_____
From: [email protected]
[mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED]
Sent: Friday, February 23, 2007 10:23 PM
To: [email protected]
Subject: Re: [Repeater-Builder] Re: 220 repeater receiver recommendations?
In a message dated 2/23/2007 6:15:19 P.M. Pacific Standard Time,
[EMAIL PROTECTED] writes:
Do you use a cable with the bird that makes it a ½ wavelength total line
length when you insert it in line? That should not change things when the
wattmeter/cable are removed.
I'm not sure I understand what you are saying. The Bird constitutes part of
the line section and if you remove it after tuning with the z match, haven't
you effectively changed the length of the line?
There is a chart in the bird manual that tells you what length of jumper
cable to use with the bird meter for each frequency band so that the
combination of the jumper cable length and the line section of the meter
equals ½ wavelength._,Then when you insert that combination into a circuit
you are inserting a ½ wavelength and whatever impedance the circuit may
happen to be, it will be the same at the other end of the bird/cable. After
tune up you can remove the meter and jumper and the circuit tuning will
remain the same.
But you still cant place the meter between the transmitter and the Z match
and tune for minimum reflected power if the transmitter output is not 50
ohms as the meters line section is set up to read minimum reflected power
only when it sees 50 ohms. You can adjust the Z match to show 50 ohms to the
wattmeter but if the transmitter output is not 50 ohms then there will be a
mismatch and you will not have tuned the Z match to the transmitter
impedance.
73
Gary K4FMX
