Keep in mind that a Z-Matcher in a GE radio has it's own test point to tune it, as do some other Z-Matchers. You don't need to use a wattmeter and worry about the line length.
Chuck WB2EDV ----- Original Message ----- From: Mike Morris WA6ILQ To: [email protected] Sent: Saturday, February 24, 2007 2:53 AM Subject: Re: [Repeater-Builder] Re: 220 repeater receiver recommendations? (Z-Matcher) At 10:19 PM 02/23/07, you wrote: In a message dated 2/23/2007 6:36:24 P.M. Pacific Standard Time, [EMAIL PROTECTED] writes: In regards to the question of a wattmeter adding length to a cable, in places where I use Z-matchers, I actually leave an N-barrel connector in line that can be removed for inserting the wattmeter without adding any cable. So when you put that barrel back, you're pretty darn close. ... Not necessarily. At low band VHF frequencies, you could probably discount the error produced by the Bird. But in high band VHF and up, it becomes progressively more critical. The constant is the physical length of the Bird line section which is 3 13/16 inches but including the terminating N connectors, the length is 5 1/8 inches. This is where it gets interesting. The line section is air line and has a different velocity constant than RG142 or RG214. Section 3-35 states: Using the THRULINE you will be inserting a 4 inch length of 50 ohm air line and the load on the transmitter will be changed from its original condition without the THRULINE. But Section 3-40 states: Since the length of line between a mismatched load and the source transforms the impedance of the load as seen at the source, line length now becomes critical. If the adjustments for maximum power transfer were made with the Model 43 in place, removing it shortens the line by four inches, plus two connectors. (emphasis mine). So one section says to allow 4 inches while the other section says to allow 5 1/8 inches. Go figure. In any event, the use of a single barrel would miss the mark at 2 meters and above. I read it as he opens up one of the male-to-barrel connections and inserts the combination of a Bird with the jumper cable that makes it plus the cable a half wave. This way nothing changes. Mike WA6ILQ ------------------------------------------------------------------------------ No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.446 / Virus Database: 268.18.3/699 - Release Date: 2/23/2007 1:26 PM
