B40

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.