Rturner@Darcom-Hq.ARPA (04/16/84)
All you HAM CP/Mers out there... I recently purchased a Kantronics UTU (Universal Terminal Unit) and interfaced it with my KayPro II. I planned to use it for RTTY/ASCII and AMTOR with MDM730 as my terminal program. I'm using an Icom IC-720A as the tranceiver. The UTU receives like a dream! I've spent all weekend listening to folks check into HF Bulletin Board Systems, and generally listening around 40 meters. Tonight, the big test...I called up a local ham and attempted to put the thing on the air. When I started transmitting, I ran into all kind of trouble. My echoed characters were strange, the system would "warm boot," and I couldn't get the tranceiver out of transmit mode. My first thoughts center around some type of RF overload of the KayPro. My tranceiver is well grounded, but I'm loading a long-wire which could be putting RF in my shack. Anyway, I'm going to experiment with VHF since there shouldn't be so much RF banging around. Anyone with similar experiences? Hints? Apologies in advance for sending this to what is probably the wrong list. Responses to me to keep down the non-CP/M static. 73, rick nf4t
ERWINVL.DLOS@XEROX.ARPA (04/20/84)
RICK,
I HAVE BEEN VERY INTERESTED IN THE KENTRONICS UNIT SINCE I SAW IT IN THE
RECENT ISSUE OF QST. IT IS STILL UNAVAILABLE HERE IN THE DALLAS AREA. I
AM IN HOPES OF BEING ABLE TO PICK UP ONE WHEN I GO TO DAYTON. SUGGEST
YOU TRY A FEW THINGS JUST TO SEE HOW THE RF (IF IT IS) GETTING INTO THE
KENTRONICS OR THE KAYPRO. TRY WRAPPING THE KENTRONICS IN ALUMINUM FOIL
AND GROUNDING IT TO YOUR STATION GROUND. GROUND LEAD SHOULD BE AS SHORT
AS POSSIBLE. ALSO BE SURE THAT YOU HAVE THE KAYPRO TIED TO YOUR STATION
GROUND WITH HEAVY BRAID. YOU SHOULD NOT DEPEND ON THE 3RD WIRE IN ANY AC
CORD FOR A GOOD RF GROUND. ALSO MAKE SURE THAT YOUR RS-232C CABLE IS
SHIELDED. IN SEVERE CASES ALTHOUGH NOT NECESSARILY WITH THE KAYPRO, I
HAVE SEEN RF "WALK" RIGHT IN ON THE SHIELD DESPITE THE FACT IT WAS
GROUNDED. THIS IS DUE TO THE SHEAR LENGTH OF THE CABLES THAT ARE USED IN
SOME OF THE COMPUTER SYSTEMS TODAY. IF THAT IS A SUSPECT YOU MIGHT TRY
TO PLACE A LARGE TORROID AROUND THE RS232 CABLE AS IT ENTERS THE KAYPRO.
I HAVE NEVER SEEN THE KENTRONICS UNIT BUT I BELIEVE THE ONLY GROUND THAT
THEY HAVE IS BY WAY OF THE RS232 CABLE. THIS IS TOO LONG OF A GROUND
PATH TO GET EFFECTIVE RF GROUNDING. YOU MIGHT EVEN TRY GROUNDING IT
BETTER AND KEEPING THE PATH AS SHORT AS POSSIBLE. PLEASE KEEP ME
INFORMED OF YOUR PROGRESS AND YOUR PERCEPTION OF THE UTU BECAUSE I PLAN
TO MARRY ONE UP WITH MY XEROX 820 ES MY YAETSU 757.
REGARDS,
VAL L. ERWIN
W5PUT
(214) 960-3174Hallidy.dlos@XEROX.ARPA (04/20/84)
Rick, What you have sounds like a classic case of RF in the shack to me, as you surmised. A long wire type of antenna tends to exhibit such characteristics unless you can provide a good counterpoise for it to operate against. Sometimes just changing bands will give an indication of this. By that I mean that you may observe an improvement in the situation by trying a different (probably higher) band. Eighty and forty meters I suspect would be the worst because an additional problem may exist. That is, coupling of the radiated RF into the AC mains. Your house wiring may be acting like a great receiving antenna, coupling large RF voltages into the power supply of your Kay-Pro! A brute force line filter may be the solution in such a case. You might also try reducing the output power just to see if this has an effect on performance just to verify that RF is the cause. I hope I have helped a little- this type of problem can be a real s.o.b. to solve. 73's, Dave Hallidy KD5RO