View Full Version : SONAR BR-21

05-14-2006, 07:33 PM
I have a question about a linear amplifier that I have in my possession.

It is a SONAR BR-21 serial number 7121.

Well, I picked it up about 5 years ago at a garage sale, when I started considering getting into amateur radio. I can't recall what I paid for it, probably 10 bucks give or take. I knew what it was, so I knew it would be worth more than the "sticker price" of the garage sale, if it were cleaned up and working, even if it wasn't working, it could be MADE to work and sold for a profit.

Well, I had it in storage for a few years, and finally pulled it out and blew the dust off of it. Since I have HF privelages now, it might be worth trying it out. However, I have NO manual for it, and while tuning it shouldn't be THAT big of an issue, I would like to have some tutorial before I start pushing RF through it.

OK, this amp was probably used by a CBer, though I have no proof of it. No matter...an amp is an amp as long as it was designed well. But there again...is this junk or a possible gem?

What is the max input power? what is the max output power it is rated for? what should I expect?

Any insight much appreciated.

73, Heath

05-14-2006, 09:20 PM
Well, fiddlesticks.

I found the owner's manual on a CB website, and the indication is that this amp is designed for operation between 25-50 mHz, so obviously it is a ChickenBander special...well, at least so much as that it ain't much good for anything else.

Back to the garage for this piece of garbage. Not even worth trying!

05-14-2006, 09:26 PM
so 12 and 10 are out?

05-14-2006, 09:37 PM
Well,10 and 12 meters isn't OUT, but my current base rig isn't capable of 12 meters..I will be putting this up for the time being. I am not sure if it is type certified or not, but I can imagine that I would be more likely to create harmful interference with this amp on those bands, which I seldom use anyway. I was hoping it would tune up for 20 meters, which is my favorite band, but nada.

Anyway, I'm not getting rid of it, just setting it aside.

Actually, there is a mod that can be done for use on 6 meters, so I MAY do that when the time is right.

05-14-2006, 09:51 PM
Hi all,

Yup, a CB leenyar but a good one made in Brooklyn NY by a very reputable manufacturer. Sonar produced not only CBs but VHF equipment as well, I once had a 5 channel portable CB and still have a 5 channel VHF marine portable, good quality stuff. Back when CB was a licensed radio service the onus was on the user, not the manufacturer so this 100W sweep tube amp was one of many made by leading manufacturers. The trouble is the average ham rig puts out the same power and 5W drive on AM for which it was designed is, well, rare to say the least. The switching hang time would have to be delayed for CW and SSB, the unit was made before SSB came to the then 23 channels.

Considering it's a boat anchor you may as well use it as one for maybe a 10' John Boat while you're bass fishing in a shallow lake. Then at the end of the season sell it on flea Bay. Hey, one's already for sale there, "It just quit on me, don't know why but it lights up." http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif

05-14-2006, 10:13 PM
Back in the day I had one of those Sonars for my chicken band radio, worked quite well as I remember.

05-14-2006, 10:33 PM
Quote[/b] ]SONAR BR-21. #This amplifier was probably used by a CBer, though I have no proof of it. #An amp is an amp as long as it was designed well. #Is this junk or a possible gem?
Heath -

I am looking at schematic (isn't the Internet great for research from your workbench?) and reading owner's manual. #The matching transmitter for this unit was the BR-20 - was that at the garage sale?.

Power supply uses a solid state bridge recitifier. #Driver tube is 12AT7. #Final is 4 tubes - 6JB6. #this is the same "sweep tube" used in the Drake 4-line. The Drake uses 3. #Current prices are around $25 - 30 each.

No band switching (no surprise - it was made for CB market), but you can short 2 links and add capacitance through a #jumper for 32 to 50 MHz operation.

With this design - you need 4 very good tubes for best efficiency and operation. This is also pointed out in the BR-21 manual - 10% degradation - change ALL four tubes.
If you assume previous owner had little knowledge and potential poor operations [lack of ongoing measures (power output, SWR) - to prevent overdriving] -- I would, at a minimum, have the tubes checked (e.g. TV-7) - so you know what you have before starting.

IF you have 4 good (to very good) tubes and change-out the electroltyics in the B+ power supply (40mfd, 450 VDC), clean it up (remove dust, etc.) it should be okay for 10 meters. #Normal warnings about working around HV apply.


05-14-2006, 10:41 PM
Yeah, as the band conditions start picking up I might consider this. Certainly, relpacing electrolytic capacitors would not be a big deal...and there are plenty of experienced guys around here with tube rigs that could get me going with installing new tubes. I might in fact go that route. I am a youngin' in comparison to some of you guys, and have very little experience with vacuum tubes save the photomultiplier tubes that I install from time to time on my lab's chemiluminescense analyzers. I understand that when new tubes are installed, they must be neutralized in a certain manner, so it would be good experience for me to change these out and get an Elmer to show me some things.

With newer and better electrolytic caps, I imagine this amp could operate at even better specs than when it was built.

Chalk this up to "future projects"

05-15-2006, 12:09 AM
It would be fun to pair it up with a CB that had been converted to ten meters. Might keep that in mind as you spot those old good buddy radios lying around.

Possibly with new electrolytics, the spectral purity of the amp might improve a bit, adding some stability. And reduced drive might make it run fine, say driving it with 2 or 3 watts or AM RF?

Have fun

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