[Rover] Interstation Interference in Multi-Op Rovers

[Sean Waite]

Thanks, I suspected it might be something like that. We get some lighter
interference on 70cn as well, which is a few more harmonics up.

My worry with the coax notch filters is bandwidth - 150MHz is pretty close
to 2m. I suppose using higher quality coax/heliax and tuning to 51MHz would
help with that.

The rigidity of heliax might make it rough in the rover, a 5' long chunk is
going to be interesting g to manage and will likely go somewhere outside
the car on the ground.

Thanks for the tips, I'll read up and experiment.

Sean WA1TE





On Thu, Sep 21, 2017, 18:26 Robin Midgett <K4IDC at comcast.net> wrote:

> I don't know how "everyone" handles this, but having had the same problem
> 20 years ago, I feel your pain. We (NT4L) never did address the issue due
> to life circumstances ending our roving adventures.
> What you're getting is most likely a harmonic from the 6m transmitter that
> lands in the pass band of the 2m Rx.
> For reference:
> http://forums.qrz.com/index.php?threads/vhf-notch-filter-with-coax.408931/
>
> http://www.repeater-builder.com/antenna/heliax-6m-filter.html
> (note the comment about the 'tuning rod stopped turning slightly below 51
> MHz'); you might try to find one of those
> Telewave 45 MHz cans, but it'll be BIG, probably much bigger than you want
> to haul around in your rover vehicle.
>
> It seems that one of the tuned stubs from large coax would be worthwhile.
> Configure one as a narrow band pass on the 6m Tx, and perhaps another as a
> notch filter on the 2m Rx.
>
> https://is.gd/yHBWkd
>
>
>
>
> On Thu, Sep 21, 2017 at 3:17 PM, Sean Waite <waisean at gmail.com> wrote:
>
> > How does everyone handle this?
> >
> > Our setup is as follows:
> > Front seat station, 2m and 70cm
> > Rear seat station, 6m and 1.25m
> >
> > The front station uses a drive-on mast with the 2 and 70cm antennas on
> it,
> > the rear station uses a hitch mount mast with the 6 and 1.25 antennas on
> > it.
> >
> > The 6m station has a bandpass filter and the 1.25 station is on a
> triplexer
> > that kinda sorta almost (not really) filters out some of the crud. We're
> > planning a bandpass filter on the 2m station, but it hasn't happened yet,
> > and I'll be building up some coax stubs (likely 6m and maybe a 70cm
> > bandstop to put on the 2m station).
> >
> > Depending on which direction the antennas are aimed, we get somewhere
> > between a faint amount of QRM up to rendering it useless on 2m when 6m
> > transmits. I think some of the filtering will help, but when you are
> > transmitting 100W of 6m into a moxon and it's aimed right up the rear end
> > of the 2m yagi I'm unsure how much that will do. We got around it
> somewhat
> > in the September rove by calling CQ at the same time.
> >
> > Any other recommendations here? One idea would be to bond the grounds on
> > all of the radios together, but I'm leaning towards that being worthless.
> > We also could put 6 and 2 at the same station, but we're hectic enough at
> > times that whichever op was on that station would be pretty busy. It
> might
> > also be a bit boring on the 222/432 station, but maybe we'd grab a few
> more
> > random contacts on there by calling CQ. The preference would be to keep
> the
> > band split unless it's truly hurting us.
> >
> > Thanks!
> >
> > 73 de Sean WA1TE (K1SIG/R)
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