[Elecraft] G5RV antenna experience on K3

[Matt Murphy]

I was using a G5RV but noticed that it performed poorly on 10 and 15m.  I
switched to a nonresonant dipole of similar overall length, fed with 450
Ohm ladder line, which works noticeably better on 10 and 15m (I think this
is due to loss from the 50' of coax I had been using to feed the G5RV).

The K3 has a filter designed to prevent IF output in the transmitted
signal, which will heat up if there is excessive reflected power on nearby
frequencies such as 40m (even if you have the load tuned to a 1:1 match
with the built in antenna tuner).  I found this out when I loaded up the
nonresonant dipole on 40m and smoke soon began coming out of the K3.

Upon further investigation, I discovered that there was a suspect PL-259
involved (not going to buy the DXE Crimped pre-made jumpers anymore).  Dale
at Elecraft advised that he'd avoid attempting to tune anything over a 5:1
or 6:1 SWR on 40m without risking destroying the filter again.

So even after replacing the jumper I have opted to use an external antenna
tuner when using the nonresonant dipole on 40m.  I had used the G5RV
extensively on 40m but never really paid attention to what SWR it was
presenting to the rig w/o the tuner.  All I can conclude from this is
either that it was under 6:1 or that Dale's estimate of a 6:1 SWR was a bit
cautious.

I have suggested a firmware update that would reduce forward power on 40m
in the presence of high reflected power, but is probably not all that high
on the priority list for Elecraft.  Another option is to remove the filter,
at which point I would imagine that any load that the KAT3 can match is
going to be fine.

73,
Matt NQ6N



On Fri, Mar 9, 2012 at 11:11 AM, W4GRJ <w4grj at satterfield.org> wrote:

> I use a G5RV mainly on MARS freqs. From 3.2 MHz to 30 MHz using the k3 and
>  internal ATU with great success. Never found a frequency it would not
> easily tune.
>
> Jack
> W4GRJ / AFA4DG
>
> On Mar 9, 2012, at 1:33, Dick Roth <raroth7 at gmail.com> wrote:
>
> > Hi there--
> >
> > Am considering putting up a g5rv antenna and was wondering what
> > experiences K3 users have with this antenna.  Is an external tuner
> > necessary?  Is internal ATU3 up to the task of taming this wire?
> >
> > Any hints will be helpful!
> >
> > --
> > 73 de Dick, ka1oz
> > Elecraft K3/100
> > GAP Titan-DX Antenna
> >
> >
> >
> >
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