Got an FR-101 and FL-101 - need to modify; any idea about schematics?

[steve_qix]

Hi !

I inherited (literally, from my uncle who died a few years ago) an FR-101 receiver and an FL-101 transmitter.

Have no idea if they work (or ever worked!), but I figure the first step is to find a schematic and have a look.... however, no schematics of these units are to be had.  There is a REALLY poor FR-101 manual on BAMA (schematics are completely unreadable), but nothing on the FL-101.

Anyway, some of the boards appear to be similar to the FT-101, but I'm sure there are a lot of differences.

Any help in this area would be greatly appreciated!

Thanks and Regards,

Steve

[kg7bz]

Check out the Fox-Tango web site. Ft-101 Section, about 2/3 of the way down. Both manuals you are looking for.

http://www.foxtango.org/ft-library/FT-Library/FT101/FT101.htm

http://www.foxtango.org/ft-library/FT-Library/FT101/FR-101.pdf

http://www.foxtango.org/ft-library/FT-Library/FT101/FL-101%20Instruction%20Manual.pdf

[Pete, WA2CWA]

I have them both. If you want stuff you can read and no assembly of pages is required. drop me a PM or check my web site.

[steve_qix]

THANK YOU THANK YOU THANK YOU !!!!

You guys are awesome!  Much appreciated.

Well, the receiver doesn't work (behaving like an RF amplifier problem - can barely hear myself when I'm transmitting).... at least the oscillator works, so if there are no open coils in the RF section, it shouldn't be too bad...

Haven't tried the transmitter yet.  Modifications for high fidelity AM look very straight forward.  The modulator appears to be identical to that used in the FT-101.

Regards,  Steve

[WB2CAU]

THANK YOU THANK YOU THANK YOU !!!!

You guys are awesome!  Much appreciated.

Well, the receiver doesn't work (behaving like an RF amplifier problem - can barely hear myself when I'm transmitting).... at least the oscillator works, so if there are no open coils in the RF section, it shouldn't be too bad...

Haven't tried the transmitter yet.  Modifications for high fidelity AM look very straight forward.  The modulator appears to be identical to that used in the FT-101.

Regards,  Steve

I have no familiarity with those particular models but I have some experience with the FT-101 series and some weak points may exist in your models also.  Since the units have probably been idle for a number of years, look for the obvious first, like a bad relay connection.  The relays in the Yaesus of that time period are notorious for having unreliable contacts.  Your loss of receiver may be due to that rather than component failure.  

[WD8BIL]

Steve...... some of the FT series had a light bulb in the receive path after the T/R relay. I and a cohort here at work have both had them open on us in our FT101s. I don't know ifn that receiver does but it's worth a look.

[W3GMS]

THANK YOU THANK YOU THANK YOU !!!!

You guys are awesome!  Much appreciated.

Well, the receiver doesn't work (behaving like an RF amplifier problem - can barely hear myself when I'm transmitting).... at least the oscillator works, so if there are no open coils in the RF section, it shouldn't be too bad...

Haven't tried the transmitter yet.  Modifications for high fidelity AM look very straight forward.  The modulator appears to be identical to that used in the FT-101.

Regards,  Steve

You will like that pair.  I still have mine from the early 70's.  I first bought new the FL-101 and used it with my NC303.  Then a few years later bought new the FR-101S to match the transmitter.  Its been awhile since I did the AM mods, but when done the TX audio is excellent.  I used the RX with the 6 kHz filter and it sounded good.  Not super HiFi, but was very decent.  The old Fox Tango organization has tons of mods that can be done with all of this type of gear.   

Joe-GMS   

[steve_qix]

I got the receiver working. It was a stuck relay in the mute system.  The thing probably hasn't been used in years, but it's working now.

The AGC and/or detector is REALLY bad on strong signals.  I forget how bad most communication receivers are.  I'll have to make some measurements and find out where the weakness exists.

But, the bottom lines is that the receiver works.  Haven't plugged the transmitter in yet.  That's next!

[WA2SQQ]

Your uncle is smiling ;-)
Who know he may request a band opening on 75 for you!

[W3GMS]

I got the receiver working. It was a stuck relay in the mute system.  The thing probably hasn't been used in years, but it's working now.

The AGC and/or detector is REALLY bad on strong signals.  I forget how bad most communication receivers are.  I'll have to make some measurements and find out where the weakness exists.

But, the bottom lines is that the receiver works.  Haven't plugged the transmitter in yet.  That's next!

Fox Tango came out with an improved AGC for the receiver Steve.  It greatly improved it over the original design, so much so that you hardly had to use the attenuator.  I never did the mod since I really never had an issue with mine.  I used the attenuator and that was always good enough for  me.     

[steve_qix]

I got the receiver working. It was a stuck relay in the mute system.  The thing probably hasn't been used in years, but it's working now.

The AGC and/or detector is REALLY bad on strong signals.  I forget how bad most communication receivers are.  I'll have to make some measurements and find out where the weakness exists.

But, the bottom lines is that the receiver works.  Haven't plugged the transmitter in yet.  That's next!

Fox Tango came out with an improved AGC for the receiver Steve.  It greatly improved it over the original design, so much so that you hardly had to use the attenuator.  I never did the mod since I really never had an issue with mine.  I used the attenuator and that was always good enough for  me.     

Hi Joe, If you know where I can get a schematic of that AGC improvement, I would sure like to see it before going about redesigning the circuit from scratch !  It would be nice to see what they did, even if I do end up with my own design.

Thanks !  Regards,  Steve

[W3GMS]

I got the receiver working. It was a stuck relay in the mute system.  The thing probably hasn't been used in years, but it's working now.

The AGC and/or detector is REALLY bad on strong signals.  I forget how bad most communication receivers are.  I'll have to make some measurements and find out where the weakness exists.

But, the bottom lines is that the receiver works.  Haven't plugged the transmitter in yet.  That's next!

Fox Tango came out with an improved AGC for the receiver Steve.  It greatly improved it over the original design, so much so that you hardly had to use the attenuator.  I never did the mod since I really never had an issue with mine.  I used the attenuator and that was always good enough for  me.      

Hi Joe, If you know where I can get a schematic of that AGC improvement, I would sure like to see it before going about redesigning the circuit from scratch !  It would be nice to see what they did, even if I do end up with my own design.

Thanks !  Regards,  Steve

Let me see what I can dig up Steve.  

Joe

[W3GMS]

Steve,
This is all I could find when going through my archives dealing with the AGC problem on the FR-101.  The same was true for FT-101's as well.  I remember the little op amp board the size of a postage stamp, but have no clue where I put it some 40 years ago.  I know I never installed it in the receiver, since I had moved on to my older boat anchors.   

Please see the attachment defining the problem and their solution to it.

Joe

[steve_qix]

Joe, Thanks for the posts.

Last night, I tried a number of experiments with the AGC.  It turns out that the heart of the problem is that the IF gain is reduced so much that the IF becomes non-linear.

I experimented with varying the ratio of RF gain reduction to IF gain reduction.  I can significantly improve the linearity at the expense of noise (more hiss in the background because the IF gain is higher).  Still experimenting...

When you posted the article and I read it, I believe the writer is trying to accomplish the same thing by boosting the AGC level fed to the RF amplifier stage.  There's a good balance in there somewhere, I hope !!

Thanks and Regards,  Steve

[W3GMS]

Hi Steve,

Yep, I believe the op amp was just a DC amplifier in order to alter the voltage to deal with the non- linearity.  I am sure it was indeed somewhat of a compromise, but still much improved over the original circuit. 

Let me know what you come up with and I will dust off my FR-101 and put the Yaesu Twins back in service!

I seemed to remember that they came up with a better FET in the front end in a separate mod but  nothing to do with the AGC problem.   

73,
Joe-W3GMS