SBE Trinidad

 

 

Classic Status: 23 channel.

Appeal: Owned by friends.

Condition: Cosmetic, Good. Electrical, Fair/Good.

Acquired: Late 90's as payment for other radio work.

 

 

This is my SBE Trinidad, a 23 channel, AM base station.  Produced starting in the early 70's, and enjoying a popular production run until the 40 channel radios came of age in 1977, the Trinidad was a fairly popular rig in our local area.  At least 5 people, whom I was close friends with, and a handful of others  ran this attractive and popular rig.  The Trinidad was a good alternative to the plain looking rigs from Radio Shack and Lafayette, and was priced competitively. The radio had most of the usual standard features and had great sounding receive audio as well as punchy transmit audio.  I never had the cash to afford one of these rigs back in the day, but my familiarity with them had placed this rig on the "must have" list for my retro collection.

Underneath the simulated woodgrained cabinet, there is a surprising amount of empty space. You could literally fit a second radio chassis in there, without too much trouble. The radio chassis itself is shared with one of SBE's cheaper mobile rigs, the Catalina II, which has spare features, and no "S" meter. That probably explains why in the Trinidad, both the "S" meter and the R.F. meter adjustments are found on external boards. The receiver is a dual conversion design, with a 10 Mhz 1st I.F. and a 455 Khz 2nd I.F. There are no crystal or ceramic filters, its selectivity derived instead from a series of hi "Q" tuned circuits. The end result is somewhat disappointing when compared to other rigs equipped with sharp filters.  But considering the cost of the rig and the target market that this radio was aimed at, the performance is not all that bad.  On the transmit side, performance was good.  Since the difference, in terms of dead key power, between any given rig is negligible, the only point of comparison becomes modulation quality and spurious output.  In this case, SBE designed the Trinidad with good overall frequency response which mated well with the most popular microphones in the 1970's, namely the Turner +3 and the Astatic D-104. The radio also employed an early design modulation limiter which was tasked at preventing modulation from exceeding 100%.  But in this design, a microphone with too much gain could result in distorted modulation instead of clean limiting.

I picked up my Trinidad about 10 years ago as a trade for services performed on a customer's radio. It didn't work when I got it (naturally), and it required a bit of work to bring back to life. It required replacement of the 9V regulator circuit (Which I replaced with a 7809 regulator), as well as the volume control and a few off-frequency crystals.  Even after the rig was working again, it had a strange problem with a small amount of distortion on the received signal. Turns out that swapping the high side of the volume pot with the wiper cured the 60 Hz hum ingress which had been the root cause of the distortion. The rig was then given a complete alignment and placed on the air.

First, the bench numbers....

Receiver: 

Sensitivity: .4uV for 10db S+N/N 

Adjacent channel selectivity: 42db @ 10Khz.

I.F. Frequency: 1st 10.635 Mhz, 2nd 455 Khz.

 

Transmitter:

AM Power: 3 watts with forward swing.

AM Modulation: 100+%, 12 watts peak.

2nd harmonic suppression: -50dbc.

Other spurious emissions: -45dbc.

 

Now for my subjective "seat-of-the-pants" review of the radio.....

 

It's hard to remain completely objective about each individual radio's performance without remembering to keep the radio's features in the proper context.  Yes, this radio does not have SSB, a super-duper noise blanker, a clock, or any host of premium features.  But in terms of raw performance, the Trinidad holds its own fairly well.  On the receive side, I was pleasantly surprised.  As I've mentioned before, my radio room in inundated with computer network interference, which seems to be especially pronounced on rigs with a 455 Khz I.F..  My Royce 640 and Cobra 135 seem especially affected by this interference.  So I was not expecting much from this straight AM rig with a lack of sharp filters.  So I was surprised when this radio did not exhibit the pitfalls of my other affected sets, and I was actually able to enjoy operating it.  The wider bandwidth receiver was not quite as effective at completely eliminating my 27.220 network spur, and I could clearly hear it if the Delta Tune was set to the "+" position.  However, I was able to hear most of the weaker stations, almost as well as on my much fancier Tram and Hy-Gain radios.  Perhaps because the receiver uses a high side 1st L.O. injection, the image rejection is better, which may explain this receiver's ability to function in the presence of my local interference.  The receive audio quality was as nice as I had remembered, and much better than on a mobile rig or one with a small tinny speaker.  One thing I did notice was that the lack of good I.F. filtering certainly allowed a higher level of adjacent channel bleed over to come through, but the wider bandwidth also enhanced the receiver audio fidelity, so there is good and bad in it.  Today, there aren't that many strong stations on adjacent channels near to where I am now, but in the CB boom days of the 70's, where almost every channel had a local group on it, this "flaw" would become a major sore spot after long.  The S meter was nice a large, and I liked the blue background, and the unique side swing. However, the meter did not have the same level of linearity that my Hy-Gain had (then again, not many rigs do).  While calibrated at the the same S9 signal level, a much smaller change in signal level (about 3 db) was required to move the meter 1 "S" unit.  Above S9 the meter was a little better, but not by much.  On the other hand, I probably pay way more attention to the S meter than the average guy, who only uses it as a reference, and not as a precision measurement device.  On the transmit side, the radio performed well. The locals seemed to like the transmit audio quality using both my Turner +3 as well as the D-104.  I was also told that the radio had a very noticeable and distinctive "clunk" when keyed.  I'm sure this is typical of many of the older rigs which used mechanical relays to switch from receive to transmit.  On the downside, the spectral purity is not as great as on other rigs.  There are spurs which, even when aligned, could still reach a level as high as -45dbc.  This is within spec for the date of manufacture for this rig, but it's possible that there may be more RFI issues as a result.

 

Overall, I like running the rig.  Mostly I enjoy the nostalgic feeling of running a rig that was a daily part of my early CB radio experience, even if I didn't have one of my own back then.  So for now, I'm making up for lost time.  The rig looks nice and the receiver audio is warm and room filling.

 

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