[1000mp] Strange effects on 15 and 17 metre bands
Tod - MN
tod at k0to.us
Thu Dec 16 13:12:55 EST 2004
This is a new, arcane problem -- at least to me. Could we get the serial
number of your 'MP Jim?
Should we conclude this is something that involves the antenna tuner circuit
only or does it occur when tuning or operating into a dummy load? If it is
an antenna tuner matter and does not occur when the tuner is out of the
circuit, does anyone have an idea if the parasitic is tied to +j or -j or to
a specific R that is not 50 ohms.
>From what has been written I am guessing that the parasitic occurs on 'key
down' and not when the rig is not keyed. It may be present but not noticed
when operating on SSB. The description of tuning in CW mode with the power
at MAXIMUM is puzzling. Does that mean the menu was set for tuning with
maximum power or that the power knob was set for maximum? As I recall the
tuning function by default uses 10 watts but a higher value can be selected.
Unfortunately, my 'MP is in Idaho and I am in Minnesota this month so I
can't try to duplicate what has been written by Jim.
I don't recall reading about this problem in the past four years or so ---
has it been covered on the reflector? If Yaesu has a 'fix' is it one that
has been issued to field repair centers?
Tod, KØTO
>-----Original Message-----
>From: 1000mp-bounces at mailman.qth.net
>[mailto:1000mp-bounces at mailman.qth.net] On Behalf Of Billy Cox
>Sent: Thursday, December 16, 2004 11:05 AM
>To: All about Yaesu 1000mp
>Subject: Re: [1000mp] Strange effects on 15 and 17 metre bands
>
>Agreed ... biggest step of the "cure" was the addition of the
>double-sided copper tape mentioned ... worked here on mine
>many years ago with no other problems.
>
>73 Billy AA4NU
>----------------------
>Hi jim
>
>It sounds like the 15m parasitic PA oscillation problem.
>
>See http://www.gi0nwg.freeserve.co.uk/tb9606a/tb9606a.htm
>
>I had the same problem a few years ago. Yaesu UK sent me a kit
>of torroids for free, you'll also need some sticky copper tape.
>
>73 Mark G4AXX
>---------------------------------------------------------------
>--------------------------
>>>> jim.bryant at btinternet.com 16/12/04 16:35:44 >>>
>I have just acquired a second-hand 1000MP and have been using
>it with no problems on 40 and 20 metres for a few weeks now.
>My main activities are on CW and data modes.
>
>Today, I tried it out on 15 metres and immediately noticed a
>problem. If I let the Automatic tuner do its stuff on CW then
>all appears OK. However, if I then switch to USB and use PSK31
>(on the same freq as I tuned it on CW) I get an infinite SWR reading.
>
>I have noticed also that I can get the same effect by tuning
>up on CW with the RF power at Maximum and achieving a low SWR
>and then backing off the RF power slowly back to zero. When it
>reaches zero, the SWR shoots up again to infinity and the
>power meter jumps up and shows a reading of about 30 watts.
>
>It is almost as if there is some parasitic oscillation taking
>place. Any ideas?
>
>Regards
>
>Jim Bryant M0JWB
>Portishead. UK.
>
>jim.bryant at btinternet.com
>
>
>
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