On 5/15/2014 5:25 PM, Rick - DJ0IP / NJ0IP wrote:
WOW, lots of data now.
>
> For a while I was beginning to sway to the side of the Pin-1
> problem. However considering all of the new data you have given us, I
> am leaning strongly to the transceiver possibly being defective, and
> second in line is common mode current.
>
> The best thing would be to find someone with an identical transceiver
> and just swap it. This may be impossible.
A bit unlikely. However, a few years ago, I used a Drake TR-7 on SSB at
full power (antenna and everything else the same) and it worked fine.
Caveat: I am sure that the TR-7 is a lot less "computerized" and
microprocessor dependent than the Omni VI. Maybe I should have kept the
TR-7. :-) A good friend and ham neighbor offered to bring over an
older Yaesu (model = ? but has a white panel). It's worth a try.
> You didn't specify how you measured the current in the two wires of
> the openwire. Do you have an RF Ammeter in-line with them, are you
> using lamps, or how are you measuring? How much imbalance is there?
Using a Palomar Engineers clamp-on RF ammeter. 0.9 A in one leg, 1.3 A
in the other leg as measured yesterday on 20 meters.
> If we knew for sure that it was not the transceiver, my next
> suggestion would be to try two things on the antenna side.
>
> <> First, I would disconnect the feedline from the dipole and connect
> it to a 50 Ohm dummy load. Then match it in the shack with the JV
> Matchbox. If the problem continues, it is probably something back at
> the house. Unless it's the feedline. So you might want to check the
> feedline. Put a 4:1 balun at each end, connect a 50 Ohm dummy to one
> side and an analyzer to the other. If no analyzer available, check
> it with a transceiver running low power. Check 80m, 20m and 10m to
> make sure it's the same SWR across all bands. Note: Most 50 Ohm
> dummy loads rise slightly in SWR on 10m so don't let that trouble
> you.
Interesting experiment but:
1) Don't have any 4:1 baluns
2) Any issues with the balanced output of the JV Matchbox to an
unbalanced dummy load? (Cantenna)
> <> Second, only when you have a dual-RF Ammeter inline so that you
> can monitor it, I would record exactly how much current is in each
> leg with 10w (a little more if you can), then begin shorting the leg
> of the antenna that over the house. I would shorten it in increments
> of 6 inches. Check RF current balance after each adjustment. WHEN I
> SAY 'SHORTEN', I do not mean cut; simply fold it back from the
> insulator and wrap around the rest of the wire, fixing it with a
> wire-tie. The goal is to get the current close to equal (less than
> 10% difference) in each leg. If your problem is really CMC, that
> just might solve it.
Again, an interesting experiment that sounds like it would indeed
balance the current in each leg of the window line. However, I put up
the antenna when I was 49 and now at 69, I really don't trust myself to
do any climbing.
> OTHER THINGS TO TRY:
>
> <> Replace the coax between the transceiver and the JV Matchbox. Try
> it both with and without the RF choke.
>
> <> Replace the JV Matchbox with something else. Use a 1:1 current
> choke between an asymmetrical matchbox and the openwire and try it on
> 80m. Don't use the built in balun on any matchbox. There are very
> few on the market that have the correct type of balun. Use a balun
> you know will work. This is the last thing I would suspect, but
> sometimes... hey, in Oklahoma we've even seen cows fly. Ya never
> know until you try.
When the cows were flying, was that an EF4 or EF5 tornado???
> <> Try another power supply.
Not sure what effect this would have. Using the TT 961 PS that I got
with the rig. OTOH, anything is possible.
> <> Move your transceiver out into the back yard and run your
> openwire to it. Try to keep the feedline at a 90 degree angle to the
> dipole.
>
> One thing for sure: there's always a reason. You just have to keep
> trying stuff until something shouts out at you and gives you a clue.
Right now, I am leaning towards the radio itself. I've gotten a bit more
info since this all started but don't want to post it to the reflector
for fear of stepping on toes (NOT the toes of anyone that has posted
here. If you want to give me your direct email, I can share that info).
> One thing for sure Carter, you have one of the most interesting
> problems we've seen here in a long time!
Well, I posted this same problem here 2 or 3 years ago and got maybe one
response, so why it is generating all these comments now is a good
question. <grin>.
Let me take this opportunity to thank you and all the others for their
thoughts, ideas and suggestions.
73,
Carter K8VT
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|