[Elecraft] K3: Using 40m Loop for 10m

[john petters]

Hi Phil,
I have a lot of experience using 10M for VHF type contacts. You have to 
approach is as a VHF band. I asssume the stations are local to you and 
are not coming in on skip. That being the case you need to find out if 
the stations are vertically polarised. If so you will get good results 
using a vertical antenna. You could use your dipole as a vertical or an 
end fed half wave CB type antenna and resonate on 10M. Do not use your 
tuner to get rid of the mismatch - this applies to any antenna fed with 
coax. If you have a mismatch on the antenna you need to put the tuner 
between the coax and the antenna itself. If you want to use tour 40 M 
loop - and this will be too large to give a good space wave (ground 
wave) signal, you could feed it with balanced feeder into a balanced 
tuner ( or into your existing tuner with a balun). It will then tune on 
all bands from 40 M up, and may work to some degree on 80M.
I used to use 10M for local contacts on FM and SSB in the 70s and 80s 
and the range, providing you get the antennas right is very good. Good 
to see 10M is being used in sunspot minima years. You never know when it 
will open up.
Hope that helps
73
John G3YPZ

David Cutter wrote:
 > Hi Phil
 >
 > I think the first thing that occurs to me is: are you feeding this 
loop with one coax and just switching between bands?
 > David
 > G3UNA
 >
 >
 >
 >   I use my K3 to participate in a daily 10m CW net (28.130, 7pm PST).
 >   I've been experimenting with two antennas for the net:  40m full 
wave, vertically-oriented loop, relying on my KAT3 for a match, and a 
home-brew 10m rotatable dipole cut pretty close to resonate at 28.130.
 >
 >   When using the loop for operating on 40m, of course I get great 
matching without the KAT3.  When using the loop for the 10m net, the 
KAT3 works hard, but it does provide close to a 1:1 indicated match.
 >
 >   When using the loop on 40m, I can vary the output from minimum to 
full (approx 120w).  But when I use the 40m loop on 10m, the power out 
shows 50w max.  If I maintain the power output control to indicate 100w, 
I get "Hi Cur" indications during a transmission that exceeds a minute 
or so.  (These Hi Cur indications are never instantaneous in these 
situations, nor are they consistent.)
 >
 >   I'm sure there is some form of safety protection for the K3 
transmitter, but I could not find documentation on how the transmitter 
might behave when it's connected to such a mismatched antenna, even with 
the presumed match using the KAT3.
 >
 >   Can someone educate me on this?  I know my 40m loop is not supposed 
to do well on 10m.  I was frankly surprised that the KAT3 matched it as 
good as it did!
 >
 >   Believe it or not, my ground wave signal for our local 10m CW net 
has been reported by the net control station as much better with the 
loop than it is with the 10m rotatable dipole.  (Using the 10m dipole, I 
can see power out of 100+ watts, and don't get the Hi Cur warnings -- 
the signal just   isn't reported by most as being strong like the loop.)
 >
 >   Any insight on this would be greatly appreciated.
 >
 >   73, Phil, WA7URV K3 #1206
 >
 >