B40

"John Giddy" wrote in message
...
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.

I agree with Eric and John. There has to be some problem with the antenna
which will degrade the performance of your radio.

There are a LOT of B40's in use and this is the first RF interference
problem I have heard of. The B40/DAD issue is more likely a symptom and not
the source of your problem.

I'd start with the BNC antenna cable connector on the back of the
transceiver. My guess is that the shield is disconnected or some corrosion
has formed on the connector parts.

Bill Daniels

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In article , Bill Daniels
writes

"John Giddy" wrote in message
.. .
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.

I agree with Eric and John. There has to be some problem with the antenna
which will degrade the performance of your radio.

There are a LOT of B40's in use and this is the first RF interference
problem I have heard of. The B40/DAD issue is more likely a symptom and not
the source of your problem.

I'd start with the BNC antenna cable connector on the back of the
transceiver. My guess is that the shield is disconnected or some corrosion
has formed on the connector parts.

Bill Daniels

I do not disagree with any of the above diagnostic procedure, but this
type of problem can be notoriously hard to pin down.

In an earlier posting, John did say:

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.

This suggests to me that the RFI may be getting into the vario via the
supply wire. Try running a wire directly from the battery to the vario.
This can have a significant effect on this type of problem.

Tim Newport-Peace

"Indecision is the Key to Flexibility."

The easiest way to rule out the assumed voltage drop problem is to wire the
b40 up on a separate battery then try transmitting.
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.




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In article , Slick writes
The easiest way to rule out the assumed voltage drop problem is to wire the
b40 up on a separate battery then try transmitting.

Unfortunately, that will also tend to remove problems caused by RF being
sent down the feed cable, so you won't know exactly what you have
achieved. Which is why I suggest wiring direct to the same battery.

Tim Newport-Peace

"Indecision is the Key to Flexibility."

I've retested using the internal (9v) battery connected to the b40. The
results are the same as when connected to the 12v glider battery
circuit. Namely, the b40 is unaffected by the transmit so long as the
DAD is not connected to it.

I'm endeavoring to obtain an SWR analyzer to measure the radio
antenna's performance. Short of that, is there any other way for me to
tell if there is too much RFI behind the panel or the DAD just has some
problem that is amplifing an acceptable level of RFI?

John wrote:
I'm endeavoring to obtain an SWR analyzer to measure the radio
antenna's performance. Short of that, is there any other way for me to
tell if there is too much RFI behind the panel or the DAD just has some
problem that is amplifing an acceptable level of RFI?

With the PTT pressed, wiggle the antenna coax cable adjacent to the
connector on the back of the radio. If the connector is the problem
(which is likely), the vario reading should bounce around as you do this...

Marc

It's a bit tough to infer anything while I did this, because the b40
reading will decay down towards zero fairly fast even if the ptt is
held closed. However, it doesn't seem that wiggling the coax cable
connector has any effect on the vario spike/behavior...

On 10 Mar 2005 16:55:54 -0800, John wrote:

It's a bit tough to infer anything while I did this, because the b40
reading will decay down towards zero fairly fast even if the ptt is
held closed. However, it doesn't seem that wiggling the coax cable
connector has any effect on the vario spike/behavior...

Could be that the bad connection is at the antenna end. A bad
connection to the load (antenna) will cause standing waves of RF on
the coaxial cable, including its outer conductor.
An SWR measurement will give you the answer here.
I hope the problem is not at the antenna end, as it could be rather
hard to access for repair.
Cheers, John G.

Different b40 attached to the DAD completely eliminated the problem.
Now DAD readouts also match analog indication on b40 when avg button is
pressed.

There must an issue with the original b40.

Thanks to all for the suggestions.