December 2001 Web Edition

Uniden PC68XL Turbo 121 From Mexico

One of my customers had a relative visit from Mexico. They brought this modified Uniden PC68 along with an amplifier for me to check out and give my opinion. Apparently this stuff is readily available down their. I haven't seen an amplifier that claimed 120 Watt peak output this small before. Very skeptical, I put it on the bench and connected it to my meters and dummy load. The radio alone only put out under a half Watt dead key with modulation swing to 5 Watts. With the amplifier on, the dead key was 21 Watts with a swing to 120 Watts peak. Wondering how it sounded, I tuned my Kenwood R5000 receiver to the same frequency and monitored the audio. To my amazement, it sounded very clean. Checking it on the scope, it exhibited some squaring of the audio sine wave, but nowhere near what it would be if the radio AMC was clipped.

Being curious, I turned down a Uniden Grant to 6 Watts PEP on sideband and connected the Turbo to it. It pumped out 135 Watts and sounded clean. Although time ran out before I could open it and take photos, they told me that there is a potentiometer for setting the relay un-key delay inside the amp.

This amp has a receiver preamp. It had marginal results on the PC68. I imagine it would help when the channel were quiet, but the test was done during the day when the skip was at it's peak. Although a low gain preamp, it didn't introduce any noticeable noise or distortion when a low level signal was injected with a signal generator. A quick test on the Grant radio didn't show any noticeable change with the preamp on or off. Although the preamp didn't really impress me, the output power and clarity did to the extreme.

They didn't know were the amplifier was produced, they thought it was manufactured in Mexico, but couldn't be sure. The store owner was protective about any information about these products. In fact, they told me that a customer couldn't just walk into the store and buy one. The amp had to be matched to a radio before it left the store. Either you brought a radio in to be setup or you bought on off the shelf and the store owner set them up together before you left. This is understandable because of the very low power requirement to drive the amp to full output. A stock CB radio would burn it out, and sound awful for the minute or two before it fried.

Click Photo For Close-up

We think we have access to everything in this country, but I haven't seen this one before. It's small size would make it popular for many applications. Even Ham operators would like to have a little extra power on 10-meters and this doesn't take up much space. It only draws 12 Amps on sideband and about 6 on AM. If it were used on FM, I would only recommend 40 Watts in that mode for any length of time. The heatsink isn't large enough for continuous full power.

When they left the my store they hooked up the radio and gave me a shout. Once again the performance was impressive. The signal cut through the skip cleanly 5 miles away. I took a little ribbing about how they had access to them and I didn't. A couple other drivers jumped in to find out what they were running and gave their compliments. Quite a setup, it's not competition class, but very impressive just the same. My thought is that they new what my impression was going to be before they brought the stuff in for me to check. _{Bob F}

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