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FT-7B mods: 11m CONVERSION | Radioaficion Ham Radio

FT-7B mods: 11m CONVERSION

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YAESU FT-7B

11m CONVERSION 26.000 - 28.000 Mhz

1. You will need 4 xtals from your favorite parts supplier:

A. 40.500 - 26.000 to 26.500

B. 41.000 - 26.500 to 27.000

C. 41.500 - 27.000 to 27.500

D. 42.000 - 27.500 to 28.000

The xtals must meet these specifications:

TYPE

HC-25 U

Load capacitance

30 pf

Series resistance

25 ohms or less

Static capacitance

7 pf or less

Drive level

5mw

2. If you want to use your fixed position here is the formula for this:

Xtal FØ = F1 - operating FØ. Let's take Ch. 19

AM as an example.

AM OR CW Fl CHART

  • 11 A - 31500.7 KHz
  • 11 B - 32000.7 KHz
  • 11 C - 32500.7 KHz
  • 11 D - 33000.7 KHz

FØ IN MHZ FOR AM 19 = 27.185 so subtract 27,185.0 from 32500.7 in band C

32500.7 - 27185.0 = 5315.7KHz This is the xtal FØ for AM 19 fixed.

For LSB add 0.8 to F1

For USB subtract 2.2 from F1

CONVERSION

1. A VTVM and a RF probe, a sweep generator and a scope are required for alignment of the premix bandpass filter and the premix unit. The local oscillator requires a VTVM and a RF probe or scope.

2. Connect your scope or RF probe to TP1901 and install a 42.000 MHz crystal in the socket for the 10m D band and place the band switch in the 10m D position and adjust T1901 for 50 mv at TP1901. CAUTION: Use only proper alignment tools that properly fit the cores when installed. Do not ever force the tool into the core!. Damage to the core will result. This helpful hint is from hard personal experience as I have had to take a small sharp instrument and chip the core or slug out of several small transformers in the past, and believe me, I always use the proper tool. If the slug is stubborn, use a little heat from your soldering station.

Place the tip on the slug and heat it up, then even the most stubborn slug will move. Break it and you have had it.

YAESU FT-7B 11m CONVERSION 26.000 - 28.000 Mhz

3. Install a 41.000 MHz xtal in the socket for the 10m B band and place the band switch in 10m B position and adjust TC1905 for 50mv at TP1901.

4. Install a 40.500 MHz xtal in the socket for the 10m A band and place the band switch in the 10m A position. Adjust TC1904 for 50mv at TP1901.

5. Install a 41.500 MHz crystal in the socket for the 10C MHz band and place the band switch in the 10m D position and adjust TC1906 for 50mv at TP1901.

FT-7B mods 11m CONVERSION 26.000 - 28.000 Mhz

 

6. Premix balance adjust is VR901. Using your RF probe, connect it to TP1902. Adjust the VFO/FIX switch to the FIX position and adjust for a minimum reading with VR901 on your VTVM.

7. The bandpass filter for TX & RX must be adjusted next. Connect your sweep generator to the antenna receptacle. Do not transmit. Remove the mike, as you will wipe out your sweep generator. This will cost you a BIG repair bill. Connect the scope to Q201 emmitter on the mix unit. Remove the IF module unit and cut off the AGC voltage. A jumper must be installed between pins 10 & 11 of the RF module unit. A 100 ohm resistor must also be connected between pins 8 & 9 on the RF module unit and adjust T1914 & T1915 for the flat-est response from 26.000 to 28.000 MHz. After alignment return set to normal.

8. Connect a dummy load to the unit and adjust T1920 for maximum out in the 10m section.

This completes the modification for this excellent mobile. The installation of the matching F0 counter makes this radio a winner. Good luck with your modification.


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