[TowerTalk] Identifying Cushcraft A4 traps

[k6ll@juno.com]

On Mon, 14 Feb 2000 23:26:28 -0500 "RJA" <konecc@mindspring.com> writes:
> 
> Can anyone help in distinguishing between the 15m traps (TB vs. TC) 
> and the
> 10m traps (TD vs. TE)??  My e-mail request to Cushcraft stated that 
> "we do
> not offer Trap diagnostics or identification as part of our 
> Technical
> Support Service" and that I should use the book "Troubleshooting 
> Antennas
> and Feedline", MFJ part number 3301 to help identify the trap.  Any 
> advice
> or experience in how to do this?  Unfortunately Cushcraft does not 
> mark
> their traps...  nor was the technical advice particularly 
> insightful.
> 
> 					-- Rich K1CC

I had the same problem with an A3, and here is the method that solved
the problem quite easily. The position of the grid dip meter is
critical, but you will eventually figure out the technique.

--------------------------
This info was obtained from Dan Morgan, W1UR.

Using a Grid Dip Meter, carefully compare the dip frequency of all six
15 m traps.
There are 4 Tc and 2 Tb traps; the Tb's for the director only.  You will
find the two Tb traps tune 200 Khz higher in frequency than the Tc's.

All you need to do is lay the open
end of the trap to the end of the Grid Dip Meter coil and tune for the
dip. This means the trap and the GDM coil are on the axis. I was amazed
at the sensitivity of this measurement! I didn't bother to calibrate the
GDM for exact frequency; just compared the meter scale frequency from
one to the other and the sensitivity of the dip.
--------------------------

By the way, Cushcraft cautions agains disassembling the traps, and
they are difficult to tell apart even after they are disassembled.
Disassembly is fairly difficult, especially if you try to do it
gently, so as not to disturb the resonant frequency.

Dave Hachadorian, K6LL
Yuma, AZ
K6LL@juno.com























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