The first link is particularly relevant. My antenna is on a balcony,
surrounded by metal. Metal railing, making up cap to balcony wall several
feet below wires. Metal mesh in building wall (stucco), about 5 feet away.
Commercial grade metal studs in building walls.
Guess that's why the
Three suggestions:
1) Add a choke balun close to the rig.
2) Add 10' piece of coax to feedline.
3) Add 1/4 wave wire from ground terminal of radio to establish ground
reference (about
10' for 12 meters). Be sure it is insulated, and end should not be accessible
to people or
animals.
You can
http://hamgineer.blogspot.com.au/2012/05/swr-changes-when-i-increase-my-tran
smit.html
Testing fwd ref pwr ratios with a Bird 43 at both pwr levels would be
interesting for a better comparison;
http://www.bird-technologies.com/~/media/Bird/Files/PDF/Products/manuals/920
-43.ashx
On 12m (only), despite the ATU bringing the SWR to 1.0 when I press the ATU
TUNE button, it shows about 2.5:1 on the bar graph when I send CW. I am
using a non-resonant antenna (fan dipole with wires for 40, 20 and 10), but
it doesn't do this on the other bands for which I don't have a resonant
Different pwr level. Do you have a 1:1 isolation balun in coax near
antenna feedpoint?
On 10/03/2012 09:58 PM, Barry wrote:
On 12m (only), despite the ATU bringing the SWR to 1.0 when I press the ATU
TUNE button, it shows about 2.5:1 on the bar graph when I send CW. I am
using a non-resonant
Barry,
I don't know the answer in your particular case, but
Normally having a difference in SWR for tuning (low power) and operation
(higher power) is an indication that you have some faulty connection in
your antenna system - look for loose connectors, places where you might
have
No balun.
Don, no loose connection I can find. Simple setup and the high reading only
happens on 12m and is consistent.
--
View this message in context:
http://elecraft.365791.n2.nabble.com/K3-Hi-SWR-when-sending-CW-tp7563645p7563651.html
Sent from the Elecraft mailing list archive at
If you have a lot of common-mode current on the coax, this can upset SWR
readings, and
will be worse the more power you run. If there is no balun and the feedline is
a multiple
of 1/2 wl on 12m (the worst case for common-mode currents), then this is
probably the reason.
On 10/3/2012 6:37 AM,
Vic,
I think you're on to something. When I vary the power, below 85W, the SWR
is 1:1. Above 85W, it starts creeping up with the power increase.
If I put some ferrites on the coax, but want to keep them indoors, is there
a best location for them?
Tnx,
Barry W2UP
--
View this message in
No Balun ok, well do you think a 10 turn 8ยจ diameter coax UB at the
feedpoint, may help reduce the shield radiation (which can mess your
indicated swr)?
On 10/03/2012 11:37 PM, Barry wrote:
No balun.
Don, no loose connection I can find. Simple setup and the high reading only
happens on 12m
I am not sure. But try it where it's convenient. Remember, for it to be
effective at HF,
you must have a few turns around a ferrite -- I'd say 4 or 5 turns should be
enough for
12m. Just clamping a ferrite bead on a cable doesn't do much.
On 10/3/2012 10:11 AM, Barry wrote:
Vic,
I think
If it's easier, a decent RF ground at the rig will usually take care of
any such issues too. For a single band, a 1/4 wavelength wire connected to
the chassis is often a sufficient RF ground. Do not connect the far end to
anything. Just run it around a baseboard or lay it on the floor out of the
Barry,
If the problem is not solved by Vic's suggestion to choke your feeder,
could you please let us know the length of the coax feeder (in feet or
metres) between your fan dipole's feedpoint and your K3. Also how long is
the part of the feeder which is indoors?
73,
Geoff
LX2AO
On
I set up a common mode choke with 3 turns of coax through 2 ferrites, similar
to the figure 2 on p. 18 of this document:
http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf
I placed it outside, near the feedpoint. it did not change anything.
Geoff, I have 20-25 ft of coax
Barry,
I doubt your choke has anywhere near the inductance needed to do the
job. I think a careful read of the paper you reference will show what
you need to do.
73, Mike NF4L
On 10/3/12 7:50 PM, Barry wrote:
I set up a common mode choke with 3 turns of coax through 2 ferrites, similar
to
40 feet is close to one wavelength on 12 meters, so that would be a
'troublesome' length
(a multiple of 1/2 wl).
If the choke is at the feedpoint, the feedline can pick up RF radiated from the
antenna.
Perhaps try it near the rig.
Alternatively, try adding a 10 foot piece of coax to the
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