[NLRS] 706MkIIg + DEM TIB/222-28 PTT problem

[Baker, Donn B]

'Morning Brent,
Not a answer, but something to look for....
Since it WORKED (twice), and DOES WORK on the bench, what is DIFFERENT =
when you used it this past weekend ?  What different cable(s), radios, =
power supplies, etc. ?  If it works "at home on the table top," =
SOMETHING is different when you move it to the Rover/portable rig.  What =
is that ?

I know it sounds simplistic, but I've been caught many times by REALLY =
obvious things that I didn't do:  connect the power supplies to a common =
ground; turn the switch ON; plug the power in, etc.=20

Good luck !

73 Donn
WA2VOI/0

>-----Original Message-----
>From: Brent Casavant [mailto:b.j.casavant@ieee.org]
>Sent: Thursday, September 18, 2003 11:02 AM
>To: Northern Lights Radio Society
>Subject: [NLRS] 706MkIIg + DEM TIB/222-28 PTT problem
>
>
>Hello everyone,
>
>Well, for the second VHF contest in a row I've been unable to use
>my DEM 222-28 transverter for the want of being able to key the
>thing.
>
>I'm using an Icom 706-MkIIg as the IF radio, and a DEM TIB to both
>drive the ALC level and split the IF signal for the transverter.
>I've used this once to check into the Sunday 222 net, and KC0IYT/N0RPM
>used it for the August UHF contest, all without problems.
>
>However both in June and last weekend, I had problems that prevented
>the use of this setup during the VHF contest.  The symptom is that
>the 706 fails to drive the PTT sufficiently to cause the TIB and
>222-28 to switch into transmit.  When I manually ground the PTT/HSEND
>line the TIB, transverter, and 706 will all switch into transmit mode.
>It's only when the 706 itself tries to drive the HSEND/PTT line that
>TIB and 222-28 fail to switch to transmit.
>
>Wondering about the 706's ability to sink enough current, I tried
>experiments hooking up only one or the other (TIB or 222-28), all to
>no avail.  We also tried keying a DEM 1296-144 and failed.  The
>problem has manifested itself both on a 13.8V power supply and a 12.?V
>battery.  And of course everything always works fine at home on the
>tabletop, making this a bear to diagnose.  The only idea I have left
>that I haven't tried is to switch out some of the IF BNC/LMR-240 cables
>from the TIB to the 222-28; I don't think they'd matter but I'm quickly
>running out of ideas.
>
>I know I've mentioned this problem on the list before, but having
>been unable to solve it I'm hoping someone might have a few more
>ideas for me.  At this point I'm even game for wild ideas!  I'm
>not even opposed to constructing some sort of additional interface
>circuit to insert between the 706's HSEND line and the DEM equipment's
>PTT line.
>
>I thank you in advance for any ideas or assistance.
>
>Brent
>
>P.S.:  If anyone has a lead on a good used oscilloscope I'd sure like
>to hear about it.  It would certainly make some of these=20
>problems easier
>to deal with.  At least dual trace; at least 50MHz, would=20
>greatly prefer
>150MHz, and would be ecstatic with a 500MHz scope; digital storage not
>required but would definitely be a bonus.  Prefer Tektronix, but open
>to anything whose brand I recognize.
>
>--=20
>Brent Casavant			http://www.angeltread.org/
>KD5EMB				-.- -.. ..... . -- -...
>44 54'24"N 93 03'21"W 907FASL	EN34lv
>_______________________________________________
>NLRS mailing list
>NLRS@mailman.qth.net
>http://mailman.qth.net/mailman/listinfo/nlrs
>