Ultimate Ranger Audio Mods - Keeping the tubes, too (with pics)!

[steve_qix]

A friend of mine, Mike N1HXA has a 4-1000 grounded grid linear amp - badly in need of a good low power RF source....

Mike brought to me a PRISTINE original Ranger (1) for possible modification.  Well, I just could not touch that transmitter.  It would have been a desecration!  The thing is just beautiful.... but, in my collection of "stuff" I have an old Ranger II that's not in too good shape cosmetically, and could therefore be modified.

Now, I am basically lazy about physical changes to existing transmitters, so anything I was going to do would have to involve MINIMUM "Drilling and Blasting".  But, the mod transformer had to go.... no way was I going to get true high fidelity audio at 175% positive modulation out of that puny little transformer...

What to do?  Well, I had an old Stancor A-3893 kicking around in my junk pile - one that I actually bought at Radio Maintenance Supply when I was 17 years old, and haven't used for about 40 years.... That's the transformer to use.  But, where to PUT it....

Well, once the old mod transformer is gone, there is actually plenty of room for the A-3893 right there where the modulator used to be.  That leaves one little problem - where to put the modulator tubes... and since the power supply is now solid state, that left 2 octal sockets just perfect for the mod tubes and that's where they ended up.

Added "push to talk" using a 3 pole relay.

The mods:  The modulator is a pair of 6DQ5 tubes used as triodes... the control grids are grounded, and audio drive is applied to the screen grids only.  This works wonderfully!  The audio driver is a solid state source follower audio driver, directly connected to the grids.  I was able to apply EASILY 20dB (maybe more) of negative feedback around the whole thing, including the modulation transformer.  Of course, the 3 diode negative peak limiter is included.

Moved the bleeder resistor to the top of the chassis, just above the mod transformer.

The audio?  Silky smooth, broadcast quality and PLENTY of positive peak capability - at least 175 to 180 percent positive.

Circuit details:  It is attached here. The driver is quite simple, and the modifications to the Ranger itself are not overly complex.

I am extremely pleased with the audio results!

[K5UJ]

Nice work Steve; I would have probably done damage to the pristine Ranger 1--good thing my only hambone destruction has been with a Ten Tec amp so far.  (Pair of Heathkit audio amps are not looking great but work well    ) 

no way was I going to get true high fidelity audio at 175% positive modulation out of that puny little transformer...

I'd like to have it explained to me why hams want such high positive modulation.  To me, it is a bad idea.  Here's why:

1.  Many vintage rx with envelope detectors can't handle it.   They even distort at around 90% positive. 

2.  In a group of hams in a RT on some frequency, most will be running average ham rigs and average positive peaks, at the most, 120% but more often symmetric audio.  The one ham who has supermodulation comes on as LOUD
 which I find annoying--let's say you have wandered away to a bench to do some work or are taking a ahem, bio-break when the guy running 170 or 200% positive takes his turn.   You have to rush back to the receiver to pot it down.

I favor compression and high average audio; if more peak power is desired I suggest increasing overall power (more carrier) and holding audio to at most 120%.

Anyway, I have seen these really high positive percentages mentioned a few times and don't understand the high asymmetric audio thing.  Maybe supermodulation is a phenom that seems to exist because it is possible to do it now (like high amounts of low frequency audio) but not everything that is possible, is desirable.

Rob

[flintstone mop]

Hi Rob
I think Steve did a typo and meant 125%..........And I can't believe what Steve did works. There is not a clip lead in sight. They're used in another project in the picture.
Fred

[IN3IEX]

Eh, eh, a hot iron is a good reason to try this:

http://amfone.net/Amforum/index.php?topic=30073.0

IEX

[WD5JKO]

Anyway, I have seen these really high positive percentages mentioned a few times and don't understand the high asymmetric audio thing.  Maybe supermodulation is a phenom that seems to exist because it is possible to do it now (like high amounts of low frequency audio) but not everything that is possible, is desirable.

    Rob,

    Most of us remember W8VYZ and his ultra modulated rig. Yes Bill had a lot of talk power, but that rig always had a sort of gravelish sound to it. Another years back was Hoisey W4CJL (founder of SPAM) with his upside down Taylor modulated rig. This was more DSB with reduced carrier, and without a product detector it did not sound right on an AM receiver. In the 1980's I played with a ultra modulated Viking I at 200% positive peaks. I did find that the asymmetry thing at this level did kick in with receiver distortion complaints from some stations in QSO with, however most stations just said my audio was clear and LOUD for a given carrier level. I took the criticism to heart and added a 3 db carrier control boost such that one syllable spoken would boost the carrier to 200 watts prior to modulation. The multiple diode circuit (4 or 5 diodes if I recall right) then only had to do its job during the "attack" time of the carrier control ramp up time. The complaints went away as I transmitted a plate modulated, carrier controlled ultra modulated Viking I that ran 800W PEP from a resting 100W carrier!

What to do?  Well, I had an old Stancor A-3893 kicking around in my junk pile - one that I actually bought at Radio Maintenance Supply when I was 17 years old, and haven't used for about 40 years.... That's the transformer to use.  But, where to PUT it....

    Steve,

   Well done OM!

  In my Viking I I used the same mod transformer, also obtained when I was 17 (!) and used it as a Heising reactor. In the last few days I've done something similar to your Ranger with my Gonset G-76. The stock mod transformer here has about a 2:1 stepdown ratio instead of the more favorable 1.4:1 for a system with a common power supply. So surely it needed to go, or did it? Well the Gonset could almost hit 100% at the clip point, so I needed to investigate the possibilities. Since the Gonset was making 50 watts and 200W PEP, I decided to make that 35 watts and 200W PEP and modulate 140%. The big change was to drop the modulated B+ with a 1K 20W resistor bypassed with a 10uf 250v cap across it. This is the old Heising modulation trick to get 100% from that setup. This works with push pull plate modulation the same way.

  I am also using a 2 diode ultra modulation circuit with a passive keep alive supply (similar to what I did with the Retro75). This keeps the modulator loaded at all times and limits the negative modulation to a preset -90% modulation. Like your 3 diode circuit, just turn down the audio, and everything becomes transparent and symmetrical again.

  So last night I was in several QSO's on 75M when the band was oscillating between long skip and short skip. Usually a 35W AM signal gets lost on 75M when the band goes long. That didn't happen however when I was hitting 140% on peaks. When the band shortened up and signals came up 20DB, my reports were very favorable from multiple stations. When the band lengthened out and the S/N ratio worsened, I was still 100% copyable.

  I have always admired your Class E rigs Steve that seem to make it to Texas in good shape, and those high peaks do not disturb my Icom R75 receiver in any way. It sounds like Angel Music to me!

Jim
WD5JKO


  

[steve_qix]

Nice work Steve; I would have probably done damage to the pristine Ranger 1--good thing my only hambone destruction has been with a Ten Tec amp so far.  (Pair of Heathkit audio amps are not looking great but work well    )  

no way was I going to get true high fidelity audio at 175% positive modulation out of that puny little transformer...

I'd like to have it explained to me why hams want such high positive modulation.  To me, it is a bad idea.  Here's why:

Hi Rob,

Well, a high degree of positive modulation will increase the effectiveness of the signal.  Consider the difference between 75% modulation and a little over 125% modulation - it's 5dB which is rather significant.  Makes quite a difference under weak signal, marginal or noisy conditions.

1.  Many vintage rx with envelope detectors can't handle it.   They even distort at around 90% positive.  

This is definitely true.  A big part of the end-to-end path of a good sounding signal is the receiver.  I can speak from experience that a significant part of my personal enjoyment of good sounding audio is the ability to hear it.  I know a that many, many hams have fixed the detectors and AGC system in their receivers to improve the audio.

If there is a one-on-one QSO going on, and/or conditions are quiet, I always back down on the modulation percentage to the point there the negative peak limiter is not operating.

2.  In a group of hams in a RT on some frequency, most will be running average ham rigs and average positive peaks, at the most, 120% but more often symmetric audio.  The one ham who has supermodulation comes on as LOUD
 which I find annoying--let's say you have wandered away to a bench to do some work or are taking a ahem, bio-break when the guy running 170 or 200% positive takes his turn.   You have to rush back to the receiver to pot it down.

That is quite a disparity! The difference between 100% modulation and, say, 150% modulation is about 3dB.  This will be noticeable, but hopefully will not blast you out of the shack    The difference between 50% modulation and 150% modulation is almost 10dB, which is quite a change and of course we've all been in QSOs like that!

I favor compression and high average audio; if more peak power is desired I suggest increasing overall power (more carrier) and holding audio to at most 120%.

Anyway, I have seen these really high positive percentages mentioned a few times and don't understand the high asymmetric audio thing.  Maybe supermodulation is a phenom that seems to exist because it is possible to do it now (like high amounts of low frequency audio) but not everything that is possible, is desirable.
Rob

The advantage of a high modulation percentage really shows up under weak signal or noisy conditions.  I get into a little bit of AM DX from time to time, and if the guy at the other end is undermodulated, I often can't hear what's being said.  The guy with a LOT of audio on the carrier gets through.

I guess the bottom line is - the transmitter/modulator should not be a limiting factor.  Almost everyone tries to achieve 100%, or close to it negative modulation.  Under completely natural conditions, there will be asymmetry due to the characteristics of the human voice.  If the audio is phased correctly, at least with my voice, this generally results in at least 125% positive modulation - and usually more, actually.

My personal preference is to eliminate limitations in the transmitter, and put out the best possible [and sometimes loudest, audio-wise] signal that I can.

[WD8BIL]

The difference between 50% modulation and 150% modulation is almost 10dB, which is quite a change and of course we've all been in QSOs like that!

Since I put the Softrock I.F. card on the R4A I've noticed a LARGE number of operators with less than 75% modulation. In many cases if it weren't for the sync detector I never would have heard them. These were the stations that would complain about being "left out" of a qso when truth be told, they weren't heard by many.
If you're gonna run 100 watt and less rigs in high noise times please put some audio on that signal!

[Todd, KA1KAQ]

The advantage of a high modulation percentage really shows up under weak signal or noisy conditions.  I get into a little bit of AM DX from time to time, and if the guy at the other end is undermodulated, I often can't hear what's being said.  The guy with a LOT of audio on the carrier gets through.

I always understood this to be the case, but never realized just how much of a difference it could make until hearing Al 'VTP on 75 one evening with the crew after his big amp had puked previously. He was basically on par with the rest of the group audio-wise, but his signal strength was S7-S9, sometimes 10 over. Everyone else was 20-40 over. Al explained that he was using his Flex into a Courier amp for just over 50 watts out with high peak modulation. Yet I was working him here in NC like a local. It was hard to believe, but the S meter certainly backed it up.

Since I put the Softrock I.F. card on the R4A I've noticed a LARGE number of operators with less than 75% modulation. In many cases if it weren't for the sync detector I never would have heard them. These were the stations that would complain about being "left out" of a qso when truth be told, they weren't heard by many.
If you're gonna run 100 watt and less rigs in high noise times please put some audio on that signal!

You've summed up one of the biggest frustrations encountered working AM, Buddly: the healthy carrier seen on the meter with marginal audio heard best on high signal peaks, sometimes dropping out at S9 levels. It's fun to meet and work new folks on the air, but you need to be able to actually hear what they're saying for it to work! 100 watts with stock/marginal audio on 75 at night is a lot like pissing into the wind: you get that warm feeling of accomplishment, but no one else notices unless they're nearby. Down in the 80m portion where it's quieter there are numerous 100watters, but most seem to be running enough audio to make it work. One fellow comes to mind though, who has plenty of carrier with spotty audio. And you know what they say about the weak stations.

Strong doesn't have to denote big carrier. Steve is dead on - proper modulation makes all the difference, and simply cranking up the gain isn't necessarily the answer.

[K5UJ]

Thanks Steve for your explanation.  Much appreciated. 

I fully understand the need for adquate audio, and even a lot of audio when working DX or when running a < 100 watt rig like a ranger (that isn't driving a 4-1000A)  when the rig, a FT1000 for example, can support a lot of modulation.   I don't think extremely high positive % is called for all of the time however.   But there are plenty of other things more important than this.

 

[W2VW]

Looks like a very nice way to make useful power from a relatively small footprint.

FB job as always Steve.

[KC2ZFA]

It would be great if you can share the audio driver schematic Steve.

Is it the same as the one you have driving 811's ?

I'm disgusted by my inability to build a hum-free tube driver for 811's.

If you add such a thing to the kits you now offer it would be a great service.

Peter

[ke7trp]

I worked Mike the other day on 15 meters AM.  He mentioned that you where working on a ranger for him and live near by.  Cant wait to hear this thing Steve. Good job and the perfect Beat down old ranger to modify!

C

[W1AEX]

I caught a bit of an early test run Steve made with the modified Ranger. The audio clip will give you an idea of what it sounds like, but believe it or not, it has been vastly improved since this clip was made. When I heard Steve messing with it again the following day it sounded much brighter and louder. The audio was so "big sounding" and impressive that I honestly thought Steve was on one of the Class E rigs. I think it's kind of humorous that the little Ranger can produce this kind of heavy, smooth, and clean audio. It should be quite formidable when it's driving the intended 4-1000 amplifier!

During the recording, the receiver was in the synchronous detection mode, hence the traces of warble here and there, and the receive bandwidth was 9kc.

Rob W1AEX

[ke7trp]

Sounds good to me.  I like the clarity and the talk power. I do not care for the big muted bassy sound that alot of people run. 

C

[w1vtp]

<snip>

I always understood this to be the case, but never realized just how much of a difference it could make until hearing Al 'VTP on 75 one evening with the crew after his big amp had puked previously. He was basically on par with the rest of the group audio-wise, but his signal strength was S7-S9, sometimes 10 over. Everyone else was 20-40 over. Al explained that he was using his Flex into a Courier amp for just over 50 watts out with high peak modulation. Yet I was working him here in NC like a local. It was hard to believe, but the S meter certainly backed it up.

<snip>

<snip>

Strong doesn't have to denote big carrier. Steve is dead on - proper modulation makes all the difference, and simply cranking up the gain isn't necessarily the answer.

That high peak modulation is partly due to a problem I am currently having with PowerSDR 2.2.3.  When I first set up for AM with this version I noticed I had WAY too much drive for my Courier - much more than with the previous 1.16.1,  It was explained to me that something happened to the coding of 2.2.3 where there is too much RF carrier.  So, I compensated for setting the drive at 13% (out of a possible 100). Even then I had too much drive for the 2 watts required for the Courier.  Next I set the Transmit AM level at 30 (out of a possible 100).  It's amazing to see the peak RF level go from 2 watts to an indicated way more than what I'd expect.  My salvation is that the Flex AF is pretty good to start with.

I'm a great believer in true fidelity in AM. If that means having head roof of 150 % then so be it.  We just need to have our rigs designed / tuned / loaded so that we can hit that mark without flat topping.  It's gratifying to get these kind of reports even with my 52 watts. Todd, I think I did have the infamous "DX" in with level 2 (out of 10) selected.  I don't know what that button does but there is always a big difference - sometimes not so good - other times with good results as you mentioned.

Al

[w1vtp]

Steve

I think I did catch a couple clip leads in there    Are my eyes fooling me or did I see a little flattening of the tank coil.  Obviously that doesn't result in flat topping 

[steve_qix]

I forgot about that recording, Rob.  My voice was VERY hoarse that day and it's quite evident in the recording.  Maybe I'll run into you in the next day or so and if you're so inclined, maybe make another recording ?     Thanks for that one, however!

Regards,

Steve

[k4kyv]

Rob,

I don't use diode type negative peak clipping, but I do use a broadcast type peak limiter, set to limit the negative peaks to near 100% modulation.  The natural asymmetry of my voice is such that when I modulate to 100% negative, the positive peaks periodically reach up to somewhere between 130% and 150%.  If the transmitter were capable of no more than 100% positive, that means I couldn't modulate all the way down to 100% negative without flat-topping the positive peaks. My transmitters are capable of about 130% positive on a good day (for some  reason, some days I can get greater positive peak capability with all the same exact settings than other days - something that has bugged me for years, and I  notice the same effect with the Gates BC rig and the HF-300 homebrew rig), allowing me to more closely approach 100% negative.

Another reason to have extra headroom is that the signal will be cleaner even at 100% positive modulation, since you are not pushing the modulator to just under the point of saturation to completely modulate the carrier. Most modulator circuits will begin to show an increase in distortion substantially below the saturation point where hard clipping (flat-topping) occurs. Unless a lot of compression/clipping/limiting is used, the maximum voice peaks occur only sporadically, and the average percentage of modulation will still be less than 100% with most voices.

If I ever run across one of those Kahn Symmetra-peak gadgets, I want to try it (or else build up the active device version that uses op-amps) and see how it effects the sound and effectiveness of the audio to keep the positive peak modulation closer to 100%.  That would allow greater modulation density and complete modulation of the carrier without driving receivers using diode detectors too far into the distortion region, and the modulator stage would operate more efficiently when operating with less reserve headroom.  Even so I would still keep some extra headroom just to keep the distortion to a minimum.

[W2VW]

All pass filter using op amps $20.00 on epay.

[K5UJ]

Don--agreed, much to say about this topic, however i do not wish to steer the topic off of Steve's FB work with the Ranger 2.   I do see at least one clip lead in there.   I believe a ham can never have too many clip leads.  they are like ball point pens--you buy a bunch and a week later they are all gone--they keep gettng used up somehow.   but anyway the thing with audio and good copy belongs in a separate thread I think.

[ke7trp]

I kept seeing the peak mod level change also.  I put a voltage logger hooked to the wall and got my answer.  The voltage would change to the input of the transmitter but that was not even the real issue. The issue was that some nights, I would get 1 volt sag,  Others, I would get a big sag of 10 to 15 volts.  I guess those where the nights everyone had the heat/air on and the pot grower down the street had all his grow lights on 

Rob,

I don't use diode type negative peak clipping, but I do use a broadcast type peak limiter, set to limit the negative peaks to near 100% modulation.  The natural asymmetry of my voice is such that when I modulate to 100% negative, the positive peaks periodically reach up to somewhere between 130% and 150%.  If the transmitter were capable of no more than 100% positive, that means I couldn't modulate all the way down to 100% negative without flat-topping the positive peaks. My transmitters are capable of about 130% positive on a good day (for some  reason, some days I can get greater positive peak capability with all the same exact settings than other days - something that has bugged me for years, and I  notice the same effect with the Gates BC rig and the HF-300 homebrew rig), allowing me to more closely approach 100% negative.

Another reason to have extra headroom is that the signal will be cleaner even at 100% positive modulation, since you are not pushing the modulator to just under the point of saturation to completely modulate the carrier. Most modulator circuits will begin to show an increase in distortion substantially below the saturation point where hard clipping (flat-topping) occurs. Unless a lot of compression/clipping/limiting is used, the maximum voice peaks occur only sporadically, and the average percentage of modulation will still be less than 100% with most voices.

If I ever run across one of those Kahn Symmetra-peak gadgets, I want to try it (or else build up the active device version that uses op-amps) and see how it effects the sound and effectiveness of the audio to keep the positive peak modulation closer to 100%.  That would allow greater modulation density and complete modulation of the carrier without driving receivers using diode detectors too far into the distortion region, and the modulator stage would operate more efficiently when operating with less reserve headroom.  Even so I would still keep some extra headroom just to keep the distortion to a minimum.

[KE6DF]

My transmitters are capable of about 130% positive on a good day (for some  reason, some days I can get greater positive peak capability with all the same exact settings than other days - something that has bugged me for years, and I  notice the same effect with the Gates BC rig and the HF-300 homebrew rig

Variations in line voltage perhaps?

But, you probably checked that.

[W1AEX]

Maybe I'll run into you in the next day or so and if you're so inclined, maybe make another recording ?

Yep, if things go as planned I'll be bringing the Viking III back to life tomorrow, so I'll have a receiver sitting on 75 meters while I work on that. If I hear you around I'll check in and make a recording of how it sounds with the latest changes. I really like the idea of the solid state (FET?) audio driver directly connected to the 6DQ5 grids. Hope that gets documented!

Rob

[w1vtp]

Maybe I'll run into you in the next day or so and if you're so inclined, maybe make another recording ?

Yep, if things go as planned I'll be bringing the Viking III back to life tomorrow, so I'll have a receiver sitting on 75 meters while I work on that. If I hear you around I'll check in and make a recording of how it sounds with the latest changes. I really like the idea of the solid state (FET?) audio driver directly connected to the 6DQ5 grids. Hope that gets documented!

Rob

Yes. Steve!  Please

[kb3ouk]

I'd say this is probably the driver circuit he used. I'm thinking of trying the same thing some day.
http://www.classeradio.com/tube_driver.htm
shelby