Radio Mods: Unlocking frequency limitations of the Yaesu FRG-8800 receiver
Paolo Viappiani (SWL I1-11437) shares the following. Please note that, as with any radio equipment modifications, the risk of performing this task is your own. This is a very simple modification, but if you feel it may be beyond your skill level, consider hiring a radio technician to perform it for you.
Unlocking the YAESU FRG-8800 frequency limitation
Images and text: Paolo Viappiani
Figure I: The FRG-8800 receiver tuned to 29.999.9 MHz.
Introduction
It is well known that due to legislative restrictions in certain countries (Germany, Australia, etc.), some receivers produced in the last few decades of the last century have limited frequency coverage.
In particular, in Germany, listening to HF frequencies above 26.1 MHz is prohibited, while in other countries, shortwave reception below 2 MHz is not allowed.
These restrictions have led most radio manufacturers to produce “shielded” versions of their HF receivers to meet various national requirements; a classic example is the world-famous SONY ICF-2001D and PHILIPS D-2935/D-2999 portable devices.
In microprocessor-controlled synthesized radios, blocking/unblocking operations for certain bands are very simple:usually, adding (or removing) an appropriate jumper near the microprocessor is sufficient to perform the task, and the correct operational steps are usually included in the service manual or specific technical bulletins; in any case, a wealth of information can be found on the internet.
Clearly, with a few exceptions, the YAESU FRG-8800 is just one of them: if you search in the original manual or online, you will find no information about this specific issue…
More Details
In the user manual for the YAESU FRG-8800 receiver, it specifies that it is manufactured as different versions according to government regulations (see Figure A below), but there is no specification in its service manual regarding the various frequency blocks or how to remove them.
Figure One
Since I recently stumbled upon the German version of the “shielded” FRG-8800 and needed to remove any frequency restrictions, I, along with my close friend Gigi Lombardo from Bassano del Grappa, Italy, began an in-depth search on the internet (with almost no results).
I also subscribed to a social media group (Fox Tango International) and posted my question, receiving some answers from members Andy Jack and Simon N. Poysden (thank you very much!).
Andy specifically invited me to contact Guy Desimone VK3GUY, the Australian repair shop for Yaesu in Japan.
Unfortunately, Guy was unable to help me, but he promised to inquire about specific matters with Yaesu Japan.
In the meantime, Gigi Lombardo continued his search and contacted some German hams, ultimately receiving a very interesting reply from Jurgen DF5TY (thank you very much, Gigi, and thank you, Jurgen!).
Jurgen suggestedto look for some pins near the FRG-8800 microprocessor and eliminate the short circuit between them…he was right!!!
A Solution to an Annoying Problem
To eliminate any frequency restrictions in the YAESU FRG-8800, please carefully follow these steps:
1) Remove the bottom and top covers of the unit; the PLL unit is located in the top chassis of the FRG-8800 (see Figure B).
Figure B – FRG-8800 PLL Board
2) Accurately locate positions TPO-16, TP-17, and TP-18 (see Figures C and D); also consider the FRG-8800 PLL schematic (details in Figure E).
Figure C – FRG-8800 PLL Board Details
Figure D – FRG-8800 PLL Circuit Board Detailed Drawing
Figure E
3) Carefully remove the screws that secure the PLL board to the chassis (and the “remote” connector on the rear panel), then flip the board over to access its track side.
4) Identify the positions of TP-16, TP-17, and TP-18 (see Figure F).
Figure F – FRG-8800 Board Track Side Detail
5) Remove (desolder) any short circuit between TP-16, TP-17, and TP-18 (Figure G shows the 25.999.9 blocking unit, Figure H shows a completely unblocked unit; Figure I shows the “unblocked” FRG-8800.
Figure G – FRG-8800 PLL Board Track Side Detail (26 MHz Blocked)
Figure H: FRG-8800 Board Track Side Detail (Receiver Completely Unblocked).
6) Carefully reinstall the top and bottom covers of the radio and enjoy the unblocked receiver.
Final Notes
It is also worth noting:
• Shorting TP16 to TP17 will suppress the FRG-8800 from receiving frequencies above 26 MHz;
• Shorting TP16 to TP18 will suppress reception below 2 MHz.
• The FRG-8800 frequency restrictions do not in any way alter the coverage of the optional FRV-8800 VHF converter.
I would like to especially thank Luigi Lombardo (my friend Gigi), who is the real developer of this procedure.
Have you ever done frequency modifications on your old radio equipment? Feel free to share!
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