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G8MNY  > TECH     01.05.22 08:11z 52 Lines 2362 Bytes #13 (0) @ WW
BID : 1159_GB7CIP
Subj: AKD's VHF/UHF Wavemeter WA1
Sent: 220501/0806Z @:GB7CIP.#32.GBR.EURO #:1159 [Caterham Surrey GBR] $:1159_GB

By G8MNY                                                (New May 05)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

This device is used to peaking up or "seeing RF" around your Tx aerial.

Here is a reverse engineered diagram of one I picked up the other day.

                                 旼컴컴컴)컴컴컴)컴1k2컫컴   |)      390k
        VHF           \/                    METER     __  |) L3     
      o  o       8p2           10k     1M              /_\           
 o컴> 쿚FF<컴o쩡컴늘컴훟     旼>FREQ       BF547   10n  쿏3  쳐컴늘컴캑
__   o  o    ) L1       39p   POT         T1/  __  ===    |)   10n  
  9V    쿢HF 쳐컫컴컴컴캑쳐)컴)컴컴쩡)캑>쳐   /_\'       |) L4     
__             1n                  D2  \e  24V   쳐컴캑        
     ===     )  쳐캑쳐쩡12k캑 PRESET            쿩1         \쿍F547 
   10n   L2 )  /\  __      22k     SET                T2 쳐컫컴캑
            ) ===   컴횯1 ===      읕큏ERO           ===   e/ 39k __
            / 쿎t  /_\ 10n          4M              쿻22       /_\
           TUNED CIRCUITS            DETECTOR   AMP            DC INVERTER

L1 = 2T 23mm dia, L2 = 4T 7mm dia, L3 & L4 1mH ?

When switched to VHF/UHF the DC interter T2 D4 & D3 is powered. It
oscillates to provide >24V, which is fed to the 24V zener Z1 to make the
maximum varicap D1 tuning voltage.

In VHF mode at max tuning voltage L2 & Ct set the highest frequency of 200MHz.
The lowest frequency of 120MHz is determined by the voltage set by the preset.

On UHF mode L1 is placed across L2 to raise the frequency between 195 to
450MHz, & the slight inductance of the ground track gives the low Z aerial
coupling needed @ UHF.

The RF detector diode D2 feeds the base of T1 to current amplify the signal for
the meter. The 4M pot sets the bias level to set meter zero so that D2 & T1
are at the point of conduction.

Also look at my TECH buls on "Piston Absorption Wavemeter", "BURNS's MF-UHF
Wavemeter TC-101", & "RF Field Indicatopr FL-30AH".

Why Don't U send an interesting bul?

73 de John G8MNY @ GB7CIP

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