AM 11 Meter AM Classic Radios and Equipment

Discussion in 'Citizens Band' started by KB3ZUW, Oct 19, 2015.

  1. KB3ZUW

    KB3ZUW Member

    11 Meters is quite active here in South Eastern PA. Sure there are still "elements" of 11 Meters that would make you want to turn off your radio upon power-up and I feel the same can be said of some of the amateur radio bands, as I unfortunately discovered after getting my general ticket.

    But there is hope. A few operators in my area, including myself, have restored and revived many of the old tube and crystal style AM radios... Browning Labs, Tram/ Diamond, International Crystal, Johnson Messenger, Pearce Simpson, Demco, Globe, Metrotek and Sonar just to name a few.

    For several years now, we have brought out the old classic 11 Meter AM rigs every Wednesday night for an 11 meter net called The Classic Radio Roundup Show. There is no cursing or QRM for 2 hours and sometimes longer into the evening. In fact we've had good success at keeping the channel "clean" enough so that our kids can come on and enjoy playing radio with each other through out the week. The The Classic Radio Roundup Show runs from 8-10 pm EST on 27.115 MHz AM. Sometimes we run a specific "manufacture theme night" or others such as "stock mic night" or "walkie talkie night" or "less than 3, 6, or 10 channel radio night" or "3 knob radio night." You get the picture. Just a bunch of folks still having some fun on 11 Meters. There's always plenty of vintage AM hardware running that would make you reminiscent of your youth. I feel very, very fortunate to have civilized operators still broadcasting in my area. The show also benefits from participation of some highly talented radio engineers and techs that know how to repair that classic AM radio equipment. It is not uncommon to have a trouble shooting session right on the air.

    I know it's a stretch and I understand the feelings that many amateur radio operators have towards 11 Meters, but would like to ask anyway if there could possibly be a section created for Classic Vintage 11 Meters AM Equipment on this forum. Maybe a list (such as the one above) of classic 11 meter equipment could be compiled that would be a guide line of allowable topics to be commented on to keep it from spiraling. Or maybe a production cut off year such as 1980 or older. Oh well, just a thought.

    In the mean time I picked up a like-new Sonar BR-21 (20-30MHz / 30-50 MHz) linear amplifier at the local ham fest yesterday. It has all the original Sonar branded tubes in it still. Sonar Radio Corporation, made in good old Brooklyn, NY. Stuff like this was designed for "relatively" clean output running at half the voltage for continuous duty operation as opposed to the "other" sweep tube amps of the day.

    Here's a few photos of the Sonar BR-21 I acquired...

  2. W5HRO

    W5HRO Administrator

    We don't really need a separate 11-meter forum here. People can just post the occasional technical stuff about it here.

    Old 11-meter radios do make good projects for 10-meter conversions, but I think the current solar cycle is getting close to being over. Once that happens it will be another 10 to 11 years before it opens up again.

    I worked on one of those BR-21 amps back in the 1970’s for a CB'er who kept killing the tubes because he continued to drive way too much power into it until he eventually fried the power transformer. I had to build him an external supply for it after that happened and add input attenuation without him knowing it. Needless to say he was the typical ordinary CB'er type and wasn’t very bright ::)

    Those BR-21's were designed for the BR-20 business band transceivers. The BR-21 is a 30W out amp. 1 watt in, around 30 watts out. I remember because I had to repair it for the guy so many times that I have never forgotten it to this day.

    Keep the input drive down and the power out at 30W max. It works best if you input a tone into your mic jack or just whistle and adjust the output for maximum peak output power while doing it. Don’t tune it for maximum carrier output if driving it with 10 watts on AM. It was designed for around 7 to 8 watts max drive on FM, but not on AM.
  3. KB3ZUW

    KB3ZUW Member

    Continuous duty rating , that's why I picked up this BR-21 amp.

    Well, actually, I heard another local operator use his hand wired Tram Diamond D201 transceiver in front of a Sonar BR-21 amplifier properly driven for some very good sounding AM audio and said wow, I want one of those :icon_thumbup: Agreed, it does appear to be well engineered with reliability in mind @ only 450 volts and 30W max... definitely how I plan to operate it, just like you mentioned, with some headroom available from the (4) 6JB6 tubes. It will make a nice exciter.

    Sonar BR21 AM Curves.jpg
  4. W5HRO

    W5HRO Administrator

    No, it was designed primarily for short 40 watt FM transmissions, but it was usable on AM with CCS ratings provided it was adjusted properly. Meaning 4 to 5 watts input yielding around 30 watts out.

    The transformer isn't hefty enough to handle 40 watt or more CCS operation. The guy kept pumping around 10 watts into it all of the time and tuned for max carrier output on AM of around 40 watts or so and that was the problem.

    P.S. The specs Sonar generally published on most of their stuff were never that detailed or exact. They were often kinda vague. Also remember that amplifiers have never been legal on the CB band so the amp was designed mainly for their FM business band radios. At the same time they probably knew CB'ers would use them and was the reason for the focus on AM specs in the manual.
  5. W5HRO

    W5HRO Administrator

    You know, you might be better off popping in a different set of sweep tubes or even 6146's and building an outboard supply for it.. Using 4 tubes in an amp and only getting 30 watts seems like a waste of time today. You could leave the existing supply in there for the filaments (maybe) and the keying tube control for sure. 6146’s may be too much for it, but a different set of sweep tubes would probably work. Cannot remember if something like 6L6’s will work at RF frequencies though, but I think you get the idea.

    Anyway, that way you would get decent power for 10-meters and/or 11-meters.
  6. WD5JKO

    WD5JKO Member

    I wonder about some alternatives here. The 6JB6's are going for about $35 apiece. I presume these are grid driven in this amplifier? Another tube seldom mentioned is the 7984. This is basically a sweep tube in a Compactron socket which is designed for VHF Low/Hi band FM. It has a 20 watt CCS Pd rating, and 35W IMS (intermittent mobile service). The good thing here is these will work well on 10/11 meters, and the tubes are cheap and plentiful. A few years back I could buy all I wanted for around $5 apiece, NOS in the box.

    A good friend of mine in the NE is using a pair of 7984's in a Central Electronics 20A. With higher plate voltage (700?), he was getting around 100 watts PEP SSB. He says they are surprisingly clean. I figure 10-15 watts apiece on AM linear operation. Could use three tubes, and a fan to cool them for the higher level. Add in some additional bias to ease the burden on the power supply. For AM linear, bias the 7984's at cutoff. See my thread here on Class BC.
  7. W5HRO

    W5HRO Administrator

    Grounded grid. It's a really simple amp.

  8. WD5JKO

    WD5JKO Member

    Oh Darn, cannot do G-G with the 7984 due to the suppressor grid is internally connected to the cathode. It must then be grid driven. There is always the "frinear" concept where we derive the screen voltage from the RF drive.
    With AM this idea might work better than with SSB since the carrier can be tweaked to set the screen voltage, and unlike with SSB there would be no lost 1st syllable as the screen voltage comes up.

    Could steel ideas from this arrangement:

    That would be fun to build, and no better place to try it than 11m. :icon_shh:

  9. W5HRO

    W5HRO Administrator

    What I was thinking is just something a little better than what's in there that would get the power up a little higher like maybe closer to 50W or 100W.

    He wouldn't want to go with too drastic of a change because all of the components in there would need to be changed like the tuning caps, the relay, etc.

    I always wanted to use a VFO with an old Sonar FS-23 and an amplifier on 10-meters :mrgreen:


  10. W5HRO

    W5HRO Administrator

    The BR-21 I worked on for the guy back in the 70's was being driven with a Midland 13-892. Those had the rheostat on the inside of the chassis where you could adjust the power out to around 10 watts. I kept trying to tell the guy to back it down to around no more that 8 watts max, but every time he took it home he would pop the lid and change it back. Not only that, but the 13-892 had a problem at 10W and would often blow the final transistors on SSB. I think I had to repair that for him too at least once. They later solved the problem with the silver 79-892 40CH model.

    I also remember adding the capacitor on the BR-21’s relay so he could use it on SSB. That just made things worse though :icon_problem:

  11. WD5JKO

    WD5JKO Member

    I have a CB amplifier in storage. It uses a pair of 4cx250f tubes grid driven. The thing was really rough inside though. It does have a Dahl power transformer, Johnson sockets, and a nice blower. Most of the rest is junk. I figured it was good for 800 watts key down from a CB radio, and that is likely saturated. Most CB'ers like "all the knobs to the right", so this was likely popular, even if the power dropped with modulation and sprayed crap between 15m and 10m while talking.

    I still like this guy at this sight. About 3/4 down is a converted CB amplifier using a big Russian tube, good for 180 watts out with 10W drive.

  12. KB3ZUW

    KB3ZUW Member

    Thanks for the ideas about the tubes for the Sonar Amp. I like the look of their product line and have a Sonar Model G (8-channel AM transmit) which matches both the BR-21 amp and BR-20 FM transceiver. Others Sonar models I have but have not restored yet, are the FS-23 mentioned above and the FS-3023. The FS-3023 is almost identical to the FS-23 with the exception of a modulation limiter board. Probably required at the request of Uncle Charlie. The FS-2340 (40 channel) model is quite popular with the classic CB radio crowd and fetches a lot more money than I am will to part with for a boat anchor CB radio.

    In my opinion, sweep tubes do not have as low IMD characteristics as their RF power tube counterparts and I have shied away from them. Still they have their place when utilized in some properly tuned amplifier and PA circuits. The only other sweep tube amp I have is a similarly designed D&A Raider that utilizes (4) 6LQ6 tubes in parallel. I'm more inclined to be interested in a 3-400z, 3-500z or 8877 amplifier ;)

    Never was in the "all knobs to the right" club. I used to install and maintain professional sound systems for night clubs and dinner theaters, so my focus in the radio hobby leans more towards "as clean as possible" audio as I can obtain. AM fits the bill with the bandwidth available for sure. I've found monitoring my RF signal with spectrum analyzer to help alleviate harmonics and an oscilloscope to monitor modulation works wonders... even on 11 meters. I've started to gather some studio gear and audio processing components to do direct audio injection when I get some time. Again Thanks for the replies :biggrin:
  13. KB3ZUW

    KB3ZUW Member

    We had our weekly Classic Radio Roundup show last week. Since the show is sometimes recorded, I wanted to sound clean and clear and selected the equipment accordingly this particular time.

    Previous week's shows had the bulk of the operators sounding somewhat distorted on the recording. Well it turns out it wasn't our transmitters, it was the overloaded Halicrafters receiver being used as the recording monitor. The gentleman that does the recording has since switched over to an SBE Trinidad transceiver and all is well again. They have a wooden casing (that's mostly empty) and a fairly large speaker for a pleasant tone when close mic'd.

    I was about to say, the FT101EE/ FT-2100B combination and Syncron desk mic with built in compression I was using should sound pretty darn good on AM with very little IMD. And it did :icon_thumbup:

    Yaesu FT101EE 2100B Combo Set.jpg
  14. KB3ZUW

    KB3ZUW Member

    Oh yeah, forgot to add that RF Parts has a second batch of their "new and improved" Taylor 572B tubes for around $80 each. I'm assuming they'll go fast, but the original Cetrons in the Yaesu 2100B are still good in my case.

    I definitely want to get a spare set of 572B's for the old chunk of iron though.
  15. WD5JKO

    WD5JKO Member

    I am sure those Taylor 572B's are good tubes. The post linked below was using a quad of original Cetron 572B's. At that time all I could get was 100 watts AM with headroom for 100% modulation. This steadily got worse as the filament emission dropped. Tired of waiting for RF Parts, I bought a quad of 811A's from the Alpha folks. Ironically, a quad of 811A's cost less than a single 572B from RF Parts! Running Class BC, I can now run 150 watts RF out with my new Alpha tubes, and this is just at the threshold of color on the plates. Overall, I see no advantage going to the 572B's at over 4X the cost, unless the amplifier has a beefy power supply with over 2KV loaded plate voltage.

    My Gonset GSB-201 Class BC story:

    Alpha 811A:

    Edit: Looks like the Yaesu FT-2100 uses a B+ around 2400 volts, so the 811A option does not apply here. With my Gonset, I have around 1500V loaded, so the 811A's are happy there.

  16. KB3ZUW

    KB3ZUW Member

    Nice right up and thanks for the link to the 811A tubes. At that price, I could order up a set for the clean looking Heath Kit/ Daystrom HA-10 Warrior I plan on restoring someday.

    Unfortunately, the previous owner cooked the 811A's that were in there, cracked the parasitic resistors and "browned" the filter choke. Not sure yet if the choke is bad but plan to check the "iron" before throwing any money at it.
  17. W5EFR

    W5EFR Member

    I actually have a decent set of locals on 11 meters as well.

    The downside is they run on channel 30, so that takes out my tube CBs I have. I do however have a extremely audio modified Cobra 29 that I worked over about 10 years ago. I removed the audio choking modulation transformer and installed a Darlington pair modulation circuit. that thing will modulate 40Hz with no trouble, and I use a Behringer mic preamp strip to limit the high end to about 4khz.

    The couple bad apples in the bunch always complain I "ain't got no audio", but the rest of the crew can't believe how natural it sounds. Quite fun really. I am currently running a MXL R40 Ribbon Mic (waiting for my new transformer to arrive from Edcor), but I change them up quite often...

    In my current situation, I am quite antenna limited, so all I have up antenna wise is a 10/11 Meter homebrew vertical, so I get my radio fix anyway I can....
  18. KA4KOE

    KA4KOE Guest

    I remember as a kid in 1979 (age 14) literally salivating over a Sonar FS23 in the local radio shop. Never did get one.....
  19. W5HRO

    W5HRO Administrator

    You know, that FS-23 has one of the best receivers in it for a radio that was designed for CB. It is very quiet. The SNR is fantastic. You can re-tune it to work up on 29.000Mc as well.

    They also have a push-pull modulator with the transformer so you can easily add the negative peak limiter too.
  20. Rede2go

    Rede2go Member

    I have been reading this thread and i know its not the most current but i will give it a try. I have a sonar br-2911. I have been looking for a schematic for it
    but have not been able to find one. It does look the same based on pictures to the Sonar br21. Mine was left to me when my father passed, and i would like
    to bring it back to live. It also seems strange that "IF" its the same as the br21 it only does 50 watts or so with 4 sweep tubes? My other thought was to change
    out the tubes to 6km6 tubes? Any of you have any thoughts or input? Thanks for reading.
  21. W5HRO

    W5HRO Administrator

    The BR-2911 was the same amp as the BR-21. You could probably use the BR-21 schematic. The 2911 was just a newer version of the BR-21 when they changed all of their radios to have the woodgrain looking front panels.

    Both amps had the same tube line-up and components. There could have possibly been some very slight component changes underneath on the bottom side of the chassis when they updated it to the BR-2911 version, but the change was mostly, if not all related to the cosmetics of the cabinet design to match their newer radios at the time. I wouldn't be surprised if that was the only difference between the two amps. Chances are the newer cabinet was the only difference.

    If you wanted to actually try and find a BR-2911 manual then you would probably need to find it via an old SAM'S Photofact, but even that may prove to be difficult.
  22. Rede2go

    Rede2go Member

    Thank you!
    I was pretty sure they were the same as they looked the same based on pictures and the
    values that ever still readable on some of the components.I can now move forward on the
    repairs and place it into my collections. To me the radios that i collect must be in working
    order,even thou there are just on display.
    Thank you again.
  23. W5RKL

    W5RKL Member

    I have a few 11 meter rigs I've moved up to 10 meter AM.
    One is a Johnson Messenger 223 that I converted to DDS VFO control. The DDS VFO is mounted inside the small Heathkit HD-1410 keyer cabinet to the right of the 223 and is powered by a 12VDC 6 amp regulated CCTV power supply.
    I recently moved a solid state Johnson Messenger III up to 10 meter AM 29Mhz crystal control.

    The Messenger III produces a solid 4 watts output into a 50 ohm dummy load.
    The Messenger 223 produces a solid 6 watts output into a 50 ohm dummy load.
    The Messenger One (White Face), crystal control on 29Mhz, produces a solid 7 watts output into a 50 ohm dummy load.

    It's fun to work low power on 10 when the band's open.

    Mike W5RKL

    Low Power on 10 meters.JPG Johnson Messenger III 10 meters.JPG 10 Meter Messenger One.JPG
  24. W5HRO

    W5HRO Administrator

    With the sunspot cycles disappearing you might need to start converting those things to the lower bands instead.

    Here's a guy that converted one of those old whiteface Johnsons to 75-meters :lol:

    P.S. See how he found the issue with the squelch control? That was I was referring to in the amplified D104 topic and how the common audio circuity especially the squelch circuit started making the mic inputs around 5K to 6K.
  25. KB3ZUW

    KB3ZUW Member

    The Johnson Messenger 223 is basically the same radio electronically as the older Johnson white face rigs, just with more crystals (channels). These could be had with a matching good sounding Turner non-amplified desk mic.

    An ad from the time mentioned it's "High level Class AB-1 Modulator" design.

    Messenger 223 Ad.jpg

    My Johnson Messenger Two Twenty Three:

    Messenger 223.jpg