Re: Digital Display for FRG-7
By memory I think you will find the mixer is a CA3028 transistor array or similar. Look in any 1970s? American? radio constructor books for details of these chips, they were used often before the days of LSI.? Three transistors, long tail differential pair in a round case with 7 legs
Basically, the oscillator into the? base of the long tail, signal into one base of the differential pair. The two products are available at the output. The LPF will remove the high product 3.455 +2.455? to? 3.455 + 3.455 = 5910 to 6910, leaving the low product 3.455 - 2.455 to 3.455 - 3.455 = 1 to 0 megs, this product passes to the counter module. This is a very elegant way to do this, as it also automatically reverses the count.....? the FRG7 actually tunes backwards. The second IF is below the first IF, and the first IF is above the signal frequency, that is the basis of drift cancelling...... both first and second signal mixers using? the same VFO....?
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Re: Digital Display for FRG-7
Enjoy it stock. Not worth the effort.
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On Jan 21, 2025, at 1:13?AM, Mark Feltham via groups.io <dodacarem@...> wrote:
? Don’t fit the digital display gents, it looks terrible and completely ruins the whole feel visually of the radio. The whole beauty of this radio is its retro appeal and I urge you to not be tempted to fit the aftermarket hideous digital display unit… It really does not do the radio any favours whatsoever. Thank you 73 On 21 Jan 2025, at 02:16, Steve Quigg (VK2TUM) via groups.io <stevequigg@...> wrote:
? Hi Simon,
Have attached a data sheet on the MSM5525 plus a couple of pics re the DFC-7.
Enjoy
<MSM5525_6.pdf> <time_step-04.jpg> <time_step-03.jpg>
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Re: Digital Display for FRG-7
Thanks everyone for your help on this...I've put Steve's diagram and instructions through PaintShop Pro and uploaded the results into the 'files' section on the group.
?
Pentagrid - I've spent most of my life working on equipment without diagrams. Data sheets are of course a great help, but it's much easier if someone has the original manufacturer's diagrams and PCB layout, as I'm sure you will agree. The metal round IC, a mixer chip, isn't identified on the diagram...and the numbers have been removed from the physical part. I thought it might be a 'Birkett Special' Plessey SL640, but the connections don't match. I don't recognise the pinout and connections; is it familiar to you?
?
The original owner had used an 18-0-18 volt transformer, with a separate 3v winding to feed the filament of the display. I'm fairly sure the counter chip is faulty, but believe I have a spare one 'somewhere safe'.
?
I would never dream of installing it in my receiver, but will re-box it and sit it on the top.
?
Cheers
?
Simon M5POO
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Re: Digital Display for FRG-7 - image resolution
Hi All,
It seems that loading an image to messages reduces it's resolution :-(
So I've put various images etc into files/DFC-7; resolution is 1600x1200 vs 1024x768.
Something to remember for the future.
?
Steve
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Re: Digital Display for FRG-7
Simon
I have fiddled with the background colour - do these help?
?
Andy  
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Re: Digital Display for FRG-7
Yes, thats exactly how it was done, the input signal was mixed with a 3.455 MHz oscillator, a low pass filter used to remove the higher mixing product, the counter chip then? read the difference.
Other Wadley loop receivers of that era used a similar arrangement, the Century 21 being one example. This method was a very simple and elegant way to get an offset? using analog? mixing, rather than digital divisors, and, being in a seperate box with its own power supply removed the dangers of any birdies and interference being introduced into the radio..
The display chip itself is simply the manufacturers data sheet implementation of that chip, so a schematic really is not required to get this working once again.
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Re: Digital Display for FRG-7
Hi Simon,
Unfortunately I don't have the originals; the attachments are as I found (somewhere; too long ago to remember) the on the web.
Re the schematic,? it is readable, albeit with some difficulty. IC2 appears to be strapped for direct reading, i.e no IF offset. Crystal X1 (DS(?)C7 in the pic) would be , I'm surmising, 3.455 MHz, mixed with the input from the FRG-7 to give a 0-1MHz signal which is input to the MSM5525. Can't make out the mixer part number, but appears to be a Texas Instruments part.
?
Cheers,
Steve.
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Re: Digital Display for FRG-7
Hi Mark
?
I would never spoil the radio. This kit sits in a box on top of the radio.?
cheers
?
simon
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Re: Digital Display for FRG-7
Thanks Steve, that’s exactly what I need. Sadly the circuit diagram is a bit low res to read clearly. Would you mind scanning the DFC-7 pages for me, or if you don’t have a scanner, could you take a photo of the diagram which fills the frame please? Cheers, Simon.?
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Re: Digital Display for FRG-7
Don’t fit the digital display gents, it looks terrible and completely ruins the whole feel visually of the radio. The whole beauty of this radio is its retro appeal and I urge you to not be tempted to fit the aftermarket hideous digital display unit… It really does not do the radio any favours whatsoever. Thank you 73
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On 21 Jan 2025, at 02:16, Steve Quigg (VK2TUM) via groups.io <stevequigg@...> wrote:
? Hi Simon,
Have attached a data sheet on the MSM5525 plus a couple of pics re the DFC-7.
Enjoy
<MSM5525_6.pdf> <time_step-04.jpg> <time_step-03.jpg>
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Re: Digital Display for FRG-7
Hi Simon,
Have attached a data sheet on the MSM5525 plus a couple of pics re the DFC-7.
Enjoy
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Digital Display for FRG-7
Hello
?
I've just joined this group and have a mint FRG-7...it came with its box and other bits.?
?
A friend gave me an old digital display unit which turns out to be a Timestep Electronics DFC-7 from 1981. It uses an OKI MSM5525RS LSI chip and a couple of others, one being an unmarked round can.
?
Does anyone, by any chance, have some information on the kit please?
?
Thanks
?
Simon, M5POO, UK
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Yes It’s an easy mod I had more trouble getting the radio out of the exterior case
M? 73
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On 17 Jan 2025, at 16:06, Reginald Beardsley via groups.io <pulaskite@...> wrote:
? Miguel,
Most welcome. Be careful about who you buy a nanoVNA from as there are lots of bad copies. The H4 has the advantage you can load time-frequency FW to it, though not both at the same time.
It would be very hard to find a damage level for an internal test point like that. The 1 V at 50 ohms for the signal generator source is as close as you get. I did not insert attenuators. Strictly I should have, but I was only showing the basic setup and forgot. Not good! However, I also know from experience that the output signal is quite low.
I just measured the default output of my H4 using a 50 ohm thru and DSO at 7.4 mW or 8.7 dBm. I did not find a way to set the output power on the nanoVNA H4.
I also strongly recommend Erik's tinySA. I have several as I use them for signal sources in addition to the SA function, though they need suitable LP filters.
FWIW I installed an IEC socket & EMI filter in mine and removed the posts for the factory cable storage setup. Vastly more convenient and it's not so pristine that it mattered.
You mention that you are missing some mechanical parts. I have a machine shop so if it's not too complex a part I can probably make one, though shipping cost might be prohibitive. Get it working properly and I think you'll feel the money was well spent. It's an interesting design of considerable fame.
Likely you will encounter component drift issues. I had to rework the fine tune capacitance to get it where it should be.
The FRG-7 was my first project radio. I also have an FT-101E and TS-520 in queue. A close friend, now SK, carried an FT-101E and FRG-7 on a circumnavigation in a 37' ketch in the '70s. Could not praise the radios highly enough. Four years at sea is a severe test case.
Have Fun!
Reg
W5UHU
On Friday, January 17, 2025 at 04:29:04 AM CST, Miguel Frutos via groups.io <m.frutos@...> wrote:
Thanks Reg,
I will get a NanoVNA as it seems very useful. Just one doubt: where can I see the limits of the signal we can inject in TP103? Don't we need an attenuator in the nano-VNA to protect the radio circuit?
- Miguel El vie, 17 ene 2025 a las 2:21, Reginald Beardsley via (<pulaskite= [email protected]>) escribió:
Here is my H4 hooked up with CH0 connected to TP103 and TP102 and CH1 connected to TP104 and TP105 per the manual.? SMA-M/BNC-F adapters and BNC-M to alligator clips.? One can do rather better with a custom cable set at the radio end.
I didn't make any effort to set the nanoVNA properly with a thru cal, etc.? It should be done for alignment, but not needed for just a demo.
Have Fun!
Reg
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That's roughly what I did. I'd have to take back apart to look. Was *very* minor.
On Friday, January 17, 2025 at 02:53:49 PM CST, Mark Feltham via groups.io <dodacarem@...> wrote:
I found the fine tune capacitance on my particular radio ?operated nicely with a series cap of 6.8pf….as the mod….
73
On Friday, January 17, 2025, 4:06 pm, Reginald Beardsley via groups.io <pulaskite@...> wrote: Miguel,
Most welcome. Be careful about who you buy a nanoVNA from as there are lots of bad copies. The H4 has the advantage you can load time-frequency FW to it, though not both at the same time.
It would be very hard to find a damage level for an internal test point like that. The 1 V at 50 ohms for the signal generator source is as close as you get. I did not insert attenuators. Strictly I should have, but I was only showing the basic setup and forgot. Not good! However, I also know from experience that the output signal is quite low.
I just measured the default output of my H4 using a 50 ohm thru and DSO at 7.4 mW or 8.7 dBm. I did not find a way to set the output power on the nanoVNA H4.
I also strongly recommend Erik's tinySA. I have several as I use them for signal sources in addition to the SA function, though they need suitable LP filters.
FWIW I installed an IEC socket & EMI filter in mine and removed the posts for the factory cable storage setup. Vastly more convenient and it's not so pristine that it mattered.
You mention that you are missing some mechanical parts. I have a machine shop so if it's not too complex a part I can probably make one, though shipping cost might be prohibitive. Get it working properly and I think you'll feel the money was well spent. It's an interesting design of considerable fame.
Likely you will encounter component drift issues. I had to rework the fine tune capacitance to get it where it should be.
The FRG-7 was my first project radio. I also have an FT-101E and TS-520 in queue. A close friend, now SK, carried an FT-101E and FRG-7 on a circumnavigation in a 37' ketch in the '70s. Could not praise the radios highly enough. Four years at sea is a severe test case.
Have Fun!
Reg
W5UHU
On Friday, January 17, 2025 at 04:29:04 AM CST, Miguel Frutos via groups.io <m.frutos@...> wrote:
Thanks Reg,
I will get a NanoVNA as it seems very useful. Just one doubt: where can I see the limits of the signal we can inject in TP103? Don't we need an attenuator in the nano-VNA to protect the radio circuit?
- Miguel El vie, 17 ene 2025 a las 2:21, Reginald Beardsley via (<pulaskite= [email protected]>) escribió:
Here is my H4 hooked up with CH0 connected to TP103 and TP102 and CH1 connected to TP104 and TP105 per the manual.? SMA-M/BNC-F adapters and BNC-M to alligator clips.? One can do rather better with a custom cable set at the radio end.
I didn't make any effort to set the nanoVNA properly with a thru cal, etc.? It should be done for alignment, but not needed for just a demo.
Have Fun!
Reg
|
I found the fine tune capacitance on my particular radio ?operated nicely with a series cap of 6.8pf….as the mod….
73
On Friday, January 17, 2025, 4:06 pm, Reginald Beardsley via groups.io <pulaskite@...> wrote: Miguel,
Most welcome. Be careful about who you buy a nanoVNA from as there are lots of bad copies. The H4 has the advantage you can load time-frequency FW to it, though not both at the same time.
It would be very hard to find a damage level for an internal test point like that. The 1 V at 50 ohms for the signal generator source is as close as you get. I did not insert attenuators. Strictly I should have, but I was only showing the basic setup and forgot. Not good! However, I also know from experience that the output signal is quite low.
I just measured the default output of my H4 using a 50 ohm thru and DSO at 7.4 mW or 8.7 dBm. I did not find a way to set the output power on the nanoVNA H4.
I also strongly recommend Erik's tinySA. I have several as I use them for signal sources in addition to the SA function, though they need suitable LP filters.
FWIW I installed an IEC socket & EMI filter in mine and removed the posts for the factory cable storage setup. Vastly more convenient and it's not so pristine that it mattered.
You mention that you are missing some mechanical parts. I have a machine shop so if it's not too complex a part I can probably make one, though shipping cost might be prohibitive. Get it working properly and I think you'll feel the money was well spent. It's an interesting design of considerable fame.
Likely you will encounter component drift issues. I had to rework the fine tune capacitance to get it where it should be.
The FRG-7 was my first project radio. I also have an FT-101E and TS-520 in queue. A close friend, now SK, carried an FT-101E and FRG-7 on a circumnavigation in a 37' ketch in the '70s. Could not praise the radios highly enough. Four years at sea is a severe test case.
Have Fun!
Reg
W5UHU
On Friday, January 17, 2025 at 04:29:04 AM CST, Miguel Frutos via groups.io <m.frutos@...> wrote:
Thanks Reg,
I will get a NanoVNA as it seems very useful. Just one doubt: where can I see the limits of the signal we can inject in TP103? Don't we need an attenuator in the nano-VNA to protect the radio circuit?
- Miguel El vie, 17 ene 2025 a las 2:21, Reginald Beardsley via (<pulaskite= [email protected]>) escribió:
Here is my H4 hooked up with CH0 connected to TP103 and TP102 and CH1 connected to TP104 and TP105 per the manual.? SMA-M/BNC-F adapters and BNC-M to alligator clips.? One can do rather better with a custom cable set at the radio end.
I didn't make any effort to set the nanoVNA properly with a thru cal, etc.? It should be done for alignment, but not needed for just a demo.
Have Fun!
Reg
|
Miguel,
Most welcome. Be careful about who you buy a nanoVNA from as there are lots of bad copies. The H4 has the advantage you can load time-frequency FW to it, though not both at the same time.
It would be very hard to find a damage level for an internal test point like that. The 1 V at 50 ohms for the signal generator source is as close as you get. I did not insert attenuators. Strictly I should have, but I was only showing the basic setup and forgot. Not good! However, I also know from experience that the output signal is quite low.
I just measured the default output of my H4 using a 50 ohm thru and DSO at 7.4 mW or 8.7 dBm. I did not find a way to set the output power on the nanoVNA H4.
I also strongly recommend Erik's tinySA. I have several as I use them for signal sources in addition to the SA function, though they need suitable LP filters.
FWIW I installed an IEC socket & EMI filter in mine and removed the posts for the factory cable storage setup. Vastly more convenient and it's not so pristine that it mattered.
You mention that you are missing some mechanical parts. I have a machine shop so if it's not too complex a part I can probably make one, though shipping cost might be prohibitive. Get it working properly and I think you'll feel the money was well spent. It's an interesting design of considerable fame.
Likely you will encounter component drift issues. I had to rework the fine tune capacitance to get it where it should be.
The FRG-7 was my first project radio. I also have an FT-101E and TS-520 in queue. A close friend, now SK, carried an FT-101E and FRG-7 on a circumnavigation in a 37' ketch in the '70s. Could not praise the radios highly enough. Four years at sea is a severe test case.
Have Fun!
Reg
W5UHU
On Friday, January 17, 2025 at 04:29:04 AM CST, Miguel Frutos via groups.io <m.frutos@...> wrote:
Thanks Reg,
I will get a NanoVNA as it seems very useful. Just one doubt: where can I see the limits of the signal we can inject in TP103? Don't we need an attenuator in the nano-VNA to protect the radio circuit?
- Miguel
El vie, 17 ene 2025 a las 2:21, Reginald Beardsley via (<pulaskite= [email protected]>) escribió:
Here is my H4 hooked up with CH0 connected to TP103 and TP102 and CH1 connected to TP104 and TP105 per the manual.? SMA-M/BNC-F adapters and BNC-M to alligator clips.? One can do rather better with a custom cable set at the radio end.
I didn't make any effort to set the nanoVNA properly with a thru cal, etc.? It should be done for alignment, but not needed for just a demo.
Have Fun!
Reg
|
Thanks Reg,
I will get a NanoVNA as it seems very useful. Just one doubt: where can I see the limits of the signal we can inject in TP103? Don't we need an attenuator in the nano-VNA to protect the radio circuit?
- Miguel
El vie, 17 ene 2025 a las 2:21, Reginald Beardsley via (<pulaskite= [email protected]>) escribió:
Here is my H4 hooked up with CH0 connected to TP103 and TP102 and CH1 connected to TP104 and TP105 per the manual.? SMA-M/BNC-F adapters and BNC-M to alligator clips.? One can do rather better with a custom cable set at the radio end.
I didn't make any effort to set the nanoVNA properly with a thru cal, etc.? It should be done for alignment, but not needed for just a demo.
Have Fun!
Reg
|
Here is my H4 hooked up with CH0 connected to TP103 and TP102 and CH1 connected to TP104 and TP105 per the manual. SMA-M/BNC-F adapters and BNC-M to alligator clips. One can do rather better with a custom cable set at the radio end.
I didn't make any effort to set the nanoVNA properly with a thru cal, etc. It should be done for alignment, but not needed for just a demo.
Have Fun!
Reg
|
Miguel,
At the time I used my HP 8560A spectrum analyzer which has a tracking generator as the nanoVNA didn't exist yet.
The setup is very simple. There are test points at which you inject the signal from the nanoVNA S11 port and test points at which you attach the S21 port to examine the log magnitude display and adjust until the display matches the manual. This is Scalar Network Analysis. Never having done it before, I did it twice. The stages interact a bit and so after I adjusted everything, I went back over it to make sure all the passbands looked correct.
I assume you have the factory manual. It's not much, but it's enough. I'll scan it if it's not in the Files section.
As you remark you don't have a signal generator I'd like to suggest that you buy a 1 MHz square wave output crystal oscillator module and set it up as a 0 dBm (1 mW) signal source. That will give you markers every 1 MHz. You'll need to add a resistive matching network with 50 ohm output impedance that lowers the signal level. Put it in a neat box and you'll have a very useful piece of test kit. That said, just building it on a breadboard with no connection will work. Just not homebuilt test gear which is the best kind. BTW If you box it, label it. I have a box of such things I built but never labeled. It's a real puzzle to figure out what they are 40 years later.
The tinySA is an excellent signal generator if you add a harmonic filter, but you can't use it as an SNA as you can the nanoVNA.
In the absence of other indications, I suggest you start at the antenna and look at the signal with a nanoVNA as you work through the circuit section by section. Connect S11 to the antenna and start tracing through the schematic with a probe connected to S21. Make sure twisting the knobs produces the desired result The mode switch has been a continuing annoyance on mine. I need to take it apart and remedy the intermittent contact.
Have Fun!
Reg
On Monday, January 13, 2025 at 04:50:11 AM CST, Miguel Frutos via groups.io <m.frutos@...> wrote:
Reginald,
I would be interested in learning how to do the alignment?using a nanoVNA, if you are kind enough to share the process. I thought nanoVNA was only for antenna / filter testing; so you use it in place of a signal generator? I don't own one but would consider getting one if it is useful.
- Miguel
El dom, 12 ene 2025 a las 3:40, Reginald Beardsley via (<pulaskite= [email protected]>) escribió: Put Deoxit on the switch contacts and align it using a nanoVNA per the factory manual. . It's an easy radio to work on and a really neat design.It deserves its reputation.
Have Fun!
Reg
On Saturday, January 11, 2025 at 08:45:10 PM CST, Chris Campbell via <481renton= [email protected]> wrote:
If the radio has been in storage long, take a can of canned air and blow all the dust off all of the tuner caps. That might help you hear something. ? I have an FRG-7 that was in storage for maybe 10 years and when I first turned it on, everything worked but it wouldn't tune anything.? ? Blowing out the dust from the preselector, MHz, and main tuner caps started it receiving. ? Also, exercise all the bandswitches. ? At least that would be a good start, if you haven't done those things already. ? Hope it helps.
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Well if the red LED is extinguishing that means at TP110 you have enough signal. But it is a tad complex this radio. May I direct you to articles in Short wave magazine written by JL Linsley Hood. September and October 1981. The first article explains how the
radio works and the second one how to align it. You need to do some research to understand the circuitry. And I would advise against tweaking any coil slugs or caps you until you know what you are doing. Connecting a sensitive longer scale voltmeter across
the S meter is a good method when aligning the set.?
First off check out the power supplies. The mains transformer is centre tapped and full wave rectified. The DC then passes through S5-b, to Q411 via the choke. There is about 17v here. The voltage regulator delivers 10v which generally supplies much of
the circuitry. Just after Q411 is zenor diode D413 which develops the 9v line. ?This is found on the green wires under the audio board. This voltage is the supply to the HG oscillator box that generates the MHz signals and also the 2-3MHz oscillator board
with Q201. The IC Q106 mixes the 2-3MHz signal and the comb of frequencies coming from Q301.?
I will stop here as Lindsley Hood explains it all very clearly.
Mike G4THN
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On 13 Jan 2025, at 10:43, Miguel Frutos via groups.io <m.frutos@...> wrote:
?
Thanks Mike for the hints which were?very helpful.
I followed your procedure without success: the lock light would never go off (sometimes it would just dim a bit). After touching VR102 as per instruction booklet, the light goes off correctly in every frequency?configuration, but still nothing is tuned.
I need to keep troubleshooting
Regards,
Miguel
El sáb, 11 ene 2025 a las 0:11, Mike Anthony via
(<g4thn= [email protected]>) escribió:
The stuff under the electrolytic caps looks like glue that was used to hold them in place before they were soldered. Look at the top of such caps. Any convex shape is bad news, they should be dead flat on top. First connect an antenna!?
If it was working before try the following. Select one of the four bands. Say band C 4-11MHz. Rotate the MHz knob to centre 7 under the curser with the red lamp off. Rotate the preselect knob to get maximum response. There are numbers there to assist.
Finally use the main tuning dial to show half way between 100 and 200. The set is now tuned to 7.150MHz. Tuning around this figure during daytime will almost certainly bring up strong amateur stations. To resolve the SSB, switch the mode switch to LSB. You
will need safe crackers fingers for this and the fine tune control helps here.?
To tune an AM broadcast station switch to either AM or AM/ANL. In general the ATT and TONE switches should be in the centre position.
If none of this works you may have a problem!
Best of luck, they are remarkable receivers.
Mike G4THN
Sent from Mike's iPad
?
Hello,
I collected a FRG-7 yesterday. I thought it was in better shape and probably overpaid?for it (EUR100).
The overall aesthetic condition can be improved:
- It's painted in black.
- The power switch cover is missing. And the light dim cover and shafts are missing.
- the rubber feet, from bottom and side are missing.
- The carrying handle is missing.
- The rear lugs to keep the power cord are missing.
I think all this can be improved. When switching on I can't tune anything, although the previous?owner sent me a video of it working fine, so I guess I have not been lucky yet.
There is something under the power capacitors, I'm not sure if this is because they are leaking. Also, some pads seem to be missing in the PCBs (not sure if this is a concern or not).
I think everything is fixable. I appreciate?any help or hints you can provide.
Regards,
Miguel
<IMG_20250110_114039.jpg>
<IMG_20250110_114628.jpg>
<IMG_20250110_114510.jpg>
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Simon Robinson
