Re: FRG-7 Current draw using an external 12V PSU
Max 250mA with the lights on with normal volume.
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FRG-7 Current draw using an external 12V PSU
Hi group, and thanks for having me!
Anyone who can tell the current draw for a FRG-7, when using an external 12V PSU? I have a nice linear little PSU, but it's only capable of delivering 0,9 A continously.
Thanks,
Hans / LB6GG
Sandnes, Norway
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Re: Need more selectivity
The filter board uses diode switching to prevent long signal lines. The diodes on the in/outs of each filter are either forward or reversed biased via a DC voltage to activate, the half rail voltage at the cathodes reverse bias the unselected filter switching it hard off.. The DC voltages are switched via the mode switch section S3a, this section was intended to switch in the pretty useless automatic? noise limiter. Mine is construcetd on a small PCB hard wired into the holes of the removed original filter.
The LED lock light glows red, green when locked. This simple arrangement uses just 3 components. When unlocked, the current from R132 in the FRG7 flows through the RED LED to ground through the 100 ohm resistor.. This raises the voltage of the green LED cathode, switching it off. When locked, the current passes from the 10 volt rail, looses 3.9 volts through the zener diode, through the green LED and to ground through the common 100 ohm resistor, When transitioning, the small window of overlap will give an orange indication on the dual LED.
The BFO, as already explained is vital when using a narrow filter on the FRG7. This design uses a ceramic resonator taken from a cheap transistor AM radio. These are cheap and nasty components, you may need to try several to get the frequency of oscillation correct. S3c on the mode switch is modified to forward bias the diode in USB mode, this switches in the 470pF capacitor to lower the frequency. Again, diode switching is used to prevent signal radiation through long wires. The BFO output is fed into the existin emitter follower of the FRG7 after the removal of the original BFO components. Mine was constructed on a small PCB and mounted directly in place of the original.
The Synchronous detector too is very simple, and although using an"obsolete" IC, the NE567 or equivalent, these are still easily available on Aliexpress.
This amazing chip has all the functions required to really improve AM reception. The existing switch position on S3b? that selects the normal diode? AM detector is rerouted to the 567 output. The 567 455kC input is connected to the C428 on the FRG7 IF pcb.? Adjustment is critical the 2k2 potentiometer must be set to 455kC, the closer the better to ensure good weak signal locking.
Mine was also constructed on a small PCB and placed above the existing IF to keep the wires very short.
Finally, to aid in quieter reception, remove emitter bypass capacitors C419 and C423, This mod will reduce the excessive IF gain and improve the AGC response. Remove R404, this will narrow the first IF response. The Smeter will likely need a small adjustment to get back its former signal level.
And very finally, on the RF signal pcb, remove R109 from gate 2 of Q104 and return the gate2 to R133 using the same resistor, this will apply AGC control to the first IF. The second mixer is pretty nasty, this will help with overload anjd cross modulation.
These mods are quite simple, but any mistakes here will damage your radio....... take care, work neatly and methodically.
Apologies for the crappy image.... I will do better if noone can figure it out.?
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Re: Need more selectivity
Mike, et al,
Thanks for the suggestions and pointing me to some of the mod files - I will definitely check them out.? This is now not as urgent as a couple of days ago as I am waiting delivery of a Heathkit HR-1680 off FleaBay so hopefully it doesn't have a lot wrong with it.
73,
--
Justin B.
KI5GKD
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Re: Need more selectivity
I would love the schematics you mentioned. These seem like worthy mods!
Thanks, Robert
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Re: Need more selectivity
Improving the FRG7 selectivity by replacing filters is problematic when going much beyond a 3-4 kC bandwidth and expecting improved SSB reception. The cause is the Yaesu? free running BFO is just not stable enough to remain in the narrower passband, if set for cold mornings, it will drift away as the day warms. To do a successful upgrade requires the BFO to be upgraded also with at least ceramic resonators to prevent BFO drift, this is a much more invasive modification.?
My FRG7 has been fully modded in this regard, I did this back in the 80s and will post pics later. The filters are diode switched using the existing mode switch, the AM/ANL position selects the narrow filter in AM mode, and is automatically selected also when in SSB/CW modes. Using existing switches save defacing the radio. The existing filter was removed and two new filters were mounted on a small daughter board. Diode gating? is used, this only requires a DC voltage and not signal voltages to be switched, making an easy job of it..
The existing BFO components were removed from the PCB and a small replacement PCB was constructed and mounted in its place.....a? one transistor oscillator stage does the trick. the ceramic resonator is capacitively loaded for the USB position.
With this done, the radio easily will hold a commercial SSB station correctly tuned for hours on end, mine spends much of its time on the Pacific aircraft? net on 8867 kHz.
Other mods I have done include synch AM detection, very easily added to this radio and? very simple improvements to the RF circuitry, including an AGC mod that includes the first IF amplifier into the AGC loop for enhanced gain control preventing cross mod on strong stations in the second mixer.
. Another very worthwhile and simple? improvement is the removal of the third IF emitter bypass capacitors, this lowers the excessive gain and noise level, and prevents frequency "skewing" at high signal levels, by introducing localised negative feedback.?
The AGC is also automatically slowed when in SSB modes.
Many of these mods are possibly of academic interest only, but mentioned here? out of completeness.
I can supply schematics if there is any interest in going this far.
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Re: Need more selectivity
radio west upgraded all their FRG-7 filters before shipping and you had the option of further upgrading of the filter including switchable filters 
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Re: Need more selectivity
look in the files section for the file Gilfer frg-7 mod, that explains the only way to improve selectivity in the FRG-7
smaller sized filters (based on number of elements) will not require legs to install
I have several bandwidths for sale if you want to do that mod
the best mod is to add a filter to the built in one and add a switch to select the bandwidth you need.
I was an acquaintance of John Kolb who developed that mod for Radio west in the early 1980's
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Re: Need more selectivity
I am *NOT* and FRG-7 expert. I bought one and completely realligned it. Sensitivity is excellent, but it was designed as a general purpose shortwave receiver, not a communications radio.
However, if you have a nanoVNA, the service manual and modest skills you can tune it more precisely to your needs. Yaesu was making a 6 kHz AM and 3 kHz SSB BW general coverage radio.
By adjusting the IF BWs and offsetting them you can perhaps get better CW selectivity, but if you're having issues with selectivity on AM & SSB doing the radio cal really is the first step. I had no problems doing it first time ever using an HP 8560A just before the nanoVNA appeared.
Don't forget that *all* RF inputs are fragile. Always start with a variable attenuator in series that you reduce from maximum until you see a signal. That ensures the best dynamic range and accuracy. Once you see the signal set things for full screen coverage. If you're buying a nanoVNA get one from R&L (US) or other of Erik's or Hugen's validated sellers. There are lots of mediocre versions. Though even those are better than nothing.
Have Fun!
Reg
On Tuesday, August 29, 2023 at 12:04:34 PM CDT, Justin Bowser - KI5GKD <justin.bowser@...> wrote:
Hi, Y'all!? Long time Frog owner but first post here.? I'm hoping the collective can help me put this radio into mainstream use in the shack.
I have been trying to pair this up with a Heathkit DX-60A I just acquired and after a few attempted CQs it became clear selectivity is lacking.? I have had this radio for about 20 years and I re-capped it not too long after I bought it and besides the re-capping it is bone stock.? Are there any mods that might help with the selectivity like a crystal filter or some other wizardry.
Thanks and 73,
--
Justin B.
KI5GKD
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Re: Need more selectivity
I have several murata filters that I have for sale that can significantly improve your selectivity and with a little extra work you can make a two filter system
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Hi, Y'all!? Long time Frog owner but first post here.? I'm hoping the collective can help me put this radio into mainstream use in the shack.
I have been trying to pair this up with a Heathkit DX-60A I just acquired and after a few attempted CQs it became clear selectivity is lacking.? I have had this radio for about 20 years and I re-capped it not too long after I bought it and besides the re-capping it is bone stock.? Are there any mods that might help with the selectivity like a crystal filter or some other wizardry.
Thanks and 73,
--
Justin B.
KI5GKD
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To start with, a complete alignment according to the service manual.
Op zondag 16 juli 2023 om 01:22:59 CEST schreef Chris Rogers via groups.io <crvee8@...>:
I have a FRG-7 that has the following non working symptoms. The Mhz led can be tuned out on the upper shortwave bands only, and a few stations can be heard at very low volume. The Mhz led does not go out on the lower bands and and no stations are heard.?
Any clue on where to look for the fault would be appreciated.
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Thanks to everyone for their tips. I will do some more investigating and see how i go.
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Hi Dayle,
Thanks for your advice. I will give it a try and see how I go.
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The fault lays in the Wadley loop section .
You need to ascertain the Mhz VFO is working, this runs from 55 mHz to 85 mHz.
Because your lock light goes out at the higher frequencies, this oscillator seems to be working fine.
The loop amplifiers then need to be checked, this can be done without any test equipment to get you in the ballpark..
Reduce the mHz tuning until the lock light begins to extinguish, and while watching its brilliance, carefully and SLOWLY adjust each coil slug looking for a greater dip in brilliance. The lock LED monitors the RF output amplitude? of the loop amplifier chain and is a very good indicator of output level.
? As this improves, tune further down in mHz frequency and repeat the adjustments until no further improvement. This applies to T109 through to T116. Do not fiddle with anything else, although this radio has quite possibly been a victim of the golden screwdriver.
IF the band pass alignment was the issue, the radio will now receive signals.
The main mHz tuning can next be aligned, also without any test equipment.
Tuning in a known BC AM signal, the slug on the VHF VCO can be adjusted to bring the mHz tuning drum into alignment, and then tuning into a known signal in say, the CB band on 27 mHz, the trimmer capacitor can be adjusted to align the 27 mHz frequency to the correct dial setting.
Once done, the signal BPF and third IF filters can be simply peaked on signal.
On Sat, Jul 15, 2023, at 10:31 PM, Chris Rogers via groups.io wrote:
I have a FRG-7 that has the following non working symptoms. The Mhz led can be tuned out on the upper shortwave bands only, and a few stations can be heard at very low volume. The Mhz led does not go out on the lower bands and and no stations are heard.?
Any clue on where to look for the fault would be appreciated.
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Do you have the manual with the alignment instructions? You need that and a nanoVNA and tinySA or two. The 2nd is for use as a signal generator. Connect CH0 of the nanoVNA to the antenna input attach a probe to CH1 and start tracing your way thru the radio doing the alignment. You'll either find or fix the fault in the process. At some point results won't match the instructions.
Key traits:
manual preselector
Barlow-Wadley loop circuit
use of harmonics of 1 MHz oscillator to change frequencies
A good white noise source (NOT a BG7TBL!!!) will let you check the performance of the preselector with a tinySA. In fact, if budget is tight a tinySA and white noise source will do everything you need for under $100. A search on EEVblog for user rhb should find comparisons of the two noise sources.
The one of this pattern
https://www.ebay.com/itm/265453613573
that I have tested is quite flat to 1 GHz and then starts to roll of. Over the narrow spans and frequencies you need to use it will be perfectly flat. I've posted 8560A screen shots of the performance. The noise source should have a 2nd voltage regulator as the MIMICs are being fed unregulated input power and it's particular about what you feed it. I plan to add a LiPo and charger.
My FRG-7 is on loan at the moment. It was the first radio I ever did an alignment on for the simple reason I didn't have the needed instruments. I very much enjoyed it. I redid it a 2nd time just to be sure I had it right and to catch any potential coupling problems between stages. Just make sure you have the correct adjusting tools as you don't want to damage a tuning slug.
Basic procedure outline
check the operation of the preselector with the noise source. You should see the peak back and forth on the SA. and it should be of uniform amplitude at the preselector output. Then check at the mixer input to see the signal amplitude is constant check the LO input to the mixer and the output. Then align the harmonic oscillator chain. Use a magnifying glass and check for craks or solder flux residue.
If you observe cracking or corrosion I recommend fluxing the entire board and reflowing it with a hot air gun. If there's one you, see there are many you don't.
Have Fun!
Reg On Saturday, July 15, 2023 at 06:22:59 PM CDT, Chris Rogers via groups.io <crvee8@...> wrote:
I have a FRG-7 that has the following non working symptoms. The Mhz led can be tuned out on the upper shortwave bands only, and a few stations can be heard at very low volume. The Mhz led does not go out on the lower bands and and no stations are heard.?
Any clue on where to look for the fault would be appreciated.
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Chirs you will likely get a hundred different answers. I had a FRG-7 that was deaf. It turned?out to be coil L101. This is a large multi segmented coil. The problem was the ends of the coil are wire wrapped into the circuit. Even though the wire wrapped posts looked sound it failed electrically. I had to clean the connection with flux multiple times and then solder it in place. Radio works fine now.
Good Luck, Bruce
I have a FRG-7 that has the following non working symptoms. The Mhz led can be tuned out on the upper shortwave bands only, and a few stations can be heard at very low volume. The Mhz led does not go out on the lower bands and and no stations are heard.?
Any clue on where to look for the fault would be appreciated.
|
I have a FRG-7 that has the following non working symptoms. The Mhz led can be tuned out on the upper shortwave bands only, and a few stations can be heard at very low volume. The Mhz led does not go out on the lower bands and and no stations are heard.?
Any clue on where to look for the fault would be appreciated.
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Re: Almost ready to give up but...
Buy an nanoVNA from a reputable dealer like R&L and follow the manual procedure. Twice. The circuits interact so the 2nd pass is to compensate for that. You're unlikely to see significant change on the 2nd pass, but it's a good feeling to see all the test points as they should be.
On Tuesday, May 30, 2023 at 09:18:31 PM CDT, Pentagrid <dayleedwards@...> wrote:
I am beginning to think this radio is actually fine, it has been misaligned.? The VFO, "mHz tuning" should span from 55.5 to 84.5 mHz.? The first IF should be centered on 55 mHz, this can be checked by feeding in a small signal into the IF chain and monitoring the output at the second mixer. The Wadley loop section should be centered at 52.5 mHz, this is checked at the source of the second mixer.? The difference frequency between 55 mHz and 52.5 mHz is 2.5 mHz, the center frequency of the second tuneable IF.? When peaking/adjusting these IFs, use a very low amplitude signal as not to overload any part of the circuitry. Its just a process of elimination and perseverance........
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Re: Almost ready to give up but...
I am beginning to think this radio is actually fine, it has been misaligned.? The VFO, "mHz tuning" should span from 55.5 to 84.5 mHz.? The first IF should be centered on 55 mHz, this can be checked by feeding in a small signal into the IF chain and monitoring the output at the second mixer. The Wadley loop section should be centered at 52.5 mHz, this is checked at the source of the second mixer.? The difference frequency between 55 mHz and 52.5 mHz is 2.5 mHz, the center frequency of the second tuneable IF.? When peaking/adjusting these IFs, use a very low amplitude signal as not to overload any part of the circuitry. Its just a process of elimination and perseverance........
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Hans Ostnell
MikeM
