B40

I have installed a B40. Only while transmitting on my radio the B40
quickly reads +5 kts and then slowly decays back to zero. Is this
normal and can it be fixed? I tried replacing the power lead to the
vario with shielded wire connected to gnd at one end and this actually
made the problem worse.

Any input would be appreciated.

you've got a serious RF problem.....the B40's are very well shielded so we
really never see this on these instruments.....
check all of your wiring and especially Radio antenna cabble to amke sure
these are not paralleled or wrapped around other cables.try re-routing the
cables and if necessary replace the coax from your antenna lead
tim

wrote in message
oups.com...
I have installed a B40. Only while transmitting on my radio the B40
quickly reads +5 kts and then slowly decays back to zero. Is this
normal and can it be fixed? I tried replacing the power lead to the
vario with shielded wire connected to gnd at one end and this actually
made the problem worse.

Any input would be appreciated.

The B40 does funny things when the voltage gets too low. Could the
radio transmission reduce the voltage to the B40 below the crucial point?


Tim Mara wrote:
you've got a serious RF problem.....the B40's are very well shielded so we
really never see this on these instruments.....
check all of your wiring and especially Radio antenna cabble to amke sure
these are not paralleled or wrapped around other cables.try re-routing the
cables and if necessary replace the coax from your antenna lead
tim

wrote in message
oups.com...

I have installed a B40. Only while transmitting on my radio the B40
quickly reads +5 kts and then slowly decays back to zero. Is this
normal and can it be fixed? I tried replacing the power lead to the
vario with shielded wire connected to gnd at one end and this actually
made the problem worse.

Any input would be appreciated.

The voltage drops a few tenths during transmit, but remains above 12
volts.

Coax for radio is routed as from factory (DG). I haven't touched any of
this wiring. It doesn't look to be routed parallel to anything except
TE and volume flask tubing.

The problem seems very sensitive to the routing and type of wire used
on the power lead to the vario (shielded worse). I put a ferrite core
on this lead and it significantly reduced the problem, but it still
exists as compared to running the b40 off of the battery with external
no power leads attached.

Greg made a very good comment on the battery voltage issue......The B40 will
show a drop (as do most other variometers) when the voltage gets low or the
battery is poor....I'd be very suspect of the battery
condition..also...check the back-up battery to be sure it's a good
battery.(check the power selector switch on the B40) EXT-OFF-INT
selector....and try the B40 on the back-up battery....if you're still
getting a needle movement on the back-up battery you've isolated the problem
from being the main battery being too low and now are back at it being an RF
problem....It's still a possibility that the factory cable is at fault or
the connector at the radio is not grounded to the shield.
tim

"Greg Arnold" wrote in message
news:2gJXd.37$KK5.7@fed1read03...
The B40 does funny things when the voltage gets too low. Could the radio
transmission reduce the voltage to the B40 below the crucial point?


Tim Mara wrote:
you've got a serious RF problem.....the B40's are very well shielded so
we really never see this on these instruments.....
check all of your wiring and especially Radio antenna cabble to amke sure
these are not paralleled or wrapped around other cables.try re-routing
the cables and if necessary replace the coax from your antenna lead
tim

wrote in message
oups.com...

I have installed a B40. Only while transmitting on my radio the B40
quickly reads +5 kts and then slowly decays back to zero. Is this
normal and can it be fixed? I tried replacing the power lead to the
vario with shielded wire connected to gnd at one end and this actually
made the problem worse.

Any input would be appreciated.

Greg Arnold wrote:

The B40 does funny things when the voltage gets too low. Could the
radio transmission reduce the voltage to the B40 below the crucial point?

It is possible that your voltmeter checks the voltage very close to
the battery. It is also possible that your instrument panel, including
radio and B-40, is wired form a common source; if power is provided
from the battery to the panel with too thin a set of wires, then you
surely have a big voltage drop during transmission, and the voltmeter
can't show it.

Pure speculation, of course.

Aldo Cernezzi

wrote:
I have installed a B40. Only while transmitting on my radio the B40
quickly reads +5 kts and then slowly decays back to zero. Is this
normal and can it be fixed? I tried replacing the power lead to the
vario with shielded wire connected to gnd at one end and this actually
made the problem worse.

Measure the VSWR of your radio antenna where it attaches to the radio.
If that is poor (3), it maybe radiating into the B40. It won't transmit
as far, either.


--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

I found the source of the problem...I have also installed a B40 Digital
Averager Display (DAD). Basically, if this is connected to the B40, I
get the big vario deflection during transmit. Once I disconnected it,
the B40 was virtually unaffected by the transmit. I connected and
disconnected it a few times to prove it was the cause. The DAD consists
of 4 twisted wires in an unshielded pvc jacket. I ran the its wires
only about 4 inches over to the back of the vario. I guess I'll have to
talk to the manufacturer about it or just return the DAD. I thought it
would be a "nice to have" since I was already in the panel doing work.

On 9 Mar 2005 17:30:05 -0800, John wrote:

I found the source of the problem...I have also installed a B40 Digital
Averager Display (DAD). Basically, if this is connected to the B40, I
get the big vario deflection during transmit. Once I disconnected it,
the B40 was virtually unaffected by the transmit. I connected and
disconnected it a few times to prove it was the cause. The DAD consists
of 4 twisted wires in an unshielded pvc jacket. I ran the its wires
only about 4 inches over to the back of the vario. I guess I'll have to
talk to the manufacturer about it or just return the DAD. I thought it
would be a "nice to have" since I was already in the panel doing work.

I would still look at the antenna connection as suggested by Eric
Greenwell. It seems to me that there is too much RF energy floating
around behind your panel. Maybe a bad shield connection at either end
of the coax cable ? An SWR test would pick this up.
AFAIK, Mike Borgelt's products are fairly immune to stray RF, but if
there is a strong field strength, it will still affect the vario.
Cheers, John G.