,
NEO




wrote:
N9NEO wrote:
snip

Will told me that in the synch detector group you requested some info
regarding my experiences with various audio amps for SW applications.
Please post a valid email addy there and I will send you the same info
I sent Dallas Lankford.

Graphics, diagrams, can't be posted in a text group and I don't/won't
have a web page.

Terry