On Jul 4, 2008, at 4:20 PM, Dan Evans wrote:
> think it had ever seen RF before. At least it looked new:-) Lastly,
> was my trusty old Par Moxon for 6 meters. The Moxon goes up, the
> cable
> is run, and then Murphy strikes! The SWR test at around 7:1!!!
> Holy
> cow! What happened? It worked fine last September.
Dan,
Just checking here... how did you measure the SWR on the Moxon? If
you were using a Bird or other external wattmeter and not to internal
metering in the FT-897, good.
If not, beware that the FT-857/FT-897 (same radio deck inside) have
had some funny issues -- especially early non "D" models -- with 6m.
I've seen everything from "Yaesu has a fix for this, send your radio
back to them." To people saying the problem is just screws backing
themselves loose inside the radio, causing the grounding internal to
the rig to get squirrelly.
But whatever the reason, the symptom is the same. Key the rig, say
nothing, and watch it start oscillating and putting out full power
continuously in SSB mode.
I attempted to use my "trusty" FT-857 for the 6m rig in my 2007 Rover,
and found that it was doing this silliness when hooked to the dual 6m
square loops (stacked) on my 12' mast on the Jeep. Plug in the
FT-847, and zero problems and 1:1 SWR.
The false SWR readings from the FT-857 were because the rig goes
*hideously* spurious when it's in this "feedback loop" scenario and
most of what it's throwing out is out of band. A regular wattmeter
sees all sorts of reflected power back, and shows a high SWR, but if
you look at it on a spectrum analyzer -- it's just "grass" everywhere.
I only mention it because 6m problems on certain antennas come up
regularly on the FT-857 YahooGroups list. Perhaps that's what you
were fighting and the Moxon is fine.
--
Nate Duehr, WY0X
nate@natetech.com
_______________________________________________
VHFcontesting mailing list
VHFcontesting@contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting
|